University of Southern California Dissertations and Theses

Superinsulation applied to manufactured housing in hot, arid climates

(USC Thesis Other)

Superinsulation applied to manufactured housing in hot, arid climates

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content SUPERIN SULATION APPLIED TO MANUFACTURED HOUSING IN HOT, ARID CLIMATES by Soner Keskinel A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF BUILDING SCIENCE (Architecture) August 1995 Copyright 1995 Soner Keskinel UNIVERSITY OF SOUTHERN CALIFORNIA THE SCHOOL OF ARCHITECTURE UNIVERSITY PARK LOS ANGELES. CALIFORNIA 900090291 This thesis, written by SCftJ e * - . . .............................. under the direction of h ............. Thesis Committee, and approved by all its members, has been pre sented to and accepted b y the Dean of The School o f Architecture, in partial fulfillment of the require ments for the degree of Dean D a " iv vii 1 5 6 7 9 12 13 21 28 34 36 37 39 43 47 48 48 51 55 63 I. TABLE OF CONTENTS. LIST OF FIGURES. LIST OF TABLES. INTRODUCTION. SUPERINSULATION. 2.1 A Historic Background in Superinsulation. 2.2 Heat Transfer and The Principles of Superinsulation. 2.3 Insulation in Superinsulation. 2.4 Airtightness. 2.5 Ventilation and Air-to-Air Heat Exchangers. 2.6 Superinsulation in Different Climates. 2.7 Superinsualtion in Hot Arid Climates. 2.8 References. MANUFACTURED HOUSING AS A CASE STUDY FOR SUPERINSULATION. 3.1 Manufactured Housing: A Brief Historical Background. 3.2 The Three Forms of Manufactured Housing. 3.3 Energy Performance of Manufactured Housing. 3.4 References. CONCEPTUAL DEVELOPMENT. 4.1 Potential Problems Arising from Manufactured Housing Requirements. 4.2 Roof Ponds. 4.3 Roof Pond Variations. 4.4 References. 5. SYSTEM DESIGN. 64 5.1 Base Case. 64 5.2 The Superinsulated Envelope. 67 5.3 Roof Pond System. 70 5.4 Mechanical Operation System. 80 5.5 Lateral Bracing. 82 5.6 References. 85 6. THERMAL PERFORMANCE ANALYSIS. 86 6.1 Methodology. 86 6.2 Analysis Results: Heating. 90 6.3 Analysis Results: Cooling. 92 6.4 Orientation. 96 6.5 Roof Pond Sizing. 97 6.6 Cost Analysis. 99 6.7 References. 106 7. CONCLUSIONS AND RECOMMENDATIONS. 106 7.1 Conclusions. 106 7.2 Recommendations for Further Research. 110 8. ACKNOWLEDGEMENTS. viii iii II. LIST OF FIGURES page number 2.1 Heat flow through an insulated and uninsulated wall 8 2.2 Relative cost o f common insulation materials 11 2.3 Controlled vs. unintentional ventilation 14 2.5 Section through an air-to-air heat exchanger 15 2.6 Counterflow core 18 2.7 Crossflow core 19 2.8 Concentric tube core 20 2.9 Rotary core 20 2.10 Heat pipe exchanger core 21 2.11 Cutaway view of the Connecticut house 22 2.12 Double-Wall construction 23 2.13 Exterior sheathing system 25 2.14 Baloon-truss system 25 2.15 Radiant barrier system 27 2.16 Indoor temperature changes due to convective cooling 32 3.1 Construction at the factory 3 8 3.2 Different forms of manufactured housing 40 3 .3 Mobile home construction 41 3.4 Heat loss percentage reductions for conservation projects 45 iv 53 53 54 54 57 58 59 61 65 66 69 71 72 73 74 75 75 76 78 79 81 83 Winter daytime roof pond operation Winter night-time roof pond operation Summer daytime roof pond operation Summer night-time roof pond operation Atascadero house: panels on track Hinged insulation system Bifold movable insualtion Center Folding Base case floor plan Base case elevations Section through the superinsualted mobile home Bifold movable insulation: closed position Bifold movable insulation: open position Cross section through the bifold insualtion panels Section showing the extension of tracks into the trellis and support brackets Shadow length from the bifold panels Shadow length from the sliding panels Cross section showing pulling panels Sliding insulation system Alternative sliding insulation system Mechanical operation of the roof pond system Diagonal strap bracing details 6.1 California climate map 89 6.2 Annual heating reductions by system component 90 6.3 Annual heating loads 91 6.4 Peak heating loads 92 6.5 Annual cooling load savings by system component 93 6.6 Annual cooling loads 94 6.7 Peak cooling loads 95 6.8 Annual heating loads for different orientations 96 6.9 Annual cooling loads for different orientations 97 vi III. LIST OF TABLES page number 2.1 Thermal properties of insulating materials 10 2.2 Heating energy savings for various locations 28 4.1 Thermal storage properties of certain materials 50 6.1 Roof pond depths for various climates 98 6.2 Cost estimate for the superinsulated envelope 101 6.3 Cost estimate for the roof pond system 103 6.4 Annual energy savings and payback periods 104 vii 8. ACKNOWLEDGEMENTS Although it is a hopeless attempt at a payback, I want to extend my thanks to all the following individuals, along with some that might escape my weakened memory, who have contributed to this work, through providing feedback, encouragement, criticism, inspiration, food, etc.: To Marc Schiler, not just for guidance, patience and timely input and being the driving force behind this concept, but for being my friend. To Goetz Schierle, for all his help in this thesis and being a wonderful human being. To the third member of the team, Pierre Koenig, for all his effort, all his time. To my classmates, for being fun, understanding, and patient, all of which are neceassary qualities to tolerate me for couple of years. To William Shurcliff, Harold Hay, JDN Nisson and G. Dutt for providing inspiration. To architects H.Gaus, M. Kluck and N. Nardi, for their feedback. To Dan Dietrich of Western Homes for giving a different perspective. To Val, Carole and the School of Architecture staff, for looking the other way when I had to sneak in a copy every once in a great while. To the Cyprus Fulbright Commision, Kristin and the rest of the staff at the Amideast. To my family; Lenise, Laika and Tugrul, for being with me when oceans away. And to Aysan. . . These pages are too worthless to contain a dedication chapter devoted to you. viii 1. INTRODUCTION Even though we have been building since the beginning of recorded history to provide comfortable shelters, architectural design and practice has changed vastly in the last century with the advent of mechanical environmental controls systems. Although these developments have resulted in improved comfort conditions and better controls over the indoor environments, the accepted practice has concentrated on burning more fossil fuel to operate these systems and ignoring the renewable energy sources that we have come to use for thousands of years. The great energy crisis of 1974 came as a wake up call to architects, engineers and the rest of the building industry. For the first time, it was realized that the price and availability of the fossil fuel on which we have been relying on is unstable and dependent on a number of global, political and economical factors that can not be controlled to yield the optimum energy use. The first reaction to this crisis from the building industry was the development of active solar collectors to utilize renewable solar energy. However it was soon realized that these systems were too complicated and expensive to provide cost-effective space heating. A more significant response was the blending of architectural and engineering principles into ‘passive solar design’, which bye-passes all the solar hardware and uses the whole building or certain components as the collector and the thermal storage. However a number of questions started to arise: Do we need to collect all this energy? Can comfort conditions be maintained by simply conserving the available energy within the thermal envelope of the building? Can we combine conservation and solar storage principles to yield optimum savings? The response to these questions have been the development of superinsulation as an energy-efficient housing technology. The principles of superinsulation as an energy conservation system has been tested initially on test models and prototypes in the mid 1970s, and as the performance results were made public and construction technology better understood, superinsulation became more popular, especially in cold climates. It is estimated that close to 20,000 houses have been built in North America in the 1980s, and this number is rising as the superinsulation technology becomes better understood and fuel prices increase. In spite of all the advances in construction techniques and the availability of performance data, superinsulation has been limited to cold climate applications using conventional on-site construction practices. Although there has been some research on temperate and hot, humid climate applications, at this stage, we are not aware of any application to existing construction technologies in hot, arid climates. Consequently, this thesis will investigate the application of superinsulation to an existing construction practice ( manufactured housing ) in hot and arid climates. 2 The purpose and the scope of this thesis can be summarized in three parts. Firstly, It will investigate the application of superinsulation to hot, arid climates. This discussion will include an overview of superinsulation principles and their utilization for hot, arid climate applications. Potential benefits will be discussed, along with problems that would arise, specifically from internal loads and an airtight envelope. Secondly, a 100% passive heating and cooling system will be developed as a hybrid of superinsulation and indirect passive ( roof pond ) principles using manufactured housing as a case study. The construction, details, and specifications will be developed to adapt the passive system into the legal, architectural and economic requirements of the existing framework of the industry. Finally, the thermal performance of this passive heating and cooling system will be analyzed using an hour-by-hour computer simulation model and radiant cooling algorithms. This process will be carried out for assessing the performance of the whole system and individual components ( envelope, thermal mass, night cooling etc.) for different orientations and four different climate zones, due to the orientation flexibility and mobility in manufactured housing. The results of this analysis will be compared to a base case which will be provided by modeling the energy performance properties recommended by the California Code of Regulations, Title 25. 3 In addition to these main objectives, a rough estimate of the cost of this thermal envelope design is to be provided and compared to the cost of conventional heating and cooling systems and annual energy savings. This simple payback period analysis, combined with the thermal performance data, resulting comfort conditions and indoor air quality, is intended to give us an overall perspective of the future potentials of this envelope design, as a fully passive heating and cooling system that embraces the renewable energy sources of the environment rather than disregard them. 4 2. SUPERINSULATION Superinsulation can be defined as an energy conservation system that operates on preserving the internally generated energy from intrinsic heat sources within an extremely well insulated and airtight thermal envelope. It has three main principles (or components): a. Increased insulation levels. b. Increased airtightness. c. Controlled ventilation and heat recovery. When discussing the definition of superinsulation or its principles, it is extremely important to emphasize that superinsulation is a system, and it involves more processes than just increasing insulation levels,[1] as the list of the three principles provided above suggests. A more thorough discussion of the these principles in the following chapters will help clarify this misconception. 5 2.1. A Historic Background on Superinsulation. Actually, superinsulation was invented a decade before the energy crises by two heat- pump salesmen, Harry Tschumi and Les Blades, who discovered that by increasing insulation levels and tightening window leakage, houses could be made to use much less energy and be better suited for heat pump applications .[1] Their invention did not catch on until the energy crises in 1974, when a number of state and federal government and HUD funded projects and university supported studies were conducted. As the thermal performance data for some of these projects became available, such as the Saskatchewan Conservation House [2,3] and the University of Illinois Lo-Cal House, [4] the interest in superinsulation plummeted with the number of superinsulated houses jumping from about 50 to over a 1000 in a single year in 1980. [5] Another interesting chapter in superinsulation is the dispute over the name ‘superinsulation.’ According to the best available informational] professor Wayne Schick of University of Illinois has used the term ‘superinsulation’ during one of his lectures on increasing the thermal performance through increased insulation levels. Since then, a number of names have been tried and attached to this concept, including ‘Low-Energy,’ ‘Micro-Load,’ ‘Autonomous,’ ‘Energy Conserving,’ ‘Self-Sufficient’ etc.,[6] but the term ‘superinsulation’ has prevailed no matter how misleading it is. 6 2.2. Heat Transfer and the Principles of Superinsulation. There are three main mechanisms of heat transfer through the thermal envelope of a house or through a particular surface ( latent heat transfer excluded ). a. Conduction : is the transfer of heat from hot to cold objects by particle interaction. The ability of a material to conduct heat is referred to as thermal conductivity which also indicates its insulating capabilities. b. Convection: is the transfer of heat through the air and fluid movements. Natural convection is the heat transfer process that resultsfrom temperature differences, whereas forced convection results from an external force that does not depend on temperature difference. c. Radiation: unlike conduction and convection processes, radiation does not take place through matter. During this process, heat energy is transferred into electromagnetic energy for transmission and converted back to heat energy at the receiver. [7] 7 • CONDUCTION THROUGH GYPSUM BOARD • CONVECTION IN AIRSPACE • RADIATION TO SHEATHING •CONDUCTION THROUGH AIR • CONDUCTION THROUGH SHEATHING AND SIDING A ..... it * fa * - * * ...... • CONDUCTION THROUGH GYPSUM BOARD » NO CONVECTION »RADIATION SCATTERED AND ABSORBED • CONDUCTION THROUGH AIR •CONDUCTION THROUGH SHEATHING AND SIDING Fig. 2.1. Heat flow through a. Uninsulated b. Insulated wall. Nisson N.N.D., G. D u tt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 22. How does superinsulation deal with these mechanisms of heat transfer in reducing heat loss or gain? Figure 2.1 provides a brief summary to the answers to this question. First, convection is reduced by reducing the penetration of air and moisture into the wall section, and then completely eliminated by the elimination of air gaps within the insulated wall. Secondly, the radiant heat transfer is prevented by scattering and absorbing the energy within the insulation material. And finally, conduction is significantly reduced by increasing the thermal resistance of the wall by added insulation. This resultant effect is the basis of the use of insulation and other principles of superinsulated systems. 2.3. Insulation in Superinsulation. As pointed out earlier, superinsulation is a system, whereas insulation is a building material. As discussed by Nisson & Dutt,[8] no matter how thick insulation material is used, that alone would not constitute a superinsulation system, just as how electrical wires would not constitute an electrical system. The effectiveness of insulation materials in retarding heat flow is rated in terms of their thermal resistance, or R-value, which is based on measured conductivity. The R-value for a 1 inch material is the reciprocal of its thermal conductivity (k) value. A very high R- value represents a material with a very high insulating capabilities. A list of certain insulating materials and thermal properties is given in Table 2.1.. As noticed, some materials have a much higher R-value per inch than others. Theoretically, air based insulation materials cannot have a higher R-value of R-5.5 per inch, although some plastic foams such as urethane and polystyrene sometimes exceed that level by using fluorocarbon gas instead of air within the insulation material. [8] 9 However, when choosing an insulation material for the thermal envelope design, R- value per inch should not be the sole criteria, simply because the materials that yield a Thenral Properties code-arard Description Thictness Conductivity Density Sped f ic Heat Resistance Fee*. Btu-Ft Lb Btu Hr •Ft*■eF Hr*Ft**°F F t5 Lb.°f Btu 1 N O T Mineral Wool/Fiber Bat t , P.-7(3) Batt, R-11 0.1682 0.0250 .60 0.2 7.53 1N02 0.2957 0.0250 .60 0.2 11.63 IN03 Bat:, R-19 0,5106 0.0250 .60 0.2 20.43 ING4 Batt, R-24 0.6965 0.0250 .60 0.2 27.86 IH05 Batt, R-30 0.8055 0.0250 !60 0.2 32.26 IN11 F i l l , 3.5 inch, R-H 0.2917 0,0270 .60 0.2 10.80 IN12 F i l l , S.5 Inch, R-19 0.4583 0,0270 .63 0.2 16.97 IN13 Cel 1ulose F i l l , 3.5 inch, R-13 0.2517 0.0225 3.0 0.33 12.96 INI 4 F i l l , 5.5 inch, R-20 0.4563 0.0225 2.0 0.33 20.37 IN21 Preforaed Mtneral Board 7/6 inch, R-3 0.0729 0.0240 15.0 0.17 3.04 IN22 1 inch, R-3.5 0.0533 0.0240 15,C 0.17 3.47 IN23 2 inch, R-E.9 0.1657 0.C240 15.0 0.17 6.55 IN24 3 inch, R-10.3 0.2503 0* uc4 0 15.0 0.17 10.42 IK 31 Polystyrene, expanded 1/2 i n c h ■ 0.0417 0.0200 1.6 0.29 2 . OS 1N32 3/d inch 0.0525 0.0200 1,2 0.29 3.12 IN22 1 Inch 0.0333 C.C200 1.5 0.29 4.16 IN34 1.25 inch 0,1042 C-.C200 1. a 0.29 5.21 1N35 2 inch 0.1667 O.G2CO 1.6 0.29 8.33 IN3£ 3 inch 0.2500 0.0200 1.6 0.29 12.50 1N37 4 inch 0.3333 0.0200 1.6 0.29 16.66 IK41 Polyurethane, Expanded 1/2 inch 0.0417 0.0133 1.5 0.38 3.14 1N42 3/4 inch 0.0525 0.0133 1.5 0.3B 4.67 IN43 1 inch 0.0833 0.0133 1.6 0.3B 6.26 IN44 1.25 inch 0.1042 0.0133 1.5 0.3E 7.63 IN45 2 inch 0.1657 0.0133 1.5 0.33 12.53 1N4S 3 inch 0.2500 0.0133 1.5 0.38 18.80 IN47 4 inch 0.3333 0.0133 1.S 0.38 25.05 Table 2. 1. Thermal properties of insulating materials. Micro-DOE2E Computer Simulation Program User’s Guide, ERG / Acrosoft Inemational, INC., Golden, CO, 1994 to higher R-value per inch thickness are typically more expensive. Fig. 2.2. demonstrates a better criteria in judging the value of an insulating material, based on cost per squarefoot per R-value. FORM ROLLS, BATTS, AND BLANKETS MATERIAL FIBERGLASS ROCKWOOL APPROXIMATE COST ( t PER SQ. FT. PER R-VALUE) 2 4 6 S 10 12 LOOSE FILL BLOWN-IN-WALL BY CONTRACTOR FIBERGLASS ROCK WOOL CELLULOSE RIGID BOARD BLOWN-IN-ATTIC BY CONTRACTOR FIBERGLASS ROCK WOOL CELLULOSE D-l-Y POURED IN ATTIC FIBERGLASS ROCK WOOL PERLITE. VERMICULITE FIBERGLASS PERLITE EXPANDED POLYSTYRENE EXTRUDED POLYSTYRENE URETHANE, ISOCYANURATE PHENOLIC ALUM INIZED FOIL PAPER SPRAYED-IN-PLACE SPRAYED-IN-PLACE CELLULOSE URETHANE -> 23 -> 1 6 Fig. 2. 2. Relative cost of common insulating materials. Nisson N .N .D ., G. Dutt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 246. 11 2.4. Airtightness It is estimated that the average house has 25-30 % of its total heat loss through air leakage. [9] The process of air leakage through the thermal envelope includes both infiltration ( incoming outside air ) and exfiltration ( outgoing inside air ), therefore heat is lost or gained not through conduction but through actual loss of air volume and through having to heat or cool the incoming air. The way superinsulation minimizes heat loss through air leakage is by: a. Eliminating gaps in insulation. b. Sealing cracks at wall opening. c. Installing an air/vapor barrier. An air/vapor barrier is a sealing sheet, typically 0.006-inch thick polyethylene, which minimizes the penetration of air and water vapor into the wall section. Thus, in addition to reducing heat loss through air leakage, air/vapor barriers also protect the insulation material from water vapor, provided that the barrier is placed on the interior surface of the wall,[6] leaving at least two thirds of the insulation towards the exterior surface of the wall. How tight can we seal the building using superinsulation construction? Although a typical superinsulated house has infiltration rates between 0.2-0.3 air changes per hour, 12 rates of 0.05 acph (Saskatchewan Conservation House) or even lower is technically attainable. However infiltration rates this low might not be desirable due to indoor air pollution. The indoor air pollutants include build-up of radon, moisture, carbon monoxide, nitrogen oxide, formaldehyde and other poisonous gases and particles from the building materials, furniture and people.[10] The only way to deal with the problems with the indoor air quality is through employing controlled ventilation and air-to-air heat exchangers. 2.5. Ventilation and Air-to-Air Heat Exchangers. Ventilation in a typical house depends entirely on unintentional air leakage. However this does not guarantee desirable indoor air quality due to the lack of control (Fig. 2.3.). Additionally, controlled ventilation becomes even more important in superinsulated houses because practically it becomes the only way of disposing excess indoor air pollutants in an extremely airtight environment. The ventilation requirements of superinsulated houses are fulfilled by using a device called air-to-air heat exchanger. An air-to-air heat exchanger actually accomplishes two goals at the same time: a. Eliminating high humidity levels and indoor air pollutants by bringing in fresh outdoor air. b. Recovering heat energy from the outgoing air stream and transferring it into the incoming air stream. DRAFTY AND ENERGY INEFFICIENT POOR VENTILATION o AVERAGE LEAKY HOUSE u MODERATELY AIRTIGHT HOUSE EXTREMELY AIRTIGHT HOUSE WITH CONTROLLED VENTILATION • DESIRABLE M INIM UM VENTILATION AIR INFILTRATION AND VENTILATION RATE Fig. 2. 3. Controlled versus unintentional ventilation. Nisson N.N.D., G. Dutt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 41. Fig. 2.4. shows a section through a typical air-to-air heat exchanger. Typically, an air- to-air heat exchanger consist of an intake fan, exhaust fan and central core where the heat exchange takes place, all housed in a single box.[9] Heat exchange takes place within the central core where the outgoing air stream loses its heat to the incoming 14 O ptional defrost device M anual switch H um idistat Filter F resh air in Insulated c a s e B alancing dam p er S ta le air e x h au st H eat transfer core S ta le air ex h au st fan C o n d en sate drain (plate type) F resh air supply fan B alancing dam per Fig. 2.4. Section through an air-to-air heat exchanger. Lenchek, T ., C. Mattock, J. Raabe, Superinsulated Design and Construction, Van Nostrand Reinhold Co., New York, NY, 1987, p. 62. of heat transferred is a direct function o f surface area and time, these sheets are usually folded to increase the amount of heat exchanged. Furthermore, additional latent heat could be recovered if the sheets are made permeable to vapor, i.e. enthalpy recovery. Enthalpy simply is the combination of heat energy and pressure-volume energy, and it is expressed as [11]: 1 5 H — U + pV where: H = enthalpy ( Btu per pound of dry air) U = heat energy p = pressure V= volume If a given quantity of air is warmed, the heat ( U ) is increased. If a small amount of water evaporates into this air, its pressure-volume energy ( pV ) is increased. If both processes occur at once, we can say that the enthalpy has increased. Keeping in mind that the laws of conservation of energy apply to both types of energy at the same time, what we are conserving is the enthalpy. [11] This concept of permeability to water brings about the first type of classification of AAHX according to their ability to recover water vapor: a. Enthalpy ( permeable surface) models. b. Non-enthalpy( impermeable to water) models. It is important to note, however, that non-enthalpy units might recover some latent heat, if condensation of water vapor occurs [9] within the exchanger core in winter. 16 In choosing between these two models one should consider if the exchange of moisture is desired. Superinsulated houses usually have the problem of very high humidity so generally non-enthalpy units are preferred for cold climates ( and possibly hot, arid climates). Hot-humid climates on the other hand can benefit from the enthalpy unit more due to the problems with high outdoor humidity. It would be nice if there was an AAHX with two cores that we can switch between, but this seems like a very expensive concept. However there is at least one manufacturer that produce a model in which the core could be taken out in one minute and replaced, namely the Mitsubishi Lossnay VL-1500. [11] Additionally, there are two types of AAHX systems classified according to their installation: central and wall mounted. The fully ducted central AAHX system is the most efficient type of distributing the air to and taking air from all parts of the house. The difference between the two is high efficiency versus low cost. Finally, AAHXs can be classified according to their core types into 6 groups: a. Flat Plate Counterflow: operates with very high efficiency due to two air streams running in opposite directions (Fig 2.5.). b. Parallel-Flow : maximum efficiency is limited to 50% due to the air streams running parallel to each other. c. Crossflow: air streams flow perpendicular to each other (Fig.2.6.). 1 7 d. Concentric-tube counterflow: high efficiency but very expensive (Fig. 2.7.). e. Rotary cores: most widely used in enthalpy models, mostly in industrial applications ( Fig. 2.8.). f. Heat-pipe cores: sealed pipes that contain a refrigerant...they operate through a condensation-evaporation cycle. Not widely used in residences yet ( Fig 2.9.) . Fig. 2. 5. Counterflow core Nisson N.N.D., G. D u tt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 190. 18 Fig. 2. 6. Crossflow core Nisson N.N.D., G. D utt, The Superinsulated Home. Book, John Wiley and Sons, New York, NY, 1985, p. 190. Fig. 2. 7. Concentrie-tube core Nisson N.N.D., G. D utt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 190. Fig. 2. 8. Rotary core Nisson N.N.D., G. D utt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 190. HEAT PIPE (SEE BE10W) HEAT IN LIQUID HEAT OUT 1 M M L Fig. 2. 9. Heat-pipe exchanger core Nisson N.N.D., G. D utt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 191. In addition to these points, in choosing an AAHX one should also consider its capacity, recovery efficiency, transferability of air contaminants into the incoming air, cost and energy (electricity) consumption efficiency etc. . 2.6. Superinsulation in Different Climates. As discussed earlier, superinsulation has mainly been used in cold and temperate climates. The construction technology developed for the application of superinsulation to existing traditional construction practice, has centered around increasing the wall and ceiling thickness to accommodate very high levels of insulation. There has been four basic wall construction techniques to achieve increased levels of wall insulation, which in some cases exceeds R-40 : a. Strapped wall: The strapped wall is a framing method for increasing the thickness and insulating value of single stud walls by utilizing the space created by nailing horizontal members onto the inside of stud wall. The biggest advantage of this system is its simplicity. Since very little special skill or training is required it is relatively cheap to adapt. On the other hand, it is extremely time consuming to build a strapped wall and it will be a very difficult task to get batt of the right thickness in the space to fill the cavities. A good example of this system is the Connecticut House 2 1 5 5 5£ Fig. 2. 10. Cutaway view of the Connecticut House Berglund, L. G., et al., “ Thermal Performance of Two Technically Similar Super-insulated residences located at 61°N and 41°N Iattitude,” Energy and Buildings. 21. 1994, p. 199. (illustrated above) which uses additional insulation in an interior strapped wall, as discussed by Berglund et al..[12] b. Double wall: Double wall, as the name suggests, is a system where a secondary curtain wall, which is usually thicker than the structural one, is constructed to provide extra space for insulation. The biggest advantage of this system is that it allows insulation of any thickness be installed at very little additional material 2 2 cost (Fig. 2. 12). However, due to the more complex nature of a double wall integration, it also requires some retooling, and crew training . Additionally Gutter. Vent in soffit Fiberglass (12 in.) 11 B = ^ ~ ^ T £ T D r y w a ll *i-in. Thermax between 2x6*s Hall system Outer wall Inner wall Drywall F i b e r g l a s s (B>i i n . ) .Vapor barrier fDrywall Horizontal section of juncture of two walls Vapor barrier Triple-glazed south window Siding Sheathing Drywall Fiberglass (8% in.) Hires Vapor barrier , Floor / f P i p e s Earth •f-U, 7 ==M ' V si, in. _ . __ fiberglass insulation Foundation wall (concrete blocks) 2 in. of Styrofoam Fig. 2.11. Double-wall construction Shurcliff, W .A., Superinsulated and Double-Envelope Houses, Brick House Publishing Co., Andover, MA, 1981, p. 37. extra care must be taken during documentation and construction because the sequence at which the wall is constructed becomes crucial (inner wall first, then vapor barrier, outer wall and finally insulation). 23 c. Exterior insulative sheathing system: This system can be used instead of or in conjunction with other systems. The most common wall assembly of this kind is 2x6 single stud walls and 2 inches of rigid foam installed on the outside (Fig.2.13a.). In this system, the air/vapor barrier is installed on the inside of the gypsum board. The advantages of this system is that it eliminates all thermal bridging, and it gives a high R-value per inch thickness. Also the insulation within the wall is kept warm and convection within the insulation is eliminated. However these advantages come at the cost of added expense (polyurethane is a more expensive material than batt or other types of insulation). d. Wall Trusses: ( Fig. 2.13b.) Non structural trusses can be used to increase the insulation depth. Similar to the double-wall, this system really gives very high R-values that can only be achieved by only double wall system. The concept is simple and the truss system is easy to install, however there might be some potential problems with the warping of the members. Another disadvantage of this system is that it is relatively new and unconventional . Even though it is a straightforward concept, it will be very hard for an inexperienced builder to produce efficiently on site. [13] In addition to these construction techniques developed for cold and temperate climates, there has been some research in the application of superinsulation to warm, humid 24 O o « o o 0 * oO 0 0 ’o O ’ Fig. 2. 13. a. Exterior sheathing b. Balloon-truss system Fisher, T .R ., “Bundling Up". Progressive Architecture. 66. 1985, p. 110. climates. There are a number o f organizations which have conducted extensive research in this area, including Oak Ridge National Laboratory in Tennessee [14] and 25 Florida Solar Energy Center, [15] The technology developed and tested by these research centers revolve around the use of radiant barriers (Fig. 2. 15.) instead of very high insulation levels. In its simplest definition, a radiant barrier consists of low emissivity surface, such as regular aluminum foil, facing an air space in a wall or ceiling section. Emissivity is the ability of a material to radiate and absorb longwave radiation and it is always expressed as a percent of a perfect black body. Typically shiny metals have a very low emissivity compared to some common building materials. The way radiant barriers work is through using this low emissivity surface to reflect the solar radiation that have arrived on the surface inside the air space and diminish its ability to reach the interior part of the wall. In winter and summer, the radiant barrier will operate in this manner to reduce the sol-air effect, that is the combined effect of the ambient air temperature and absorbed solar radiation, which will result in reducing the cooling loads in summer and heating loads in winter. [16] The most intensive research in this area have been conducted by the Florida Solar Energy Center, which includes side-by-side prototype performance comparisons. The results of these studies have shown that radiant barriers installed in wall and attic spaces reduce the heat influxes through these surfaces by about 28-30 percent, which resulted in 2-4 percent reduction in the actual cooling loads. [17] 26 Fig. 2. 14. Radiant barrier system Fisher, T.R., “Bundling Up". Progressive Architecture. 66. 1985, p. 110. These results can be interpreted as quite successful for hot and humid climates, especially when it is remembered that this apparently small reduction is actually a 27 higher percentage of the total gains from the envelope, since airtight and superinsulated houses become more internal load dominated. The jury is still out on the winter performance however, since solar radiation into the space is hindered, in spite of providing better thermal resistance to heat conduction. This point might not be important for hot, humid climates because of their much milder climates, however when we are considering their application to hot, arid climates with rougher winters, it becomes an important issue. 2.7. Superinsulation in Hot, Arid Climates. There has been very little research in investigating the potential application of superinsulation principles to hot, arid climates. Although the available literature and research reports do not discuss a direct application process and performance analysis, there are some encouraging findings that promote further interest. An interesting article [18] by Evan Mills of the Lawrence Berkeley Laboratory, which mainly focuses on energy improvements in manufactured housing, gives a comparison of different approaches to energy efficient design. Included in this discussion is a project carried out by Swedish Council of Building Research, which simulated the thermal performance of a superinsulated panelized house in a number of U.S. cities. Actual data taken from the computer simulations for Los Angeles show that annual auxiliary heat requirement was found to be 0 MJ / sq.meter-°C (Table 2. 3). However, the cooling load, which is of greater interest to a hot climate application, was not tabulated. ; O eteriplioiu o f m onitored en d lim ulaled m anufactured hom e!* TP Project Name Bid$ . Type Location No. or Bid ft. SH Fuel Goad. Floor Area ( m l South CUx. Area (m*) NR. Glazings (SI) R* Watl (SI) R* Ceil. (SI) R- Sub- FToor Con*. Strat -e*y Site Furnace Output <M3/mJ*y) D ciite Days (18.3 C°) MONITORED - | Bl M od BUTTE. MT 1 er 99 8 I 7.9 10.6 3.3 M 58 ‘*701 2 A1 Pin, CONCORD. MA 1 er 130 9 2.3 3.3 — a 632 .'738 3 SERI Pam BOULDER. CO 1 er 200 27 — — — — P 128 089 4 SERI Mob. SPENCER. Wl 1 1 94 8 — — — P 167 * 168 3 SERI Pan. BOLTON. MA 1 cf 140 16 — ~ — » ■ * * P 166 . 842 6 RYMARK t M od FREDRICK. MD 1 cr 149 8 2 2.3 3.3 * “ ■ P.c 124 639 7 RYMARK rr Mod. FREDRICK, MD 1 et 149 15 3 2.5 5.3 p.e 163 639 B LA.NL Mob. LOS ALAMOS. NM 1 ef 98 9 2 — — ■» a 93 326 9 LITTLE ROCK Mob. LITTLE ROCK. AR 3 h 98 — 1.9 2.3 1.9 HUD-1 416 843 10 LITTLE ROCK Mob. LITTLE ROCK, AK 3 h 98 — . 2 1.9 3.5 1.9 e 332 843 11 LITTLE ROCK Mob. LITTLE ROCK. AK 4 h 98 * — 2 3.3 6.7 3.9 C 170 843 12 TECH V Mod KNOXVILLE, TN 1 er 111 14 2 3.3 6.7 3.3 P.c 167 1914 13 Tl Mob. TALLAHASSEE. FL I ef 91 L2 2.5 1.9 H UD J 154 631 14 T2-HUD Mob. TALLAHASSEE, FL 1 er 91 1 2.3 3.9 3.2 c 117 831 13 KEMNAY Pan. N. SCOTLAND 8 er 109 — 2 3.7 4.6 6.0 c 82 164 16 KEMNAY Pan. N. SCOTLAND 10 er 99 — 2 3.7 4,6 6.0 c 67 r 164 17 IMPALA Pin. MADISON. Wj 1 er 138 — 3 8.5 10.0 4.8 c ,l 120 <277 SIMULATED A HUD STD. Mob. PHOENIX. A2 I er 70 4 1.9 1.9 1.2 HUD-! 162 844 A HUD STD. Mob, ATLANTA. GA 1 Cf 70 4 1.9 1.9 1.2 HUD-I 408 1702 A HUD STD. Mob. SEATTLE, WA 1 er 70 4 2 1.9 2.5 1.9 HUD-II 389 2608 A HUD STD. Mob. BtSMARK, ND 1 er 70 4 2 1.9 2.3 1.9 HUD-U 1198 3007 6 D1 M od FARGO. ND 1 8 161 13 2 3.9 8.8 3.9 u 239 3132 c UJ Mob. RICHMOND, VA 1 h 109 17 2 1.9 3.3 3.3 p * 200 2171 D U2 Mob. DENVER, CO 1 h 109 17 2 1,9 3.3 3.3 p.c 345 3324 E W | Mob. SPENCER, Wl 1 ft 89 1 3 3,5 5.8 3.9 c 193 4188 F A2 Pan. BOULDER,CO 1 ef 226 27 3 3.3 3.3 3.3 a 66 3324 G SWEDISH F in , LOS ANGELES, CA 1 Cr 124 7 3 5.8 1.3 4.9 a.a 0 673 G SWEDISH Pin. ATLANTA, GA 1 er 124 7 3 3.8 83 4.9 *,* II 1702 G SWEDISH Pan.' ALBUQUERQUE, NM 1 er 124 7 3 3.8 8.3 4.9 L I 37 2367 G SWEDISH Pan. BOISE, IP 1 er 124 7 3 5.8 8.3 4.9 M 63 3223 G SWEDISH Pan. MINNEAPOLIS, MN 1 Cf 124 7 3 3.1 8.3 4.9 M 184 4515 Table 2. 3. Heating energy savings for various locations Mills, E., “ Measuring the Energy Efficiency of Manufactured Homes," Energy and. Buildings. 8. 1985, p. 291. Another interesting study was conducted by the Kuwait University, which concentrated mainly on the cooling load and electricity consumption of air conditioning units. [19] 29 Annual and peak cooling loads for a base case house was compared to an alternative design which included increased insulation, airtightness and heat recovery (essentially superinsulated). The results of computer analysis using DOE-2 software showed over 65% reduction in both peak and annual cooling loads (Annual Load reduced from 205 000 to 60 000 kWh, and peak load reduced from 86 kW to 30 kW). However,one should note that in addition to superinsulated features, some design changes have been made from the base case to the alternative solution, including the window size, location and orientations. More importantly, the alternative design is not a passive solar building, and it operates basically on cooling the space by mechanical air conditioning which, in spite of significant reductions in cooling, consumes expensive electricity to meet considerable cooling annual and peak loads. So what are the possible problems that the application of superinsulation to hot, arid climates would bring? The single biggest problem is the internal loads, which contribute to the reduction of heating loads in winter but become a summertime liability. As explained earlier, one of the main principles of superinsulation is airtightness. This concept, along with the improved insulation principle, actually works quite well for reducing the infiltration and conduction (respectively) of ambient hot air into the indoor spaces. However, as the building envelope becomes tighter and more resistive to external conditions, the house becomes internal load dominated. In other words, the buildup of intrinsic heat from people, lights and equipment becomes the major component of the cooling load. This might increase not only the annual cooling load, but the peak load itself, which in return eliminates potential savings from a smaller air-conditioning unit and consumed electrical energy. The first possible solution to this problem could be modifying the ventilation scheme and schedule. The air-to-air heat exchanger still operates successfully in exchanging heat between incoming and outgoing air streams, preserving cooler indoor conditions when the ambient air temperature is higher. [20] However, as the internal loads increase during the day, the amount of air to be brought in needs to be increased also. One alternative solution to this problem could be using a heat exchanger with higher capacity (80-120 cfm) and higher recovery efficiency ( + 80 %). However, since the peak intrinsic load in a typical residence usually occurs between 7-10 pm in the evening,[21] using natural ventilation at these hours when heat gain from the ambient air is not a threat could be a more efficient solution. The concept of using night-time natural ventilation works quite well with the second strategy in dealing with the internal heat buildup, which is the addition of thermal mass. A high thermal mass corresponds to a material that has a high heat storage capacity, and certain common building materials such as concrete, brick and stone have a high capacity for thermal mass. Thermal mass is an extremely useful tool in designing with the natural forces in hot, arid climates where there is a large diurnal temperature swing (Fig. 2. 14.). 3 1 Storing heat within the thermal mass, and delaying the transfer of heat to and from the indoors due to the time lag factor of the mass, reduces the temperature swing within the living area. However, to deal with prolonged hot periods during the summer, this mass could be cooled during night-time using natural ventilation. This is called convective cooling and it operates on the principle on creating a heat sink during the night and using this sink to store internal and external heat gain during the day. For this strategy 40 0 1 I 30 rt 0 1 20 10 ' t I i i * i | 1 i i i / O i i w 1 i j J\ „! _ , / i . i t' K \ s HI - > ■ ■ 1 . . . 1 12 24 12 24 12 T i m e ( H r s ) O U T D O O R AIR T E M P E R A T U R E IN D O O R TEfK R A TU R E W IT H N O C T U R N A L V E N T IL A T IO N IN D O O R T E IP E R A T O R E O F C L O S E D R O O M N O C T U R N A L V E N T IL A T IO N Fig. 2. 14. Indoor temperature changes due to Convective Cooling Givoni, B., “ Passive Cooling - State of the A rt,” Proceedings. 12th National Passive Solar Conference. ASES. Boulder, CO, 1987 32 to work, it is extremely important to keep the building closed and airtight during the day to minimize heat gain from the ambient air. Experimental studies on the effect of night ventilation of thermal mass [22] have shown that ventilation of thermal mass results in a temperature reduction of3.5-5.5°F during the daytime, as compared to unventilated buildings (Fig. 2.16). Other possible ways of dealing with the increased internal loads include venting the Hot Water Heater and other heavy equipment, and using energy-efficient equipment and appliances. Actually this has been a controversial topic among superinsulation experts due to the fact that energy-efficient appliances, in addition to using less energy, produce less heat. However, as pointed out by Nisson & Dutt,[23] it should be remembered that using these appliances to reduce auxiliary heating conditions could turn out to be more expensive due to the cost of electric energy. More significant for hot climate applications, is the reduction in the intrinsic heat and the shortening of the cooling season by using more energy-efficient appliances. 33 2. 9. References. [1] Nisson N.N.D., G. Dutt, The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 6. [2] Besant, R.W., R.S. Dumont, and G. J. Schoenau, “The Saskatchewan Conservation House: Some Preliminary Performance Results,” Energy and Buildings. 2. 1979, p. 163. [3] Besant, R.W., R.S. Dumont, and G. J. Schoenau, “The Passive Performance of the Saskatchewan Conservation House,” paper presented at the AS-ISES Passive Solar Conference. San Jose, 1979. [4] Schick, W.L., R.A. Jones, W.S. Harris, S. Konzo, “Circular C2.3, Illinois Lo cal House,” published by Small Homes Council, University of Illinois, Urbana, IL, 61801. 1979. [5] Nisson & Dutt, 1985, p. 10. [6] Shurcliff, W .A., Superinsulated and Double-Envelope Houses, Brick House Publishing Co., Andover, MA, 1981 [7] Nisson & Dutt, 1985, p. 36. [8] Nisson & Dutt, 1985, pp. 17-21. [9] Nisson & Dutt, 1985, p. 189. [10] Nisson & Dutt, 1985, p. 46. [11] Shurcliff, W .A., Air-to-Air Heat Exchangers fo r Houses, Copyrighted to the Author, Cambridge, MA, 1981 [12] Berglund, L. G., et al., “ Thermal Performance of Two Technically Similar Super-insulated residences located at 61°N and 41°N lattitude,” Energy and Buildings. 21. 1994, p. 199. [13] Nisson & Dutt, 1985, p. 111. [14] Levins, W .P., M.A. Kamitz, “ Cooling Energy Measurements of Single Family Houses with Attics Containing Radiant Barriers,” QRNL/CQN-200. Oak Ridge National Labs.. Oak Ridge, TN, 1986. 34 [15] Fairey, P.W ., “ The Measured Side-by-Side Performance o f Attic Radiant Barrier Systems in Hot, Humid Climates.” Florida Solar Energy Research Center. Cape Canaveral, FL, 1985. [16] Fairey, P.W ., “ Radiant Barriers for Cooler Houses,” Solar Ape. 9 . 1984, p. 34. [17] Medina, M ., D.L. O ’Neal, W.D. Turner, “ The Effect of Attic Ventilation of Thermal Performance of Radiant Barriers,” Journal of Solar Energy Engineering. 114. 1992, p. 235. [18] Mills, E., * * Measuring the Energy Efficiency of Manufactured Homes,” Energy and Buildings. 8. 1985, p. 291. [19] Fereig, S.M ., M.A. Younis, “ Effects of Energy Conservation Measures on the Life Cycle Cost of Kuwaiti Residential Buildings.” Energy and Buildings. 8. 1985, p. 71. [20] Shurcliff, W .A., Superinsulated and Double-Envelope Houses, Brick House Publishing Co., Andover, MA, 1981 [21] Nisson & Dutt, 1985, p. 59. [22] Givoni, B., w Passive Cooling - State of the Art,” Proceedings. 12th National Passive Solar Conference. ASES. Boulder, CO, 1987 [23] Nisson & Dutt, 1985, p 205. 35 3. MANUFACTURED HOUSING AS A CASE STUDY FOR SUPERINSULATION. As a recently developed energy efficient technology, superinsulated construction principles have mainly been limited to the traditional balloon or platform framed, on site construction practices in northern parts of the U.S. with minor modifications. After the initial explosion in the number of houses constructed, the growth of superinsulation have slowed down, partly due to the stabilization of energy prices, and partly due to the difficulties and cost of training traditional on-site construction crews for each different project. It is extremely crucial to encourage the construction of super energy-efficient houses of tomorrow, which could most logically be achieved through mass production. In addition to this, thermal performance of factory built houses has shown less than desirable results, due to more relaxed construction regulations and industries efforts in reducing the initial cost at the expense of quality. The poor thermal performance of factory-built homes becomes more critical, especially when one considers its impact on national energy consumption as well its negative effect at the individual level, due to the typical low-income profile of the occupants. For the reasons discussed above, manufactured housing is chosen as a case study for the application of superinsulation to hot, arid climates. 3.1. Manufactured Housing: a Brief Historical Background. Although prefabricated houses have been built in North America dating back to the pilgrim times,[1] the industrialization of building systems that formed the roots of today’s manufactured housing did not take place until around 1930 by the foundation of FHA. In the following years, he biggest test for home manufacturing came during the Second World War. The need for providing emergency war housing by meeting three requirements (speed, flexibility, reduction of labor) gave the industry a great opportunity for growth.[1] However quality was sacrificed for quantity and as a result, prefabrication gained a reputation of being “cheap” or “ poor construction”. Following the war when there was a national demand for permanent private housing, the prefabrication industry had to work diligently to overcome the public’s concept of a “prefab” .[2] Around 1950, other types of prefabrication started to make noticeable inroads, such as the pre-engineered metal buildings and integration of various components into housing. Additionally, the development of a special type of manufactured housing, namely mobile homes contributed to the development of prefabrication in America, especially in providing cheap, temporary housing after the war, with producing about the half of new housing in 1969. [3] Although the popularity of manufactured housing has leveled off during the last two decades due to poor thermal performance during the energy crises, fluctuations in 37 Fig. 3. 1. Construction at the factory Rabb, B., J. Rabb, Good Shelter: A Guide to Mobile, Modular, and Prefabricated Houses, Including Domes, The New York Times Book Co., New York, NY, 1975, p.34. interest rates and other dynamic factors, the area of manufactured housing holds a great deal of potential development, pending more research in areas that require improvement. 3.2. The Three Forms of M anufactured Housing. Factory-built houses can be classified into three groups (Fig 3. 2.): mobile, modular and prefabricated homes. a. Mobile Homes: Mobile homes are factory-assembled non-permanent structures usually 8’ to 14’ in width and 32’ or more in length built on a chassis for hauling to a site where it need not comply with the prevailing building code.[2] Usually financed as chattel property, taxed as a “vehicle or personal” property (Fig. 3. 2). These advantages include: - Cost: Mobile homes are the cheapest form of private detached housing available in the United States - Little on-site labor: The only forms of on-site labor needed are the installation of services. - Mobility: The potential to be moved occasionally, is an attractive feature for Americans who are pretty mobile themselves. 39 On the other hand there are some disadvantages: - Finance: Mobile homes are financed much like automobiles, at much higher rates than real estate. - Lower construction quality - Indoor air quality and fire safety - Size I N D U S T R I A L I Z E D H O U S I N G MOBILE Generally Non-Code Conforming 3 SINGLE WIDE MOBILE HOME I. DOUBLE WIDE MOBILE HOME ' » " " FOLD-OUT MOBILE HOME ■ -------- MOBILE OTHER M O D U L A R r ---- SECTIONAL HOUSE - - r — SECTIONAL BOX r SECTIONAL STACK-ON I FOLD-OUT ■ ' THREE DIMENSIONAL I MECHANICAL CORES r - I _______ , 1 MISC. | T I COMPONENTIZED Generally 1 1 Generally Conforms 1 Conforms To Codes 1 1 To Code* I COMPONENTS ] j j PACKAGED OR PREFABRICATED I SHELL 1- .. , | MISCELLANEOUS | COMBINATIONS OF BOTH Fig. 3. 2. Different forms of manufactured housing Reidelbach, I. A., Jr., Modular Housing 1971, Cahners Books, Cambridge, MA, 1971, p. 73. . 40 -— 3. 3 . M o b i l e h o m e c o n s t r u c t io n Y o u r M o b ile H o m e E n e r g y and Re pai r G u i d e H el ena, M O f'vfe* b. M odular Homes: Modular homes are permanent structures consisting of one or more modules assembled in a factory in accordance with a building code, and qualified to be financed and taxed as real property when placed on a permanent foundation. Advantages of this form of manufactured housing in comparison to mobile homes: - Appreciation - Long term financing - Site flexibility - Floor plan flexibility On the other hand modulars have the disadvantages [2] of : - Design limitations - Code conformity Another popular name given to modular homes is “sectional” or “three-dimensional”. One should also remember that the construction and width requirements are similar to mobile homes, the main difference being the permanent foundations. c. Prefabricated (componentized) Homes: Factory-assembled components to be shipped to a site for assembly to form a building or house. There are a number of methods that are included in the generic term “pre-fabricated” : “precut”, “panelized”, “pre-engineered” etc., all of which are used by manufacturers 42 themselves. Precut and pre-engineered are the same thing ; panelized is a branch of the prefabricated housing industry which, instead of shipping precut pieces of lumber sends fully factory-assembled panels to be erected on foundation.[4] In addition to all the advantages of modulars, componentized homes have the additional advantage of delivery convenience. However, due to the extra work on site, cost and time of construction are slightly increased. [4] 3.3. Energy Performance of Manufactured Homes. Although the American National Standards Institute had developed construction standards which were adopted by the Mobile home Manufacturers’ Association in 45 states in 1963, it wasn’t until the development of 1976 HUD ‘Manufactured Home Construction and Safety Standards’ that the thermal performance of manufactured housing was regulated. [5] Both HUD & ANSI publish their required standards for mobile and other manufactured home construction and thermal performance. Additionally, some states have adopted their own standards as a derivative of HUD and ANSI’s. In the state o f California, this standard is called the California code of Regulations, Title 25, Factory-Built Houses. 43 This code supplies the recommended levels of thermal envelope insulation, and infiltration, heating and cooling equipment requirements and other thermal performance related issues. The adoption of these codes was a response to poor thermal performance during the energy crises. This poor thermal performance, especially in mobile homes, had caused considerable waste of fossil fuel, resulting in higher cost for both the national and the individual levels. The mobile home owners, who constitute about 2/3’s of manufactured home owners, pay for an average annual energy intensity of 1043 MJ/sq- meter versus 830 MJ/sq-meters for site-built homes, which translates to over $3.5 billion in annual energy bills.[6] In addition to this, mobile home owners represent a lower income profile, yet pay for usually higher energy unit costs due higher reliance on electricity and liquid propane. After the establishment of the HUD standards, a number of analysis was performed to evaluate the thermal performance of mobile homes resulting from the adoption of these standards. A study conducted by Oak Ridge National Laboratory in 1978 [5] for example, compares the HUD standards to alternatives that include further improvements in the thermal envelope. Their conclusion state that * * . . . the 1976 thermal standard promulgated by the Department of HUD requires considerably less investment in energy-efficient design than the optim al. . . [7].” 44 Another interesting DOE-funded research was conducted by the Solar Energy Research Institute [8] between 1988-1991 which analyzed the thermal performance improvements resulting from changes in specific components of the envelope, such as addition of storm windows, roof insulation, wall insulation etc.. The results have shown the effectiveness of heat loss reductions for roof and wall insulations and airtight envelope (Fig. 3. 4). In the light of these findings, there have been a number of programs established to improve the thermal performance of existing mobile homes, such as the National Home Weatherization Assistance Program, which provide specially developed retrofit packages costing up to $ 2000. Although the cost effectiveness of these weatherization Fig. 3. 4. Heat loss percentage reduction for conservation projects. Krigger, J.T., Your Mobile Home Energy and Repair Guide, Saturn Resource Management, Helena, MO, 1992, p. 6. 45 programs have been proven, [9] it is recognized that the thermal performance problems of mobile homes should be solved within the factory construction process and the capabilities of the factory-built housing industry. One study that included superinsulation as an energy efficiency improvement alternative in mobile homes was conducted by Evan Mills of Lawrence Berkeley Laboratory. [5] This study concentrated on different approaches on improving the thermal performance of manufactured housing using data from simulated and monitored alternative design performance analysis. According to Mills, the most energy-efficient strategy was found to be “ ... the manufacturers standard model and includes triple glazing, high insulation levels and an air-to-air heat exchangers,[10] “essentially describing the principles of superinsulation. 46 3. 4. References: [1] Cutler L.S., S.S. Cutler, Handbook o f Housing Systems fo r Designers and Developers, Van Nostrand Reinhold Co., New York, NY, 1974. [2] Rabb, B., J. Rabb, Good Shelter: A Guide to Mobile, Modular, and Prefabricated Houses, Including Domes, The New York Times Book Co., New York, NY, 1975. [3] Cutler & Cutler, 1974, pp. 26-38. [4] Rabb & Rabb, 1975, p. 37. [5] Krigger, J.T., Your Mobile Home Energy and Repair Guide, Saturn Resource Management, Helena, MO, 1992, p. 3. [6] Mills, E., “ Measuring the Energy Efficiency of Manufactured Homes,” Energy and Buildings. 8. 1985, p. 291. [7] Hutchins, P.F., E. Hirst, “ Analysis of Mobile Home Thermal Performance,” Energy and Buildings. 3. 1981, p. 279. [8] Krigger, 1992, p. 6. [9] Burch, J„ Fishbaugher, M ., Judlayt, “ A Utility Bill Study of Mobile Home Weatherization Savings,” Energy and Buildings. 20. 1993, p. 11. [10] Mills. 1985, p. 293. 47 4. CONCEPTUAL DEVELOPMENT To be able to test the applicability of superinsulation to hot climates, it is very important to design an effective superinsulated system that responds to the specific climatic needs of the area. Additionally, this 100% passive system has to respond to the construction requirements of manufactured housing, which is to provide a case study for this research. 4. 1. Potential Problems Arising from the Manufactured Housing Requirements One of the biggest problems arising from the application of superinsulated principles to manufactured housing is the limitations in size, specifically width requirements. Most states have a 12 feet limit on the width of transportation vehicles or loads on highways (14 feet limit with a special permit). This limitation in building width eliminates any plausible use of double wall, truss wall or strapped wall superinsulated systems. Therefore the only possible application of a wall system is through using a high R-value per inch material such as polyurethane in an exterior sheathing wall system. Secondly, due to the extensive use of glues and other adhesive materials that contribute to the buildup of formaldehyde, radon, humidity and other indoor pollutants is an 48 additional problem, especially in an environment with small volume. Therefore the indoor air quality could be a bigger problem in superinsulated manufactured housing, which could be solved by allowing higher volume o f air for ventilation then a typical superinsulated house. The recommended levels o f controlled ventilation were around 0.5-0.6 air changes per hour during the earlier days of superinsulation.[1] However, for manufactured housing applications, this rate should be raised to 1.0 a.c.p .h ., which could be maintained by using a higher recovery efficiency exchanger (say 80%) that is not expensive and uncommon today. This rate should be maintained for the summer also, except for the periods when night ventilation o f the thermal mass is desired. However, a more important problem arises when thermal mass need to be added to superinsulated manufactured housing . As discussed earlier, thermal mass is a necessity for developing a passive solar system for hot, arid climates. However, due to the limitations in width, wall cavity, and transportable weight, it is not possible to use high mass construction materials in factory-built homes. How can thermal mass be added to manufactured housing then? The solution to this problem could only be solved by adding mass on site, that is by adding water on site, as the thermal storage material. At 62.26 Btuh/ft2 °F , water can store about three times as much heat per unit temperature as concrete o f equal volume. Although the time lag factor o f a water storage system is not as significant as masonry storage systems’ due to the convection o f water within the storage volume, this superior 4 9 storage capacity enables it to store enough energy to heat up the space for 24 hours if needed. This heat transfer into the house takes place through radiation and T h e rm a l H e a t S u b a e a n c e S p e c i f i c H e a t D o n a le y C o n d u c t i v i t y C a p a c i t y j / k g - ° i c H T T >/lb-°T k g /m * l b / f t 3 W /m .°S B T O h / f t - ° P H J BTUh f t J *6 F A lu m in u m ( A l l o y 1 1 0 0 ) 0 9 6 0 .2 1 4 2 7 4 0 171 231 1 3 8 2 . 4 5 5 3 6 .5 9 A e p h a l t 9 2 0 0 .2 2 2 1 1 0 1 3 2 0 . 7 4 0 . 4 3 1 .9 4 1 2 9 .0 4 B r i c k , b u i l d i n g 8 0 0 0 . 2 1 9 7 0 12 3 0 . 7 0 . 4 1 . 5 7 6 2 4 .6 0 C t m n t ( P o r t l a n d c l i n k o r ) 6 7 0 0 . 1 6 1 9 2 0 1 2 0 0 . 0 2 9 0 . 0 1 7 1 . 2 8 6 1 9 .2 0 G e n e r a t e ( a e o n * ) 6 5 3 ( 4 7 3 ) 0 .1 5 6 ( 3 9 2 ) 2 3 0 0 14 4 0 . 9 3 0 . 5 4 1 .5 0 2 2 2 .4 6 I r o n : c a a t 5 0 0 (3 7 3 ) 0 .1 2 ( 2 1 2 ) 7 2 1 0 4 5 0 4 7 . 7 ( 3 2 7 ) 2 7 . 6 ( 1 2 9 ) R u b b a r : v u l e a n i r e d , a o f t 1 0 0 0 0 .4 8 1 1 0 0 6 8 . 6 0 . 1 0 . 0 8 2 . 2 0 0 3 2 .9 3 S a n d 8 0 0 0 .1 9 1 1 5 2 0 9 4 . 6 0 . 3 3 0 , 1 9 1 . 2 1 6 1 8 .0 7 S t o o l ( m i ld ) 500 0 .1 2 7 8 3 0 4 8 9 4 5 . 3 2 6 . 2 3 . 9 1 5 5 8 .6 8 S t o n a ( q u a r r i e d ) 8 0 0 0 . 2 1 5 0 0 9 5 1 . 2 0 0 1 9 . 0 0 T a r : p i t c h 35 0 0 0 .5 9 1 1 0 0 67 0 . 8 8 0 . 5 1 2 . 7 5 0 3 9 .5 3 W ood: O a k , w h i t e 2 3 9 0 0 .5 7 0 7 5 0 4 7 0 . 1 7 6 0 . 1 0 2 1 .7 9 3 2 6 .7 9 W a te r 4 1 8 0 ( 3 9 3 ) 0 .9 9 9 ( 6 8 ) 9 9 8 . 2 6 2 . 3 2 ( 6 8 ) 0 .6 0 2 0 . 3 4 8 4 . 1 7 3 6 2 . 2 6 Table 4. 1. Thermal Storage Properties of Certain Materials ASHRAE Handbook of Fundamentals 1981, American Society of Heating, Refrigerating and Air Conditioning Engineers,Inc, Atlanta, Georgia, 1981, p. 39.2 convection, and is directly regulated by the temperature differential between the house and the material. Thus, only enough heat energy is transferred into the space to bring about a state of equilibrium. On the other hand, this thermal mass can be used in coping with the increased cooling loads in summer time through convective cooling by night ventilation. This strategy is even more significant in superinsulated houses, since it provides the opportunity to cool the mass of the building to a point that the daytime intrinsic gains can be dumped 50 into this heat sink. Additionally radiative cooling can also be achieved by using water as thermal storage material in a “roof pond” system. 4.2. Roof Ponds. Water can be used as a thermal storage material within the wall or the roof system. Due to the difficulty of incorporating water walls into the architecture of manufactured housing, roof ponds become more favorable for this application. Although roof ponds have been used as thermal storage systems for years in different configurations (evaporative ponds, shaded ponds etc.), the breakthrough development in the design of this system came in 1971 with the incorporation of movable insulation into the roof pond system by architect Harold Hay.[3,4] Commercially marketed as SKYTHERMr , Hay’s system uses water in clear UV treated PVC bags with polyurethane insulating panels on tracks. A high-conductivity metal deck supports the water bags, which is also the ceiling for the structure. The panels, which are supported by tubular beams, are pulled and retracted using cables or chainsoperated manually or by a motor. The real value of the roof pond water storage system is that it could be used both for heating and cooling conditions. To achieve this, the system is operated as follows: 5 1 a. Winter Daytime: During the day in winter, the movable insulation panels are opened to allow the absorption of solar radiation by the water bags. The stored energy then radiates into the space through the metal deck and heats the house (Fig 4.2), The only problem with this configuration is the increased heat loss through conduction through the roof due to decreased thermal resistance. However the conduction heat loss is less than half of radiant heat gain, therefore is fully compensated for. b. Winter Night-time: During the night, the insulating covers are closed which minimizes the heat loss through the roof. Energy stored within the roof pond continues to be radiated into the space and contributes to keeping the space warm, along with the intrinsic heat gain (Fig 4.3.). c. Summer Daytime: The conditions described above are reversed for summer use. To minimize gains from solar radiation and ambient temperature ( sol-air effect), the insulating panels are kept closed during daytime. Whatever solar radiation penetrates the insulating panels are stored in the water ponds along with the build-up of internal heat gains (Fig. 4.4.). The insulating panels also protect the PVC film from degradation and therefore allow for maximum absorption of solar radiation during winter. [5] 52 Fig. 4.1. Winter daytime roof pond operation Fig. 4. 2. Winter night-time roof pond operation Fig. 4.3. Summer daytime roof pond operation t Fig. 4.4. Summer night-time roof pond operation d. Summer Night-time: During the summer night the windows of the building are opened first to cool the thermal mass by cross ventilation. At the same time the insulating panels are opened to allow for radiant cooling of the roof pond. The build-up o f intrinsic heat gains are flushed into the sky dome. Additionally the resistance of the roof structure is reduced, which aids in heat loss through conduction to the ambient air with lower temperature. The radiant cooling capacity of the roof depends on the skycover and the percentage of the roof that is able to see the sky dome. Even though roof ponds can be used in other more northern climates for both cooling and heating, they are most effective in the hot arid climates with a low percentage of sky cover for cooling conditions. 4.3. Roof Pond Variations There are a number of variations to the roof ponds stemming from changes in location (northern vs. southern latitudes), climate ( arid vs. humid ), building configuration, cost and other factors. These variations include exposed vs. shaded ponds, movable insulation (SkythermR ) vs. fixed insulation with movable fluid, concrete vs. metal deck etc.. There have been a significant number of computer simulation and monitored data [6,7] results from studies comparing different roof pond systems which imply the SkythermR system to be the most effective radiative roof cooling system in maintaining 55 comfort conditions within the space. In addition to this, research by Clark et al. [8] and Hay [9] indicate that this system can be used effectively in most U.S. climates without significant snow loads, with minor modifications such as addition of fans and/or dehumidifiers. It should be quite obvious that the effectiveness of the SkythermR passive cooling and heating system, depends greatly on movable insulation design. For this reason, we will focus on analyzing different movable insulation alternatives for an effective system design. The operable insulation systems development includes a number of factors for thermal heating and cooling performance conditions. The most important of these factors are the obstruction of the sky dome and solar access. Naturally, to allow for maximum heat gain capacity, the roof pond surface has to have maximum access to horizontal solar radiation. Similarly, the radiative cooling capacity of the pond depends greatly on the amount of obstruction to the night-time skydome. The higher percentage of skydome the water bags see, higher the cooling capacity of the pond . . . Among the number of possible movable insulation systems, the most popular one is the original SkythermR horizontal sliding tracks system. The first application of this system was in the Hay residence in Atascadero. [5,9] This system consists of aluminum extrusions that provide the tracks, and 2” rigid polyurethane panels on wheels that are mounted on top of the tracks. The tracks are extended over the garage area and the insulating panels are parked over the tracks in garage in the open mode. The tracks are of aluminum extrusion and are supported by a steel beam across the short span of the building. The strength of this system lies in the fact that it provides almost no obstruction to solar radiation during winter days, and to the skydome during summer nights. For this reason this system is equally effective in providing both cooling and heating. As a mater of fact, the Atescadero house system was found to maintain interior temperatures of 62-79 °F without any backup heating or cooling, even though outside temperatures ranged from 26 to 100 °F.[9] Fig. 4. 5. Atascadero house: panels on tracks Hay, H.R., “ A Naturally Air Conditioned Building." Skytherm Processes and Engineering. Los Angeles, CA, 1975. 57 On the downside, the aluminum extrusions and tracks can be costly, unless the detailing of the tracks is somewhat simplified. Also, there exists the need for additional space to park the panels in open insulation position. Although the thermal performance is quite efficient in both cooling and heating, there is still a significant heat gain during the summer day from the panels and the edge gaps. Possible solutions to this problem include increasing the thermal resistance of the panels to reduce heat gain through conduction, addition of reflective aluminum foil to the both sides of the panels to reduce radiant gains and better sealing of the edges in the closed position. Fig. 4. 6. Hinged insulation system 58 PLEASE NOTE P ages not included with original material ana unavailable from author or university. Filmed a s received. 59 UMI Another movable insulation configuration is the bifold movable insulation panels, first developed for the Pala project.[9] This configuration is similar to the horizontal sliding panels, in the sense that it uses tracks and panels on wheels as documented by Niles & Haggard. [10] The difference is that these panels are retracted into a vertical, bifold format without the need for added space for storage of the panels. This system could be operated by a motor and solar radiation sensors or manually and can seal tightly when closed. The strength of this system is its relative reduction in cost and its ability to be used in both heating and cooling conditions. However, the bifold system is more efficient for heating conditions due to the fact that solar radiation can be reflected into the pond by the open panels, and that the cooling capacity of the roof is slightly reduced because of partial blocking of the sky. Furthermore, the orientation of the house becomes crucial not just in limiting the solar access of the water ponds but the surrounding houses as well. In addition to these thermal performance related problems, the bifold system has the problem of instability under windy conditions. Finally, a centerfolding movable insulation system can be developed as a variation of the bifold system (Fig. 4. 9.) This system operates by retracting the panels into vertical configuration in the center of the roof. This process could be achieved by a simple pulley system that is operated manually. 60 Fig. 4. 8. Center-folding movable insulation The biggest advantage of this system is the simplification of the operation system . On the other hand, both the heating and cooling capacity is limited due to the obstruction o f the sky. Also, the orientation becomes an important variable, similar to the bifold insulation system. Among all the variations, the sliding horizontal tracks system (SkythermR ) has been the most widely used configuration. The problems with this system such as cost, simplified detailing and architectural integration can be solved by the integration of design 6 1 infrastructure and mass manufacturing practices, [11] which is within the scope of this thesis. In addition to variations in movable insulation design, there are other factors which greatly influence the design and performance of the roof pond system. These factors, which include pond depth, insulation resistance and window area, are discussed in great detailed by Niles [12] using monitored and simulated data for different California climate zones. These factors should be examined in detail for a particular system design. 6 2 4. 4. References: [1] Lenchek, T., C. Mattock, J.Raabe, Superinsulated Design and Construction, Van Nostrand Reinhold Co., New York, NY, 1987, p. 61. [2] Hay, H.R., “ Energy, Technology and Solarchitecture,” Mechanical Engineering. November, 1973, p. 18. [3] Hay, H.R., * * A Naturally Air Conditioned Building.” Skvtherm Processes and Engineering. Los Angeles, CA, 1975. [4] Hay, H.R., “ Roof Mass and Comfort,” Proceedings of the Second National Passive Solar Conference. Vol 1. 1978, p. 23. [5] Clark, G. et al., “ Results of Validated Simulations of the Roof Pond Residences,” Proceedings of the Eighth National Passive Solar Confrerence. Santa Fe, NM, 1983, p. 863. [6] Yadav, R. et al., “ Digital Simulation of Indoor Temperatures of Buildings with Roof Ponds,” Solar Energy. 31. 1983, p. 205. [7] Clark, G. et al., “ Validated Simulations of the Thermal Performance of Roof Pond Residences in U.S. Climates,” Final Report from the Trinity University to USDQE. Contract No. DE-ACCE03-79cs30201. 1985. [8] Hay, H.R. “ Skytherm Natural Air Conditioning for a Texas Factory,” Proceedings of the Second National Passive Solar Conference. 1. 1978, p. 23. [9] Hay, 1978, p. 26. [10] Niles., P.W .B., and K. Haggard, Passive Solar Handbook fo r California, California Energy Commission, 1980, p. 253. [11] Hay, H.R., “ Integration of Passive Deatils and Systems,” Proceedings of the Annual Meeting of ASES. Houston, TX, 1982, p. 815. [12] Niles, 1978, pp. 233-248. 63 5. SYSTEM DESIGN A typical single-wide mobile home is chosen as the base case to test the application of superinsulation and passive cooling priciples to manufactured housing and to allow for the design of the passive heating and cooling system in the light of these principles. The structural, architectural and thermal properties of this base case is determined by the recommendations supplied by the California Code of Regulations, Title 25. [1] The thermal envelope design of the superinsulated system is then applied to this case, with no architectural design changes, other than the ones necessary to accomodate the thermal system. The resulting design will have to comply with the Title 25 recommendations for structural and architectural integrity. 5.1. Base Case. The base case chosen for the application of the heating and cooling system is the standard two bedroom, single-wide mobile home (Fig. 5.1.). This model is 12 feet wide, 54 feet long, and has a gross floor area of 648 square feet. The total wall area of the mobile home is 990 square feet, and this includes 867 square feet of opaque wall and 81 square feet of window area (which encompasses 14 % of floor area). When oriented with the long side along the east-west axis, the southern and northern sides has 64 almost equal amount of glazing. The west and east walls carry only about 30 % of the total glazing area, and there are no doors in the short walls. The interiors are 7.5’ high, b e d ro o m kitchen living roo m be' Iroom OPAQUE WALL AREA: 8 6 7 SOFT WINDOW AREA : 81 SQFT ( 14% of FLOOR AREA) DOOR AREA 4 2 SOFT ROOF POND AREA : 5 7 2 SQFT T F t V T Fig. 5. 1. Base case floor plan. with a total interior volume of 4515 cubic-feet, and include a living room (180 sq.ft.), a kitchen (130 sq.ft.), a bathroom (63 sq.ft.), and two bedrooms ( 72 and 120 sq.ft.). In the state of California, the construction, structural integrity and minimum thermal requirements of the model is recommended by the California Code of Regulations, GROSS AREA ROOF AREA FLOOR AREA GROSS WALL AREA VOLUME : 6 4 8 SOFT : 6 4 8 SQFT 5 9 4 SOFT : 9 9 0 SQFT : 4 5 1 5 CUFT 65 Title 25, Chapter 3 - Factory-Built Housing & Mobile Homes. According to these recommended levels, the base case wall system is assumed to have a thermal ELEVATIONS EH NORTH ELEVATION m ini limn SOUTH ELEVATION W EST ELEVATION EAST ELEVATION 0 2 4 a FT l_ J I______ I Fig. 5. 2. Base case elevations. resistance of R-8 walls, which consists of interior wallboard, minimum 1.5 inches of batt insulation, air space and exterior siding. The floor system is assumed to consist of interior floor board, 2.5 inch batt insulation, air space and exterior subfloor board, resulting in the minimum required floor resistance of R-l 1. The R-16 roof structure 66 1955027129 consists of a ceiling board, 4 inches of batt insulation, air space and exterior metal roof. The doors of the mobile home was assumed to be of standard hollow wood metal frame windows with single pane glazing and exterior shutters. Using recommended levels for perimeter heat loss due to air leakage, the average rate for the base case was calculated to be 1.4 air changes per hour. 5.2. The Superinsulated Envelope System. The base case was modified with no architectural changes, to accommodate a superinsulated envelope. The limitations in width and height, as well as cost efficiency and mass production issues were taken into consideration during the envelope design and modification process. This envelope includes a wall area consisting of 1/2 in. plaster, an air/vapor barrier, 3.5 in. batt insulation within the wall cavity, 1.5 in. exterior polyurethane sheathing, 3/4 in. air space with a radiant barrier and exterior siding, resulting in a wall resistance of R-25. door, with the Title 25 infiltration 67 The floor system consists of vinyl floor boards, air/vapor barrier, 1/2 in floor sheathing, 6 in. batt insulation within the cavity, 1/4 in. outside asphalt board, and 2 in. insulation on the outside to reduce thermal bridging from the floor beams to the subfloor undercarriage, all of which combine to provide a floor resistance of R-22 (Fig. 5.3. on the following page). Other improvements to the thermal envelope include double-pane windows, addition of envelope air/vapor barriers and careful sealing and caulking of door and window cracks to reduce the infiltration rate to 0.4 air changes per hour. To eliminate the high indoor humidity and pollutant build-up problem in a tightly constructed indoor environment, an air-to-air heat exchanger is used. The exchanger chosen to provide controlled ventilation is Mitsubishi-Lossnay VL1500, which is one of the more popular, highly efficient ( 75-80 %), highly flexible ( 28-71 cfm airflow in each airstream) and inexpensive ( $ 355-405) models. This exchanger is operated 24 hours a day in winter with varying air volume capacities at different times of the day, depending on occupancy and indoor air quality conditions. Summer-time operation is similar, except for the times when the exchanger is turned off and natural ventilation is used, which typically occurs at night. 6 8 2 1 /4 ’ m ovoble insulation inflated w ater b a g s (winter) m etal deck ceiling m achine scrvted 3" fiberglass batt 2" polyurothe 3 / 4 v fn led air sp ac e radiant barrier alum inum siding 1*3 furring air/v o p o r barrier 4*punched chonel stu d s air/v a p o r barrier 1 /2 " gypsum board 1 / 2 ' floor board a ir/v a p a r barrier 3 /8 " floor shealhing {f fiberglass b att 10* punched nailable double stu d s 16 gauge 24" o x . 3 /B ’ asp h alt im preg. board subfloor steel b eam with th erm al break 2" fibergloss bolt subftoor insulation co n crete pier Fig. 5. 3. Section through the superinsulated mobile home 69 5.3. The Roof Pond System The adopted roof pond system is similar to the SKYTHERMr system,[2-4] in the sense that it consists of water contained in clear plastic bags with a black polyethlylene liner at the bottom that absorb solar radiation. These bags are supported by a steel corrugated deck which also acts as the ceiling of the unit. As discussed in the previous chapters, a number of alternative movable insulation systems exist. The first details developed show a bifold movable insulation system,[5] which operates on the principle of retracting the panels to a vertical position either manually or by a 1/4 HP reversible motor (Fig. 5.4. and 5.5.). To initiate this motion of the pulling cable, the panels lean against each other to form a slight angle (6-8°). When the panels are closed, they are sealed at the edge by neoprane gaskets, and sealing brackets operating on pivot points and springs. Similarly, in the center condition, the two panels are sealed by neoprane gaskets inside a hinged channel with top flaps. The water drainage problem could be solved in two ways: either at the level of the bags, or at the metal deck level. At the top of the bags, water could be collected in gutters formed by attaching the top flap of the polyethylene bags under the middle or edge beams (Fig. 5.5.). Water is then taken to the side walls and drained outside. 70 © (jSin Oj_ _ _ _ _ _ _ H t _ _ _ _ _ _ 2 ft (1) sealing plate (2) edge beams -2x8 (3) internal gutter (4) channel frame (5) inflated air cell (6) 4” deep water (7) aluminum siding (8) polyurathane insulation (9) metal deck (10) insulation panels (11) neoprane gasket (12) cover flap (13) hinged channel frame (14) polyethylene bags (15) internal gutter (16) external gutter Fig. 5. 4. Bifold movable insulation: closed position Niles., P.W .B., and K. Haggard, Passive Solar Handbook fo r California, California Energy Commission, 1980, p. 252. 7 1 ?in 0 . 2 f t (1) sealing plate (2) pivot point (3) scupper drain (4) panel tracks (5) insulation panels (6) outside gutter Fig. S. S Bifold movable insulation: open position Niles., P.W .B., and K. Haggard, Passive Solar Handbook fo r California, California Energy Commission, 1980, p. 252. 72 The other alternative to drain water is to collect it on top of the metal deck and use scuppers at certain intervals. For this system to work, however, the metal deck needs to be angled slightly towards the side equipped with scuppers. 1 (1) polyurethane insulation panels (8) return cable (2) channel frame (9) aluminum extrusions-tracks (3) sealing plate (10) 40-mil steel deck with flat top plate (4) thermal break (11) inflated air cell (5) pulling cable (12) polyethylene liner (6) pile weather stripping (13) 4” deep water (7) wheel bracket (14) polyethylene water bags Fig. 5. 6. Cross section through the bifold roof pond system 73 The cross section through the bifold insulating panel system is shown in Fig. 5.6. The pulling cable (no. 5. in Fig. 5.6.) activates the movement of the insulation panels. Attached to the panels are series of wheels in brackets (no. 7.), which move along aluminum extrusions (no. 9.) to erect the insualtion panels in the open position. The water bags lie below the level of insulation panels and are supported by a 40-mil. steel deck which also happens to be the ceiling of the indoor space. The polyethlene bags can be inflated (no. 11.) in winter to increase the thermal resistance of the roof system. An alternative to the bifold movable system is the flat horizontal tracks system. First developed by Harold Hay,[2-4] this system operates by sliding the insulation panels clear of the roof pond area to increase solar and night time sky access. An additional advantage of this sytem is that it does not diminish the neighboring structures’ solar access capacity as much as the bifold system (Fig. 5.8 & 5.9). As discussed earlier, the problem of space needed to park the panels is solved by utilizing the trellis structure, Fig. 5. 7. Section showing extension of tracks into the trellis and support brackets 74 which is quite popular in mobile home parks, or providing series of brackets that can be attached on the wall to support the extension of the tracks (Fig. 5.7.). However, the supports for the trellis as well as the connections need to be moment resisting. L = 26 ft Fig. 5. 8. Shadow length from the bifold panels (Dec 21, Noon) L = 15 ft Fig. 5. 9. Shadow length from the sliding panels (Dec 21, Noon) 75 < § > (1) top insulation panel (2) channel prame (3) aluminum channel (4) neoprane gasket (5) bottom panel (6) inflated air cell (7) water (8) metal deck (9) polyrthylene bags Fig. 5.10. Cross section showing pulling panels 76 The sliding insulation system operates by initiating the movement of the top panels either by a motor or a simple pulley system. Once the top panel starts moving, it pulls the bottom panels along, through a simple attchment, using aluminum channels (no. 3. in Fig. 5.10.) and neoprane gaskets (no. 4 of Fig. 5.10.). This motion comes to a halt when the top panel reaches the edge of the trellis or support bracket. This system is shown in transverse section in Fig 5. 11.. The top panels ride on the tube beam (no. 15.) which is encased by aluminum extrusions (no. 9.) to provide tracks for the bottom panels. The weight of the panels are carried by the metal tube spanning 12 feet spaced at 6 feet o.c.. Since cost effectiveness is a major consideration, the flat top plate is removed from the corrugated metal deck and the water bags are allowed to fill in the gaps of the deck ribs (no. 12.). This deck is of heavier gage than the original (18 or even 16) to provide over 70 psf of allowable bearing load capacity. Another alternative design for the sliding system is developed as shown in Fig. 5.12. . Here, the main difference is the suspension of the top panels using metal channels to reduce the number of wheel brackets (no. 6.), sealing plates (no. 3.) and panel encasements. The system is operated in the same manner with the top panels pulling the bottom panels, with the exception that the bottom panels are not broken apart and better sealed. 77 (1) insulation panels (2) aluminum channels (3) teflon seal (4) sealing plate (5) wheels (6) thermal break (7) top sealing plate (8) tee (9) aluminum extrusions (10) metal deck (11) inflated air cell (12) polyethylene liner (13) water (14) insulation/thermal break (15) metal tubelar beam Fig. 5.11. Sliding insulation system 78 (1) insulation panels (2) thermal break (3) sealing plate (4) aluminum channels (5) C-channels (6) wheels (7) wheels (8) water (9) inflated air cell (10) metal deck (11) polyethylene liner (12) insulation/thermal break (13) bottom channel Fig. 5.12. Alternative sliding insulation section 79 These alternative roof systems are both developed to work the insulation panels effectively to allow for the absorption of solar radiation during winter days and radiant cooling at summer nights. The depth of the water bags should be kept between 4 and 6 inches, so that the roof live load from the water bags does not exceed 20 to 30 lbs/sq.ft.. However, it should be recognized that the water depth is a resultant of a number of climatic factors, which will be examined in the thermal analysis. 5.4. The Mechanical Operation System. Roof Ponds can be operated either manually or mechanically. Although manual operation is more cost effective and does not require a great deal of physical force for operation, a mechanical operation system yields better thermal performance due to better sensor control capabilities, besides being more convenient for daily use. The mechanical movable insulation system consists of a motor (typically a 1/6 or 1/4 reversible motor), a cable or chain drive and sensors. As a whole, these components work tpgether by the operation of three different switches: a. Mode Switch. b. Sol-Air Sensor Switch. c. Set Thermostat Temperature Switch. 80 M OVABLE IN SU LA TIO N P A N E L S R E V E R SIB LE MOTOR S O L -A IR S E N S O R M ODE SW ITCH D IFFEREN TIA L TH ERM O STA T U P IF U P IF HEATING U P IF T „ > ; DOW N IF CO O LIN G ) T, Fig. 5. 13. Mechanical operation of the roof pond system. Niles., P.W.B., and K. Haggard, Passive Solar Handbook fo r California, California Energy Commission, 1980, p. 313. The mode switch is adjusted manually, depending on if heating or cooling operation is desired. Once this switch is set for the desired mode of operation, the movable panels are moved by the behavior of the other two switches, which are controlled by the readings from the sensors. 8 1 For the roof panels to open during the heating mode, two main conditions need to be satisfied: a. The temperature reading from the outside sol-air sensor has to be greater than pond temperature during daylight hours. b. The set thermostat temperature must be greater than indoor air temperature. Similarly, for the insualtion panels to open during the cooling mode: a. The pond temperature must be greater than the sol-air temperature. b. The indoor temperature must be higher than the thermostat set point temperature. 5.5. Lateral Bracing. Buildings exposed to seismic forces must be braced in some way to prevent racking, especially in the seismic zones of Southern California. Specifically walls should be designed to transmit shears between the roof and ground levels. The use of shear panels is limited by the exterior sheathing in the superinsulated wall system. For this reason, diagonal straps are to be used to brace the walls against lateral 8 2 Diagonal bracing Min. 16 go. Horizontal load □•tail "8 y m ftridging Anchor dtonnol 'M in. 16 0a. Diogooal toniion strapi So« dvtail "A" D m Dalail A r ta anch dw w h#l o N i Fig. 5. 14. Diagonal strap bracing details. Koenig, P ., Pre-Fabricated Systems Handbook, Use School of Architecture, 1979 83 forces. Another advantage of this latteral support system is that straps are usually the most economical means for providing bracing in load-bearing stud construction. The lateral bracing system is crucial for the safety of the superinsulated mobile unit when we consider the addition of 20 to 30 psf roof load. The exterior walls in the long direction along with the short exterior walls need to be braced in this manner to transmit shears between the roof level with added weight and the ground. Additionally, one of the interior bedroom walls in the short direction need to be laterally braced, when one considers the 54 foot length of the unit. This length might cause outwards movement and bowing in the middle parts, for which one of the central interior panels need to be braced with diagonal straps. The recommended straps are DTS- 4x12 s which is of heavier gage than typical 2x14 - 14 gage diagonal straps of standard stud bearing construction. However, the success of the bracing system depends on the attachments at the end of each strap (Fig. 5.14). End connections must transfer full design load to make the strap fully effective. [6] To ensure the integrity of these connections, the most common practice includes welding the straps to anchor chanels at the bottom track, and bolting both of the bottom channels. At the top connection detail, typically a second stud is neccessary at the track attachment point to carry the vertical load down. 84 5. 6. References [1] California Code of Regulations, Title 25, Chapter 3 - Factory Built Housing & Mobile Homes, Subpart F, 1994, p. 4070. [2] Hay, H.R., “ Energy, Technology and Solarchitecture,” Mechanical Engineering. November, 1973, p. 18. [3] Hay, H.R., “ A Naturally Air Conditioned Building." Skvtherm Processes and Engineering. Los Angeles, CA, 1975. [4] Hay, H.R., “ Roof Mass and Comfort,” Proceedings of the Second National Passive Solar Conference. Vol 1. 1978, p. 23. [5] Niles., P.W.B., and K. Haggard, Passive Solar Handbook fo r California, California Energy Commission, 1980, p. 252. [6] Koenig, P., Pre-Fabricated Systems Handbook, Use School of Architecture, 1979. 85 6. THERMAL PERFORMANCE ANALYSIS The most accurate assessment of the energy performance and cost effectiveness of the superinsulated system can be obtained by monitoring a built prototype under desired climatic conditions. However, it is extremely crucial to provide an estimate on the performance of the system by using a mathematical model before actual construction. A verified, hour-by-hour computer simulation is the most accurate method to predict how the system is going to perform under different climatic conditions. 6.1. Methodology: The thermal performance of the superinsulated mobile home is analyzed using DOE2.E [1] hour-by-hour computer simulation tool. DOE2 is a computer modeling software which calculates the heating and cooling load of a building assuming a fixed indoor air temperature. Although this prevents us from assesing the indoor comfort conditions as a resultant of temperature flactuations, by setting different fixed room temperatures for heating and cooling conditions we are able to get the thermal loads for different tolerance and desired comfort levels. The computer simulation was first to completed for the base case, thermal charcteristies of which was determined using Title 25 recommended levels. Subsequently, the 86 developed superinsulated manufactured housing model was analyzed using the same program. This analysis was carried through at three different stages: a. Modeling the base case b. Modeling the superinsulated envelope c. Modeling the thermal mass and night ventilation Due to the inability of DOE2 programs to calculate the heating and radiant cooling capacity of roof ponds, a verified mathematical algorithm [2] is used to calculate the minimum depth and the cooling capacity of the water bags. The base case and the superinsulated mobile home were both modeled for the simulation runs according to their thermal profiles described earlier. Their occupancy, lighting and equipment loads and schedules as well as the infiltration and shade schedules were modeled using a number of sources.[1,3,4] Due to the mobile nature of this housing type (mobile home manufacturers typically deliver their product within a 200 mile radius), it is necessary to show the compatibility of the superinsulated mobile home with different climate zones in a hot arid area. Although some variation is unavoidable, it is crucial to show that backup heating and cooling will not be needed for a passive system in different locations. For this reason, the thermal analysis of the system is carried out for four different climate zones within the Southern California area. These climate zones are: a. South Coast Climate: This is a mild, semi arid climate with a low daily temperature swing. The summers are much milder than the inland and desert summers and winters are warmer, with less than 2000 heating degree days. Weather data for Los Angeles is used to analyze the thermal performance of the system for this zone. b. Warm Inland Coastal Climate: By virtue of its more inland location, this climate is a little harsher than south coast, with hot, arid summers and slightly cooler winters. The daily temperature swing is very high in summer (35-37°F), which is highly desirable for passive cooling. Winters tend to be mild, except for higher elevation locations where freezing occurs. Riverside weather file is used to model the behavior of the unit for this climate. c. Central Valley Climate: This is a continental climate with large daily and seasonal ranges of temperature. Summers are very hot, and specifically the frequent occurrence of consecutive days with very high temperatures along with moderately higher humidity requires further design considerations. Additionally, winters are cooler than the south coast and inland climates with well over 2000 heating degree days. A typical location for this climate zone is Fresno. ss d. Hot, Desert Climate: This is very hot and arid desert climate with a large daily range . Although primary design considerations for this zone is cooling, some high desert areas like China Lake needs to be analyzed for heating efficiency. Cn i c m l Cily ! • • Wttftord N l W i C M # ZONE S E w ttU * O fM m iw U rr Vallay f " * lit. ShN(a • O lM ltllll Fori ■ > < *i«h I '| . • Aulh N t ttn a it I • H at Crvtfe / 1 • Minata) , « • / » N ttf SluN 0 S u i> / \ / \ • O u n y / • O r M / l h ) i C i n y » i | * I \ • • t O M l p f t f l f l IIMVflll* | * R « Zone Clim ate Description 1 Coastal 2 South Coast 3 Warm Inland/Coastal 4 Central Valley 5 Cold Mountain 6 Hot Desert • Uhiah ftfliryivHI# Santa Rosa * 0 \ s |rl San F fln c a M Civic C tliM f X a dafcl ( ? < a o P t R«ow»o4 c ltr * 4 f M ountain V in t \ • A u b u r n • W oodloidt • PlacanriliJ Foliom m\ Vac*r*H« v - FattfM d * irichmond \ 1 * SfOtMon ^ land \ i a n FiantltCO Aw port V 9 ^ . > « J « . • »»<*•** l " \ » M trc*« N^miCou \ J 15F»» & f - r z °n e 4 ZONE 1 \ \ tt a n o \ • C tan t C ro ia I \ I N I ■ H a w n F if lt . M*m»M • L ai V a ^ ii At Piadtai Btanc. S a n iu ta O bitpA a In y o h n n ZONE 6 Edwards AF0 ZONE 3 S an ta M arta D tggtti S an d b v rg • Lompoc • V iciom il# • V ucca Vallay O n W M ug L rn A ngela* Civic C m l r t l o t A ngelas A upori CLIMATE AREA M A P Santa Ana ZONE • Iro n M ountain * T w rntym n* Pftltnd S a n B p tn ir d iflo lir e r s td tx I B a tc h ,) * P alm S p rin g * * Anaheim * 1 L iJ a i i i i 4 '* Sin V ic p n le tmpanat S«n Otago . Ja rre ll H r r ir & tf**9 * 0 n#am r * r d BEylhc • V vrtu Fig 6. 1. California climate map (analyzed cities shown by triangle) Niles., P.W .B., and K. Haggard, Passive Solar Handbook fo r California, California Energy Commission, 1980, p. 305. 89 Finally the thermal performance of the mobile home system was analyzed for different orientations to determine the site adaptation potential. 6.2. Analysis Results: Heating The thermal performance of the superinsulated system has revealed significant savings in annual heating loads in all of the four climate zones. Most of these savings are provided by the addition of the superinsulated envelope (Fig. 6.2.) The analysis results L.A. R1V.SIDE FRESNO C.LAKE CD Roof Pond Thermal Moss Superins. Envelope Fig. 6. 2. Annual heating reductions by system component. 90 3 demonstrate the dramatic reductions in annual heating loads by the superinsulated envelope improvements and the addition of water as thermal mass, as well as the remaining load to be met by roof pond heating. According to the analysis for the four climate zones, annual heating savings have ranged from 19.3 MBTUs ( $168.3 in annual heating bills) in Los Angeles to 29.1 MBTUs ( $218.2) in Fresno, as compared to the base case (Fig 6.3.). / BASE CASE SUPERINSULATED RIVERSIDE FRESNO C.LAKE Fig. 6. 3. Annual heating loads Similarly the peak loads have decreased significantly, resulting in reductions that ranged from 12 KBtu/h in Los Angeles to 16.7 KBtu/h in Riverside (Fig. 6.4.). As the building envelope is made tighter and thermal mass is added, the building becomes 9 1 / B A S E CASE SUPERIN5ULATED L.A. RIVERSIDE f r e s n o C.LAKE Fig. 6. 4. Peak heating loads extremely efficient in generating heat intrinsically and storing the heat within the thermal mass for use in early morning hours when the demand is largest. As a result, the peak heating loads needed to be handled by the roof pond system is lowered to 3.9 to 4.6 KBtu/h, which indicates that the ponds will be sized for cooling conditions. 6.3. Analysis Results: Cooling Under the cooling conditions, the system performed quite successfully compared to the base case. Even though the thermal savings from the cooling conditions could not be 92 compared to the heating load reductions, the economical savings become even more significant considering the price of electricity. As the step-by-step analysis is performed, the effectiveness of each system component is observed for the four climate zones (Fig. 6. 5.). The superinsulated envelope performed uniformly very well, reducing the annual cooling loads by about 40-50 % on the average. Night ventilation of thermal mass strategy was found to be quite effective also. However, it was observed that the total cooling load savings for some of the zones (Coastal Inlands) was far more than others (High Desert). After analyzing the weather data for Riverside, it was determined that the very high summer temperature swings (37°) that resulted in low night ambient temperatures has increased the 3 5 - ' 3 0 - ' #1 Night Vent, of Moss Super ins. Envelope □ Roof Pond Cooling L.A. RIV.S1DE FRESNO C.LAKE Fig. 6. 5. Annual cooling loads savings by system component 93 convective cooling capacity of the space. On the other hand, although the temperature swings are also high for the desert climate of China Lake, the absolute values for ambient temperature are consistently high with night time temperatures over 70 degrees, which prevents an effective cooling of the mass to create the heat sink for daily storage. The annual cooling load reductions have ranged from 20.9 MBTU to 31.5 MBTU which resulted in annual savings from $ 415 to $ 720 using electricity. It should be remembered again that the computer analysis is not able to analyze the savings resulting from the roof pond cooling. / BASE CASE SUPERINSULATEO RIVERSIDE FRESNO C.LAKE Fig. 6. 6. Annual cooling loads As the building envelope is made tighter and more resistive to ambient air and solar radiation, and thermal mass is added, the building becomes internal load dominated with the heat from occupants, lights and equipment accounting for the majority of the cooling load at the moment. As a result, a shift is observed from the early afternoon hours for the base case peak cooling load to the evening hours for the superinsulated system. In addition to this the peak loads are reduced dramatically, to yield 8.8 KBtu/h to 11.9 Btu/h (Fig. 6. 7). Since these loads are higher than the heating requirements, they will be used to determine the size of the roof pond. ^ B A S E CASE SUPERINSULATED L.A. RIVERSIDE FRESNO C.LAKE Fig. 6. 7. Peak cooling loads 95 6.4. Orientation In addition to being quite versatile for different climate zones, the superinsulated mobile home must perform equally well for various orientations. North-South, East- West and NE-SW orientations were simulated for each climate. Both under the heating and cooling conditions, insufficiently small annual load fluctuations of 0.03- 0.29 MBtu was observed due to changes in orientation (Fig. 6.8. and Fig 6.9.). E a s t-W e s l ^/NE-SW N o rth -S o u th L.A. RIVERSIDE FRESNO C.LAKE Fig. 6. 8. Annual heating loads for different orientations 96 3 7 / E ast-W esl / N E - S W N orfh-South L.A. RIVERSIDE FRESNO C.LAKE Fig. 6. 9. Annual cooling loads for different orientations 6. 5. Roof Pond Sizing To provide additional heating and cooling in relieving the remainder of the thermal loads, the depth of the roof pond system needs to be determined using a thermal analysis tool. Due to the fact that DOE2 computer simulation program is not able to model roof pond cooling unlike a few other commercially available hour-by-hour simulation tools, manual calculation methods needed to be used to determine the roof pond capacity. This is achieved by using a simplified algorithm developed by Fleishhacker, Bentley and Clark. [2] which has been verified by monitoring the prototypes built at Trinity University.[6] This model uses peak cooling loads, internal and external gains along with climatic characteristics to determine the minimum required pond depth. Using this algorithmic model, required roof pond depths are calculated for the four given cities, and the results are listed in Table 6.1. Although the depth required in Riverside and Los Angeles was less than 4 inches due to their smaller peak loads and lower minimum DB temperatures, the analysis for China Lake and Fresno showed less than desirable pond depths required to eliminate all auxiliary cooling. The system required the use of an electric fan stirring up the room at nights to reduce the pond depth to under 6 inches for these climate zones with high daily solar gain and high night temperatures. CITIES Depth without fan Depth with 115 fpm fan Los Angeles 3.57” 2.25” Riverside 3.71” 2.30” Fresno 9.80” 4.86” China Lake 11.40” 5.94” Table 6.1. Roof pond depths for various climates 98 The results of this analysis show that the roof pond system can be used to eliminate auxiliary cooling loads and that the depth of the pond could be kept under 6 inches with minor modifications for each climate. 6.6. Cost Analysis The results of the thermal performance analysis, along with the details of the system, needs to be stated in monetary terms to evaluate the meaning of this 100% passive system regarding potential savings in a low income housing type such as mobile homes. To achieve this goal, a simplified cost estimate is performed. This analysis was carried out using various sources [7-11] to determine the added initial cost of the superinsulated and roof pond systems. Specifically, cost estimate for the roof pond components proved to be an extremely difficult task, due to their limited commercial availability. To obtain information on these parts, a number of roof pond experts were contacted including the inventor of the system, Harold Hay, along with a number of factory-built home manufacturers who assisted in evaluating the cost aspects of the system’s application to manufactured housing. 99 After calculating the total cost of the system, the resultant savings of the system is evaluated which includes the annual energy savings and savings from not installing heating and cooling equipment. The annual savings were calculated using the thermal performance data and current unit prices provided by the Department of Water and Power and the Gas Company for the four cities. The estimate for the cost of the heating and cooling equipment was determined from manufacturers and other sources.[10] There have been a number of life cycle cost analyses for both superinsulation and roof pond systems as it compared to a conventional construction. [7,11,12] The results of these studies show that both systems have similar maintenance costs of passive and auxiliary systems in both short (15 years) and long terms (45 years) as well as similar replacement frequencies (12-20 years for both roof pond components and air conditioner compressors and furnaces). For this reason, a cost analysis showing the expected payback periods of the superinsulated mobile home systems was determined to be adequate. First, a study was conducted to determine the additional installation costs for superinsulated envelope systems using various sources.[4,9-ll] These costs include the most current labor and material costs within a range of reasonable estimate, and are provided in Table 6.2. on the following page. 1 0 0 Material Low Estimate ($) High Estimate ($) 2” additional batt for the walls 92 145 1.5” polyurethane wall insulation 546 585 3.5” additional batt for the floor 120 182 double pane windows (added cost) 275 315 wall air/vapor barriers 78 102 floor air/vapor barriers 50 79 caulking and sealing 145 175 air-to-air heat exchanger 395 475 Total 1731 2078 Table 6.2. Cost estimate for the superinsulated envelope According to this analysis, improvements within the thermal envelope will result in an initial installation cost of between US $ 1731 and 2078. It should be noted that the new building materials added to the existing mobile home as part of the superinsulated system have at least the same life span and replacement frequency of the existing design components. After this step, the overall additional cost of the roof pond heating and cooling system needs to be calculated. Provided cost estimates for roof pond components showed a greater degree of variation than superinsulated system, due to the problems with commercial availability of components, rarity of roof pond houses and differences of 101 opinion on which materials to use for the system. Values provided by the Rockwell International to the DOE, [8] original and post-retrofit Atascadero House Project [12] and information from current standards [9] are all integrated to give a low and high estimate for the cost of the system. According to this estimates, the total cost of the roof pond system with mechanized controls is between $ 3562 and 4196 (see Table 6.3. on the following page) . Since this figure is the cost of the whole roof including the structural members, the comparative cost of the exiting base case roof needs to be subtracted from this value. The estimated cost of the typical base case roof, including metal or wood trusses or structural beams, gypsum board ceiling, R-13 insulation within the roof structure and exterior waterproofing and roof sheets are estimated to be between $ 1480-1775. Therefore the additional cost of the roof pond system is only $ 2082 with a conservative, and $ 2421 with a generous estimate . When the total cost of the integrated system of superinsulated envelope and the roof pond system is combined, it is observed that the total additional cost of the passively heated and cooled system falls within the range of US $ 3803- 4499. The cost of the additional lateral bracing system required to support the 20 to 30 psf of roof load is calculated to be around U.S. $ 1200-1400,[8,10,14] which brings the total initial added cost of the unit to $ 5103- 5799. 1 0 2 Component Low Estimate ($) High Estimate ($) Insulation panels , including channels 513 611 Liner (polyethylene) 138 197 Water containing bags (polyethylene) 825 880 Metal deck, 2.5” deep - 18 gage 635 715 Channel beams 85 95 Tracks and wheels 375 405 Seals and thermal breaks 135 170 Automated system ( including motor, chains and sensors) 675 890 Metal support brackets 190 230 Annual operation cost 1 3 Total 3562 4196 Table 6.3. Cost estimate for the roof pond system Since this is a 100 % passive design with no auxiliary heating and cooling requirements, the savings from installing a furnace and an airconditioner unit is to be deducted from this total cost. The average price of a small furnace ranges from $ 635- 820 depending on efficiency, whereas the unit air conditioners and evapoerative coolers typically used in mobile homes are within $ 440-720. When these costs are subtracted, 103 the net overall installation cost of the passive system in comparison to a typical mobile home is determined to be between $ 3928-4259. As a final step in determining the resultant energy savings from the design of the passive system and the payback periods corresponding to the above cost estimate, the cost of the saved fuel energy is calculated assuming a natural gas cost at $ 0.065 per therm (low income program rates from the Gas Company) and a furnace efficiency of 70%. The electricity cost for cooling energy (resistant) is estimated to be $ 0.085 per kWh for the low income savings program. The results are tabulated in Table 6.4.. Cities savings in heating ($) savings in cooling ($) payback period (in years) Los Angeles 182 494 5.9 - 6.4 yrs. Riverside 214 520 5.2 - 5.9. yrs. Fresno 277 574 4.5 - 5,1 yrs. China Lake 226 667 4.2 - 4.7 yrs. Table 6.4. Annual energy savings and payback periods. As seen from the table, the passive system has a payback period of less than seven years in all of the cities. The significance of this short payback period becomes more 104 pronounced when it is evaluated in the light of the surveys that study the homeowners approval of energy saving features that have similar payback periods. According to a study conducted by the University of North Carolina, [13] mobile homes were found to be the household type most likely to demand energy efficient features in new homes, with 100% of occupants agreeing on a 6 year payback period for energy saving features. 105 6.7. References [1] Micro-DOE2E Computer Simulation Program User’s Guide, ERG / Acrosoft Inemational, INC., Golden, CO, 1994 [2] Fleishhacker, P., et al., “ A Simple Verified Methodology for Design of Roof Pond Cooled Buildings,” Proceedings of the Seventh National Passive Solar Conference. ASES. 1982 [3] ASHRAE Handbook of Fundamentals 1981, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, Georgia, 1981 [4] Nisson N.N.D., Dutt G., The Superinsulated Home Book, John Wiley and Sons, New York, NY, 1985, p. 246. [5] Niles., P.W.B., and K. Haggard, Passive Solar Handbook for California, California Energy Commission, 1980, [6] Clark, G. et al., “ Validated Simulations of the Thermal Performance of Roof Pond Residences in U.S. Climates,” Final Report from the Trinity University to USDOE. Contract No. DE-ACCE03-79cs30201. 1985 [7] Hay, H.R., “ A Naturally Air Conditioned Building.” Skvtherm Processes and Engineering. Los Angeles, CA, 1975, p. 23. [8] Marlatt, W.P. et al., “ Roof Pond Systems,” A Report to the USDOE by Energy Systems Group. Rockwell International. Contract No. DE-AM03-76SF00700. 1984 [9] Kiley, M.P., and W.B. Morelle (editors), 1994 National Construction Estimator, 42nd Edition, Craftsman Book Company, CA, 1994, pp 223-245. [10] Sweet’s Group, Sweet’s General Building and Renovation Catalogue, McGraw- Hill, Inc., 1994 [11] Lenchek, T., C. Mattock, J.Raabe, Superinsulated Design and Construction, Van Nostrand Reinhold Co., New York, NY, 1987, p 164. [12] Hay., H.R. et al., “ Research Evaluation of a System of Natural Air- Conditioning,” A Report by California Polytechnic State University. HUD Contract No. H2026 R. 1975 106 [13] Burby, R. J,, and M.E. Marsden (editors), Energy and Housing:Consumer and Builder Perspectives, Oelgeschlager, Gunn &Hain, Publishers, Inc., Cambridge, MA, 1980 [14] Koenig, P., Prefabricated Systems Handbook, USC School of Architecture, 1979. 1 0 7 7. CONCLUSIONS AND RECOMMENDATIONS 7. 1. Conclusions After a review of the design development process, system constiuction details and the thermal performance analysis of the superinsulated mobile home, it is concluded that superinsulation can be applied to manufactured housing in hot, arid climates to yield significant energy savings in a passive system. The three main principles of superinsulation, namely higher insulation, airtightness and controlled ventilation with heat recovery, were successfully integrated into the existing framework of the manufactured homes industry with minor modifications. The combined exterior insulative sheathing and radiant barrier wall system increased the overall width of base case of the mobile home unit by 4 inches total. However, it is recognized that this width can be optimized depending on the climate and material costs, as well as desired room widths. The integration of the thermal roof pond system proved to be more complicated, however, due to the addition of extra weight and space requirements for the movable panels. These problems are solved by providing alternative movable insulation schemes, some of which required utilization of support brackets attached on-site or the 108 trellis structures. The original details from existing roof pond systems were also modified to yield a simpler, less expensive operation system. The thermal analysis predictions show dramatic reductions by the superinsulated envelope system in both annual heating and cooling loads to near zero levels. Significant reductions in peak loads ensured that a relatively shallow pond would be adequate to respond to the remaining thermal loads. Due to the superb performance of the superinsualtion components, annual energy savings directly related to the addition of the roof pond was limited. However, the real value of the addition of this fairly expensive roof system comes from the elimination of all auxiliary heating and cooling equipment (i.e. a furnace or an air conditioner/evaporative cooler), which is possible under state and federal codes and regualtions on manufactured housing. In summary, the resulting design is a 100 percent passive heating and cooling system which combines and balances the passive solar and conservation principles .The thermal analysis of the combined system proved to be very effective in reducing heating and cooling loads in all of the four hot, arid California climate zones. The system proved to be extremely versatile when analyzed for different orientations also, which is a crucial requirement for mobile homes. 109 In addition to the superb thermal performance and energy savings , the resulting unit has better indoor air quality (which is a major concern for manufactured housing) due to mechanical ventilation, better wind resistance due to added mass, and better seismic resistance due to extra care in resolving the lateral bracing system. However, on the down side, the durability of movable insulation panels and plastic bags exposed to exterior conditions is a concern. Although more durable polyetylene plastics have been developed in recent years and specified for use in this mobile home unit, and efforts have been made to protect the panels by aluminum foil or sheets, the success of these approaches will be better evaluated with time. 7.2. Recommendations for Further Research Although the predicted results of this system development proved to be quite successful, this research needs to be taken one step further by the construction and monitoring of a prototype u n it, which will contribute greatly to the assessment of actual thermal performance savings and cost effectiveness before mass production. Additionally there are some specific areas of research that fall within the scope of this thesis, that could result in useful and interesting findings. Some of these specific topics might include: 110 a. developing the details of a fixed insulation roof pond system which uses a pump to move the water above or below the insulation panels. Although additional cooling through water eveporation is not necessary for the climates analyzed, this wet pond system might eliminate some of the problems associated with movable insulation. A cost analysis to compare this system to the proposed movable insulation system will give a better evaluation for mass production. b. retrofitting leaky thermal envelopes using superinsulation principles, especially for mobile homes and other low income housing. c. evaluating the effects of energy savings from this passive heating and cooling system on mobile homes park and at the national level. d. investigating the possibility of adapting a solar water heater or a heat- pump water heater for further savings. e. developing a more detailed life cycle cost analysis for the prototype and cost and market analysis for mass production. f. monitoring a number of existing mobile home unit to determine the effects of occupant behavior and lifestyle habits on energy performance. ill INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films die text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. Hie quality of this reproduction is dependent upon the quality o f the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. A Bell & Howell Information Company 300 North Zeeb Road. Ann Arbor. M l 48106-1346 USA 313/761-4700 800/521-0600 UMI Number: 1376467 UMI Microform 1376467 Copyright 1995, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Statistical analysis of the damage to residential buildings in the Northridge earthquake

PDF

A statical analysis and structural performance of commercial buildings in the Northridge earthquake

PDF

Shading mask: a computer-based teaching tool for sun shading devices

PDF

An analysis of technical and liturgical aspects of lighting in sacred Christian spaces

PDF

A computational model of NMDA receptor dependent and independent long-term potentiation in hippocampal pyramidal neurons

PDF

Determine the optimum block type for use in Saudi Arabia

PDF

Fault tolerant characteristics of artificial neural network electronic hardware

PDF

A physiologic model of granulopoiesis

PDF

Comparison of evacuation and compression for cough assist

PDF

A thesis

PDF

The Hall Canyon pluton: implications for pluton emplacement and for the Mesozoic history of the west-central Panamint Mountains

PDF

A study of the solution crystallization of poly(ether ether ketone) using dynamic light scattering

PDF

The study of temporal variation of coda Q⁻¹ and scaling law of seismic spectrum associated with the 1992 Landers Earthquake sequence

PDF

The relationship between alcoholism and crime: autonomic and neurpsychological factors

PDF

A kinetic model of AMPA and NMDA receptors

PDF

An analysis of nonresponse in a sample of Americans 70 years of age and older in the longitudinal study on aging 1984-1990

PDF

The relationship between fatty acid composition of subcutaneous adipose tissue and the risk of proliferateive benign breast disease and breast cancer

PDF

Cross-cultural comparisons of long-term care practices: modifications to financing and delivery approaches in seven countries

PDF

Pulse oximetry failure rates

PDF

Respiratory system impedance at the resting breathing frequency range

Asset Metadata

Creator Keskinel, Soner (author)

Core Title Superinsulation applied to manufactured housing in hot, arid climates

School School of Architecture

Degree Master of Building Science

Degree Program Architecture

Degree Conferral Date 1995-08

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

Tag architecture,engineering, civil,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Schiler, Marc (committee chair), [illegible] (committee member), [Keng] (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c18-2171

Unique identifier UC11357429

Identifier 1376467.pdf (filename),usctheses-c18-2171 (legacy record id)

Legacy Identifier 1376467-0.pdf

Dmrecord 2171

Document Type Thesis

Rights Keskinel, Soner

Type texts

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

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA