University of Southern California Dissertations and Theses

Full scale contour crafting applications

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Full scale contour crafting applications

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Content FULL SCALE CONTOUR CRAFTING APPLICATIONS by Laura Haymond A Thesis Presented to the FACULTY OF THE SCHOOL OF ARCHITECTURE UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF BUILDING SCIENCE May 2008 Copyright 2008 Laura Haymond ii ACKNOWLEDGEMENTS A huge thank you to Doug Noble, Kara Bartelt, and Marc Schiler for all their help and support. Also to Behrokh Khoshnevis whose aid was essential in completing this thesis. And to Eve Lin and Mina Chow whose friendship and persistence kept me going. iii TABLE OF CONTENTS Acknowledgement ii List of Figures iv Abstract vii Chapter 01: Introduction 1 Chapter 02: Automation in Construction 8 2.1 Rapid Prototyping 12 2.2 The System of Contour Crafting 17 Chapter 03: Proposed Applications for Contour Crafting 22 3.1 Using Contour Crafting for Urban Infrastructure 22 3.2 Contour Crafting for Emergency Response 24 3.3 Single Family Housing 27 Chapter 04: Alternative Construction Methods in Single Family Housing 29 4.1 Steel Framing 30 4.2 Insulated Concrete Forms 33 4.3 Prefabricated Housing 37 Chapter 05: Applying Contour Crafting to Single Family Housing 43 5.1 Site Work 43 5.2 Structure 47 5.3 Systems 59 5.4 Finishes 76 Chapter 06: Sustainability Potential of Contour Crafting 83 6.1 Reducing the Carbon Footprint 84 6.2 Life Cycle Costs 86 6.3 Recyclability 87 6.4 Contour Crafting and LEED 87 Chapter 07: Conclusions and Future Work 100 7.1 Future Work 102 Bibliography 104 iv LIST OF FIGURES Figure 1 Waste Generated On Site During Construction 1 Figure 2 Fatal Injuries Divided by Industry 4 Figure 3 Non Fatal Injuries Divided by Industry 4 Figure 4 SMART System Outline 11 Figure 5 Stereolithography 13 Figure 6 Selective Laser Sintering 14 Figure 7 Electron Beam Modeling 15 Figure 8 3D Printer Diagram 16 Figure 9 Object Generated Through 3D Printing 16 Figure 10 Behrokh Khoshnevis and Full Scale Wall Extruded by Contour Crafting 17 Figure 11 Contour Crafting System 18 Figure 12 Forms Extruded Using Contour Crafting 19 Figure 13 Full Scale Wall Section Extruded Using Contour Crafting 20 Figure 14 Projected Cost Contour Crafting 21 Figure 15 Contour Crafting for Infrastructure 23 Figure 16 Steel Framed House Under Construction 30 Figure 17 Standard ICF 33 Figure 18 ICF Blocks available from ARXX 33 Figure 19 Stacking ICF Blocks 34 v Figure 20 Curved Forms Available with ICF 35 Figure 21 Sources of Energy Loss and Savings Through ICF 36 Figure 22 An ICF House Survives Hurricane Katrina in 2006 36 Figure 23 Manufactured Home 38 Figure 24 Module Prefabricated Housing 39 Figure 25 Prefab Kit of Panels 40 Figure 26 Examples of Colored Concrete Used For Exterior Pavers and Walkways 45 Figure 27 Example of Contour Crafted Planter 45 Figure 28 Possible Irregular CC Planter 46 Figure 29 Summary of Suitability of Contour Crafting for Site Work Tasks 46 Figure 30 Possible Integration of CC to Generate Crawlspace Foundation 48 Figure 31 Typical CC Wall Section and Wood Framed Wall Section 49 Figure 32 Typical Metal Decking 52 Figure 33 Possible Connection of Beam to CC Wall 53 Figure 34 Solid Extruded CC Stairs 54 Figure 35 CC Used to Generate Stair Guidance Ledges 54 Figure 36 Possible Method of Generating Vaulted Roofs with CC 56 Figure 37 Integration of Door and Window Openings with CC 58 Figure 38 Summary of Suitability of Contour Crafting for Structure Elements 59 vi Figure 39 2x4 Furring Against Concrete or Masonry Walls 62 Figure 40 Schematic Plumbing Wall for Contour Crafting 63 Figure 41 Possible Solutions for Embedded Wall Electrical Receptacles 66 Figure 42 Typical Composite Flooring 67 Figure 43 Typical Floor Electric Receptacle 68 Figure 44 Example of Raceways 69 Figure 45 Summary of Compatiblity Between Contour Crafting and Known Electrical Wiring Methods 70 Figure 46 Possible Generation of LED Lightshelf By CC 71 Figure 47 Summary of Integration Compatibility Between Known Types of Lighting and Contour Crafting 72 Figure 48 Table taken from Edward Allen and Rob Thallon's Fundamentals of Residential Construction 73 Figure 49 Adapted Forced Air HVAC System to CC 74 Figure 50 Compatibility Summary of Integrating Contour Crafting with Known HVAC Solutions 76 Figure 51 Examples of Colored Concrete Floors for Interior Spaces. 78 Figure 52 Compatibility of Contour Crafting with Known Floor Finishes 79 Figure 53 Summary of Compatibility of CC and Wall Finishes 82 Figure 54 Contour Crafting and LEED 88 Figure 55 CC Wall R-Value 93 Figure 56 HEED Results for Contour Crafted Home 94 Figure 57 Comparison of Contour Crafting to Other Existing Methods of Costruction 100 vii ABSTRACT Contour Crafting (CC) is an extrusion based method of rapid prototyping being introduced as a method of automating construction. This thesis takes a critical look at applying the system of Contour Crafting to single family housing and how the system could integrate with regards to site work, structure, systems, and finishes. This thesis also explores the potential sustainability of CC with regards to the reductions in carbon footprints and life cycle costs and utilizing LEED for Homes as a means of defining other potentially sustainable aspects of CC. The purpose of this thesis is to determine the strengths and weaknesses of the systems Contour Crafting and to determine if this new method of construction is appropriate for single family housing. 1 Chapter 01: Introduction In the field of construction there is a set of ever present issues plaguing the industry. Issues regarding quality control, labor efficiency, waste management, time needed for construction, cost control, and injuries to workers are particularly dominant. Traditional methods of construction of yielded no significant improvements regarding these issues. Therefore new methods of construction need to be explored as a means of solving these particular problems. According the Environmental Protection Agency (EPA), it is estimated that in a single year construction and demolition generated 136 million tons of building related debris and waste that ended up in landfills. According to the U.S. Green Building Council, this accounts for 30% of the waste generated by the United States annually. In a time when green building and sustainable thinking has taken a foothold in the forefront of the building industry, these numbers cannot be ignored. The site in Figure 1 is too common a sight within the construction industry. Figure 1 Waste Generated On Site During Construction Copyright 2008 Haymond 2 Contributing to these statistics are aspects of the construction industry that have persisted through time despite attempts made to correct said aspects. Construction is plagued with “high accident rates, low quality, insufficient control of the construction site, and the vanishing of skilled workforce” (Warszawski 01). Quality control in particular can be a frustrating and often costly point of contention between architects and contractors. Mistakes made on the construction site, for example, can result in discrepancies between the drawings and the actual built product. Such mistakes often lead the requirement of tearing down said discrepancies to be rebuilt. These actions lead to more waste being generated to contribute to the 136 million tons. Discrepancies in construction between the as-built product and the architect’s drawings lead to costly corrections in time, money, and resources. In order to offset some of these expensive corrections the construction industry has taken several approaches. Alternative construction methods are being explored such as the prefabrication of housing has been developed and improved upon, and automation in construction has been introduced into the industry. Automating construction, however, has been met with mixed responses. Currently automation in construction is limited to specific tasks within the industry, such as painting, but this is changing. For example, Japan is currently combining task specific robots in the attempt of automating both tunnel construction and bridge construction (Gambao 01). As these are both high risk 3 construction examples, the concern for human safety stands as a strong contributing factor. According to a census performed by the US Department of Labor, the construction industry accounted for 1,226 fatal work injuries in the year of 2006. This gave the construction industry the highest number fatalities of any industry sector as illustrated in Figure 2 and the fourth highest rate of fatalities of all industries . This is in addition to the 3,857 injuries reported in the year of 2006 shown in Figure 3 thus giving the construction industry a rate of 1out of 20 workers being injured on the job. As the construction industry continues to grow these numbers will only increase if steps are not taken and alternatives not found. 4 Figure 2 Fatal Injuries Divided by Industry Copyright 2007 U.S. Bureau of Labor Statistics, U.S. Department of Labor Figure 3 Non Fatal Injuries Divided by Industry Copyright 2007 U.S. Bureau of Labor Statistics, U.S. Department of Labor 5 Increased automation in construction is often put forth as a solution to the dominant persisting challenges plaguing the construction industry, however this method has been a point of debate within the industry for decades. As automation capabilities go on to improve other industries such as manufacturing and automobile construction, there is a distinct lack of advancement in the way buildings are being put together. Some of the reasons behind this are due to forces that resist the introduction of automation into the construction industry, fear of loss of jobs for example. However, as a means of creating a safer and more environmentally friendly means of constructions, all possible alternatives must be pushed. Rapid prototyping is the method through which 3-dimensional objects generated by a computer are given physical form. There are two approaches in how methods are developed through which this process is done, additive and subtractive. Subtractive methods, such as sintering, carve the desired form from a solid piece of material, usually plastic or metal. Additive methods, such as Stereolithography and Fused Deposition Modeling (FDM), build up the desired form layer by layer using a variety of plastics and metal alloys. Usually additive systems involve a heat source, such as a laser, and a powder form of the material desired. The form is then generated by melting layer by layer of material until the entire form has been constructed. 6 While there has been significant advancement in the field of rapid prototyping with regards to speed, available material, accuracy of systems, etc. , attempts to extrapolate known systems into the field of construction have been faced with certain limitations inherent in the systems themselves. All subtractive systems, which generate 3D forms by subtracting material from a given source, are limited in size by how large a solid piece of material can be procured. Standard additive systems are limited by different aspects of their system. 3D Printing devices are limited by the size of the chamber with its moving platform, as are Electron Beam Melting (EBM) and FDM systems. Current additive systems are also constrained by the types of materials they use, both metal alloys and plastics often ill suited to general construction. The sheer complexity and scale of general construction has generally served as a deterrent from trying to employ rapid prototyping as a means of automating any part of the construction save individual components used more in manufacturing. The Contour Crafting system was developed by University of Southern California Professor Behrokh Khoshnevis as a means of employing rapid prototyping technology to extrude the walls of a building using concrete or adobe as a construction material. While the system is still in the development phase Professor Khoshnevis has suggested that Contour Crafting will revolutionize the construction industry. 7 The purpose of this study is to take a critical look at this new system and how it can be applied to the various purposes projected by Khoshnevis. The intention is to isolate the most appropriate use for this new technology through a critical analysis of the pros and cons of this new system per proposed application. Once the most appropriate function has been confirmed this study will then break down said application into a more detailed critical analysis to discern where exactly this new technology is, how it can be used, and what the potential challenges will be when applied to full scale use. After the potential challenges have been determined prospective solutions will then be generated in order to bring this evolving technology to market. As seeking out and exploring more sustainable construction alternatives is one of the forefront concerns of the current market, another focus of this study will be an attempt to determine if Contour Crafting is a sustainable alternative to the standard method of construction dominating the market. This will be done by examining both the embodied energy of both systems and the life-cycle costs of Contour Crafting and the traditional alternative. The possible sustainability of Contour Crafting will also be explored by using computer simulation tools to compare the performance of a building made with Contour Crafting to an equivalent building constructed by the market dominant method of construction. 8 Chapter 02: Automation in Construction In 1986 in his article, “Construction Robotics: A Perspective,” Whittaker points out that, “labor efficiency is alarmingly low in construction.” He goes on to note how the construction industry is plagued with, “a high accident rate; low quality; insufficient control of the construction site; and the vanishing of a skilled workforce,” (Whittaker 1986). Ten years later John G. Everett noted in his article, “Construction Automation: Demands and Satisfiers in the USA and Japan,” that, “the construction industries in the United States and Japan face problems in productivity, quality, safety, and skilled-labor availability,” (Everett 1996). As a method of improving these aspects of the construction industry the use of robotics has been pursued. According to Ernest Gamboa, author of the article “Robotics and Automation in Construction,” published in IEEE Robotics & Automation Magazine in 2002, automation in construction is divided into 2 major categories: civil infrastructure and house building. Civil infrastructure includes robots and automatic processes with regards to road building, tunnel construction, excavation, bridge construction, etc. Automating processes regarding home building typical focus on structure erection, structure assembly, concrete compaction, finishes, etc. Gamboa further divides processes within these two major divisions into the development of new processes and the adaption of existing processes for automation (Gamboa 2005). 9 Within the field of civil infrastructure Gamboa cites several R&D projects that have been going on around the world. The first mentioned is the development of the EU Computer Integrated Road Construction in Europe which proposed to, “develop precision systems for the real-time control of the positioning of road construction equipment” (CORDIS 2003). This system that projected a 5% savings and significant improvement over quality control of road construction. The field of automating tunnel construction and excavation projects in Japan has also grown. Considering the significant risk of injury to workers with regards to tunnel construction the approach of creating full automation of tunnel construction has been taken up by several companies. Japanese companies are also heavily investing in the research and development of automation processes to aid in the construction of large infrastructure elements such as bridges and dams. One such project as Gamboa noted was the use of SCARA robots for dam construction (Gamboa 2005). Within the field of automating construction processes relevant to home construction there appears to be an emphasis on high rise residential buildings. Japanese companies in particular have been focusing on this field in part due to increasing urban density. However, as varied aspects of home building exist so do the approaches in automating them. These approaches range from developing robots to handle painting to utilizing spray robots all the way to automating the manufacturing of individual wall panels. 10 One of the fields of automating construction that Gamboa does not speak about is the use of automation with regards to constructing large scale office and retail space. The category falls under neither civil infrastructure nor house building but possesses interest and a series of developments all its own. Many of these developments even having been already been tested out in the field. One of the first demonstrations of in the field use of automation in construction was the use of the SMART system in Japan in 1994. The SMART system was developed within the context of promoting Computer Integrated Construction (CIC) as an, “approach to assist construction firms by introducing computer technologies in response to the difficult environment in which they currently operate,” (Yamazaki 1998). The SMART system itself is described by Yamazaki is illustrated in Figure 4 and described as, “an integrated automated construction system which automates a wide range of construction procedures, including the erection and welding of steel-frames; the placement of pre-cast concrete floor planks, exterior and interior wall panels; and installation of various units. The system utilizes prefabricated components extensively including columns, beams, floorings and walls, and the assembly of these components is simplified by the use of specially designed joints. In addition, this assembly process is orchestrated by real-time computer control, resulting in construction site operation in a highly automated way.” 11 Figure 4 SMART System Outline Copyright 1998 Yusuke Yamazaki The SMART system works by constructing an entire floor of a building floor by floor before propelling itself upward to begin on the next floor. In the field this system proved most valuable for larger scale construction, particularly in constructing office space and residential spaces. In a case study done on the commercial HDB HUB building in Singapore it was revealed that by utilizing the SMART system the owner acquired savings in the form of 4 months off construction time, 17% in manpower requirements, and a minimum of $4 per m 2 when compared to the industry standard (Singapore Building and Construction Authority 2005). 12 The concept of building up a structure layer by layer is ancient in of itself. Bricks are set with mortar, stone walls by Romans constructed by fitting stones together without mortar, adobe walls built up from the earth, etc. While the concept of layering as a means of construction lies steeped in the past, innovative new technologies and new approaches have landed this technique squarely in the present as a means of providing potential for the future. With the development of computers and the advancement of being able to define three dimensional objects virtually, there developed the need for a method of taking virtually defined three dimensional objects and translating them into physical objects with the same properties. As a means of fulfilling this need various approaches to what were eventually labeled as “rapid prototyping” techniques were developed. 2.1 Rapid Prototyping One of the earliest means of providing rapid prototyping capabilities was through the use the stereolithography (SLA). Patented in 1986, this approach used a combination of photosensitive polymers, lasers, mirrors, a UV oven, and a movable platform to generate 3D objects. Objects were defined through computer models and built up through cross-sectional pieces approximately .05mm to .15mm in thickness. Once the desired form was completely generated using the photo-curable resin the object was baked using UV light to harden the desired form. 13 Figure 5 Stereolithography Copyright 2001 Princeton University SLA was limited to only being effective for low volume prototyping, approximately 1-10 samples, and was also constrained by available materials. Another constraint was the size of model available was limited to only models capable of fitting within the photo-curable resin chamber. As a result SLA proved most adequate for printing patterns for plastic and metal parts, test fitting prototypes, and presentation models. During the same time period, mid 1980’s, another process was developed called Selective Laser Sintering (SLS)and patented by Dr. Carl Deckard of the University of Texas in Austin. SLS uses lasers and powders of either ceramics, metals, polymers, or plastics to build up 3d forms. Powder of the desired material is 14 automatically spread over an adjustable platform and the needed cross section for the desired object is melted using the heat from the lasers. Once completed another thin layer of material powder is spread of the previous one and the process is repeated, the heat from the laser fusing the new layer to the previous one. Figure 6 Selective Laser Sintering Copyright 2008 Arptech One of the advantages of SLS over SLA is the choice of available materials that can be used. As a result SLS is better at generating objects comparable to what would be available through conventional manufacturing. Another advantage of SLS over SLA is the fact that after the 3d form has been generated there is little to no other required processing, in contrast the UV oven SLA objects must be baked in before removal. The only real limitations of SLS are the inability to combine 15 materials to create more complex pieces, and the size of the generated objects in constrained to the dimensions of the adjustable platform. Currently SLS is most often used to generate functioning plastic and metal parts for engineering prototypes. Another method of generating the physical form of a computer model is through Electron Beam Modeling (EBM) shown in Figure 7. Utilizing an electron beam, temperatures up to 2500˚C, and a vacuum chamber, this technology melts metal powder layer by layer to create forms. Due to its method of scanning and layering, EBM is considerably faster than previously described methods of rapid prototyping. With superior speed and materials such as titanium alloys available for use the EBM technology is in high demand for producing medical implants and other similar technologies. Figure 7 Electron Beam Modeling Copyright 2008 Synergeering Group 3D Printing is another popular rapid prototyping technology, although not used for generating medical implants. It is used, however, for generating full color 16 models by utilizing inkjet print heads, supporting powder (plaster, cornstarch, or resin), and an adjustable platform shown in Figure 8. Figure 8 3D Printer Diagram Copyright 2007 Rapid Prototyping Center With the ability to produce models at 2-3 layers per minute, 3D printing is well suited for creating fast, rough, full color models of desired objects as illustrated in Figure 9. However, because the models lack accuracy required for manufacturing, 3D printing tends to not be used for creating models intended for manufacturing purposes or for generating molds. Figure 9 Object Generated Through 3D Printing Copyright 2007 Computer Language Company Inc. 17 Standard methods of rapid prototyping lack the ability to be extrapolated into the field of construction for several reasons. The most prominent is the inability to scale the discussed methods to the size required for construction. Creating a vacuum chamber for EBM to generate a house in is impractical. As is building a movable platform large enough to generate a house using SLA, SLS, 3D Printing, etc. Secondly the materials available through these methods are ill suited to construction. A house made of titanium alloy is cost prohibitive, and the photo- curable resin used by SLA isn’t strong enough to resist the load demands on the structure of a home. 2.2 The System of Contour Crafting In 1998 Behrokh Khoshnevis (right) introduced a new technology system called Contour Crafting (CC) that he described as, “a method of layered manufacturing (LM) process that uses polymer, ceramic slurry, cement, and a variety of other materials and mixes to build large scale objects with smooth surface finish,” (Khoshnevis 1998). Using computer guided trowels and layering fabrication techniques, Contour Crafting has the capacity to extrude a variety of shapes with smooth surfaces as shown in Figure 11 (Khoshnevis 2001). Figure 10 Behrokh Khoshnevis and Full Scale Wall Extruded by Contour Crafting. Copyright 2001 Khoshnevis 18 Figure 11 Contour Crafting System Copyright 2001 Khoshnevis The purpose of Contour Crafting was to create a system that would solve some of the main problems plaguing the construction industry: 1. Generate a more accurate product. 2. Reduce the cost of construction. 3. Reduce the time needed for construction. 4. R 5. R In on Contou repeatedly scale Fabr objects usi models in discrepanc being cons F In a secon Figure 13. were also m Reduce on th Reduce wast various artic ur Crafting, t y to emphasiz ication by C ing a scaled accordance cies or huma structed. Figure 12 Form d study a ful Various atte made. he job injuri te generated cles publishe the topic that ze the accura Contour Craft down protot to the 3D Au an error unle ms Extruded Us ll scale wall empts to imb ies d by construc ed by both B t CC is contr acy of this n fting,” the re type are disc utoCAD file ss such exist ing Contour Cr section was bed objects i ction. Berokh Khosh rolled by a c new system. sults of tests cussed and y e provided sh ted in the co rafting Copyrig extruded us in the cemen hnevis and o computer is m In particular s done with s yielding smo hown in Figu omputer mod ght 2001 Khosh sing cement nt such as rei other authors mentioned r, in “Mega- smaller oth accurate ure 12. No del before nevis shown in inforcement 19 s e t 20 Figure 13 Full Scale Wall Section Extruded Using Contour Crafting Copyright 2001 Khoshnevis In a separate study done in 2007 by USC Student Joanne Zhang, the projected cost of Contour Crafting was reported in comparison to the market average cost other types of construction including both traditional and manufactured. For this particular study a 1600 square foot 3 bedroom 2 bathroom home was used to generate industry average costs. The results showed that Contour Crafting is expected to be significantly cheaper than other current methods of construction on the market see Figure 14. 21 Conventional Modular Manufactured CC Cost per S.F. $135 $115 $90 $33.75 % of Conventional 100% 85% 67% 25% Figure 14 Projected Cost Contour Crafting Copyright 2007 Joanne Zhang In his article, “Automated Construction by Contour Crafting,” Khoshnevis begins to explore how Contour Crafting could be combined with other robotic technologies in an attempt to begin the integration process of systems and finishes with the CC system. Unfortunately, in this article, the systems are tackled in a singular fashion instead of exploring an integrated solution. Also, the topic of how exactly these solutions would be integrated at what stages with Contour Crafting construction is left untouched. 22 Chapter 03: Proposed Applications for Contour Crafting Currently there are a variety of potential applications being explored for the use of Contour Crafting by Professor Khoshnevis. Urban infrastructure, emergency response construction, general construction from housing to skyscrapers combined with even the possibility of using CC for space colonization create a veritable spectrum of possible application. However, in each application there are both pros and cons in attempting to utilize CC as a construction method. The following general analysis has been completed by comparing the current dominant method of construction for each application to the proposal of how Contour Crafting would be used for each purpose. The purpose of this general analysis is to isolate the application for which Contour Crafting can provide the greatest potential with the current development of the construction method. 3.1 Using Contour Crafting for Urban Infrastructure Currently the concept behind utilizing CC as a means of maintaining and building urban infrastructure focuses on freeways as a typological example. The proposal involves building a rail track system along the edge of either an existing freeway or new construction that would support the Contour Crafting machinery as illustrated in Figure 15. Then, as the road was being built or repaved, the system could be turned on when there is little traffic and would simply follow the tracks while laying down a new cover of concrete or asphalt. Th to be intuit engineers crew. Few and fewer reduce the face after y An could be c the road fo das depend traffic wou in the dead Figure 15 Co he benefits of tive. Autom required to o wer construct people expo e health risks years of exp nother benefi ompleted. In or hours for w ding on the c uld take long d of night. E ontour Crafting f automating ating the sys oversee the e ion workers osed the toxi s and long te osure. it would be t nstead of hav weeks on en circumstance ger when com Either way hi g for Infrastruct g the repavin stem would r entire proces would trans ic chemicals erm health pr the speed by ving to close nd, the repav es. Obviousl mpared to a ighways wou ture Copyright ng of highwa require less ss as oppose slate to fewe and fumes o roblems man y which main e down the e ving could be ly a highway highway wh uld be able to t 2001 Khoshnev ays appears a people, poss d to an entir er work relat of asphalt. T ny constructi ntenance of t entire road or e completed y with more here the road o built and m 2 vis at first glanc sibly two re constructio ed injuries This would ion workers the freeway r sections of in a matter o constant d is deserted maintained in 23 ce on f of n 24 a more efficient manner which would reduce the need for major costly repairs further down the line. One of the difficulties to be overcome with adapting existing roads to being able to be repaved by Contour Crafting would be the placement of the guiding tracks. For highways in an urban setting where there is often private property that is adjacent to the freeway this would be particularly problematic. The tracks would also add to the cost of widening any existing freeways as the tracks would have to be uprooted and rebuilt along the side of the new freeway. Another issue would be the safety concern that this system would create with regards to those guiding tracks. As is the same concern with railroads or light rails, any tracks built would have to be closely supervised to ensure they were clear with immediate emergency brakes readily available. This is especially true for existing freeways that have been sunken down into the urban fabric. Potentially Contour Crafting seems well suited to highway maintenance, especially when involved in new construction where space for the needed tracks can be allocated and accounted for. 3.2 Contour Crafting for Emergency Response In the face of any disaster such as hurricanes, earthquakes, fires, tsunamis, etc. the ability to rapidly respond to the immediate needs of the victims is critical. One of those greatest needs is the demand for emergency shelter after so many people have been forced from their homes for various reasons. In this application 25 CC seems to be best suited for putting up quick, stable shelters one after another with minimal projected manual labor required. Since utilities such as running water are often bused into on site until the permanent utility systems are repaired, these emergency shelters are not required to have the same integrated systems expected of standard housing in the US. An exterior delivery system for these services is sufficient. As such the CC system would only be required to leave space for plumbing and electrical conduits to puncture walls instead of requiring them to be imbedded behind finished surfaces. The amount of punctures required would also be minimal since emergency housing is only designed to meet the minimum needs of their inhabitants until the more permanent structures can be erected and the community restored. Through this application Contour Crafting would be able to provide large amounts of emergency structures quickly and efficiently. Especially since the equipment required for the CC system to function is only a fraction of the equipment required to build shelters through more traditional means. Considering the a deployable version of the CC system is under development so all the scaffolding the rapid prototyping machinery were attached to a truck that could be driven from one emergency site to the next, the only limiting factors become raw materials that would have to be shipped in and grading that would have to be done manually before the CC systems was unloaded. As long as enough raw material was available and the grading was able to be completed in a timely manner, the CC 26 system would be able to provide effective superior emergency housing to disaster victims. However, one thing about emergency housing is that the structures are suppose to be temporary structures used while the community itself is rebuilt. Part of this is because emergency housing is usually not built for permanent inhabitance. Trailers, tents, module houses that are easily built and easily torn down are the preferred choice. The entire purpose, after all of emergency housing is not to provide a new permanent home, but to provide an acceptable temporary residence while a more permanent one is being built. As a result, a permanent concrete structure like the one to be provided by CC crafting seems inappropriate. After all, when the community is rebuilt what would happen the neighborhoods of emergency housing that were erected? If a temporary structure like a trailer is used then after the trailer has outlived its usefulness it can then moved to another location or dismantled and recycled into something else. A concrete structure is a different matter entirely. While some concrete can be recycled into ‘fly ash,’ concrete is generally not perceived as a recyclable material. Not without heavy amounts of labor and energy used to break it down and transport the pieces elsewhere. 27 As a result, it appears more appropriate to explore the possibility of using Contour Crafting to rapidly rebuild the permanent community as opposed to using the CC system to try and construct temporary emergency housing. This is still an excellent emergency response as it would significantly reduce the time required for a community to recover from a major disaster. 3.3 Single Family Housing One of the most critical benefits of using Contour Crafting system for single family housing is the speed by which the system constructs. Currently the estimate is approximately twenty-four hours for a 2,000 square foot home. While this is probably an optimistic assumption, the Contour Crafting system is significantly faster than traditional methods of construction. Faster construction can be translated into a faster turnover rate for new construction and less money needed to spend on interest for expensive loans. This cuts the cost of new construction significantly using only one of the many potential benefits Contour Crafting has to offer. Another potential pro is the accuracy Contour Crafting would provide for new construction. One of the costly delays in construction is when there is a discrepancy between the architect’s drawings and what is built. This an result in the contractor having to tear down what was built or the architect having to figure out how to change the design around the discrepancy. Either way both time an money are spent to solve the problem. 28 Using Contour Crafting this type of scenario is likely to be completely removed from the equation. Since the computer builds according the 3D model provided there is no discrepancy between what is imputed and what is built. While quality control would have to still be overseen. Through this analysis it has been isolated that the application with the greatest potential benefit of Contour Crafting with the current state of the system is single family housing. For the purpose of this analysis the phrase traditional construction shall henceforth refer to wood stud framing as used in market dominant single family housing. 29 Chapter 04: Alternative Construction Methods in Single Family Housing Before proceeding onto the analysis of the application of Contour Crafting to single family housing, a look must first be taken at already existing alternatives to traditional construction methods. Within the market of single family housing there exist a range of construction options and approaches. However, due to cost of construction, time required, and other factors one construction method has maintained domination over the single family market. According the National Association of Home Builders, “that 87.7% of the 1.7 million homes built in the U.S. in 1999 were stick-framed,” (NAHB 1999). Since wood framing accounts for the majority of single family housing construction all references to traditional or conventional construction will henceforth refer to standard wood framing. In order to offset the many downsides of traditional construction there have been several other approaches explored in an attempt to find a better way of building. However, of these methods none have demonstrated such a clear superiority over the traditional means of construction so as to threaten wood framing’s dominance over the market. Alternative methods are, however, gaining ground as the industry becomes increasing frustrated with the deficiencies of standard wood framing. Of these alternative construction methods several have begun gaining momentum as their popularity builds. Of note and making their way out onto the mass market are prefabricated housing, insulated concrete forms (ICF’s), and steel framing. 30 4.1 Steel Framing The method of steel framing for single family housing with regards to replacing wood framed construction refers to the process of using cold-formed steel members for walls, floors, and roofs as illustrated in Figure 16. The actual construction method is very similar to wood framing as noted by Jason Greene, a contractor in the home building industry since 1995 who puts up approximately 20 steel framed homes a year, “If you are a good framer with wood, you are going to be a good framer with steel...” (PATH 2006). Currently steel framing makes up approximately 2% of all new single family construction (Gifford 2005). Figure 16 Steel Framed House Under Construction. Copyrigth 2006 PATH One of the most significant benefits to building with steel is the flexibility gained through the extra strength to width ratio inherent in steel when compared to wood. This allows designers to design with much longer spans and create more open spaces than would be available using wood framing. The significant increase in strength of steel over wood also translates into more resistance again natural 31 disasters like earthquakes and windstorms. Steel is also immune to pests like termites, though susceptible to rust, and more resistant to fire than wood. Another benefit is the ability to construct homes using recycled steel and recycling the steel after the home is demolished. All steel members used are required to be made of 25% recycled content and have 100% recyclability (PATH 2007). According to Alliant Energy, an utilities provider in the Midwest, reported while doing research on alternative methods for home construction that a “typical home can be built with about six recycled cars worth of steel, compared to more than 40 trees for wood framing,” (Allian Energy 2007). Another sustainable aspect of steel framing is the reduction of waste generated on site. Jason Greene reported that, “When you plan a steel frame correctly, it reduces the amount of waste that goes to a landfill… Since everything we do is cut to length, on-site waste can be carried off in a 50-gallon drum. On a wood frame, it’s a couple dump trucks. Typically what we do waste, we just turn around and recycle.” There are downsides though to replacing wood framing with steel. One is the conductivity of heat is greater through steel than wood, opening up the home to significant increased heating and cooling loads if not properly insulated (Deter 1996). Another negative aspect of steel framing is the added cost. While the cost of steel is considered more stable than that of lumber, case studies have revealed steel framing costs approximately 1%-2% more than conventional construction (PowerHouse 2007). Of the sources of this extra cost is the extra planning time 32 before construction begins. Since the majority of steel elements are cut in a factory precise planning and ordering are essential to avoid costly delays. This approach, however, translates to steel framing having less waste generated on site than wood framing. One of the greatest challenges facing the residential steel framing industry is the lack of skilled labor available to erect the building. Historically the construction industry is notorious for resisting change and with regards to steel framing there is no difference. While the approach is similar the tools are different and so general contractors have to instruct framers how to use the different tools. After all, “the biggest challenge in terms of labor is finding a trained workforce accustomed to using the tools and specifying and designing correctly with steel. It is the lack of experience of the workers in using steel that tends to be driving labor rates.” Dan Feazell, the president of a prominent steel framing company in Virginia remarked that, “a lot of people are intimidated by steel. The wood framers have been using wood their whole life. People are very slow to change, so to do something different, even though it’s a very small change, is difficult.” However, he later remarked that, ““it used to be that the informed homeowner were driving the growth. Now we’re getting more builders coming to us.” As more steel framing is used in the residential industry the more common the skills will become (Gifford 2005). 33 4.2 Insulated Concrete Forms Insulated Concrete Forms are a method for building concrete walls. They are generally composed of forms made of rigid insulation foam that leave a standard space of 6” for concrete. After the concrete is poured exterior finishes and water proofing are secured to the insulation foam Figure 17 Standard ICF Copyright 2007 ICFA Figure 18 ICF Blocks available from ARXX. Copyright 2007 ARXX which remains as part of the completed wall. For interior surfaces the insulation foam is used for mounting drywall. Finished ICF walls are typically 10” thick and 34 while all ICFs are similar in principle, various manufacturers and companies provide just as various components, shapes, cavity sizes, etc. Typically ICFs are manufactured with two approaches in mind, either as an interlocking system of blocks or panels tied together using plastic ties. Interlocking systems are factory made made blocks that are then stacked to form the desired shape of the wall much like, “plastic children’s blocks,” (ICFA 2008). Interlocking blocks range in size from 8”x1’4” to 1’4”x4’. Wall panels are larger in nature ranging in size from 1’x8’ to 4’x12’. These components are then arranged in accordance to the desired home layout before being filled with concrete and completed with desired finish. Figure 19 Stacking ICF Blocks. Copyright Quadlock 2007 ICFs are an effective way of bypassing some the serious drawbacks of traditional construction. First of all ICFs produce less construction waste on site. Since components come in predefined dimensions there is minimal waste. Plus, the walls can be built up and verified before the concrete is poured. If there is a mistake 35 the blocks can be taken apart and then built back up correctly. Any blocks ordered and unused can be saved for use at the next site. This significantly reduces the waste generated on site during construction. The flexibility of ICFs is another attribute over standard construction. While slightly confined to the modules produced by the company chosen for the particular project, there is wide variety of sizes available to conform to the needs of the design. Even curved ICFs are manufactured and available to build up curved walls, though they are more expensive than the standard ICFs. Figure 20 Curved Forms Available with ICF. Copyright 2007 Quadlock In 1997 the National Association for Home Builders (NAHB) performed a study comparing the overall performance of homes built with ICFs to homes built with traditional wood framing. The study revealed that homes built with ICF had a net savings of requiring 44% less energy to heat and 32% less energy to cool. These savings were attributed to ICF homes which have a continuous R-Value, less air infiltration and increased thermal mass than standard wood framed homes. In fact, Leadership in Energy Efficient Design (LEED) rating system for new construction has awarded all 10 available points under the category of Energy 36 Optimization (ICLA 2007). With regards to LEED it can also be noted that by using ICFs other points for the categories Environmental Quality and Indoor Air Quality were also achievable. Figure 21 Sources of Energy Loss and Savings Through ICF Copyright 2007 ICFA As pointed out by the Insulated Concrete Forms Association (ICFA), “While some natural hazards, such as floods and earth-quakes, are restricted within certain geographic regions, wind storms respect no such bounds.” As has been witness, wind storms can cause a significant amount of damage. Since ICFs are up to 8.5 times stronger than traditional wood framing, ICF buildings have been observed resisting severe weather better than wood framing (ICFA 2007). Figure 22 An ICF House Survives Hurricane Katrina in 2006. Copyright 2006 PATH 37 However, despite these advantages, ICFs are still not as common on the market as standard wood framing. This is due, in part, to the increased cost of ICF construction with regards to traditional wood framing. According the ICFA, a standard wood framed homes cost approximately $60-$100 per square foot. An equivalent ICF home typically added $1-$4 per square foot to the overall costs. ICFA also added that if the energy savings were included then ICFs resulted in only costing $.25-$3.25 more per square foot. 4.3 Prefabricated Housing Prefabricated housing, also referred to as prefab, are homes manufactured off-site in advance, typically in standard sections that are shipped to be easily assembled on site. Prefab housing can be divided into three separate categories: fully manufactured homes, manufactured modules that are combined on site, and systems of prefabricated parts, often panels, that are then fitted together to generate the whole on site. Manufactured homes are an entire dwelling factory made that is then shipped to the site and set on a permanent foundation as shown in Figure 23. According to Tiffany Connors, author of “How Prefab Houses Work,” the manufactured home is, “typically considered a low-cost alternative to regular construction because of their assembly-line construction,” (Connors 2007). Of course, since the entire home is factory built before arriving on site, there is limited flexibility or opportunity for customized attributes. 38 Figure 23 Manufactured Home Copyright 2007 Lecajun Modular homes, on the other hand, provide more opportunity for flexibility in design than manufactured homes. They also range more greatly in price as a result of more options and incorporating personal touches. Modular homes are dwellings composed of factory built modules that are fitted together on site into the desired configuration. While obviously requiring more onsite construction time than placing a manufactured home onto its concrete foundation, module homes still require significantly less time to construct onsite than standard wood framed construction. 39 Figure 24 Module Prefabricated Housing. Copyright 2007 The Ramsay Home Project Requiring even more time onsite, though still faster than wood framing, and able to provide even more flexibility that full module homes are prefab housing built with prefabricated panels. These homes are built from a manufactured kit of parts containing entire wall panels that are set up onsite and fastened together like a puzzle. Figure 25 provides an example of one of these kits. Panelized housing, while still somewhat confined to panel dimensions, can be configured in a variety of ways and even used to form segmented curved walls. 40 Figure 25 Prefab Kit of Panels. Copyright 2007 Michel A. Laflamme The initial benefits regarding prefabricated housing are attributed to the ability to building all components in a factory where the environment is controlled and not subjected to outside conditions. The entire process utilizes, “modern assembly line techniques, which reflect the input from specialists from various facets of the building trades. The streamlined process results in fewer errors and greater efficiencies,” (Gale 2007). Sarah Gale, author of “Prefab Housing and Sustainability,” published by Greener Buildings, goes on to mention that, “the factory craftsmen work together in normal shifts in a quality-controlled environment, not up on a ladder or out in the rain.” This aspect of prefab housing contributes to fewer injuries and errors resulting from the construction process 41 (Gale 2007). The quality controlled environment also reduces the risk of mold or pests as a result of the wood in wood framing getting wet while under construction. Warping due to moisture is also avoided. Another benefit to homes being factory built is the reduction of waste generated. According to Steve Glen, a developer and CEO of the California prefab housing firm LivingHomes, “Thirty to 40 percent of materials from a conventional home construction project can end up in landfills. In prefab construction, it's 2 percent," (Gale 2007). Also in the process of building prefab components, what waste there is can often be recycled or used elsewhere in the manufacturing process. While some prefabricated housing has been recognized as more environmentally friendly, such as LivingHomes which has managed to design a, “zero energy, zero water, zero waste, zero carbon and zero emissions” prefabricated housing design strategy (Gale 2007). It is a misconception to believe that prefabricated housing is in and of itself more sustainable than traditional wood framing. Just as there is a variety of companies that provide prefab housing solutions, so does exist a wide range of levels of quality found in these products. Not all of them are generated in an environmentally friendly manner with environmentally friendly materials. Nor does prefabricated housing necessarily produce a more energy efficient product than standard wood construction. After all, there is the possibility that shipping all those parts to a construction site from a 42 factory instead of using more local materials could generate more greenhouse gasses that standard construction. As in traditional construction, it is up to the client and designer to pursue a more sustainable and energy efficient product as opposed to relying on the inherent sustainability of the product itself. 43 Chapter 05: Applying Contour Crafting to Single Family Housing In order to apply Contour Crafting to single family housing the process of construction has been broken down into the following categories; Site Work, Structure, MEP, and Finishes. Each category was then further broken down into specific components to which CC was applied in order to isolate strengths and weaknesses of Contour Crafting with regards to single family housing. 5.1 Site Work Site work can be defined as everything that must happen on a site before any type of building may take place and the components of the site outside the scope of actual building construction. This includes, but is not limited to, grading, installing drainage, irrigation, hardscape, and softscape. Since Contour Crafting is a method of extruding forms certain aspects of site work can be initially isolated as being outside the scope of Contour Crafting’s capabilities. This is not to say that Contour Crafting could not be incorporated with other automatic systems to generate a more automated response to construction, but that CC is itself ill suited to specific tasks. Grading is an example of a component of construction that falls outside Contour Crafting’s scope. Installing drainage and irrigation are other examples. While machinery more suitable for these aspects of construction could utilize the metal scaffolding set up for Contour Crafting, such as a mechanical claw used to set pipes and irrigation elements in place, this would be an example of integrating CC with other available robotic technologies as opposed 44 to CC being capable of this task itself. A robotic arm could also possibly be utilized to aid in the installation of softscape elements such as trees. Within the category of site work, however, there are aspects for which CC is well suited. Extruding retaining walls once the grading has been cleared and leveled is a primary example. Extruding pavers along paths also falls under Contour Crafting’s capabilities. Contour Crafting could also be used to build planters as directed by a computer model. With regards to pavers Contour Crafting could be used to extrude the pavers in place as solid cement objects or as hollow cement objects filled with insulation. The required strength and expected traffic on the intended walkway would determine which approach was more appropriate. Using CC to generate hardscape elements would allow for the opportunity of utilizing design approaches that would previously be perceived as too labor intensive to execute economically. Further design opportunities could be available with the mixture of pigments into the cement as it is set by the CC system. As Figure 26 shows, colored cement is already available on the market as an alternative to traditional outdoor pavers. Utilizing pigments in the same fashion 3D printers use them to print full color models could provide an opportunity for unique styles that would be considered cost prohibitive using standard methods of construction. 45 Figure 26 Examples of colored concreted used for exterior pavers and walkways. 2008 Copyright ConcreteNetworks.com Planters are another example of utilizing CC for site work. Since Contour Crafting is suitable for extruding walls and planter barriers can be defined as reduced walls then CC appears suitable as a method of extruding the desired barriers required for planters. An example of how a planter built by Contour Crafting would be put together is illustrated below in Figure 27 and Figure 28. Figure 27 Example of Contour Crafted Planter Copyright 2008 Laura Haymond 46 Figure 28 Possible Irregular CC Planter Copyright 2008 Laura Haymond Figure 29 below shows a summary of how Contour Crafting and standard methods of construction are applied to site work. However, wherever Contour Crafting is deemed “not suitable” conventional construction techniques could be utilized instead. Contour Crafting Site Clearing not suitable Grading not suitable Hardscape (pavers, walkways, driveways, etc.) SUITABLE Softscape/Planting not suitable Planters SUITABLE Irrigation not suitable Drainage not suitable Figure 29 Summary of Suitability of Contour Crafting for Site Work Tasks Copyright 2008 Laura Haymond In summary with regards to site work Contour Crafting appears to be only suitable for selected tasks that can be solved through extruded construction. All other tasks require conventional construction methods or a separate automated response not available through CC. 47 5.2 Structure After the site work has been completed to a certain point construction on the actual home can begin. Within the category of structure the tasks required can be divided into the following sections; foundation, walls, insulation, floors, stairs, roofs, and punctures for doors and windows. Integration with MEP and issues regarding finishes were addressed later on in the analysis as separate categories. 5.2.1 Foundation Foundations can be divided into three sections; basements, crawlspaces, and slabs. After excavation Contour Crafting would be able to lay down a slab of the desired thickness on which to extrude the walls needed to define the basement. Therefore Contour Crafting is suitable for both basement foundations and slab foundations. Crawl spaces would prove more complicated as they are not generated through a monolithic form like basements or slabs. However, Contour Crafting could be used in conjunction with either wood or metal as a means of generating the desired results. How Contour Crafting might be used with beams and joists is illustrated below in Figure 30. 48 Figure 30 Possible Integration of CC to Generate Crawlspace Foundation Copyright 2008 Laura Haymond One issue with regards to foundation construction is that all site work must be completed before Contour Crafting can be used. Currently CC has only been tested on flat surfaces. Also, the scaffolding frame use to support the Contour Crafting equipment must be set up so as to enable CC access to all points of the site where CC is expected to be of use. This may be the cause of a potential conflict with neighbors or a limitation on the size of structure available. 5.2.2 Walls The intended function of Contour Crafting with regards to general construction was to automate the ability to extrude walls in their desired form. Therefore, Contour Crafting’s dominant strength lies in generating walls according to input received from a 3D model. 49 Walls extruded using CC are done so by layering material such as cement or adobe an inch at a time to form cavity walls filled with insulation material as the walls are built up. Openings are left for windows and doors as specified by the 3D model and the walls are built up until the desired height is reached. Where the walls are located, how thick they are, etc. would all be information conveyed from the 3D model to the CC system. An illustration of a 6” CC wall compared to a standard 6” wood framed wall are shown in Figure 31. Figure 31 Typical CC Wall Section and Wood Framed Wall Section Copyright 2008 Laura Haymond Technically the cavity walls could be filled with concrete when extra strength was required, however with regards to single family housing this appears unnecessary in most conditions. 50 One of the strong advantages Contour Crafting has over conventional construction methods is the flexibility available through the method of extruding form. In experiments conducted by Khoshnevis with a scaled down version on CC, the system was able to generate curved forms with the same amount of effort as orthogonal forms. Translated onto the field this means that Contour Crafting could be used to generated curved walls as easily as straight ones. This would open up a new palette of geometry with which architects can design, since curved elements are typically very labor intensive and therefore cost prohibitive with conventional construction methods and even so among less conventional construction methods. Another advantage of CC compared to standard framing with regards to wall construction is the accuracy and quality control available through Contour Crafting. Since walls are defined by the 3D model and executed through an automated system the only source of human error would lie in the generation of the model itself. Since there is no human intervention between the 3D model and the walls built by the CC system there would be no opportunity for discrepancies due to human error between how the walls were defined and how the walls were built. Since discrepancies on site between what is built and what was defined by the architect often leads to costly modifications. 51 Lack of quality control in the final product of walls is another problem inherent in conventional construction. When describing the advantages of using steel framing over wood framing it was mentioned that poorly built wood framed walls can have the problem of not being straight. It was mentioned that by using steel framing this particular problem could be significantly reduced. With CC this problem could be all but avoided. Quality control in the wall itself is another problem inherent in wood framing. Since lumber allows for a certain amount of variance in dimensions wood framed walls can end up possessing unintended differences in thickness at various points along the wall. These variances can end up making the wall appear unstable or requiring extra effort to compensate for the error. With CC this would not be an issues since the cement is laid down as thick as desired and the wall is extruded as thick as defined by the 3D model. 5.2.3 Insulation Also defined by the 3D model would be the amount of insulation needed in the wall. Currently the insulation being proposed would be injected by the Contour Crafting system periodically as the walls were extruded. With an already established 1” thick cement on either side a 6” CC wall would thereby possess 4” of cavity space to fill with insulation. An 8” CC wall would have approximately 6” of insulation. Unlike in wood framed walls where insulation is interrupted whenever there is a stud, the insulation in a CC wall would run continuously, 52 reducing the opportunity for temperature transfer through the wall. This is a significant improvement over steel framing as well where proper insulation is a concern due to the thermal transfer properties of metal. Also under development is the possibility of using a soy based insulation as a more sustainable alternative to chemical insulations. 5.2.4 Floors Conventional wood framed floors are built through the layering of joists, subflooring, and finished flooring. While CC would not be suitable for laying down the actual structure on which subflooring and finished flooring could be laid as desired, CC could be used in conjunction with metal decking since metal decking requires a 1” topping coat of cement. This is illustrated in Figure 32 Figure 32 Typical Metal Decking Copyright 2001 Ching CC walls would also have to be design to leave grooves and provide support for joists and beams on which to rest. Bolting of said elements to a CC wall would be 53 done through standard methods of securing wood or metal elements to concrete. Possible connections are shown in Figure 33. Figure 33 Possible Connection of Beam to CC Wall Copyright 2008 Laura Haymond 5.2.5 Stairs When considering the method by which Contour Crafting generates walls the first impression is that stairs could be extruded as solid elements, each riser layered then topped as shown in Figure 34. 54 Figure 34 Solid Extruded CC Stairs Copyright 2008 Laura Haymond However, considering the other methods of building stairs available, this method would be a waste of materials. Another method would be to extrude a stair guidance ledge only on either side of the stairwell. A ledge for each runner would be extruded on either side of the staircase to await the installation of the horizontal runners and vertical risers by workers, shown in Figure 35. Figure 35 CC Used to Generate Stair Guidance Ledges Copyright 2008 Laura Haymond 55 This would reduce materials used when compared to the previous method but would still yield a very massive stair element, which may or may not be the intention of the designer. For extended design options other stair systems commercially available could be used, Contour Crafting only being used then to generate the walls surrounding the stairs and around the opening left on the second floor for access. 5.2.6 Roof Within conventional construction there are many different roofs available for single family homes. Pitched, flat or a combination there of are the most common. Domed roofs tend to be more expensive to build and so therefore are less common in single family housing. For flat roofs Contour Crafting could use the same approach used in integrating floor systems. Grooves built into the wall for beams, decking used over the beams, and CC used to place the top coat of cement over the decking. Since even a flat roof has to have a minimum slope to contend with drainage of rainfall, Contour Crafting could simply build up the roof, filling the form with insulation as it went, before providing a final coat of cement over the final form. Greater difficulty would be integrating CC with a pitched roof. However, one of the most common methods of roof construction today is the use of prefabricated truss systems which are brought to the site and then lifted into place. Such a system could be integrated through the same method as the floor system, 56 with grooves being used to leave space for the incoming truss system. However, the rest of this process would be done in a traditional manner with Contour Crafting having no further influence. Therefore, for this type of roof, there would be little difference between CC and traditional wood framing. The only advantage would be that spaces left for securing the truss would guarantee their placement and alignment. Conversely, for domed or vaulted roofs Contour Crafting would have a significant impact on how the roof was constructed. Professor Khoshnevis has already explored how conceptually CC would be used to build a vaulted roof, where the system mimics the methods once done by hand as shown in Figure 36. In scaled down tests CC has also shown its ability to generate tapered forms that could be translated into general construction. What the exact requirements for these forms would be dependent on the material used and the slope intended in the design. Figure 36 Possible Method of Generating Vaulted Roofs with CC Copyright 2001 Khoshnevis 57 5.2.7 Doors and Windows In order to place doors and windows into a Contour Crafted structure openings would have to be left according to the exact dimensions of the desired door or window. While these openings would possess no difficulty in themselves, there would be a problem when regarding the header of said rough openings. Cement has conventionally been known to perform poorly in tension or as a tension element. Hence this is why pure cement or concrete beams are uncommon in conventional construction. In order to span the top of any opening for a door or window the introduction of a new element appears necessary to either act as the needed tension element or convert the needed tension back into compression. There appear to be two possible solutions for this dilemma. One is to place a beam, either manually or through a robotic arm, that is long enough to overlap slightly on either side of the rough opening which would be embedded in cement by the next pass of the CC system. Of course, this would mean that if a robotic arm was used the beams would have to be stored in close proximity and within range of the robotic arm to be used. The other choice would be to install the door or window frame once Contour Crafting had generated enough of the rough opening to secure placement. After the frames were installed then Contour Crafting would simply build around the frame, using the frame to span the opening. These phases are illustrated below in Figure 37. 58 Figure 37 Integration of Door and Window Openings with CC Copyright 2008 Laura Haymond This method would require more coordination between labor and the CC system depending on the number and placement of doors and windows. Once the rough opening was set any door or window could then be installed with standard methods. After the cement was cured the window or door frame would be able to be removed later on if in need of repairs or replacement. 59 5.2.8 Summary With regards to structure Figure 38 below displays a summary of where the Contour Crafting appears to be a suitable alternative to conventional methods. Contour Crafting Foundation SUITABLE Walls SUITABLE Insulation SUITABLE Floors SUITABLE Roofs Pitched not suitable Flat SUITABLE Domed/Vaulted SUITABLE Doors and Windows Rough Openings SUITABLE Figure 38 Summary of Suitability of Contour Crafting for Structure Elements Copyright 2008 Laura Haymond 5.3 Systems One dominating factor of any method of construction is the ability to integrate necessary systems with the particular method of construction in question. Systems requiring integration can be broken down into the following categories; mechanical, electrical, plumbing, and lighting. With regards to Contour Crafting one of the immediate concerns is the fact that walls are constructed using cement. Despite the fact that CC walls are cavity walls and therefore could house all necessary systems within themselves, such systems would be encased in cement. Should anything go wrong, such as a pipe bursting, the cement would have to be cut through in order to open up the wall and gain access to the pipe. Cutting through cement is more difficult than cutting through wood or drywall. While not impossible, it would mean that if all systems 60 were encased in CC walls they would be more difficult to repair than conventionally built homes over the lifespan of the building. The difficulty of making repairs to systems encased in concrete is one of the reasons concrete walls are avoided for single family homes. Contour Crafting, however, possesses a flexibility and accuracy through being automated that conventionally poured concrete does not. As a result Contour Crafting can produce forms that would be considered cost prohibitive if done with traditional form work. Utilizing this property of CC there is the possibility of generating a new response to integrating systems with cement walls. 5.3.1 Plumbing Within the scope of single family housing plumbing requirements are among the most demanding with regards to interior wall space required. Plumbing is also one of most damaging components of single family housing when something goes wrong and so by nature requires more accessibility than other systems. Plumbing elements are also less flexible than other systems such as electrical wiring. As a result plumbing not only requires more accessibility, but more continuous accessibility than other systems. Occasional access at specific points throughout the house is not ideal. 61 Ideally all pipes would be easily accessible through removable panels that could be replaced once repairs were finished. However this would require more hardware and be more expensive to build than conventional methods. Typically pipes are run in between studs in wood framed walls. To access pipes within the wall a cut must be made through the finish, typically drywall, and the piece removed. This is especially the case if any drywall requires being replaced after water damage due to the pipe needing repairs. After the pipes have been repaired new drywall is installed and the finish redone. Since this process is already an accepted standard within the single family housing industry, a process which would require an equivalent approach would be acceptable. Within the construction industry there is the occasion when plumbing is required along a concrete wall in a single family house, typically the condition is found in basements. Since the concrete wall is a foundation wall and therefore cannot be compromised, a furring approach using 2x4 wood studs is used, as demonstrated in Figure 39. 62 Figure 39 2x4 Furring Against Concrete or Masonry Walls Copyright 2008 HowStuffWorks.com While this method could be utilized for all walls containing plumbing elements the result would be essentially the need to build 2 walls wherever plumbing was needed. This would negate some of the advantages of using Contour Crafting in the first place since such an approach would result in added construction cost, materials, labor, loss of usable space, and be subsequently undesirable. So would simply building all indoor walls requiring plumbing using conventional wood framing or metal. There is, however, another possible approach 63 generated through combining CC’s agility with the concept of furring. As illustrated below in Figure 40, instead of requiring essentially two walls CC could be used to create an indentation in the wall into which the pipes could be fitted. Then, instead of a furred wall made by 2x4 studs, a much smaller furred wall composed of 2x2 studs would be all that was needed. While this would indeed create a wall that was thicker than other non-plumbing walls, otherwise known as ‘wet walls,’ the resulting wall would require less material than an entire new wall. In addition, the only material needed to be removed when the pipes were in need of repair would be the finish and insulation. The CC wall would be able to remain intact. 64 Figure 40 Schematic Plumbing Wall for Contour Crafting Copyright 2008 Laura Haymond Another advantage to this approach would be that plumbing would be forced to follow paths and punctures set up by Contour Crafting, leaving little room for onsite error during the construction period. No sudden need for unplanned soffits due to a pipe being run a different direction than planned. On the other hand, more precise coordination would mean more time spent on building and coordinating the 3D model before construction began. After all, when dealing with cement and concrete there is little room for error. 65 5.3.2 Electrical Due to the more flexible nature of electrical components there is less need for continual direct access than plumbing components demand. As a result more of the electrical components could be embedded in the concrete walls with access points generated when necessary. Necessary access would be required at points where a receptacle, switch, junction box, and where ceiling light fixtures would be located. Unfortunately, the number of receptacles and access points around the perimeter of a room poses potential problems with maintain structural integrity. Electrical receptacles are typically located 12” above the finish floor at varying points around the room to provide access to electrical services for use by residential appliances, lighting, and other electrical equipment. Their precise location is governed by local code. Unfortunately because the receptacles are located horizontally around the room they pose the issue of creating buckle points, or structural weak points in the cement wall. Some potential solutions that still allow for embedding receptacles into the wall are illustrated in Figure 41. 66 Figure 41 Possible Solutions for Embedded Wall Electrical Receptacles Copyright 2008 Laura Haymond However, these solutions, as illustrated, generate new issues regarding continuation of insulation, or the need for extra material. As a result it appears inappropriate to embed horizontal electrical elements in the wall, instead leaving only the required wiring for switches near already reinforced door frames as embedded components. In response to this result it seems more suitable to employ a method of delivery for electrical services that maintains surface accessibility. Therefore another possible solution would be to locate electric receptacles and all subsequent electrical wiring in the floor instead of the wall. This would mean that the only electrical requirements remaining would be vertical wiring for switches and conduits used to feed wiring into the ceiling system. 67 Employing this solution would be easiest for floor systems that were raised off the cement topping of the metal decking previously mentioned. For floor finished utilizing the cement topping as the finished floor, such as the colored cement, or as the only subflooring, such as with tiles or stone, this solution would be more difficult but not impossible. Wiring could be run within the grooves of the metal decking, being made accessible when needed by Contour Crafting leaving a space where an electric receptacle is intended to be placed, an example shown in Figure 42. Figure 42 Typical Composite Flooring Copyright 2001 Ching 68 The cap for the electric receptacle could then be bolted directly into the floor. A standard floor electric receptacle is shown in Figure 43. Figure 43 Typical Floor Electric Receptacle Copyright 2006 Stein Unfortunately, due to the need for floor receptacles to be able to support weight such as foot traffic or having equipment rolled over them, floor receptacles are generally more expensive than standard wall receptacles which are not required to support weight or structure. If this solution was used it would be an increase in the overall cost of the building which would offset some of the original reduction in cost expected through the use of CC. 69 A third solution would be to utilize surface raceways to run electrical wiring along the base of the wall. This would be the most flexible of the proposed solutions as it would keep all electrical wiring accessible for needed repairs and upgrades. Said raceways could also be used to run any data or telecommuting cables desired, illustrated in Figure 44. This means that over the lifespan of the building, as technology progressed and demands changed, the cables and wiring within the raceway would be more easily upgraded than any cement embedded wiring. As Stein specifies in Mechanical and Electrical Equipment for Buildings 10 th Edition, raceways are appropriate when, “outlets are required at frequent intervals and where rewiring is required or anticipated.” Considering the current speed of technology advancement a delivery system that is more flexible and more easily upgraded seems more suitable than a more rigid system embedded in the cavity of a wall. For overhead requirements, such as for overhead lighting, a vertical conduit could be embedded in the wall as a path for cables which would then be run along the ceiling in between the metal decking and ceiling finish, cuts being made wherever a junction box or other element was necessary. This is a method already in use and would require only a small opening through the CC wall to pull wires up Figure 44 Example of Raceways Copyright 2006 held by Stein 70 through the wall vertically before running them horizontally as needed through the ceiling. Again, since all vertical conduits would be embedded in cement coordination before construction is essential in order for success. Below, Figure 45 is a table summarizing the compatibility of Contour Crafting and the different methods of running electrical components discussed. Compatibility Comments Wall Mounted Receptacle Not Very Compatible Potential for compromising of structure, increased need for materials, and breaking of insulation layer Floor Mounted Receptacle Compatible Standard methods apply with minimal need for adaptation for integration Raceway Compatible Recommended since most flexible solution for future upgrades Ceiling Mounted Junction Boxes and Receptacles Compatible Standard methods apply Figure 45 Summary of Compatiblity Between Contour Crafting and Known Electrical Wiring Methods Copyright 2008 Laura Haymond 5.3.3 Lighting With new forms and new approaches in what is available in a single family home comes new opportunities for lighting solutions. In particular the opportunity to employ the use of LED (Light Emitting Diode) lights in a single family setting appears to have expanded. With the introduction of non-orthogonal forms through Contour Crafting there is an opportunity for integrating LED strips with said forms, as shown in Figure 46. 71 Figure 46 Possible Generation of LED Lightshelf By CC Copyright 2008 Laura Haymond While this type of lighting may be easier to integrate with Contour Crafting, typical wall mounted sconces would pose a problem, especially in the majority of electrical wiring is kept to the surface instead of being embedded in the wall. This means that the cables needed for a wall sconce would be run along the surface of the wall, perfectly visible as opposed to the preferred embedded approach. Wall sconces, however, are not typically used for interior spaces and are more conventionally found as part of the exterior lighting solution. The typically preferred method of lighting homes being lamps and ceiling installations. Standard ceiling fixtures could be installed through conventional methods since the ceiling would not be made of cement through Contour Crafting. Below, Figure 47, is a table summarizing the compatibility between Contour Crafting and known types of lighting. 72 Compatibility Comments Ceiling Mounted Compatible Standard methods apply Mounted Wall Sconce Not Compatible Exception being battery operated fixtures Table or Floor Lamps Compatible Stand alone fixtures needing access to an outlet Recessed strip LEDs Compatible If located near ceiling or mounted near and supplied by outlet Figure 47 Summary of Integration Compatibility Between Known Types of Lighting and Contour Crafting Copyright 2008 Laura Haymond 5.3.3 HVAC When discussing the methods of heating and cooling a single family home there are an array of contributing factors which drive the selection of the system. According to Allen and Thallon’s Fundamentals of Residential Construction, HVAC systems can be divided into the following categories with the initial pros and cons identified in Figure 48. 73 Advantages Disadvantages Forced Air Rapid response time Ability to filter air and control humidity Ability to both heat and cool Relatively noisy Ducts are bulky Difficult to zone Radiant Panel Quiet Invisible Zoning is simple Slow response time No cooling or air filtration Hydronic Baseboard Quiet Zoning is simple Baseboard placement can limit furniture arrangements No cooling or air filtration Local Source Zoning is automatic Low first cost Most are relatively noisy No air filtration Figure 48 Table taken from Edward Allen and Rob Thallon's Fundamentals of Residential Construction Copyright 2006 While each system comes with an inherent set of pros and cons, with regards to Contour Crafting a new set of pros and cons are added. According to Edward Allen, “forced-air heating is by far the most prevalent heating system in North Amercia, accounting for over 60 percent of all residential heating,” (Allen Thallon 2006). With regards to forced-air systems, since such systems are typically more horizontally oriented with only the occasional vertical shaft needed. As a result the most pressing concern regard integration with Contour Crafting would be the punctures required through the walls so as to have 74 uninterrupted service to spaces within the home. An example of this is illustrated in Figure 49. Figure 49 Adapted Forced Air HVAC System to CC (left) Copyright 2001 Allen (right) Copyright 2008 Laura Haymond However, since these punctures would be near either floors or ceilings the structure integrity of the wall would not likely be compromised, though careful consideration for this would have to be taken by the structural engineer. For floor vents, either supply or return, where punctures where needed through the cement topping CC would be instructed to not lay down cement where said opening was required, reducing the need for costly cuts later on and removing the need for labor intensive formwork currently used in the field. Vents in the ceiling would be run through conventional methods already used in the field with no interference or contribution from the CC system. 75 Another system used for heating is utilizing radiant heat by means of a system, either electric or tubes containing water, to heat the floor of a space. There are numerous advantages and disadvantages to using a radiant heating systems versus a forced air system ranging from energy efficiency to noise pollution to response time. However, considering such a system is typically located beneath the floor or embedded in cement radiant heating would be compatible with Contour Crafting. The wiring, or tubing, would have to be laid down before CC laid down the cement topping onto the metal decking, or laid between the cement topping and the finish floor depending on the finish desired. This process, therefore, would require precise coordination between workers and the CC system. Hydronic heating systems utilize a central boiler, circulating pumps, hot water, and fin tube convectors to supply heat to various spaces throughout the home. When integrated with Contour Crafting there is the concern that any tubes containing water should be accessible without having to cut through cement to access said element. Therefore all components of a hydronic heating system would have to be surface mounted. Local source heaters include heating or cooling systems operating without being connected to a central source of heat or cooling. These include but are not limited to baseboard heaters, through the wall air conditioners, and electric wall heaters. Since these systems do not rely on being integrated but are, instead, 76 freestanding there are few requirements needed to adapt them to be used with Contour Crafting. What requirements do exist vary from system to system. As a result the table below, Figure 50, summarizes the compatibility of integrating Contour Crafting with the main methods for fulfilling HVAC demands. Compatibility Comments Forced Air Compatible Requires considerable integration with structure before construction Radiant Panel Compatible Requires integration with structure before construction Hydronic Baseboard Not Compatible All pipes need to be surface mounted Local Source Compatible Requires little to no integration with structure Figure 50 Compatibility Summary of Integrating Contour Crafting with Known HVAC Solutions Copyright 2008 Laura Haymond Ideally the Forced Air system would be reserved for cooling needs and other systems for heating would be employed, preferably radiant heat through use of embedded pipes for heated water. This, however, would be more expensive since this would mean installing two systems instead of just one. 5.4 Finishes Another prominent concern with regards to applying Contour Crafting to single family housing is the issue of finishes, both interior and exterior. This section explores existing methods of finishing surfaces and how they could be adapted to be used with Contour Crafting. This section also explores what new kinds of methods of finishes might be available through the use of Contour Crafting. 77 5.4.1 Floor Finishes Within the field of interior floor finishing approaches there already exist methods that employ a concrete topping to provide a smooth even surface on which to begin work. Since Contour Crafting uses cement to create a smooth flat slab over steel decking then any method of flooring using this as a base would be appropriate. Tiles, for bathrooms or kitchens, can be applied directly onto a flat concrete slab using a bonding agent such as a, “thin coat of dry-set mortar, latex- portland cement mortar, epoxy mortar, or an organic adhesive,” (Ching 2001). Another approach to floor finishes could stem from the introduction of pigments into the Contour Crafting process. As mentioned previously regarding Site Work, with the use of pigments Contour Crafting could “print” a full colored pattern into the cement as it is laid down. Very similar in process to the way a color printer creates a full colored image or a 3D color printer generates a full colored model. This method could be used in areas where tiles, stone flooring, terrazzo flooring, or another hard surface was desired. Instead of laying down tiles or slabs of stone the desired pattern could be “printed” right into the cement topping coat of the steel decking, requiring no further work. This would significantly reduce the amount of labor required from subcontractors and, as a result, floor patterns and colors would be available for floors that would be considered cost prohibitive through conventional construction methods. Colored cement is already being used on the market for residential floors as shown in Figure 51 so this type of a floor 78 finish would only be using a new technology to implement an already accepted method of flooring. Figure 51 Examples of Colored Concrete Floors for Interior Spaces. Copyright 2008 ConcreteNetworks.com For softer floor coverings, such as carpet or wood flooring, a different approach would be required. For carpeting a typical carpet pad would be needed in order to improve comfort and reduce impact sound transmission. The carpet chosen would then be placed over the carpet pad as is typical in the industry already. For wood flooring there are typically two methods, block flooring and strip flooring. Block wood flooring can be applied directly onto a concrete slab wit the use of a vapor barrier if needed and set with mastic or other adhesive. Therefore block wood flooring could be set directly onto a cement Contour Crafted floor using the same technique. Strip wood flooring would require the use of sleepers, typically 2x4s or 1x3s to support the paneled wood over the cement slab. Another common floor finish is resilient flooring which includes, but is not limited to, linoleum, vinyl, rubber tile, vinyl composite, cork tile, etc. When using these types of floor finishes it is recommended to provide an additional 1” concrete topping over lightweight concrete slabs (Ching 2001). Contour Crafting could 79 easily add another 1” layer of cement over the already existing topping layer where needed by this type of flooring. Below, in Figure 52, is a summary of discussed floor finishes and their compatibility with Contour Crafting along. Compatibility Comments Wood Flooring Strip Flooring Compatible Requires sleepers Block Flooring Compatible Applicable directly to slab Carpet Compatible Requires carpet pad Tile Compatible Applicable directly to slab Stone Compatible Applicable directly to slab Terrazo Compatible Applicable directly to slab Colored Concrete (Cement) Compatible If pigments are used while being set by Contour Crafting then 1” cement topping could be finished floor Resilient Flooring Compatible May need another 1” of cement topping Figure 52 Compatiblity of Contour Crafting with Known Floor Finishes Copyright 2008 Laura Haymond 5.4.2 Wall Finishes For interior and exterior walls there are a variety of finishing techniques that can be employed. Technically any method of finishing concrete walls could be adapted to be used with Contour Crafting. In previous publications Khoshnevis has mentioned that Contour Crafted walls were “paint ready” upon completion. However, other exterior finishes already used in the single family construction industry such as plaster, stucco, siding, and veneers could also be adapted to be used with Contour Crafting. 80 For a desired stucco finish there would only be the necessary two coats already used when a stucco finish is applied to masonry or concrete walls. With the use of a bonding agent plaster can be applied, “directly to dense, nonporous surfaces such as concrete,” (Ching 2001). Otherwise the use of ¾” channel studs as stiffeners and metal lath can be used to secure gypsum plaster to a masonry or concrete wall. Stone or masonry veneer, both often found in residential construction, have already been adapted for being used with concrete frames. Their only adaptation would be the need to include their requirements, such as space for wedge insert boxes for masonry veneers, into the 3D model so that Contour Crafting could build these requirements into the generated wall structure. After that standard construction methods could apply. For siding there appear to be three approaches, securing plywood first to the Contour Crafted wall then using that to secure the siding, securing the siding directly to the CC wall, or using CC to generate the wall with the texture of siding then painting said wall after completion. Theoretically all of these methods could be automated in the future and then integrated with the Contour Crafting system using the same scaffolding CC requires, however, Contour Crafting itself is not capable of automating these systems as of yet. However, there is a finish that Contour Crafting could be capable of, using colored cement as a wall finish. 81 The previously mentioned use of colored concrete could also be employed with regards to wall finishes, both interior and exterior. This method would create a smooth cement walls that was colored as specified by the 3D model, requiring no further work once completed. Color would be embedded into the cement, making chips and cracks over the years less visible compared to cracks made in paint or tears in wallpaper when the color beneath the finish differs from the color of the finish. While this method would not be suitable for any walls containing plumbing elements, other walls would be suitable for this type of finish. Particularly, any walls in rooms not possessing “wet walls” or walls containing plumbing elements would be especially suitable. Over the life-span of the building if there was a desire for a change in color or finish the Contour Crafted wall could be used as an under lay over which to place the new desired finish without having to remove the previous finish. This, of course, would only be the case once since after which any added finish would have to be contended with before a new finish was added. 82 Compatibility Comments Exterior Wall Finishes Stucco Compatible Standard methods apply Siding Compatible Depends. May need additional plywood Veneers Compatible Standard methods apply Colored Cement Compatible If pigments used then built in as CC wall is generated Interior Wall Finishes Plaster Compatible Applied directly to CC wall Drywall/Gypsum Board System Not Very Compatible Requires additional furring Tile Compatible Applied directly to CC wall Figure 53 Summary of Compatibility of CC and Wall Finishes Copyright 2008 Laura Haymond 5.4.3 Ceiling Finishes Since any ceiling finish would have to be applied after the flooring or roofing was installed Contour Crafting is unlikely to be able to gain access in order to aid in the application of any ceiling system. As a result all ceilings and ceiling finishes would have to be applied in the conventional manner already used on the field. The only exception to this would be possibly a domed or vaulted roof, as previously mentioned in Section 5.2.5 where colored cement or even uncolored cement could act as the finish. 83 Chapter 06: Sustainability Potential of Contour Crafting With growing concerns regarding what are considered environmentally friendly methods and materials any new method of construction must take environmental concerns under consideration. Simply saving on construction costs is not enough to justify the use of a new system if it increases environmental damage. In order to justify the use of a new system, Contour Crafting must have the potential of being employed as a sustainable alternative to traditional methods of construction with regards to carbon emissions, embodied energy, life-cycle costs, and the use of recycled materials. While an often site-specific integrated approach is required in order for any building to be less hazardous to the environment than previous approaches, the method of construction chosen has a great impact on the sustainability of any project. While no construction method can be considered inherently sustainable, there are practices considered more sustainable than others. In order to further understand the sustainable potential of Contour Crafting in application to single family housing it was reviewed using the USGBC LEED for Homes point system published in 2008 as a guideline. LEED was selected as a baseline since the guidelines set by LEED have become the current accepted national standard for defining sustainable building practices. 84 The use of HEED (Home Energy Efficient Design), a simulation software which calculates the energy usage of a home is also employed as a means of demonstrating whether a CC home would be more energy efficient than the exact same house built with conventional methods and acceptable market standards. 6.1 Reducing the Carbon Footprint In order for a single family home to be built using traditional wood framing all materials must first be brought to the site via trucks. After initial grading is completed, cement mixers for the foundation, flat bed trucks to haul in the lumber, etc. are required to continue the construction process. After the materials have been accumulated for a particular phase then they are assembled on site by workers. All during this process construction workers are coming to the site via car or truck. Every day for months workers drive to the site and drive home at the end of the day, each day adding to the greenhouse gases required to build that particular home. The longer construction takes the higher the resulting initial carbon footprint of the home. Contour Crafting reduces this aspect of construction in several ways, through speed of construction, reduced need for manual labor, and materials used for the construction process. The flooring, roofing, window, and door systems are still constructed manually, in conjunction with the CC walls, but the total time should be significantly reduced. 85 While the expectation of Professor Khoshnevis for Contour Crafting to build a 2-story 2000sf home in under 24 hours may be somewhat optimistic, there is no doubt that CC is significantly faster than standard wood framing. By automating this part of the construction process, Contour Crafting reduces the amount of time spent on a site thereby reducing the negative environmental impact of prolonged construction. Concerns such as silt and runoff due to disturbed topsoil are reduced notably through diminished exposure to weather before being permanently reset into the landscape. Also, the fewer times workers are needed on site the fewer times they must travel to the site and the more efficient the construction process becomes. Despite the carbon emission saved through speed of construction, trucks transporting the cement powder and polymer would still be needed to bring the materials to the site. A similar truck would also be needed to transport the equipment necessary for utilizing the Contour Crafting system, including the reusable steel necessary for the scaffolding to support the CC system as it worked. Once the system was finished the scaffolding would be folded down, loaded back onto the truck and driven to the next site with any leftover material available. The ability to use any leftover material is because the Contour Crafting process only mixes the cement and polymer right before application, thereby reducing the amount of waste generated on site. The possible use of adobe mixed with the polymer would also be able to reduce the distance required for the trucks to travel. 86 In spite of the possible need for more trucks coming to the site, Contour Crafting offsets this need by reducing the amount of manual labor required for the construction process. The expected reduction in manual labor needed on site can be perceived as another sustainable aspect of Contour Crafting. Seeing that a reduction in labor translates to a reduction in the number of people required on site and thereby a reduction in the amount of carbon emissions generated by the overall construction process. 6.2 Life Cycle Costs One of the pressing concerns in CC is the use of cement as the primary building material due to its high embodied energy. While it is true that cement requires more energy to produce than some other building materials, it is also true that cement has a longer expected life span than other building materials. Therefore homes built with Contour Crafting using cement would be expected to have a longer life span with reduced need for structural repairs than wood frame homes, offsetting the initial high embodied energy of cement through lower life-cycle costs. The use of adobe mixed with a polymer is also under development. While the expected life span of an adobe structure would be less than that of a cement structure adobe possesses significantly less embodied energy than cement. 87 Further reduction in the life-cycle costs of CC would be available through the recyclability of materials used, cement or adobe. 6.3 Recyclability Currently under development is the ability to add fly ash to the mixture of cement and geopolymer. The intent is to use a higher percentage of recycled material in the walls, thereby reducing the initial environmental impact of construction. Once the building has reached the end of its life span the cement used is ground back into powder suitable for reuse when combined with more polymer. If proven effective in the field, this process would greatly reduce the carbon footprint of the resulting building and offset the initial high embodied energy of cement. The ability to reuse any adobe used would also further reduce the already significantly less embodied energy properties of adobe. 6.4 Contour Crafting and LEED Currently in the USA LEED (Leadership in Energy Efficient Design) has become the standard method of measuring the sustainability of a project. Essentially a point system set up to encourage sustainable decision making, LEED has been employed here as a means of helping to define the sustainability potential of Contour Crafting, specifically LEED for Homes. During the process of applying the Contour Crafting system to the 2008 LEED for Homes point system it became apparent that CC was directly applicable only to points concerning the construction method used and the over all quality of 88 the resulting shell structure. However, due to the nature of Contour Crafting and requirements necessary for the construction process to be effective, other areas of LEED for Homes became affected through the use of CC. As a result LEED for Home points regarding Contour Crafting can be divided into those directly affected, indirectly affected, and points unaffected by the use of CC. Unaffected points ended up being credits gained through client choices, inherent site properties, management approaches, efficiency of appliances chosen, etc. These points as they are broken down are illustrated in Figure 54. LEED CATEGORY DIRECTLY AFFECTED INDIRECTLY AFFECTED NOT AFFECTED ID 0 4 7 LL 0 0 10 SS 2 2 18 WE 0 0 15 EA 5 0 33 MR 16 0 0 EQ 0 1 20 AE 0 0 3 Figure 54 Contour Crafting and LEED Copyright 2008 Laura Haymond As Figure 54 illustrates, Contour Crafting was only directly pertinent to certain points regarding Sustainable Sites (SS), Energy and Atmosphere (EA), and Materials and Resources (MR). 89 6.4.1 Innovative and Design Process (ID) With regards to the Innovative and Design Process category it should be noted that due to the nature of CC an integrated approach to design is optimal. Since mistakes made with cement are costly in both time and labor to repair there is an inherent need for an accurate integrated 3D model to guide the Contour Crafting system on site. Attempts to make adjustments on site after the cement or adobe had been set would also be costly. As a result there is more preparation required for using Contour Crafting than standard wood framing as there is less room for error. In order to obtain an integrated approach to design and construction and to maximize the effectiveness of using Contour Crafting, an integrated team as described by LEED for Homes should be assembled from the beginning of the project. In section ID2 the durability of the resulting constructed product is brought under scrutiny. The quality control of Contour Crafting and the inherent superior strength of cement walls versus wood framed walls is an advantage in this context. 6.4.2 Location and Linkage (LL) In the category Location and Linkage points are site specific and have little to do with the method of construction. Consequently the use of Contour Crafting would have no impact on this section of LEED for Homes. 90 6.4.3 Sustainable Sites (SS) Under the category of Sustainable Sites, since the majority of this category revolves around landscaping approaches there is little opportunity for there to be any benefits in using Contour Crafting over conventional construction. However, with regards to pest control, SS 5, CC benefits over standard wood framing are significant. 6.4.3.1 Site Stewardship The intent of Site Stewardship in LEED for Homes is to, “minimize long- term environmental damage to the building lot during the construction process.” While the built area and other factors for acquiring this credit are in direct response to design and landscaping choices, Contour Crafting can be used to help meet the prerequisite for this part of LEED for Homes. One of the concerns of construction is that during the construction process there is an increased risk of silt and other negative run off from the site. Since Contour Crafting is significantly faster than standard wood framing this risk is reduced as the time the site is exposed to the elements without the final landscaping is reduced. 6.4.3.2 Non Toxic Pest Control One of the purposes of the Sustainable Sites is to, “design home features to minimize the need for poisons for control of insects, rodents, and other pests.” In this section, SS 5, a total of 2 points can be obtained following guidelines intended 91 to reduce the need for pest control through poisons. One of these guidelines is to “seal all external cracks, joints, penetrations, edges, and entry points with caulking.” However, Contour Crafting creates seamless walls that would require no further actions to seal up openings. The only caulking needed would be for penetration such as doors and windows, elements that would require caulking anyway for weather resistance purposes. Another point could be gained through using “noncellulosic (i.e. not wood or straw) wall structure” and having “solid concrete foundation walls.” Since Contour Crafting uses cement walls the requirements for both of these aspects of Sustainable Sites are an inherent part of the CC system. 6.4.3.3 Local Heat Island Effect In an attempt to reduce the negative effects of heat islands, LEED awards 1 point for the use of light colored concrete for 50% of driveways, patios, sidewalks, etc. Contour Crafting uses light colored cement as its main material and can be used for either extruding sidewalks and driveways or extruding the forms needed for pouring concrete if extra strength is needed. 6.4.4 Water Efficiency (WE) The Water Efficiency section of LEED for Homes refers the reduction of water usage, utilizing recycled water, storm water approaches, etc. While Contour Crafting can be compatible with integrating these systems, CC is not directly involved and so effects no points in this category. 92 6.4.5 Energy and Atmosphere (EA) The Energy and Atmosphere section of LEED for Homes is concerned with optimizing the energy performance of the final building by reducing the amount of energy needed by the resulting home to function. 6.4.5.1 Insulation The insulation of the building is calculated through the R-Value of the exterior walls. The higher the R-Value the less energy is lost through the walls. According to the 2006 International Energy Conservation Code (IECC) the approximate R-Value requirement for a wood framed wall is 13. This is not including colder climates which have a raised expected R-Value due to the severity of the local climate. In order to be awarded the 2 points by LEED for Homes regarding insulation the expected R-Value must be exceeded by 5%. Selecting polyurethane foam for the insulation as it is already used in the field, the resulting calculation for a standard 6” wall built by Contour Crafting is illustrated in Figure 55. 93 MATERIAL R-VALUE Outside Air Film .17 Poured Concrete (1”) .08 Polyurethane Foam (4”) (4x6.25) 17 .00 Poured Concrete (1”) .08 Indoor Air Film .68 GRAND TOTAL 18.01 Figure 55 CC Wall R-Value R-Values of materials provided by ColoradoENERGY.org Copyright 2008 Laura Haymond Since 18.01 exceeds 13 by 38% the requirements for LEED regarding an increased R-Value are met. In the need for more insulation it should be noted that the design need only specify walls with increased cavity space for Contour Crafting to extrude and fill with more insulation. This is in contrast the complications wood framing often has when increased insulation is required. In order to further demonstrate the energy efficiency of CC walls versus conventional wood framed walls the simulation software HEED was used. 2 identical homes where entered into the software, the models having the only difference being the R-value entered for the each home. One had what the software considered “code compliant” while the other had the R-Value listed in Figure 55. The results are illustrated below in Figure . 94 Figure 56 HEED Results for Contour Crafted Home Copyright 2008 Laura Haymond 95 Figure 56 (Continued) 96 Figure 56 (Continued) 6.4.5.2 Air Infiltration Contour Crafting extrudes seamless walls filled with foam insulation. This significantly reduces the risk of “air leakage in and out of conditioned spaces.” In addition, since the entire process is computer guided, there is a reduced risk of non flat cavities resulting in gaps between installed windows and the wall structure. 6.4.6 Materials and Resources (MR) The Materials and Resources section of LEED for Home centers around efficient use of materials and resources and the selection of environmentally friendly materials. It is in this category that Contour Crafting is most applicable. 97 6.4.6.1 Material Efficient Framing The purpose of these credits is to encourage on site waste reduction through better framing practices. In fact, off site manufacturing is rewarded with 4 points out of the 5 possible since it significantly reduces on site generated waste. Contour Crafting , however, only mixes a small amount of cement and polymer as needed. Any unused cement powder and polymer can be shipped to the next site ready for use. As a result the only waste generated on site would be due to finishes and systems installation, but not to framing. 6.4.6.2 Environmentally Preferred Products Currently under development is the addition of fly ash to the cement polymer mixture. By combining fly ash with locally produced cement points in this category can be gleamed. Of course, environmentally conscious choices would also have to be made with regards to finishes and interiors in order to acquire all points available in this category. The adobe mixed with the polymer as the main construction material can also be perceived as a local environmentally preferred product. Also under development is the possible use of a soy based insulation. Such a material would be clearly more environmentally preferred than the previously mentioned polyurethane foam already in use in the field. However, the resulting R- Value would have to be equivalent or even greater than the polyurethane foam. 98 6.4.6.3 Waste Management As previously mentioned Contour Crafting produces significantly less on site waste than conventional wood framing construction. Since the entire process is computer guided under supervision there is a higher quality control and reduced likelihood of error. In addition, any unused construction material is just shipped to the next side ready for use. 6.4.7 Indoor Environmental Quality (EQ) The Indoor Environmental Quality section of LEED for Homes is mostly centered around contamination control through HVAC systems and other approaches. While these systems would require integration with Contour Crafting, CC has no direct involvement. 6.4.7.1 Moisture Control One of the inherent benefits of Contour Crafting is the natural resistance of cement to mold. While this does not include the resistance of finishes to mold, it does keep any would be contamination from spreading to structural members as is possible with wood framing. After all, it requires much less material to replace a finish than to rebuild a wall that has been contaminated. 6.4.8 Awareness and Education (AE) This section of LEED for Homes is centered on educating the tenants, home owner, or building manager about the systems used within the design. However, since this section has little to do with the actual construction process used Contour 99 Crafting has no direct involvement. The only indirect involvement is the lack of maintenance expected to be required of Contour Crafted homes with regards to structural maintenance. While there is no single answer to the ever pressing question of how to build more sustainably, Contour Crafting appears to have the potential to be part of a solution. However, while single walls and small models have already been generated by Contour Crafting, in order to fully asses the sustainable potential of this system several tests and subsequent case studies must be made. 100 Chapter 07: Conclusions and Future Work Below Figure 57 illustrates a summary of the strength and weaknesses Contour Crafting has compared to not only standard wood framing, but alternative methods of construction previously mentioned. Superior Above Standard Various Standard Below Standard Contour Crafting Steel Framing ICFs Prefab Panels Prefab Modules Wood Framing Resistance to Pests Strength and Resilience R-Value of Exterior Walls Recyclability of Materials Construction Site Waste Allows for design flexibility Speed of On Site Construction Hazard to workers Cost Lifespan of Building Ease of Repairs Pre-Construction Prep Air Infiltration Thermal Mass of Walls Compatibility with Existing Finishes Recycled Material Content Local Materials 101 Ease of Additions Resistance to Mold Figure 57 Comparison of Contour Crafting to Other Existing Methods of Costruction Copyright 2008 Laura Haymond Over all it appears that the most appropriate use of Contour Crafting for single family housing is as a replacement for framing and as a method of laying down concrete where desired. One of Contour Crafting’s greatest strengths is the geometric flexibility the system provides. Combined with its speed and accuracy CC would be able to significantly reduce the needed amount of time and labor framing typically requires. However, the on site coordination required by CC would still mean that some workers would be needed on site. Finishes, cabinetry, plumbing, HVAC, electrical, etc. subcontractors would also have to be expertly coordinated in order to maximize the the reduction in time needed for construction that Contour Crafting is attempting. However, due to the significantly reduced margin of error and the difficulty of on site adjustments the pre planning for a CC home would be significantly increased. This means more time, energy, and resources would have to go into the 3D model before construction ever began. Another issue to contend with is the difficulty of doing additions to an already existing building. Unlike ICFs which can be used to easily add on to an existing structure, CC would have extreme difficulty maneuvering around a structure already in place. Plus, from a sustainability stand point, for a simple 102 addition it becomes difficult to justify the transportation of the machinery and scaffolding required for CC. 7.1 Future Work Currently under development are actual materials to be used by Contour Crafting. Only after said material has been finalized can calculations regarding strength, elasticity, thermal expansion and contraction and other such properties be thoroughly accounted for. Said properties and calculations will have a great influence on the actual performance of a Contour Crafted home and are critical to the continuing development of CC as an alternative method of construction. However, the most critical piece of future work for Contour Crafting is an actual field test with a single family home. After all, it will only be by taking CC to an actual site to build a real home will certain strengths and weaknesses of Contour Crafting be revealed. Also, a field test will be the only way to verify the methods of integration proposed in this thesis. Once a field test has been completed new calculations relating to assessment of cost, embodied energy, carbon footprint size, etc. can be performed. How a CC building actually performs can also be measured and compared to the simulated work down in this thesis. Contour Crafting is not necessarily the best method of construction for every site and every design. It does, however, appear to have some significant advantages that warrant further development and testing. While there is no one solution for the many problems facing the construction industry today, CC does 103 hold the potential for being a part of the overall solution for finding better ways to build, for residents, workers, designers, and for the environment. 104 BIBLIOGRAPHY Alexander, Donnel. Interview with Berokh Khoshnevis. October 2007. Southland Publishing. 8 October 2007 <http://www.newangelesmonthly.com/article.php?id=57&IssueNum=5>. Allen, Edward and Rob Thallon. Fundamentals of Residential Construction 2nd Edition. Hoboken, New Jersey: John Wiley & Sons, Inc.,, 2006. Bosscher, Paul and Robert II Williams. "Caple-Suspended Robotic Contour Crafting Systems." International Design Engineering Technical Conference and Computers and Information in Engineering Conference. IDSTC-CIE, 2006. 1-9. Chamberlain, D.A. and E. Gambao. "A Robotic Systems for Concrete Repair Preparation." IEEE Robotics and Automation (2002): 36-45. Cole, Raymond J. "Energy and greenhouse gas emissions associated with the construction of alternative structural systems." Building and Environment (1999): 335-348. Emmanuel, R. "Estimating the environmental suitability of wall materials: preliminary results from Sri Lanka." Building and Environment (2004): 1253 – 1261. Everett, John G and Hiroshi Saito. "Construction Automation: Demands and Satisfiers in the United States and Japan." Journal of Construction Engineering and Management (1996): 147-151. Gambao, Ernesto and Carlos Balaguer. "Robotics and Automation in Construction." IEEE Robotics and Automation (2002): 4-7. Green, Jason. "Steel Framing: Strengthening Homes and Businesses." Case Study. 2006. Ha, Quang, et al. "Robotic Excavation in Construction Automation." IEEE Rbotics and Automation (2002): 20-29. 105 Hacker, Jacob N, et al. "Embodied and operational carbon dioxide emissions from housing: A case study on the effects of thermal mass and climate change." Energy and Buildings (2008): 375–384. Howell, Greg. "Costs of Accidents and Injuries to the Construction Industry." Journal of Construction Engineering and Management (1998). Hwang, Dooil and Koshnevis, Behrokh. "An Innovative Construction Process- Contour Crafting (CC)." 22nd International Symposium on Automation and Robotics (2005): 1-6. Hwang, Dooil. "Contour crafting - The emerging construction technology." IIE Annual Conference and Exposition (2005): 1-8. Kehoshnevis, B, et al. "Experimental Investigation of Contour Crafting using Ceramics Materials." Rapid Prototyping J 7.1 (2001): 31-42. Khoshnevis, Behrokh. "Houses of the Future: Construction by Contour Crafting." University of Southern California Urban Initiative (2004): 1-6. Khoshnevis, Behrokh, Dooil Hwang and Zhenghao Yeh. "Mega-scale Fabrication by Contour Crafting." Int. J. Industrial and Systems Engineering (n.d.): 1-20. Khoshnevis, Berokh. "Automated Construction by Contour Crafting." (n.d.). —. "Automated Construction using Contour Crafting - Application on Earth and Beyond." 19th International Symposium on Automation and Robotics in Construction (2002): 489-494. —. Contour Crafting. 10 January 2007 <http://contourcrafting.com/>. Khoshnevis, Berokh. Deployable Contour Crafting. United States of America: Patent WO/2007/050968. 5 March 2007. Khoshnevis, Berokh, et al. "Crafting Large Prototypes." IEEE Robotics & Automation Magazine (2001): 33-42. Labor, Bureau of. WORKPLACE INJURIES AND ILLNESSES IN 2006. Statistics. Washington DC: United States Department of Labor, 2006. 106 Lagorio, Christine. Could This Robot Build A House in a Day? 28 February 2007. 17 September 2007 <http://www.cbsnews.com/stories/2007/02/16/business/realestate/main2487598_pa ge2.shtml>. Lemley, Brad. "The Whole House Machine." Discover (2005): 60-63. Longo, Domenico and Giovanni Muscato. "The Alicia Climbing Robot." IEEE Robotics and Automation Magazine (2006): 42-50. Oloufa, Amr A. "Quality Control of Asphalt Compaction Using GPS-Based System Architecture." IEEE Robotics and Automation (2002): 29-36. Penin, L.F., et al. "Roboticized Spraying of Prefabricated Panels." IEEE Robotics and Automation (1998): 18-30. Sartori, I. "Energy use in the life cycle of conventional and low-energy buildings: A review article." Science Direct (2007): 249–257. Stein, Benjamin, et al. Mechanical and Electrical Equipment for Buildings 10th Edition . Hoboken, New Jersey: John Wiley & Sons, 2006. The Home Depot. Plumbing 1-2-3. Des Moines, IA: Meredith Books, 2005. —. Wiring 1-2-3. Des Moines, IA: Meredith Books, 2005. Thormark, C. "The effect of material choice on the total energy need and recycling potential of a building." Building and Environment (2006): 1019-1026. Venkatarama Reddy, B.V. "Embodied energy of common and alternative building materials and technologies." Energy and Buildings 35 (2003): 129–137. Yamazaki, Yusuke and Junichiro Maeda. 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Abstract (if available)

Abstract Contour Crafting (CC) is an extrusion based method of rapid prototyping being introduced as a method of automating construction. This thesis takes a critical look at applying the system of Contour Crafting to single family housing and how the system could integrate with regards to site work, structure, systems, and finishes. This thesis also explores the potential sustainability of CC with regards to the reductions in carbon footprints and life cycle costs and utilizing LEED for Homes as a means of defining other potentially sustainable aspects of CC. The purpose of this thesis is to determine the strengths and weaknesses of the systems Contour Crafting and to determine if this new method of construction is appropriate for single family housing.

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Asset Metadata

Creator Haymond, Laura (author)

Core Title Full scale contour crafting applications

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Publication Date 05/14/2008

Defense Date 03/28/2008

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag automation construction,contour crafting,full application of contour crafting,OAI-PMH Harvest,sustainable housing

Language English

Advisor Schiler, Marc E. (committee chair), Bartelt, Kara (committee member), Noble, Douglas (committee member)

Creator Email lhaymond@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m1241

Unique identifier UC1120119

Identifier etd-Haymond-20080514 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-78444 (legacy record id),usctheses-m1241 (legacy record id)

Legacy Identifier etd-Haymond-20080514.pdf

Dmrecord 78444

Document Type Thesis

Rights Haymond, Laura

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu