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Comparison of four different types of prefab homes and a site-built home
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Content
COMPARISON OF PREFAB HOMES AND A SITE-BUILT HOME:
QUANTITATIVE EVALUATION OF FOUR DIFFERENT TYPES OF PREFAB
HOMES AND A SITE-BUILT HOME
by
Taehyun Kim
_______________________________________________________________
A Thesis Presented to the
FACULTY OF THE SCHOOL OF ARCHITECTURE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF BUILDING SCIENCE
August 2009
Copyright 2009 Taehyun Kim
ii
Dedication
I dedicate this thesis to my parents and my older brother, with love and
thanks for their support and encouragement.
iii
Acknowledgements
I would like to express my appreciation to the faculty of the Master of
Building Science program in the USC School of Architecture for their commitment
to this crucial field, and for the enthusiasm and dedication that they share with
graduate students. This thesis would not have been possible without the
knowledgeable feedback that I received from the faculty during my research process.
I want to thank my thesis committee members, Professor Douglas Noble,
Professor Marc Schiler, Professor Karen Kensek, and Professor Murray Milne. Their
advice and comments during the course of my research has been very helpful and I
am appreciative of their time and effort in reviewing this research.
Also, I am very grateful for the willingness of some of the prefab home
manufacturers to share information with me on their prefab homes, including
drawings, construction costs, and construction timelines of the prefab homes.
Finally, I am grateful to my parents for their continuous supported and
encouragement in my academic effort, without which this research would not have
been possible.
iv
Table of Contents
Dedication ii
Acknowledgements iii
List of Tables vi
List of Figures viii
Abstract xii
Keywords xiii
Chapter 1: Introduction to Prefab Homes 1
1.1. What are Prefab Homes? 1
1.2. Hypothesis Statement 4
1.3. Importance of Prefab Homes 4
1.4. Research Purpose of Prefab Homes and a Site-Built Homes 5
1.5. The Four Recognized Types of Prefab Homes 5
1.6. Study Boundaries 8
1.7. Deliverables 9
Chapter 2: Background of Prefab Homes 11
2.1. Background of Manufactured Homes 11
2.2. Background of Modular Homes 15
2.3. Background of Panelized Homes 21
2.4. Background of Pre-cut Homes 24
Chapter 3: Methods of Proposed Measures 27
3.1. Analysis of Energy Performance 27
3.2. Data Collection of Prefab Homes and Site-built Homes 31
Chapter 4: Construction Costs ($/sf) and Timelines of Prefab Homes and 32
Site-built Homes
4.1. Construction Costs ($/sf) and Timelines of Manufactured Homes 32
4.2. Construction Costs ($/sf) and Timelines of Modular Homes 37
4.3. Construction Costs ($/sf) and Timelines of Panelized Homes 52
4.4. Construction Costs ($/sf) and Timelines of Pre-cut Homes 59
4.5. Construction Costs ($/sf) and Timelines of Site-built Homes 63
4.6. Summary of Construction Costs ($/sf) and Timelines of Homes 64
v
Chapter 5: Energy Consumption (kBTU/sf/year) Comparison of Prefab Homes 67
in HEED
5.1. Overall Schemes of Energy Simulation in HEED 67
5.2. Energy Performance of the Energy Code Minimum Home from 68
HEED
5.3. Energy Performance of Manufactured Homes in HEED 69
5.4. Energy Performance of a Modular Home in HEED 72
5.5. Energy Performance of a Panelized Home in HEED 74
5.6. Energy Performance of Pre-cut Homes in HEED 75
5.7. Summary of Energy Consumption (kBTU/sf/year & $/sf/year) of 77
Prefab Homes in HEED
Chapter 6: Evaluation of Prefab Homes and a Site-built Home by Construction 79
Costs, Construction Timeline, and Energy Performance
6.1. Construction Cost Evaluation of Prefab Homes and a 79
Site-built Home
6.2. Construction Timeline Evaluation of Prefab Homes and a 80
Site-built Home
6.3. Energy Efficiency Evaluation of Prefab Homes and a 81
Site-built Home
Chapter 7: Conclusions 93
Chapter 8: Areas for Future Research 96
Bibliography 101
Appendix: Contacts and Addresses 104
vi
List of Tables
Table 1: Manufactured Home HUD Code Requirement for Insulation R-values 7
Table 2: Summary of Construction Costs of Prefab Homes and Site-built 64
Homes
Table 3: Summary of Construction Timeline of Prefab Homes and Site-built 66
Homes
Table 4: Chart of the Six Simulations 67
Table 5: Energy Consumption of the Fleetwood Festival II –Model 4563S 70
from HEED
Table 6: Energy Consumption of the Mt. Adams - #GE561F from HEED 71
Table 7: Energy Consumption of the Desert House Prototype from HEED 73
Table 8: Energy Consumption of the Plymouth from HEED 74
Table 9: Energy Consumption of the LV Home from HEED 75
Table 10: Energy Consumption of the it House from HEED 76
Table 11: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr 81
of Prefab Homes and a Site-built Home with Their Own HVAC Systems in
California Climate Zone 9
Table 12: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr 83
of Prefab Homes and a Site-built Home with Their Own HVAC Systems in
California Climate Zone 16
Table 13: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr 85
of All Homes with “Gas Furnace (0.93 AFUE) and Air Conditioner (13 SEER)”
in California Climate Zone 9
Table 14: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr 87
of All Homes with “Gas Furnace (0.93 AFUE) and Air Conditioner (13 SEER)”
in California Climate Zone 16
vii
Table 15: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr 89
of All Homes with “Heat Pump (7.7 HSPF and 13 SEER)” in California
Climate Zone 9
Table 16: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr 91
of All Homes with “Heat Pump (7.7 HSPF and 13 SEER)” in California
Climate Zone 16
viii
List of Figures
Figure 1: Dymaxion House Designed by Buckminster Fuller in 1929 2
Figure 2: A Prefab Home after World War II 3
Figure 3: Transporting a Manufactured Home 12
Figure 4: A Photo and Plan of Fleetwood Festival II – Model 4563 by 13
Fleetwood Manufactured Homes
Figure 5: A Photo of the Mt. Adams -#GE561F by Columbia Manufactured 14
Home
Figure 6: Construction Photos of a Modular Home 16
Figure 7: A Photo of Desert House Prototype by Marmol Radziner Prefab 17
Figure 8: A Photo of Hive Modular B-line Medium 001 by Hive Modular 18
Figure 9: A Photo of Z6 House by Livinghomes, Ray Kappe 19
Figure 10: Modules of Z6 House 20
Figure 11: Construction Photos of a Panelized Home 21
Figure 12: A Photo of Plymouth by Pacific Modern Homes 22
Figure 13: A Photo of Tilt-up Slab House 23
Figure 14: Transporting of Panels for a Pre-cut Home 24
Figure 15: A Photo of LV Home by Rocio Romero 25
Figure 16: A Photo of it House 26
Figure 17: Area of California Climate Zone 9 28
Figure 18: Degree Day (Base 65°F) of California Climate Zone 9 29
Figure 19: Area of California Climate Zone 16 29
Figure 20: Degree Day (Base 65°F) of California Climate Zone 16 30
ix
Figure 21: Graphics of the Fleetwood Festival II – Model 4563S by Fleetwood 33
Manufactured Homes
Figure 22: Graphics of the Mt. Adams - #GE561F by Columbia Manufactured 34
Homes
Figure 23: 3D Graphic of the Alpine – 1490SF by Factory Expo 35
Figure 24: Graphics of the Mini Home – 12 x 33 + Loft 36
Figure 25: Graphics of the Desert House Prototype by Marmol Radziner 38
Prefab
Figure 26: Graphics of the Hive Modular B-Line Medium 001 39
Figure 27: Graphics of the Hive Modular X-Line 001 40
Figure 28: Graphics of the Hive Modular X-Line 002 41
Figure 29: Elevations with Daylight and Shadow of the Z6 House by 42
Livinghomes, Ray Kappe
Figure 30: Graphics of the Z6 House by Livinghomes, Ray Kappe 43
Figure 31: Graphics of the Single Bar – Standard by RES4 45
Figure 32: Graphics of the 2-Bar of L Series by RES4 46
Figure 33: Graphics of the 2-Bar Slip of Double Wide Series by RES4 47
Figure 34: Graphics of the 3-Bar ‘T’ of T Series by RES4 48
Figure 35: Graphics of the 3-Bar Duplex of Triple Wide Series by RES4 49
Figure 36: Graphics of the 3-Bar Bridge of Z Series by RES4 50
Figure 37: Graphics of the WeeHouse - Large 51
Figure 38: Graphics of the Plymouth by Pacific Modern Homes, Inc. 53
Figure 39: Graphics of the Tilt-up Slab House 54
Figure 40: Graphics of the Cantilever House 55
x
Figure 41: Graphics of Cube 5 by H-haus 56
Figure 42: Graphics of the FlatPAK house 58
Figure 43: Graphics of the LV Home by Rocio Romero 59
Figure 44: Graphics of the it House 61
Figure 45: Graphics of the Young Residence 62
Figure 46: HEED Model of the Fleetwood Festival II –Model 4563S 69
Figure 47: Model of the Mt. Adams - #GE561F in HEED 71
Figure 48: Model of the Desert House Prototype in HEED 72
Figure 49: “Window, Door and Sunshade Design” in HEED 73
Figure 50: Model of the Plymouth in HEED 74
Figure 51: Model of the LV Home in HEED 75
Figure 52: Model of the it House in HEED 76
Figure 53: Bar Chart of Construction Costs of Prefab Homes and Site-built 79
Homes
Figure 54: Bar Chart of Construction Timeline of Prefab Homes and Site-built 80
Homes
Figure 55: Energy Performance of Each Home with its Own HVAC System in 82
California Climate Zone 9 from HEED
Figure 56: Energy Performance of Each Home with its Own HVAC System in 84
California Climate Zone 16 from HEED
Figure 57: Energy Performance of All Homes with “Gas Furnace (0.93 AFUE) 86
and Air Conditioner (13 SEER)” in California Climate Zone 9
Figure 58: Energy Performance of All Homes with “Gas Furnace (0.93 AFUE) 88
and Air Conditioner (13 SEER)” in California Climate Zone 16
xi
Figure 59: Energy Performance of All Homes with “Heat Pump (7.7 HSPF and 90
13 SEER)” in California Climate Zone 9
Figure 60: Energy Performance of All Homes with “Heat Pump (7.7 HSPF and 92
13 SEER)” in California Climate Zone 16
xii
Abstract
There are currently many prefab homes in the world. Prefab homes are
becoming more and more popular because of assumed advantages such as low price
and a short construction period, as well as their efficiency advantages in terms of
building science, such as energy efficiency, sustainable materials or methods, and so
on. This thesis used a list of criteria: energy efficiency, construction costs, and
construction timeline of prefab homes and a site-built home to help identify which
home might be preferred by people based on the results of the criteria. This thesis
provides a range of information on prefab homes that has been primarily gathered via
the internet and by contacting the creators of the individual homes. In addition, it
provides a comparison of the similarities and differences and case-study examples of
the four types of prefab homes: manufactured, modular, panelized, and pre-cut
homes. The major research point of this thesis is to evaluate and compare the energy
usage of four types of prefab homes and a site-built home because a key selling point
of prefab homes might be based on their energy efficiency. Furthermore, other useful
studies are cited to provide the construction costs and timeline of prefab homes and a
site-built home. Therefore, the energy performance of several prefab homes and a
site-built home were simulated by using the software, HEED, and then their energy
performance was shown and compared. Some prefab homes and site-built homes
were also researched for their total construction costs and timeline by contacting
their manufacturers and reviewing websites.
xiii
Keywords
Prefab homes, Energy efficiency, Manufactured homes, Modular homes,
Panelized homes, Pre-cut homes, Construction costs, Construction timelines, HEED
1
Chapter 1: Introduction to Prefab Homes
1.1. What are Prefab homes?
1.1.1. Definition of Prefab Homes
Prefab homes are “types of buildings that consist of several factory-built
components or units that are assembled on-site to complete the unit.”[1]
1.1.2. History of Prefab Homes
The first prefab home, known as a panelized house was sent from England to
Massachusetts in the 1600s[26]. Later, kit houses were created for miners during the
1849 Gold Rush in California[1]. House kits were being sold by the Aladdin
company in 1906[5]. Sears, Roebuck and Co. became well-known as a kit home
manufacturer in the early 1900s [5]. In this time period, people often preferred to
construct their homes in rural areas, at least in part due to the better transportation
opportunities offered by the newly-invented automobile. People sometimes preferred
kit homes to site-built homes because the kit homes could be mass-produced in a
factory, and easily transported to the building site [5]. Furthermore, the installing
electricity, wiring, pluming at a factory was cheaper than that on a building site[5].
Kit houses were popular as “vacation homes or beach bungalows” for the upwardly
mobile people[5]. Figure 1 shows “dymaxion house, a metal dome-shaped house
which was designed by Buckminster Fuller in 1929, and it could easily be taken
apart and shipped[26].
2
Figure 1: Dymaxion House Designed by Buckminster Fuller in 1929
http://www.good.is/post/a-timeline-of-prefab-history/
Prefab homes (especially mobile homes) gradually became more popular
during “World War II” because military personnel needed a lot of facilities as
accommodations. Following the war, mobile homes were introduced to supply
housing to military personnel[5]. An example of a prefab post-war home is on
display at the “Chiltern Open Air Museum” in England, and is shown in Figure 2. It
had a steel frame and was made with corrugated asbestos cement[1].
3
Figure 2: A Prefab Home after World War II
http://en.wikipedia.org/wiki/Prefabricated_buildings
Following WW II, the use of mobile homes expanded dramatically, to the
extent that mobile homes represented “15 % of the nation’s buildings” in the U.S. in
the 1960s. However, most of these homes were built without much thought being
given to their aesthetic appearance, due to rush to build new housing[26]. In 1976,
the U.S. federal government legislated against the
1
HUD code which designated
“manufactured homes,” as a type of prefab homes that was distinct from the previous
mobile homes. In this time period, the HUD code stipulated the required “heating,
1
U.S. Department of Housing and Urban Development Code refers to the federal
code applying manufactured homes
4
cooling, plumbing, electricity, structure, construction, fire safety, and energy
efficiency of the manufactured homes[5].” In 1994, the code was updated by the
government to include more numerous and higher standards[5]. Since the creation of
2
SIP panels that could be pre-cut and assembled, prefab homes have been an
interesting area for architects, who have been especially focused on the
transportation and ease of construction of prefab homes since the 2000s[5].
1.2. Hypothesis Statement
In this research project, four different types of prefab homes and a site-built
home are compared based on the following list of criteria: energy consumption
(kBTU/SF/year), construction cost ($/SF), and construction period. These criteria
might therefore be used by potential house buyers to support a purchase decision.
1.3. Importance of Prefab Homes
As they are built in a factory as well as on the building site, prefab homes are
less influenced than site-built homes by the weather conditions during the
construction process. This factor could reduce building times in some areas that
experience frequent rain or snow. In addition, prefab homes could be transported
from factories to other cities and installed. Furthermore, the modular characteristic of
2
Structural Insulated Panel
5
many prefab homes enables their formation in various shapes, such as “T,” “L,” or
“Z” shapes.
1.4. Research Purpose of Prefab Homes and a Site-Built Homes
This research is an important structuring of information for people who may
want to buy prefab houses, for students of architecture, or for architects who are
interested in specific information on prefab homes. In particular, the research results
in this thesis will show which prefab homes are the least expensive, both in terms of
construction costs and operating costs, and will discuss cases in which a prefab home
might be preferable to a site-built home based on the evaluation of the criteria. It is
points such as these that might be of the most interest to potential home buyers.
Therefore, after four different types of prefab homes and a site-built home are
compared, people would probably have an understanding of which type of home
would better for their specific situation. As such, people for whom money and time
is an overriding concern might benefit from the results of this research, though others
might give more value to other comparison criteria, such as the aesthetics, materials,
and durability of the homes.
1.5. The Four Recognized Different Types of Prefab Homes
Although this chapter explains short definitions of the four recognized
different types of prefab homes, further description is indicated in Chapter 2.
6
1.5.1. Manufactured Homes
Since June 15
th
, 1976 when the “HUD code” began to be applied to pre-
fabricated homes, homes entirely constructed in a factory have been referred to as
manufactured homes.
1.5.2. Modular Homes
Building sections with cabinets, plumbing, and almost everything required
for homes are built in a factory in compliance with state and local building codes.
1.5.3. Panelized Homes
Two-dimensional panels with doors, windows, and wiring are made in a
factory and are attached together on the building site in compliance with state and
local building codes.
1.5.4. Pre-cut Homes
Panels without any additional materials such as doors, windows, and wiring
are built in a factory, and are attached together on the building site in compliance
with state and local building codes.
1.5.5. Mobile Homes
Mobile homes (excluding the recreational vehicles referred to as “mobile
homes”) are homes that were built before June 15, 1976 using the same methods as
manufactured homes. Mobile homes received the designation of “manufactured
homes” on June 15, 1976, when the HUD code took effect [8]. Thus, people have
often incorrectly used the term, “Mobile Homes,” in this context since June 15, 1976.
7
1.5.6. A Difference Between “HUD Code and California Title 24”
The HUD code, a federal building energy code, applies only to manufactured
homes. Modular homes, panelized homes, and pre-cut homes are required to comply
with state and local building codes. The modular, panelized, and pre-cut homes that
were researched in this thesis followed the California Title 24 energy building code,
and were simulated in California climate zones 9 and 16.
Table 1: Manufactured Home HUD Code Requirement for Insulation R-values ; [22]
http://apps1.eere.energy.gov/consumer/your_home/designing_remodeling/index.cfm/
mytopic=10220
In the HUD code, California has been classified as being in zone 2 since 1994
[23]. As shown in Table 1, the two manufactured homes used for energy simulation
in this research, Fleetwood Festival II and Columbia Manufactured – GE 561F, are
required to achieve an R-value of 22 for the ceiling, an R-value of 13 for the walls,
and an R-value of 19 for the floors, because the homes are double-wide. On the other
hand, California Title 24 requires homes other than manufactured homes to have an
8
R-value of 19 for the ceiling, and an R-value of 13 for both the walls and the floors
[24]. These values become important in the energy simulation section of this thesis.
1.6. Study Boundaries
1.6.1. What exactly is in the domain of study?
Three criteria were used to compare prefab and site-built homes: energy
consumption (kBTU/sf/year) for two California climate zones, construction costs
($/sf), and construction timeline. As such, some prefab and site-built homes were
compared in this thesis based on these criteria.
1.6.2. What is NOT included in the domain of study?
There are a number of specific models of prefab homes that were not studied
and compared in this thesis. In addition, there are numerous criteria that could be
used for comparison other than the three standards used in this thesis, such as
aesthetics, size, surroundings, and stability, among others. Furthermore, factors such
as quality of materials, color, durability, and roof shape could also be criteria for
comparison among some buyers. In addition, although only HEED was used in this
research, there are numerous other energy tools that can be used, including Energy-
10, Energy-Pro, eQuest, Designbuilder and others. HEED was selected for use due to
time limitations, as well as for its advantage of being able to show the energy
performance of several homes on a single page. Similarly, more climate zones could
be considered to better understand the energy performance of prefab homes and a
site-built home, though only California climate zones 9 and 16 were selected in this
9
thesis. To have more data and make this research more definitive, many more prefab
homes and site-built homes than those studied in this thesis could be studied.
1.6.3. Why is that the boundary?
Time constraints on this research resulted in the selection of two climate
zones and 16 case studies to compare prefab homes and a site-built home. Two
California climate zones (9 and 16) will be used for energy-modeling in this thesis.
This research could be more definitive if the four types of prefab homes were
simulated in other climate zones, but calculation time is a constraint. It is also
prohibitively difficult to gather information on prefab homes from countries other
than the US. Thus, 2 manufactured homes, 1 modular home, 1 panelized home, and 2
pre-cut homes were simulated in HEED to compare their energy performance, and
construction costs and timeline for 4 manufactured homes, 5 modular homes, 5
panelized homes, 3 pre-cut homes, and 3 site-built homes were studied in this thesis.
For these reasons, this thesis cannot be considered definitive.
1.7. Deliverables
First of all, this thesis will indicate the definitions and the important
distinctions between the four different types of prefab homes. After some examples
of prefab homes are simulated in HEED to evaluate their energy performance, this
thesis will show which homes are potentially more energy efficient than other
homes. Furthermore, the construction costs and timelines of some prefab homes and
10
site-built homes will be examined, allowing architects and clients to understand
which choices have the lowest costs and/or the shortest construction time.
11
Chapter 2: Background of Prefab Homes
Below, case studies of prefab homes were compared based on how big they
are, and how many rooms they have, and where they are built. Only a few example
cases of each type were introduced to describe what they are. However, more cases
as well as these cases were researched for their construction costs and timeline in
further chapters.
2.1. Background of Manufactured Homes
2.1.1. Characteristics of Manufactured Homes
Manufactured homes are completed in a factory, in compliance with a federal
building code known as the HUD (“Housing and Urban Development”) code [3].
When manufactured homes are made in a factory, they are constructed on a “non-
removable steel chassis” [3]. They are then moved to their site to be installed using
their own wheels. They are temporarily installed on pads and piers on the building
site, usually lifting the wheels slightly off the ground.
12
Figure 3: Transporting a Manufactured Home
http://manufactured-
home.net/images/manufactured_homes/manufactured_homes_250x251.jpg
13
2.1.2. Case Studies of Manufactured Homes
1) Fleetwood Festival II – Model 4563S by Fleetwood Manufactured
Homes
Figure 4: A Photo and Plan of Fleetwood Festival II – Model 4563 by Fleetwood
Manufactured Homes
http://www.fleetwoodmanufacturedhomes.net/festival-ll/4563S.htm
14
This house is one of the manufactured homes made by Fleetwood
Manufactured Homes. Its outside dimensions are about 56’ in width and 26’8” in
length, giving it an area of about 1492 square feet. It has 3 bedrooms and 2
bathrooms and is available in California and Arizona. It is completely built in a
factory with electrical, mechanical, plumbing and all other additional materials
included, and then is temporarily installed on the site. This home type was used for
comparison in this thesis.
2) The Mt. Adams - #GE561F by Columbia Manufactured Home
Figure 5: A Photo of the Mt. Adams -#GE561F by Columbia Manufactured Home
http://www.columbiamfghomes.com/models/GE561F.htm
15
The Mt. Adams - #GE561F is one of the manufactured homes made by
Columbia Manufactured Homes. At 27’ in length and 56’ in width, it is similar in
size to the Fleetwood Festival II. It also has 3 bedrooms and 2 bathrooms. Though it
is made in factories that are located in Oregon and Washington, it is available not
only in Oregon and Washington but also in Northern California. When it is
completely made in a factory, customers can add options such as porch, extra room,
or a deck to its plan.
2.2. Background of Modular Homes
2.2.1. Characteristics of Modular Homes
All state, local, or regional building codes are applied to modular homes.
Each section of the home, such as living room, bedroom, bathroom, and kitchen, is
built in a factory[3]. The sections are then carried to the building site on truck beds
and are assembled together permanently [3]. Modular homes are sometimes slightly
cheaper than site-built homes [3].
16
Figure 6: Construction Photos of a Modular Home
http://www.marmolradzinerprefab.com/custom_prefab_homes.php
17
2.2.2. Case Studies of Modular Homes
1) Desert House Prototype by Marmol Radziner Prefab
Figure 7: A Photo of Desert House Prototype by Marmol Radziner Prefab
http://www.marmolradzinerprefab.com/prototype.html
This home is one of the custom prefab homes made by Marmol Radzinder
Prefab. It is comprised of four house modules with a total area of 2100 square feet
and six deck modules with a total area 2450 square feet. It has 2 bedrooms and 2
bathrooms, and it is located in Desert Hot Springs. Sections are built not only with
the plumbing, electrical, mechanical and cabinetry included, but also with interior
and exterior finishes applied in the factory[10]. This home was used for comparison
18
in this thesis. At the time of the writing of this thesis, this house is for sale for $1.85
million[14].
2) “Hive Modular B-line Medium 001” by Hive Modular
Figure 8: A Photo of Hive Modular B-line Medium 001 by Hive Modular
http://www.hivemodular.com/slideshow1.html
“Hive Modular B-line Medium 001” is one of the Hive Modular Products
made by Hive Modular. It is 2-story house with 3 bedrooms and 3 bathrooms. Its
overall dimensions are 56’ in length and 24’ 5” in width, so it has an area when
finished of 1780 square feet. This house is built with all sections finished in the
19
factory, including plumbing, countertops, electrical, mechanical, and any other
applied finishes.
3) Z6 House by Livinghomes, Ray Kappe
Figure 9: A Photo of Z6 House by Livinghomes, Ray Kappe
http://www.livinghomes.net/tour.html
“Z6 House” is the first Livinghome designed by Ray Kappe. As it is a
modular home, it is comprised of 11 modules, with 5 modules for the first floor, 5
modules for the second floor, and 1 module for the roof floor as shown in Figure 10.
20
Figure 10: Modules of Z6 House
http://www.aiatopten.org/hpb/grid2007.cfm?project_id=851§ion=16
It is a single-family residence, with an area of 2480 square feet. It is a 2-story house,
with 4 bedrooms and 2.5 bathrooms. It is located in Santa Monica, California. The
design concept of the Z6 House is based on the phrase “Six zeroes: zero waste, zero
energy, zero water, zero carbon, zero emissions, and zero ignorance”[11].
21
2.3. Background of Panelized Homes
2.3.1. Characteristics of Panelized Homes
Panelized homes must comply with all state, local, or regional building codes
[7]. Two-dimensional finished panels are built with doors, windows, and wiring
chassis in a factory, and assembled on the building site [7].
Figure 11: Construction Photos of a Panelized Home
http://buildyourfreehouse.com/panelized-homes.php
22
2.3.2. Case Studies of Panelized Homes
1) Plymouth by Pacific Modern Homes
Figure 12: A Photo of Plymouth by Pacific Modern Homes
http://www.pmhi.com/Plan-Plymouth.htm
Plymouth is one of the panelized homes made by Pacific Modern Homes. It
has an area of about 1613 square feet, with 3 bedrooms, 2 bathrooms, and 2 garages.
After wall panels for this home are made with windows and doors in a factory, they
can be assembled on-site by a team of 4 people, which must include one carpenter,
one carpenter’s apprentice, and two laborers. The Plymouth is then completed with
plumbing, roof trusses, and any other finishes.
23
2) Tilt-up Slab House
Figure 13: A Photo of Tilt-up Slab House
http://www.syndesisinc.com/arch/hess.html
This Tilt-up Slab House, Synthesis, was designed by David Hertz, and is
located in Venice, California [15]. It is 2-story residential building with 4 bedrooms,
3.5 bathrooms, and 2 garages. It is approximately 32’ in width and 80’ in length. One
aspect that makes it different from other prefab homes is that the Tilt-up Slab House
is comprised of concrete panels. 6 long concrete panels are used on the west side
wall.
24
2.4. Background of Pre-cut Homes
2.4.1. Characteristics of Pre-cut Homes
Pre-cut homes conform to state, local, or regional building codes [8]. In a
factory, panels which do not include doors, windows, and wiring chassis are made.
They are then assembled on the building site, with other materials and finishes.
Figure 14: Transporting of Panels for a Pre-cut Home
http://www.rocioromero.com/LVSeries/pdf/LVS_DESIGN.pdf
25
2.4.2. Case Studies of Pre-cut Homes
1) LV Homes by Rocio Romero
Figure 15: A Photo of LV Home by Rocio Romero
http://www.rocioromero.com/LVSeries/pdf/LV.pdf
A standard LV home is about 1190 square feet with 2 bedrooms and 2
bathrooms. As it is one of the pre-cut homes, there are not “predrilled holes for
plumbing, insulation, interior finished, and sill and top plates” in its wall panels
when they are made in a factory.[13] So, the wall panels are installed with electricity,
mechanical and any other finishes on the building site after they are transported to
the site.
26
2) it House
Figure 16: A Photo of it House
http://www.tkithouse.com/
The basic it House is 1,100 square feet with 2 bedrooms and 1 bathroom. As
it House is one of the pre-cut homes, every part of this home is pre-cut and pre-made
in a factory. For example, for it House, the structural frame is made with aluminum
and roof is made with panels in a factory, first. Then, each frame and panel is
installed on a building site. Overall the house is covered with glass as walls.
27
Chapter 3: Methods of Proposed Measures
3.1. Analysis of Energy Performance
3.1.1. Simulation Tool – HEED
The main tool used in this analysis is HEED, which calculates the energy
performance of a home meeting the energy code. A primary purpose of this thesis is
to understand the energy efficiency of several types of prefab homes and a typical
site-built home. Because HEED automatically simulates a typical site-built home
under the energy code it is useful when making comparisons with other homes. In
addition, HEED is a good tool for simulating and comparing several homes because
it shows the results of energy performance of several homes on a single page. The
version of HEED used is HEED 3.0 (Build 38, April 29, 2008), which is the latest
version of HEED (M. Murray, 2008).
In addition to HEED, the energy simulation tool used for this research, there
are other energy simulation tools including eQuest, Energy-Pro, Energy-10,
DesignBuilder, and others. However, these tools do not show the energy
performance of several schemes on a single page, and so HEED was chosen for this
research so that the energy performance of the four different types of prefab homes
and a site-built home could be viewed and compared easily. With more time, the use
of such other tools could be undertaken for future research.
3.1.2. Two Different Climate Zones
Most of the prefab and site-built homes researched in this thesis are built in
California, so two California climate zones are used in HEED in this thesis. The two
28
zones are climate zone 9 and 16. The first California climate zone chosen is
California climate zone 9, whose reference city is Los Angeles.
Figure 17: Area of California Climate Zone 9
http://www.pge.com/includes/docs/pdfs/about/edusafety/training/pec/toolbox/arch/cl
imate/california_climate_zone_09.pdf
As California climate zone 9 represents Los Angeles, it is the zone in
California with the highest population density. It is influenced both by coastal
weather and inland weather, so “the coastal wind brings cool and moist air, and the
inland wind brings hot and dry air.”[12] Overall, California climate zone 9 is hot in
the summer and does not usually experience frost in winter.
29
Figure 18: Degree Day (Base 65°F) of California Climate Zone 9
http://www.pge.com/includes/docs/pdfs/about/edusafety/training/pec/toolbox/arch/cl
imate/california_climate_zone_09.pdf
The second climate zone selected for this study is climate zone 16. California
climate zone 16 represents the city of Bishop.
Figure 19: Area of California Climate Zone 16
http://www.pge.com/includes/docs/pdfs/about/edusafety/training/pec/toolbox/arch/cl
imate/california_climate_zone_16.pdf
30
This climate zone 16 covers the largest area of all of the California climate zones (1
to 16), spanning from the Oregon Border to San Bernadino county.[12] As this
climate zone is a high, mountainous, and semi-arid area, it is mostly cold.
Figure 20: Degree Day (Base 65°F) of California Climate Zone 16
http://www.pge.com/includes/docs/pdfs/about/edusafety/training/pec/toolbox/arch/cl
imate/california_climate_zone_16.pdf
These two climate zones are substantially different from each other, and will
thus likely give noticeably different results in the HEED analysis.
31
3.2. Data Collection of Prefab Homes and Site-built Homes
3.2.1. Websites
Some of the fundamental information about prefab homes in this study is
collected from books and websites. However, the books and websites referred to
often do not have exact specifications, but provide an overall explanation of homes.
First of all, in order to simulate for energy performance, specifications and drawings
of homes are necessary. Furthermore, to compare construction costs ($/sf) and
timelines, the websites of prefab manufacturers are more useful than books, because
the websites of most companies these days provide substantial information about
their products. It is difficult to obtain specific information regarding construction
time and expense from books.
3.2.2. Contact with Manufacturers of Homes
On the other hand, there might not be sufficient information on the websites
of architectural companies to satisfy the list of criteria in this thesis. Websites of
architectural companies do not tend to show elevations of their houses, but usually
provide plans of the houses. In order to simulate energy performance precisely, the
elevations of homes and specifications such as the R-values of walls, floors, and
ceilings, U-factors and dimensions of windows, and overhang must be entered in
HEED. Some of that information was obtained by contacting the home
manufacturers via email or telephone.
32
Chapter 4: Construction Costs ($/sf) and Timelines of Prefab Homes
and Site-built Homes
For this chapter, specific prefab homes and site-built homes were researched
to determine their specific construction costs and timeline. These costs and
construction timelines were obtained by contacting the home manufacturers via
email or telephone. In addition, some information about construction costs and
timelines was obtained from manufacturers’ websites. Based on this information, the
total construction cost of each home was estimated in terms of $/sf as well as the
construction timeline for each including time in factory, and on the building site.
4.1. Construction Costs ($/sf) and Timelines of Manufactured Homes
4.1.1. Fleetwood Festival II – Model 4563S by Fleetwood Manufactured
Homes
According to the cost information on the Fleetwood Festival II – Model
4563S that was received from Mr. Wild, an employee of Fleetwood Manufactured
Homes, its retail price is $64,342. This includes the foundation ($15,000, about
$10/sf), awning, deck, and landscaping. There are other costs that must be added to
the retail price to arrive at the total price, including costs for setup ($6,000 to 8,000),
skirting ($2,000), and stairs ($1,200). Therefore, the total price of the home is about
$74,542, which is around $51/sf, when the setup fee is estimated as $7,000.
However, the total price does not include the transport fee, which is $3/mile/section,
because the transport fee varies according to the distance between the factory and the
33
site. The home requires less than 2 weeks of construction time in the factory and a
week on the building site.
Figure 21: Graphics of the Fleetwood Festival II – Model 4563S by Fleetwood
Manufactured Homes
http://www.fleetwoodmanufacturedhomes.net/festival-ll/4563S.htm
34
4.1.2. The Mt. Adams - #GE561F by Columbia Manufactured Homes
Figure 22: Graphics of the Mt. Adams - #GE561F by Columbia Manufactured
Homes
http://www.columbiamfghomes.com/models/GE561F.htm
35
The retail price of the Mt. Adams - #GE561F by Columbia Manufactured
Home (approximately 1,620 square feet) is $75,988 (around $47/sf), including all
costs other than the foundation cost, which is around $25,000 (approximately
$15/sf), according to an employee of Columbia Manufactured Homes. Therefore, the
home’s total cost, including retail price and foundation cost, is $100,988, which is
around $62/sf. In addition, a transport fee for 100 miles is included in the total cost;
the total transportation cost would vary depending on the final distance. In terms of
construction time, 4 and 1/2 weeks in the factory and 1 to 2 weeks on the building
site are required to complete the home.
4.1.3. Alpine – 1490SF by Factory Expo
Figure 23: 3D Graphic of the Alpine – 1490SF by Factory Expo
http://www.azchampion.com/Alpine.asp
36
Cost information about the Alpine – 1490 square foot by Factory Expo, was
not readily available, although there is fairly good information about the
specifications of the home on the home page of Factory Expo. I was only able to
learn the total cost of the home, $71,711, which includes costs such as foundation,
setting, and other supplements from an employee of Factory Expo. The construction
time for the home usually involves 4 weeks in the factory and 2 weeks on the
building site.
4.1.4 Mini Home – 12 x 33 + Loft
Figure 24: Graphics of the Mini Home – 12 x 33 + Loft
http://sustain.ca/category/park-models/
37
Mini Home makes various models, including “12 x 33 + Loft,” “miniHome
SOLO,” “SOLO SE,” and others. The purchase prices for homes made by Mini
Home start from $200/sf. Including foundation cost (around $10/sf), shipping fee,
and miscellaneous costs, the total price of the “12 x 33 + Loft” chosen for this thesis
is $149,900, which is approximately $260/sf based on a size of 576 square feet. The
home requires a construction period of 5 months in the factory and 1 month on the
building site.
4.2. Construction Costs ($/sf) and Timelines of Modular Homes
4.2.1. Desert House Prototype by Marmol Radziner Prefab
According to Ms. Day, an employee of Marmol Radziner Prefab, the Desert
House Prototype typically costs $50/sf for the foundation, $25/sf for delivery and
setting, $50/sf for the installation of finishes, $50/sf for mechanical and electrical,
$130/sf for materials, and $195$/sf for labor. This cost information only includes the
interior space of the home and does not include its deck space. Thus, the total cost
for the interior of the home is about $500/sf, which is $1,050,000 based on an
interior size of 2100 square feet, with a deck being an added expense. In addition, the
home’s transport fee is $8/mile/module and the home is composed of 10 modules.
For construction period, 3 months is required at the factory and 3 months on the
building site.
38
Figure 25: Graphics of the Desert House Prototype by Marmol Radziner Prefab
http://www.marmolradzinerprefab.com/prototype.html
39
4.2.2. Hive Modular
Figure 26: Graphics of the Hive Modular B-Line Medium 001
http://www.hivemodular.com/slideshow1.html
40
Figure 27: Graphics of the Hive Modular X-Line 001
http://www.hivemodular.com/slideshowb1.html
41
Figure 28: Graphics of the Hive Modular X-Line 002
http://www.hivemodular.com/slideshow3b.html
42
There are many modular series produced by Hive Modular, including B-line,
C-line, X-line, and M-line. On the website of Hive Modular, the Hive Modular
products are priced between $140 to $200/sf, depending on where they are built and
the choice of materials and needs. However, in California, Mr. Asmus of Hive
Modular priced the homes at $200 to 235/sf, on average. This price of $200 to 235/sf
includes the foundation ($25,000; which is about 14$/sf), finishes, labor, and other
additions. These costs could vary depending on the specific home, site, materials,
and other circumstances. The average construction timeline for the home is 16
weeks, with 10 to 12 weeks of work in the factory and 4 to 6 weeks on the building
site.
4.2.3. Livinghomes by Ray Kappe
Figure 29: Elevations with Daylight and Shadow of the Z6 House by Livinghomes,
Ray Kappe http://www.aia.org/aiaucmp/groups/aia/documents/pdf/aias077537.pdf
43
Figure 30: Graphics of the Z6 House by Livinghomes, Ray Kappe
http://www.aia.org/aiaucmp/groups/aia/documents/pdf/aias077537.pdf &
http://www.livinghomes.net/tour.html
44
On the website of Livinghomes, the costs of its products are listed as $180 to
$250/sf, which do not include “engineering, foundation, and other needs.”[16] Thus,
another $70 to 90/sf should be added, to represent “finishes, fixtures, appliances,
foundation, and miscellaneous needs.” These values generally reflect the costs not
only of the four standard homes, “RK1, RK2, RK4.1, and RK5.1,” by Ray Kappe,
but also the four, “KT1.1, KT1.2, KT1.3, and KT2” by Kieran Timberlake.
Representatively, all four standard homes by Ray Kappe have a base cost of $325/sf,
as they are built with LEED-silver level materials or better. Thus, the cost of
Livinghomes by Ray Kappe is $325/sf, though this could be higher if better materials
are used. The homes require a month of work in the factory and 5 months on the
building site.
4.2.4. The Modern Modular by Resolution: 4 Architecture
There are many modular plans designed by Resolution: 4 Architecture
(RES4). The various products of RES4 include Single Bar, L Series, T Series, Z
Series, Double Wide, Courtyard, and Triple Wide, and vary in the size and
arrangement of their modules. According to cost information obtained through email
contact with RES4, a typical RES4 prefab home with basic finishes has an average
factory cost of $125/sf, including engineering, cabinets, counters, plumbing fixtures,
and tiles, and average on-site wrap-up costs of $125/sf, which include the foundation
($25/sf), so its total average cost is about $250/sf. However, these are variable
depending on location, site conditions, materials, options, and class of construction.
45
RES4 usually requires 4 months in the factory and 4 months on the site to build their
products.
Figure 31: Graphics of the Single Bar – Standard by RES4
http://re4a.com/images/typologies/pdf/MM_I1.pdf
46
Figure 32: Graphics of the 2-Bar of L Series by RES4
http://re4a.com/images/typologies/pdf/MM_L1.pdf
47
Figure 33: Graphics of the 2-Bar Slip of Double Wide Series by RES4
http://re4a.com/images/typologies/pdf/MM_2w1.pdf
48
Figure 34: Graphics of the 3-Bar ‘T’ of T Series by RES4
http://re4a.com/images/typologies/pdf/MM_T1.pdf
49
Figure 35: Graphics of the 3-Bar Duplex of Triple Wide Series by RES4
http://re4a.com/images/typologies/pdf/MM_3w1.pdf
50
Figure 36: Graphics of the 3-Bar Bridge of Z Series by RES4
http://re4a.com/images/typologies/pdf/MM_Z1.pdf
51
4.2.5. WeeHouse - Large
Figure 37: Graphics of the WeeHouse - Large
http://weehouse.com/flash/SFWA_index.html#/2008/
The retail price of the WeeHouse-Large is $149,000, which is about $183/sf
based on a size of 812 square feet. Additional costs include $3,000 for installation,
$3,000 for crane rental, $6,000 for connection of electric, sewer and water, $28,000
(about $35/sf) for the foundation, and $10,000 for site landscaping. Thus, the total
52
cost for the home including the retail price and additional costs is around $149,000,
or $245/sf. These estimates, which were based on the assumption that the home
would be built in California, were provided by Ms. Gabler of WeeHouse. In addition,
a transport fee of $5/mile/truck to $7/mile/truck is required. The home is usually
completed in 7 to 8 months, including 6 weeks in the factory and 6 months on the
building site.
4.3. Construction Costs ($/sf) and Timelines of Panelized Homes
4.3.1. Plymouth by Pacific Modern Homes
According to a brochure from Pacific Modern Homes, the retail price of
Plymouth with 1613 square feet is $45,670, which does not include the foundation
($43,000 or around $27/sf), HVAC ($3,500), fireplace ($800), and labor ($50,000).
Specifically, the retail price consists of $7,200 for roofing, rough electrical and
plumbing, $3,560 for insulation and drywall, $4,700 for doors and interior trim,
garage doors, and paint, $15,240 for cabinets and countertops, and $14,970 for the
finishing of plumbing and electrical, appliances, and installed carpet and vinyl. Thus,
the total cost of Plymouth is about $143,557, or $89/sf. The required construction
period is 2 weeks at the factory and 2 months on the building site.
53
Figure 38: Graphics of the Plymouth by Pacific Modern Homes, Inc.
http://www.pmhi.com/Plan-Plymouth.htm
54
4.3.2. Tilt-up Slab House
Figure 39: Graphics of the Tilt-up Slab House
http://dogtownink.com/27/tilt-up-slab-house-david-hertz/
The costs required to construct a “Tilt-up Slab House” are not specifically
known, even by its company, Syndesis, Inc. There were not specific construction
costs of the home, but only the total budget required completing the home in a book,
Prefab, which was $270,000 in 2000; which was around $118/sf based on its floor
55
area of 2,295 square feet. [15] The required construction period was one month at the
factory and 6 months on the site.
4.3.3. Cantilever House
Figure 40: Graphics of the Cantilever House
http://www.andersonanderson.com/WebsiteAAA/Cantilever%20House.htm & [21]
Though Cantilever House by Peter Anderson is very well-known for its
peculiar vierendeel structure and architectural concept; however, its cost details are
56
not known. Peter Anderson has disclosed that the construction cost was $200/sf. The
home was completed in 3 months, only 2 weeks of which were spent in the factory.
4.3.4. Cube 5 by H-haus
Figure 41: Graphics of Cube 5 by H-haus
http://www.h-haus.com/Models/Details/Cube5.html
57
The base building package of the Cube 5 is $259,833, or about $124/sf. This
does not include the foundation cost of $28,861, which is about $14/sf as its floor
area is 2,100 square feet. Therefore, its total cost might be around $138/sf based on
the estimate from H-haus. In addition, there are numerous packages and options to
upgrade from the base building package, such as the “upgraded base building
package” for an additional $16,962, the “cultured stone package” for an additional
$21,102, the “solar panel and storage package” for an additional $10,506, and the
“terrace deck” for an additional $29,114.”[17] 10 weeks in the factory and 4 months
on the building site are required to construct the home.
4.3.5. FlatPAK house
As specific cost information is not available from FlatPAK house, I could
only refer to the retail price of FlatPAK houses, which is $200 to 300/sf. Although
the retail price includes “appliances, HVAC system, patio, and general contacting
services,” it does not include “site survey, building permits, septic system, soil test,
site work, and plumbing and electrical lines.”[18] This means that the total cost of
completing a FlatPAK prefab home is higher than the retail cost. As the construction
timeline for the FlatPAK house is not available, either, only the retail price is shown
in this thesis. Thus, the construction timeline for this house should be researched
more by future work.
58
Figure 42: Graphics of the FlatPAK House
http://www.flatpakhouse.com/
59
4.4. Construction Costs ($/sf) and Timelines of Pre-cut Homes
4.4.1. LV Home by Rocio Romero
Figure 43: Graphics of the LV Home by Rocio Romero
http://www.rocioromero.com/LVSeries/LV.htm & [15] (pp54-58)
The retail price of the base line of the LV series is $36,870, which does not
include additional costs such as foundation, labor, and finishes. According to
60
information obtained through the brochure and from Ms. Williams of LV Home, on
average the total cost of building an LV home is about $120/sf, including kit costs,
shipping, foundation, and finish costs. In the Midwestern United States it can be built
from between $100 to 120/sf, while in California as well as certain select areas on
the East Coast the average range is from $175 to 195/sf due to higher labor costs.
Thus, the total price might be around $212,750, or $185/sf in California. In addition,
the LV home’s transport fee is around $4/mile. 28 days are the minimum time to
deliver the home to the building site, and then 1 to 2 months of work is required on-
site.
4.4.2. it House
According to the it House website, the retail price for a basic package is
$125/sf. However, according to Mr. Koch of it House, the total budget required to
complete the house is $175/sf, including the foundation cost, which can range from
$14,500 to $41,000 depending on locations and site conditions. Taking the average
of the range, the foundation cost might be $27,750 or about $25/sf. Construction
takes about 8 weeks in a factory before delivery, and another 12 weeks on the
building site.
61
Figure 44: Graphics of the it House
http://www.tkithouse.com/
62
4.4.3. Young Residence
Figure 45: Graphics of the Young Residence
http://westandclear.com/2008/09/15/for-sale-wintersoles-young-residence/
63
According to the owner, Ms. Young, the foundation cost is $23,000, or
around $24/sf based on the home’s floor area of 950 square feet. The foundation cost
is included in the total cost to complete the house of $120,000 or $126/sf.[15] The
house required 4 months to assemble on site, and “total construction took
approximately 6 months.”[15]
4.5. Construction Costs ($/sf) and Timelines of Site-built Homes
4.5.1. Average in 2006
The average construction cost of a site-built home in 2006 was about $95/sf,
as determined by Mr. Whitacre et al. in a project called “Building Strategies Study:
single family homes”. This cost of $95/sf might vary according to size, location,
materials, and other factors. The average time required to complete a site-built home
was about 10 months.
4.5.2. House Plans - # 18 – 1036 – 1412 SF
According to the specific brochure of the home # 18 – 1036 – 1412 square
feet by House Plans, the home could be built in San Bernardino, California with a
budget of $131,519, or around $93/sf[19]. This total cost of $131,519 includes
$72,495 for materials, $57,190 for labor, and $1,834 for equipment[25]. Specifically,
$8,406 for foundation, $20,149 for rough carpentry, $7,926 for exterior finish,
$6,521 for interior wall finish, and $6,300 for roofing, flashing, and fascia are also
included in the total cost[25]. 6 months are required to build the home.
64
4.5.3. Standard 1 Story – 1600SF
According to Sayler Publications, Inc., the total cost ($/sf) of the “Standard 1
Story – 1600 square feet” will differ slightly depending on the frame structure used.
There are five examples given, with different frame structures. Based on the book,
“Residential Square Foot Building Costs – 2009 Edition” by Sayler Publications, Inc,
the cost is shown to be $122.2/sf for “wood siding on wood stud frame,” $130.6/sf
for “brick veneer on stud frame,” $121.5/sf for “stucco on stud frame,” $140.9/sf
with “brick, concrete block back-up,” and $127.9/sf with “concrete block.”[20] Thus,
by taking the average of five different structures, we can obtain a total home
construction cost of $128.62/sf.
4.6. Summary of Construction Costs ($/sf) and Timelines of Homes
Table 2: Summary of Construction Costs of Prefab Homes and Site-built Homes
Table 2 shows construction costs($/sf) of all prefab homes and site-built
homes studied in this research. With the exception of the Mini Home – 12 x 33
65
+Loft, manufactured homes and site-built homes tended to be cheaper than other
homes. Modular homes tended to be more expensive than other homes, with the
Desert House Prototype being the most expensive.
While the different specific costs each home were explained, due to the
challenge of finding the same list of specific costs between house models, such as
foundation, finishes, skirting, stairs, setting and other costs, only the total costs of all
homes were compared. In addition, for some of the homes researched the foundation
costs are shown separately in Table 2.
For some of the homes; i.e. Mini Home – 12 x 33 + Loft, H-haus, Flat PAK
house, and Livinghomes by Ray Kappe; costs were found on their manufacturers’
websites only, and thus since no one at the companies was contacted the total
construction costs may not be that reliable. Furthermore, costs quoted by
manufacturers are subject to change depending on the inclusion or exclusion of
various options, the quality of materials, environmental factors such as weather, and
differences in labor costs between cities or states.
Table 3 shows the construction timelines by number of months for all homes
studied, with construction time in the factory and on the building site described
separately. For some manufactured homes; Fleetwood Festival II, Factory Expo –
Alpine – 1490SF, and Columbia Manufactured – GE561F – 1620SF, on-site building
times were dramatically shorter than for the other homes studied. In addition, site-
built homes tended to be the slowest to complete. It should also be considered that all
66
construction timelines shown in Table 3 are subject to change depending on building
location and the possibility of weather-related delays.
Table 3: Summary of Construction Timeline of Prefab Homes and Site-built Homes
67
Chapter 5: Energy Consumption (kBTU/sf/year) of Prefab Homes in
HEED
5.1. Overall Schemes of Energy Simulation in HEED
First of all, the specific 6 prefab homes; “Fleetwood Festival II– Model
4563S,” “Columbia Manufactured - Mt. Adams - #GE561F,” “Desert House
Prototype,” “Plymouth,” “LV Home,” and “it House” were simulated in HEED with
their original HVAC systems in California climate zones 9 and 16. Then, in order to
compare with fair energy performance results, all were simulated with the “AFUE
93% gas furnace,” which is the HVAC system of “Desert House Prototype,” and
“Code Minimum Heat Pump (13 SEER and 7.7 HSPF),” which is the HVAC system
of “LV Home.” Thus, each prefab home was simulated 6 times with three different
HVAC systems and two California climate zones, 9 and 16 as shown in Table 4.
Six Simulations Climate
Zone
Results in
Chapter 6
Each home with its own HVAC system 9 6.3.1 – (1)
Each home with its own HVAC system 16 6.3.1 – (2)
All used Gas Furnace (.93AFUE) & A/C (13SEER) 9 6.3.2 – (1)
All used Gas Furnace (.93AFUE) & A/C (13SEER) 16 6.3.2 – (2)
All used Heat Pump (7.7HSPF & 13SEER) 9 6.3.3 – (1)
All used Heat Pump (7.7HSPF & 13SEER) 16 6.3.3 – (2)
Table 4: Chart of the Six Simulations
68
Except for the use of three different HVAC systems, each prefab home was
simulated using their own materials, such as insulation, window type, window frame,
and any other composing factors. In terms of the orientation, the side of each home
with the most windows was faced south because the orientation did not strongly
affect energy consumption of homes by HEED. That is, when orientation changed
south into north, east, or west in HEED, the results of energy consumption were
similar.
Note that a total of 6 houses were used to show as case studies for energy
performance because of two problems: (1) the drawings of some prefab homes were
not available from the companies, and (2) for the sake of consistency, the study was
limited to 1-story homes with an area of approximately 1,500 square feet.
5.2. Energy Performance of the Energy Code Minimum Home from HEED
HEED usually shows the energy performance of a typical home made with
the minimum materials required to meet energy code, in a specific climate zone. In
California climate zone 9, according to HEED, “aluminum without a thermal break
for a window frame, clear double pane Low-E glass for windows, current energy
code with heavy mass walls (R-2.44 wall, R-30 ceiling, and R-19 floor), slab on
grade carpeted for a foundation, and energy code minimum furnace (78% AFUE)
and air conditioner (13 SEER)” are selected for a single family residential with 1
story and 1500 square feet. Also, in California climate zone 16, “wood or vinyl
operable window for a window frame, clear double pane Low-E in wood or vinyl
69
frame (0.4 U-factor), current energy code insulation (R-21 wall, R-38 ceiling, and R-
19 floor), raised vented crawl space with ceramic tile over wood floors for floor
condition, and energy code minimum furnace (78% AFUE) and air conditioner (13
SEER)” are used for the single family residential house in HEED. In addition, indoor
temperature is set between 60 to 75 °F in both Climate zones 9 and 16. Based on
these options, since HEED follows the minimum energy code, HEED is
automatically setting and indicating that the energy consumption of a home in
California climate zone 9 was 33.64kBTU/sf/year, or $0.65/sf/year, while the home’s
energy consumption in California climate zone 16 was 53.94kBTU/sf/year, or
$0.89/sf/year.
5.3. Energy Performance of Manufactured Homes in HEED
5.3.1. Energy Performance of the Fleetwood Festival II– Model 4563S
Figure 46: HEED Model of the Fleetwood Festival II –Model 4563S
According to the specifications on the website of the Fleetwood
Manufactured Homes, “double pane low-e glass with 0.39 U-factor in wood or vinyl
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window frame, R-11 wall insulation, R-28 ceiling insulation, and R-11 floor
insulation, 2 x 4 wood studs with wood or vinyl siding, carpeted wood floors, 12”
overhang, and energy code minimum gas furnace (78% AFUE) and air conditioner
(13 SEER)” are usually used for the Fleetwood Festival II – Model 4563S. Table 5
shows the energy consumption of the home with its original HVAC system, “AFUE
93% gas furnace” which is installed in the Desert House Prototype, and “Code
Minimum Heat Pump (13 SEER and 7.7 HSPF),” which is installed in the LV Home
in California climate zones 9 and 16 in two units, kBTU/sf/year and $/sf/year.
California Climate
Zone 9
California Climate
Zone 6
kBTU/sf/year $/sf/year kBTU/sf/year $/sf/year
Gas Furnace (.78 AFUE) &
Air Conditioner (13SEER)
30.14 0.52 62.47 0.88
Gas Furnace (.93 AFUE) &
Air Conditioner (13 SEER)
28.53 0.50 55.80 0.80
Heat Pump (7.7 HSPF & 13
SEER)
23.74 0.57 44.68 1.77
Table 5: Energy Consumption of the Fleetwood Festival II –Model 4563S from
HEED
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5.3.2. Energy Performance of the Mt. Adams - #GE561F
Figure 47: Model of the Mt. Adams - #GE561F in HEED
The Mt. Adams - # GE561F is also a manufactured home, but uses better
materials than those used for the Fleetwood Festival II. “Energy star double pane
low-e glass with 0.39 U-factor in wood or vinyl window frame, R-13 wall insulation,
R-28 ceiling insulation, and R-22 floor insulation, 2 x 6 wood studs with wood or
vinyl siding, carpeted wood floors, 12” overhang, and energy code minimum gas
furnace (78% AFUE) and air conditioner (13 SEER)” are usually used in the Mt.
Adams - # GE561F. The home was run with three different types of HVAC systems
in California climate zones 9 and 16 in HEED. The energy performance of the home
is shown in Table 6.
California Climate
Zone 9
California Climate
Zone 6
kBTU/sf/year $/sf/year kBTU/sf/year $/sf/year
Gas Furnace (.78 AFUE) & Air Conditioner
(13SEER)
26.87 0.47 53.58 0.76
Gas Furnace (.93 AFUE) & Air Conditioner
(13 SEER)
25.59 0.46 48.13 0.69
Heat Pump (7.7 HSPF & 13 SEER) 21.79 0.51 39.05 1.48
Table 6: Energy Consumption of the Mt. Adams - #GE561F from HEED
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5.4. Energy Performance of a Modular Home in HEED
5.4.1. Energy Performance of the Desert House Prototype
Figure 48: Model of the Desert House Prototype in HEED
The Desert House Prototype has a steel frame for its basic wall structure with
“double pane low-e glass with 0.28 U-factor, R-19 wall insulation, R-38 ceiling
insulation, and R-38 floor insulation, and carpeted slab on grade as its foundation.”
Furthermore, the home has an overhang with varying dimensions, with west and
south overhang of around 3 feet, but no overhang on the north side because there is
no window. Even though the overhang is not shown in HEED as Figure 48, there is
an option to design window, door, and sunshades in HEED, so the overhang was
added as shown in Figure 49.
The home’s HVAC system is “Gas furnace with AFUE rating of 93% and 13
SEER-air conditioner,” which was applied to all of the prefab homes in the thesis for
their second simulation. Table 7 shows the home’s energy performance in two
climate zones.
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Figure 49: “Window, Door and Sunshade Design” in HEED
California Climate
Zone 9
California Climate
Zone 6
kBTU/sf/year $/sf/year kBTU/sf/year $/sf/year
Gas Furnace (.93 AFUE) &
Air Conditioner (13 SEER)
28.28 0.53 60.37 0.88
Gas Furnace (.93 AFUE) &
Air Conditioner (13 SEER)
28.28 0.53 60.37 0.88
Heat Pump (7.7 HSPF & 13
SEER)
23.04 0.52 48.12 2.14
Table 7: Energy Consumption of the Desert House Prototype from HEED
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5.5. Energy Performance of a Panelized Home in HEED
5.5.1. Energy Performance of the Plymouth
Figure 50: Model of the Plymouth in HEED
The home has “double pane low-e glass with 0.39 U-factor in wood or vinyl
window frame, R-13 wall insulation, R-30 ceiling insulation, and R-19 floor
insulation, 2 x 6 wood studs with wood or vinyl siding, slab on grade carpeted, 24”
overhang, and energy code minimum gas furnace (78% AFUE) and air conditioner
(13 SEER).” From HEED, Table 8 shows the energy consumption of the home first
with its HVAC system, next with the “AFUE 93% gas furnace” installed in the
“Desert House Prototype,” and finally with “Code Minimum Heat Pump (13 SEER
and 7.7 HSPF)” which is installed in the “LV Home.”
California Climate
Zone 9
California Climate
Zone 6
kBTU/sf/year $/sf/year kBTU/sf/year $/sf/year
Gas Furnace (.78 AFUE) & Air
Conditioner (13SEER)
25.04 0.41 62.89 0.86
Gas Furnace (.93 AFUE) & Air
Conditioner (13 SEER)
23.92 0.40 56.03 0.78
Heat Pump (7.7 HSPF & 13 SEER) 20.60 0.44 44.63 1.78
Table 8: Energy Consumption of the Plymouth from HEED
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5.6. Energy Performance of Pre-cut Homes in HEED
5.6.1. Energy Performance of the LV Home
Figure 51: Model of the LV Home in HEED
The LV Home differs from other prefab homes in that it has better insulation
(R-38 for walls, R-50 for ceiling, and R-19 for floor), and “code minimum heat
pump with 13 SEER and 7.7 HSPF.” In addition, “double pane low-e glass with 0.39
U-factor, 2 x 6 wood studs with wood or vinyl siding, and carpeted slab on grade”
are in place in the home. As the “code minimum heat pump with 13 SEER and 7.7
HSPF” is the home’s HVAC system, it was applied to all of the prefab homes that
were simulated in the thesis for the third simulation. Energy consumption of the
home in California climate zones 9 and 16 is indicated in Table 9.
California Climate
Zone 9
California Climate
Zone 6
kBTU/sf/year $/sf/year kBTU/sf/year $/sf/year
Heat Pump (7.7 HSPF & 13 SEER) 28.39 0.66 48.28 1.75
Gas Furnace (.93 AFUE) & Air
Conditioner (13 SEER)
31.44 0.62 57.41 0.84
Heat Pump (7.7 HSPF & 13 SEER) 28.39 0.66 48.28 1.75
Table 9: Energy Consumption of the LV Home from HEED
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5.6.2. Energy Performance of the it House
Figure 52: Model of the it House in HEED
“The low-e coating on solar ban 60 glass with 0.29 U-factor in wood or vinyl
window frame, R-28 wall insulation, R-28 ceiling insulation, and R-19 floor
insulation, 3.5” of polyisocyanurate, slab on grade over radiant barrier, and 3’
overhang” is the default configuration of the it House. Because an HVAC system is
optional for the home, there is no specific HVAC system in the it House, so “energy
code minimum gas furnace (78% AFUE) and air conditioner (13 SEER)” were
chosen as the original HVAC for the first simulation. Table 10 shows the energy
performance of the it House from HEED.
California Climate
Zone 9
California Climate
Zone 6
kBTU/sf/year $/sf/year kBTU/sf/year $/sf/year
Gas Furnace (.78 AFUE) & Air
Conditioner (13SEER)
33.08 0.64 71.62 1.00
Gas Furnace (.93 AFUE) & Air
Conditioner (13 SEER)
31.93 0.63 64.11 0.91
Heat Pump (7.7 HSPF & 13 SEER) 28.57 0.68 53.27 2.08
Table 10: Energy Consumption of the it House from HEED
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5.7. Summary of Energy Consumption (kBTU/sf/year & $/sf/year) of Prefab Homes
in HEED
This chapter showed the energy performance of six specific prefab homes in
terms of kBTU/sf/year and $/sf/year. Homes were compared using not only their
default HVAC systems but also using two other HVAC systems, the Gas Furnace
(.93AFUE) & Air Conditioner (13SEER), which is the HVAC system used in the
Desert House Prototype, and Heat Pump (7.7HSPF & 13SEER), which is the HVAC
system used in LV Home, in order to compare their energy consumption in the same
situation.
With the exception of the Desert House Prototype, most of the homes were
most energy efficient in terms of $/sf/year when simulated with the Gas Furnace
(.93AFUE) & Air Conditioner (13SEER) than when simulated with their default
HVAC systems. In this simulation, however, the LV Home was indicated as less
energy efficient in terms of kBTU/sf/year when using its default HVAC system
because its default HVAC system, an electrically-powered heat pump, requires less
energy than a gas furnace but has higher costs, due to the differences in cost between
electricity and gas use.
When simulated with the Heat Pump (7.7HSPF & 13SEER), all homes were
more energy efficient than with their default HVAC systems in terms of
kBTU/sf/year, but required more operating costs. In particular, in California climate
zone 16, which is primarily a cold area, the cost of operating the Heat Pump
(7.7HSPF & 13SEER) was much higher than in California climate zone 9, which is
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hot in summer and usually does not have frost in winter. This is because the
electrically-powered Heat Pump requires more energy for heating than for cooling.
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Chapter 6: Evaluation of Prefab Homes and a Site-built Home by
Construction Costs, Construction Timeline, and Energy
Performance
6.1. Construction Cost Evaluation of Prefab Homes and a Site-built Home
Figure 53: Bar Chart of Construction Costs of Prefab Homes and Site-built Homes
Overall, manufactured homes and site-built homes tended to be cheaper than
modular homes, panelized homes, and pre-cut homes. However, among the
manufactured homes, “Mini Home – 12 x 33 + Loft” was much more expensive than
the rest of the manufactured homes that were researched in the thesis. With the
exception of the “Mini Home – 12 x 33 + Loft,” manufactured homes seemed to be
the cheapest. On the other hand, modular homes seemed more expensive than other
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homes. On average, site-built homes had lower construction costs than modular
homes, panelized homes, and pre-cut homes. Particularly expensive was the “Desert
House Prototype,” which at $500/sf was about 10 times the cost of the two
manufactured homes, “Fleetwood Festival II – 1492SF” and “Factory Expo – Alpine
– 1490SF.” Figure 53 shows the construction costs of prefab homes and site-built
homes.
6.2. Construction Timeline Evaluation of Prefab Homes and a Site-built Home
Figure 54: Bar Chart of Construction Timeline of Prefab Homes and Site-built
Homes
Manufactured homes had a shorter timeline in terms of construction on the
building sites, because they are almost entirely built in factories. Overall, as
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manufactured homes had construction costs that were cheaper than other homes, they
tended to be built faster than other prefab homes and site-built homes. On average,
site-built homes seemed to have a slower construction timeline than prefab homes.
Even though the construction costs of site-built homes were cheaper than modular
homes, panelized homes, and pre-cut homes, as shown in the previous sub-chapter,
the site-built homes had a longer construction period than the modular homes,
panelized homes, and pre-cut homes. In addition, modular homes required a longer
construction time than other prefab homes, as they were more expensive. The
construction time of prefab homes and site-built homes is shown in Figure 54.
6.3. Energy Efficiency Evaluation of Prefab Homes and a Site-built Home
6.3.1. Energy Performance of Prefab Homes and a Site-built Home With
their own HVAC Systems
(1) California climate zone 9 : Each home with its own HVAC system
Site-built Manufactured Modular Panelized Pre-cut
Code
Minimum
Fleetwood
Festival II
Columbia
Manufactured
–GE 561F
Desert
House
Prototype
Plymouth LV Home it House
kBTU/sf/yr 33.64 30.14 26.87 28.28 25.04 28.39 33.08
$/sf/yr 0.65 0.52 0.47 0.53 0.41 0.66 0.64
Table 11: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr of
Prefab Homes and a Site-built Home with Their Own HVAC Systems in California
Climate Zone 9
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Figure 55: Energy Performance of Each Home with its Own HVAC System in
California Climate Zone 9 from HEED
83
Overall, most of the prefab homes that were simulated in the thesis showed
energy consumption of around 30kBTU/sf/year, except for “Plymouth,” which was
indicated as the most energy efficient in the first simulation. LV Home was shown to
be the least energy efficient in terms of $/sf/year because while the heat pump used
in LV Home uses less energy, it requires greater expense, as electrical energy is
more expensive than gas. The it House showed the most energy consumption in
terms of kBTU/sf/year among all houses except for the code minimum home. The
energy performance of prefab homes and the code minimum home with their own
HVAC systems in climate zone 9 is shown in Table 11 and Figure 55.
(2) California climate zone 16 : Each home with its own HVAC system
Site-built Manufactured Modular Panelized Pre-cut
Code
Minimum
Fleetwood
Festival II
Columbia
Manufactured
–GE 561F
Desert
House
Prototype
Plymouth LVHome it House
kBTU/sf/yr 53.94 62.47 53.58 60.37 62.89 48.28 71.62
$/sf/yr 0.79 0.88 0.76 0.88 0.86 1.75 1.00
Table 12: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr of
Prefab Homes and a Site-built Home with Their Own HVAC Systems in California
Climate Zone 16
Except for the “Columbia Manufactured - #GE 561F,” most prefab homes
showed more energy consumption than the code minimum home because their own
materials, such as insulation and many windows, were applied to HEED in
California climate zone 16, and these prefab homes might often be designed for other
climate zones with hot weather. LV Home showed more energy cost in terms of
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$/sf/year, though it showed less energy consumption than other homes. With the
prefab homes’ original HVAC systems, the energy performance of the prefab homes
and the code minimum home in California climate zone 16 are shown in Table 12
and Figure 56.
Figure 56: Energy Performance of Each Home with its Own HVAC System in
California Climate Zone 16 from HEED
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6.3.2. Energy Performance of All Homes with “Gas Furnace(0.93 AFUE)
and Air Conditioner(13 SEER)
(1) California climate zone 9 : All homes used “Gas Furnace(0.93
AFUE) and Air Conditioner(13 SEER)
Site-built Manufactured Modular Panelized Pre-cut
Code
Minimum
Fleetwood
Festival II
Columbia
Manufactured
–GE 561F
Desert
House
Prototype
Plymouth LVHome it House
kBTU/sf/yr 33.64 28.53 25.59 28.28 23.92 31.44 31.93
$/sf/yr 0.65 0.50 0.46 0.53 0.40 0.62 0.63
Table 13: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr of All
Homes with “Gas Furnace (0.93 AFUE) and Air Conditioner (13 SEER)” in
California Climate Zone 9
In this simulation, most of the homes were more energy efficient than the
ones used in the first simulation because the “Gas furnace .93 AFUE” uses less
energy than the “Gas furnace .78 AFUE,” which was applied to two manufactured
homes, the Plymouth, and it House. Interestingly, LV Home showed
31.44kBTU/sf/year in this simulation, which was lower energy efficiency than
28.39kBTU/sf/year in the simulation, 6.3.1-(1), However, at 0.62$/sf/year, LV Home
had a lower energy cost with the Gas furnace than the cost of 0.66$/sf/year shown in
the first simulation, in which LV Home used its default HVAC system, a heat pump,
because while a gas furnace requires more energy than the electrically-powered heat
pump, it costs less to operate. Table 13 and Figure 57 show the results of the energy
consumption simulation of all homes with the 93% AFUE Gas Furnace and the 13
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SEER Air Conditioner in California climate zone 9, in terms of kBTU/sf/year and
$/sf/year.
Figure 57: Energy Performance of All Homes with “Gas Furnace (0.93 AFUE) and
Air Conditioner (13 SEER)” in California Climate Zone 9
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(2) California climate zone 16 : All homes used “Gas Furnace(0.93
AFUE) and Air Conditioner(13 SEER)
Site-built Manufactured Modular Panelized Pre-cut
Code
Minimum
Fleetwood
Festival II
Columbia
Manufactured
–GE 561F
Desert
House
Prototype
Plymouth LVHome it House
kBTU/sf/yr 53.94 55.80 48.13 60.37 56.03 57.41 64.11
$/sf/yr 0.79 0.80 0.69 0,88 0.78 0.84 0.91
Table 14: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr of All
Homes with “Gas Furnace (0.93 AFUE) and Air Conditioner (13 SEER)” in
California Climate Zone 16
Most prefab homes showed higher energy efficiency in this simulation that
all homes used the Gas Furnace with 0.93 AFUE than in the simulation, 6.3.1-(2)
that all homes used their own HVAC systems in zone 16, but still had more energy
consumption than the code minimum home in climate zone 16, with the exception of
the “Columbia Manufactured - #GE561F.” The energy consumption of the it House
was higher than all other homes, which may be due to the fact that the it House has a
much larger area for windows than other homes. The results of this simulation in
terms of kBTU/sf/year and $/sf/year are shown in Table 14 and Figure 58.
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Figure 58: Energy Performance of All Homes with “Gas Furnace (0.93 AFUE) and
Air Conditioner (13 SEER)” in California Climate Zone 16
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6.3.3. Energy Performance of All Homes with “Heat Pump (7.7 HSPF and
13 SEER)
(1) California climate zone 9 : All homes used “Heat Pump (7.7HSPF
and 13SEER)”
Site-built Manufactured Modular Panelized Pre-cut
Code
Minimum
Fleetwood
Festival II
Columbia
Manufactured
–GE 561F
Desert
House
Prototype
Plymouth LVHome it House
kBTU/sf/yr 33.64 23.74 21.79 23.04 20.60 28.39 28.57
$/sf/yr 0.65 0.57 0.51 0.52 0.44 0.66 0.68
Table 15: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr of All
Homes with “Heat Pump (7.7 HSPF and 13 SEER)” in California Climate Zone 9
Overall, except for the LV Home, for which the original HVAC system,
“code minimum heat pump with 13 SEER and 7.7 HSPF” was applied in the third
simulation, other prefab homes showed more energy efficiency in terms of
kBTU/sf/year than in previous simulations, 6.3.1-(1) and 6.3.2-(1) which were
performed in California climate zone 9. However, their energy costs in terms of
$/sf/year were more expensive in this simulation than in previous simulations, 6.3.1-
(1) and 6.3.2-(1). The energy performance of all homes with the heat pump in
California climate zone 9 is shown in Table 15 and Figure 59.
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Figure 59: Energy Performance of All Homes with “Heat Pump (7.7 HSPF and 13
SEER)” in California Climate Zone 9
91
(2) California climate zone 16 : All homes used “Heat Pump(7.7HSPF
and 13SEER)”
Site-built Manufactured Modular Panelized Pre-cut
Code
Minimum
Fleetwood
Festival II
Columbia
Manufactured
–GE 561F
Desert
House
Prototype
Plymouth LVHome it House
kBTU/sf/yr 53.94 44.68 39.05 48.12 44.63 48.28 53.27
$/sf/yr 0.79 1.77 1.48 2.14 1.78 1.75 2.08
Table 16: Energy Consumption Analysis in terms of kBTU/sf/yr and $/sf/yr of All
Homes with “Heat Pump (7.7 HSPF and 13 SEER)” in California Climate Zone 16
In this simulation, all of the prefab homes with the heat pump seemed to be
more energy efficient in terms of kBTU/sf/year than the code minimum home, but
required more costs for energy consumption in terms of $/sf/year than the code
minimum home. Even though the “Columbia Manufactured - #GE561F” showed
substantially better energy efficiency in terms of kBTU/sf/year than the code
minimum home, its energy cost was about twice that of the code minimum home.
The energy analysis of all homes with the heat pump in California climate zone 16 is
shown in Table 16 and Figure 60.
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Figure 60: Energy Performance of All Homes with “Heat Pump (7.7 HSPF and 13
SEER)” in California Climate Zone 16
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Chapter 7: Conclusions
In this research, the energy performance of 2 manufactured homes, 1 modular
home, 1 panelized home, and 2 pre-cut homes was simulated using HEED in two
different California climate zones for comparison. Furthermore, some specific data
was collected on prefab homes and site-built homes in terms of construction costs
and timeline.
Looking at the construction costs of prefab homes and site-built homes, the
manufactured homes studied tended to be cheaper than the other homes, with the
exception of the Mini Home – 12 x 33 + Loft, which was more expensive than all of
the panelized homes, pre-cut homes, and site-built homes in the research. In addition,
Table 7 and Figure 22 show that site-built homes are the second least expensive type
of home to construct. Of all home types researched, modular homes tended to be
most expensive. The Desert House Prototype, a modular home, was not only about 5
times more expensive than site-built homes, but was also much more expensive than
all of the other homes researched. According to Leo Marmol who is the president of
Marmol Radziner, the Desert House Prototype is much more expensive than other
homes because it was built with better finishes and it was a customized house.
Modular homes made by Marmol Radziner are typically custom homes; the company
does not churn out large numbers of similar modular homes. In addition, there are
many factors that influence building construction costs. Although the construction
costs of all homes studied in this research were based on the premise that the homes
were being built in California, the construction costs may vary if the homes are
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completed in other cities or states. In addition, construction costs could change
depending on the qualities of the materials, the options added, the work methods of
the constructors, the class of construction, and the distance of the site from the
factory, the weather conditions, and so on.
A general correspondence was found between the construction timelines of
homes and their construction costs, in that the homes with the lowest costs also have
the shortest construction time, with the exception of site-built homes, which require
the longest period of time to complete. In addition, manufactured homes require a
longer construction period in the factory than on the building site. On the other hand,
a longer construction period is required on the building site than in the factory for
panelized homes and pre-cut homes. Even though the construction timeline of all
homes studied in this research was collected through contact with the home
manufacturers and through their websites, the construction timelines could be subject
to change depending on weather conditions, time to contract, class of construction
such as standard or custom, and other factors.
In the overall comparison of energy consumption, the Plymouth, a panelized
home, was the most energy efficient in California climate zone 9, while the
Columbia manufactured - #GE561F, a manufactured home, used less energy than the
other homes in California climate zone 16. In addition, despite the fact that the
electric heat pump (7.7 HSPF and 13 SEER) for the LV Home’s HVAC system
required less energy than the gas furnaces, its operating costs were much higher than
those of the gas furnaces. This was particularly noticeable in California climate zone
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16, which is a mostly cold area, than in California climate zone 9, which is hot in
summer and usually does not have frost in winter, because the heat pump uses more
energy for heating than cooling. In addition, looking at the energy efficiency results
of all simulations in terms of $/sf/year, LV Home and it House, both of which are
pre-cut homes, tended to be less energy efficient than other homes in both of the
climate zones simulated. This lower energy efficiency could be due to the fact that
they have more window areas than the other homes simulated.
To learn about prefab homes and site built homes, this thesis researched the
construction costs, construction timelines, and energy efficiency of prefab homes and
site-built homes. Though the results obtained can hardly provide a definitive answer
regarding which type of home is cheaper, faster to build, or more energy efficient
than others, they could generally indicate that the manufactured homes tended to be
cheaper and faster to build than others.
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Chapter 8: Areas for Future Research
This thesis focused on the specific goal of evaluating the construction costs,
construction timeline, and energy consumption of prefab homes and a site-built
home. However, a comprehensive judgment of which type of home is the best for a
given situation would require a considerable amount of additional work, as more
criteria would be required in addition to the three used in this thesis. Though some of
the manufactured homes studied and the Plymouth might be preferred by some
buyers due to their low costs, short construction period and energy efficiency, buyers
for whom money and time is less of an object might choose other homes, based on
criteria such as aesthetics, size, surroundings, and stability, among others.
Similarly, if a buyer simply wants to have a huge house, he or she might not
care about the construction costs, and thus might prefer other homes to the Plymouth
or one of the manufactured homes.
The aesthetics of a home might be the most crucial factor for home choice.
Some of the homes studied in this research seem to have a very simple box-style
design. In this sense, the Desert House Prototype, LV Home, it House, or another
home might be selected by people on the strength of their aesthetic appearance, even
though they are more expensive or less energy efficient than some of the
manufactured homes or the Plymouth.
Which of the materials used in homes could be a criterion for buyer
preference. The Desert House Prototype has a steel frame structure, which is more
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expensive to install than the wood structure that is typically used for manufactured
homes. This could be a factor influencing buyer preference.
Furthermore, the quality of materials might be a factor for selection. Buyers
for whom money is less of an object might want to use the best quality of materials
for their homes, despite the added expense.
The ability to customize a home might be crucial for home buyers. Although
customized homes might be more expensive than standard homes, i.e. the basic home
models sold by manufacturers, some buyers may wish to have a designed home that
is different from the standard homes. For example, the Desert House Prototype was
custom-built, and was the most expensive of the homes studied in this research. For
some buyers, such customization may be worth the expense.
On the other hand, for some buyers the number and type of fixtures and
appliances, such as furniture, cabinets, countertops, and so on, could be a factor
influencing selection. Some buyers may not wish to buy appliances separately when
buying a home, and would thus seek a home that includes furniture, countertops,
refrigerator, sofa, and even beds. Alternately, some buyers wish to purchase such
items separately.
The sustainability of a home could be a crucial criterion for comparison. For
example, the Z6 House studied in this research received a platinum rating from
LEED. Although this research did not consider the sustainability of prefab homes
and site-built homes, they could be studied with according to this criterion as a future
task.
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In areas subject to frequent typhoons or earthquakes, people might consider
durability of homes. For this reason, testing the durability of prefab homes and site-
built homes would be a part of future work.
Although land costs vary depending on locations, land costs and construction
costs studied in this research might be an important factor for some people to
consider. Land costs must also be paid by the home buyers when they want to buy
the land on which their homes are installed.
In addition to homes costs, some people might first check the roof type. Even
though roof shape could be considered part of a home’s aesthetic appearance, there
might be some buyers who specifically only like flat roofs rather than sloped roofs.
In addition, the type of lighting or floor used could be a criterion. Some buyers may
prefer fluorescent lamps, while others may prefer incandescent electric lamps. For
floors, some people might prefer carpet, while others might prefer a wood floor.
The colors of the interior and exterior surfaces of homes could be a selection
criterion for some buyers. Though there is a great deal of scope for painting most of
the houses studied, to a certain extent this issue relates to the characteristics of the
materials of the walls, because bricks are usually kind of red, and concrete is gray.
Some buyers might consider whether there is a fireplace in a home or not.
Nowadays, some houses do not have a real fireplace; in fact, some have an imitation
fireplace that has a heating function. As such, some buyers might prefer to use a real
fireplace.
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In addition to the comparison criteria stated above, there are other criteria that
might be considered by buyers when choosing a house.
To make this research more definitive, it is necessary to make comparable
lists of the specific construction costs of homes. However, the specific information
provided in the construction costs shown in this research is different in each case.
For example, the Fleetwood Festival II shows not only its total construction cost but
also some specific costs for setup, skirting, foundation, and stairs. However, the
Desert House Prototype does not show costs for setup, skirting, and stairs, but shows
different specific costs for materials, finish installation, pluming, and so on.
Therefore, as an aspect of future research it is suggested that the lists of specific
construction costs of all homes that were studied in this thesis could be expanded.
Also, due to the challenges of collecting cost information, this research shows
the foundation cost separately for some homes but not for all. In addition, only Flat
FAK house, a panelized home, does not show its construction timeline even though
its total construction cost is shown. This could also be an area for future work to
make this research more definitive.
In addition, there are many prefab homes and site-built homes other than
those researched for this thesis. Although this thesis determined that manufactured
homes tended to be cheaper and faster to complete than other homes, there might be
much more expensive manufactured homes that require a longer construction period.
Put another way, there might be cheaper modular homes with a shorter construction
100
period than the modular homes researched in this thesis. Furthermore, manufactured
homes in other states or countries might be much more expensive than other homes.
Finally, if the energy performance of the prefab homes in this thesis had been
simulated in climate zones other than California climate zones 9 and 16, they might
have shown different results in terms of energy consumption. As such, when
evaluating a home for use in other areas, there might be homes that are more energy-
efficient than the ones discussed in this research. The 6 prefab homes chosen for a
comparison energy performance are all residential buildings, with 1 story and around
1,500 square feet of space. Similarly, if homes with 2 or 3 stories, or a bigger or
smaller size than 1,500 square feet had been simulated for this research, they might
have shown different results in terms of energy performance. Also, the simulation of
more prefab homes than the 6 prefab homes used in this research could provide more
definitive results in terms of energy consumption. Moreover, to achieve more
accirate results in terms of energy performance, future work might require the use of
other energy simulating tools such as Energy-10, Energy-Pro, eQuest,
DesignBuilder, and software other than HEED. Simulations using other software
might give different results in terms of energy consumption.
Therefore, a truly definitive comparison of prefab homes and site-built homes
would require a much greater amount of research and analysis.
101
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Princeton Architectural Press.
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128-133.
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[1] Prefabricated building. (2009, May 6). In Wikipedia, the free encyclopedia.
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[26] Spunt, A. "A Timeline of Prefab History." GOOD Magazine,
http://www.good.is/post/a-timeline-of-prefab-history/ [Accessed May 18, 2009].
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104
Appendix: Contacts and Addresses
Will Wild
Caballero Ranch, LLC, Fleetwood Manufactured Homes
15300 S. Brand Blvd. Office, Mission Hills, CA 91345
Tel. 310-804-7323
Fax. 818-361-4952
RanchLLC@aol.com
Ken Rader
Vice President – Marketing, Pacific Modern Homes, Inc.
Tel. 916-685-9514
ken@pmhi.com
Andy R. Thomson
Sustain Design Studio
Tel. 888-301-6464
andy@sustain.ca
Lisa Day
Marketing Director
Marmol Radziner + Associates
www.marmol-radziner.com
12210 Nebraska Avenue, Los Angeles, CA 90025
Tel. 310- 826-6222
Fax. 310-826-6226
lisa@marmol-radziner.com
RESOLUTION: 4 ARCHITECTURE
150 west 28th Street Suite 1902, New York, New York, 10001
Tel. 212-675-9266
Fax. 212-206-0944
www.re4a.com
info@re4a.com
Betsy Gabler
Marketing and Business Development
Alchemy Architects
856 Raymond Avenue, Saint Paul, MN 55114
Web site: alchemyarch.com
Blog: http://alchemyarch.blogspot.com/
Tel. 651-647-6650
Fax. 651-646-1246
betsy@alchemyarch.com
105
Peter Anderson, FAIA
ANDERSON ANDERSON ARCHITECTURE
San Francisco Office
90 Tehama Street, San Francisco, CA 94105
Tel. 415-243-9500 ext 224
www.andersonanderson.com
peter@andersonanderson.com
David Randall Hertz F.A.I.A. LEED AP
S.E.A. Studio of Environmental Architecture
SYNDESIS/ SYNDECRETE®
1920 Olympic Blvd., Santa Monica, Ca. 90404
Tel. 310-829-9932
Fax. 310-829-5641
www.Studioea.com
www.syndesisinc.com
www.syndecrete.com
hertz@studioea.com
Columbia Manufactured
benson@gorge.net
Michael Young
mj13young@aol.com
Donna S. Williams
Sales Manager
Rocio Romero
PO Box 30, Perryville, MO 63775
Tel. 573-547-9078, ext. 104
Fax. 314-785-7117
sales@rocioromero.com
www.rocioromero.com
Alan Koch
Taalman Koch Architecture
2404 Wilshire Blvd #11F, Los Angeles, CA 90057
Tel. 213-380-1060
Fax. 213-3801260
alan@taalmankoch.com
Abstract (if available)
Abstract
There are currently many prefab homes in the world. Prefab homes are becoming more and more popular because of assumed advantages such as low price and a short construction period, as well as their efficiency advantages in terms of building science, such as energy efficiency, sustainable materials or methods, and so on. This thesis used a list of criteria: energy efficiency, construction costs, and construction timeline of prefab homes and a site-built home to help identify which home might be preferred by people based on the results of the criteria. This thesis provides a range of information on prefab homes that has been primarily gathered via the internet and by contacting the creators of the individual homes. In addition, it provides a comparison of the similarities and differences and case-study examples of the four types of prefab homes: manufactured, modular, panelized, and pre-cut homes. The major research point of this thesis is to evaluate and compare the energy usage of four types of prefab homes and a site-built home because a key selling point of prefab homes might be based on their energy efficiency. Furthermore, other useful studies are cited to provide the construction costs and timeline of prefab homes and a site-built home. Therefore, the energy performance of several prefab homes and a site-built home were simulated by using the software, HEED, and then their energy performance was shown and compared. Some prefab homes and site-built homes were also researched for their total construction costs and timeline by contacting their manufacturers and reviewing websites.
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Asset Metadata
Creator
Kim, Taehyun
(author)
Core Title
Comparison of four different types of prefab homes and a site-built home
School
School of Architecture
Degree
Master of Building Science
Degree Program
Building Science
Publication Date
05/27/2009
Defense Date
05/26/2009
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
construction costs,construction timelines,energy efficiency,HEED,manufactured homes,modular homes,OAI-PMH Harvest,panelized homes,pre-cut homes,prefab homes
Language
English
Contributor
Electronically uploaded by the author
(provenance)
Advisor
Noble, Douglas (
committee chair
), Kensek, Karen (
committee member
), Milne, Murray (
committee member
), Schiler, Marc (
committee member
)
Creator Email
taehyunk@usc.edu,USCarch@hotmail.com
Permanent Link (DOI)
https://doi.org/10.25549/usctheses-m2279
Unique identifier
UC1418300
Identifier
etd-Kim-2958 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-237513 (legacy record id),usctheses-m2279 (legacy record id)
Legacy Identifier
etd-Kim-2958.pdf
Dmrecord
237513
Document Type
Thesis
Rights
Kim, Taehyun
Type
texts
Source
University of Southern California
(contributing entity),
University of Southern California Dissertations and Theses
(collection)
Repository Name
Libraries, University of Southern California
Repository Location
Los Angeles, California
Repository Email
cisadmin@lib.usc.edu
Tags
construction costs
construction timelines
energy efficiency
HEED
manufactured homes
modular homes
panelized homes
pre-cut homes
prefab homes