Northwest Energy Efficient 

Manufactured Housing Program: 

High Performance Manufactured 

Home Prototyping and 

Construction Development

Tom Hewes and Brady Peeks

BA-PIRC

November 2013
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iii

Northwest Energy Efficient Manufactured Housing Program: 

High Performance Manufactured Home Prototyping and 

Construction Development

Prepared for:

The National Renewable Energy Laboratory

On behalf of the U.S. Department of Energy’s Building America Program

Office of Energy Efficiency and Renewable Energy

15013 Denver West Parkway

Golden, CO 80401

NREL Contract No. DE-AC36-08GO28308

Prepared by: 

Tom Hewes and Brady Peeks

Northwest Energy Works of the 

Building America Partnership for Improved Residential Construction

37368 Blue Heron Rd.

Corvallis, OR 97330

NREL Technical Monitor: Stacey Rothgeb

Prepared under Subcontract No. KNDJ-0-40339-03

November 2013
iv

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v

Contents

List of Figures ............................................................................................................................................vi

List of Tables ..............................................................................................................................................vi

Definitions..................................................................................................................................................vii

Acknowledgments ...................................................................................................................................viii

Executive Summary...................................................................................................................................ix

1 Introduction and Background............................................................................................................. 1

1.1 Mathematical Modeling—BEopt....................................................................................................3

2 Results of Prototyping the Measures................................................................................................. 5

2.1 Continuous Exterior Rigid Foam Wall Insulation..........................................................................5

2.2 Triple-Glazed Windows .................................................................................................................8

2.3 Improved Ceiling Thermal Performance......................................................................................11

2.4 Heating, Ventilation, and Air Conditioning System.....................................................................15

2.5 Domestic Hot Water System ........................................................................................................19

3 Discussion ..........................................................................................................................................22

4 Conclusions/Lessons Learned.........................................................................................................24

Bibliography ..............................................................................................................................................26

Appendix A: Outline of Construction Processes ..................................................................................28

Improved Attic Construction Practice ....................................................................................................28

Wall With Exterior Foam Sheathing Construction Practice...................................................................30

Triple-Pane Window Installation Practice..............................................................................................31

Ductless Mini-Split Heat Pump Hybrid Electric Zonal Heating System................................................32
vi

List of Figures

Figure 1. BEopt V2.0 modeled annual consumption by end use ........................................................... 4

Figure 2. Wall cladding with exterior foam sheathing............................................................................. 6

Figure 3. Exterior foam installed ............................................................................................................... 7

Figure 4. Exterior foam-sheathed home after transport ......................................................................... 8

Figure 5. Flexible flashing window sill pan ............................................................................................ 10

Figure 6. Backer rod and caulking as secondary air seal..................................................................... 10

Figure 7. Sill pan for sliding glass door.................................................................................................. 11

Figure 8. Compressed R-38 batts with baffles at eaves........................................................................ 12

Figure 9. Transition to blown-in insulation for deeper attic cavity area ............................................. 13

Figure 10. Baffle retaining compressed loose-fill insulation near eave.............................................. 14

Figure 11. Core sampling of dense-packed insulation ......................................................................... 15

Figure 12. DHP indoor head mounted in main zone.............................................................................. 17

Figure 13. DHP compressor on end wall with indoor head on other side of wall—“up and in” 

installation........................................................................................................................................... 18

Figure 14. DHP mounting location integrated into home design......................................................... 18

Figure 15. HPWH screened inlet located in vented crawlspace........................................................... 20

Figure 16. HPWH modifications to allow fully ducted operation ......................................................... 21

Unless otherwise noted, all figures were created by Northwest Energy Works.

List of Tables

Table 1. Detailed HPMH Specifications..................................................................................................... 3

Table 2. DHP Installation Approaches .................................................................................................... 16

Table 3. Cellulose Loose Fill Insulation in Attic .................................................................................... 28

Table 4. Fiberglass Loose Fill Insulation in Attic .................................................................................. 28

Unless otherwise noted, all tables were created by Northwest Energy Works.
vii

Definitions

ACH Air changes per hour

BA-PIRC Building America Partnership for Improved Residential Construction

BPA Bonneville Power Administration

CFL Compact fluorescent lamp

cfm50 cubic feet per minute at 50 Pascals

DAPIA Design Approval Primary Inspection Agency

DHP Ductless heat pump

DHW Domestic hot water

EF Energy factor

ft2 Square foot

GE General Electric

gpd Gallons per day

gpm Gallons per minute

HPMH High performance manufactured home

HPWH Heat pump water heater

HVAC Heating, ventilation, and air conditioning

kW Kilowatt

kWh Kilowatt-hours

LED Light-emitting diode

MH Manufactured housing

NEEA Northwest Energy Efficiency Alliance

NEEM Northwest Energy Efficiency Manufactured Housing Program

NEW Northwest Energy Works

PNNL Pacific Northwest National Laboratory

RTF Regional Technical Forum

SEEM Seasonal Energy and Enthalpy Model

UES Unit Energy Savings

Uo U overall

W Watt

WSEP Washington State University Extension Energy Program
viii

Acknowledgments

We want to thank Eric Martin and the staff of the Florida Solar Energy Center’s (FSEC) 

Building America Partnership for Improved Residential Construction team who supported this 

project and who performed BEopt analysis for this project phase (especially David Beal of 

FSEC). Thanks also to Graham Parker and Sarah Widder at the Pacific Northwest National 

Laboratory, in addition to all the other project partners. The region’s manufactured housing 

(MH) industry is a key partner in this project. Northwest Energy Works (NEW) worked with 

many of the factories’ engineering, production, and quality management personnel to develop 

and test each measure proposed for inclusion in the new High Performance Manufactured 

Housing (HPMH) specifications. The majority of the DHP prototyping was done at Fleetwood of 

Oregon and Kit Homebuilders West. Industry partners included the following:

Champion Home Builders, Weiser, Idaho

Fleetwood Homes of Oregon, Woodburn, Oregon

Fleetwood Homes of Idaho, Nampa, Idaho

Golden West Homes, Albany, Oregon

Kit Homebuilders West, Caldwell, Idaho

Marlette Homes, Hermiston, Oregon

Nashua Homes of Idaho, Inc., Boise, Idaho 

Palm Harbor Homes, Millersburg, Oregon

Skyline Corporation, McMinnville, Oregon

Valley Manufactured Housing, Sunnyside, Washington.

Special thanks go to Mark Johnson and Sarah Moore at Bonneville Power Administration (BPA), 

and other regional utility partners in this project. BPA is an active partner in developing the new 

specifications and helping to bring other regional utilities to the table with the intent to develop a 

regional HPMH program. If and when the HPMH package begins to be included in new 

manufactured home construction, utility incentive funds will leverage this project’s efforts by 

bolstering consumer demand (or lowering manufacturer costs) for higher efficiency homes.

Special thanks to Jeff Pratt, president of The Heat Pump Store. The Heat Pump Store specializes 

in ductless heat pumps (DHPs), and its staff trained the factory personnel to install DHP zonal 

heating and cooling systems. 
ix

Executive Summary

The Building America Partnership for Improved Residential Construction, BPA, and NEW, the 

current Northwest Energy Efficient Manufactured Housing Program (NEEM) administrator, 

have been collaborating to conduct research on new specifications that would improve on the 

energy requirements of a NEEM home. In its role as administrator, NEW administers the 

technical specs, performs research and engineering analysis, implements ongoing construction 

quality management procedures, and maintains a central database with home tracking. 

This project is the second phase of a larger effort to develop a package of readily deployable 

measures able to reduce energy used for space conditioning, water heating and lighting by 50%

over typical manufactured homes produced in the Northwest. The project’s first phase worked 

directly with the MH industry to develop the measure specifications and perform energy 

modeling to confirm that the 50% energy savings target had been met. The modeling results were 

peer reviewed by the Northwest Power and Conservation Council’s Regional Technical Forum. 

The project, conducted with support from the Building America team, Partnership for Improved 

Residential Construction, produced a peer-reviewed Short Term Results report that describes the 

HPMH specification and energy modeling in detail. This project phase built upon that work by 

prototyping and assessing the performances of the HPMH-specified high performance building 

assemblies and mechanical systems that are not commonly deployed in the MH setting.

This project explores in detail the technical feasibility of building the primary measures of the 

HPMH. The following basic technologies were prototyped in partnership with the industry:

• Shell modifications, including increasing insulation quantities in attics, floors, and walls 

and upgrading the efficiency of windows

• New wall assemblies with reduced thermal bridging (e.g., exterior rigid foam sheathing)

• New roofline designs and insulation strategies that allow for more insulation 

• Heating, ventilation, and air conditioning system modifications built around the use of a 

DHP with zoned supplemental heating in secondary zones 

• Domestic hot water modifications, primarily reliance on a heat pump water heater 

(HPWH) instead of traditional electric tank water heating.

These technologies and their applications are discussed at some length within the report, along 

with descriptions of prototyping with the industry and progress in securing design approvals for 

the proposed changes. The key lessons learned are:

1. The technologies being recommended for the HPMH are available and can be readily

deployed in the factory setting. An HPWH capable of ducting in its process air from 

outside and exhausting it to outside is not available yet for the domestic market.

2. Electric energy savings ranging from about 8,000 kWh/yr up to nearly 11,000 kWh/yr

over today’s regional baseline home can be expected from using the HPMH specification.
x

3. A prototype model home should be built at each of the nine manufacturing plants in the 

region. Prototyping a HPMH home with each manufacturer will encourage them and their 

retailers to take ownership throughout the process of formulating new specifications.

4. Prototyping whole HPMH homes will be necessary to accurately price the HPMH option.

The project’s research findings are proving useful to regional stakeholders, because they make 

possible discussions between regional utilities and the industry. The goal for those discussions 

will be to develop a workable model for regional utility collaboration that targets incentives 

upstream to home manufacturers in support of the HPMH.
1

1 Introduction and Background

This project represents the second phase of an effort supported by the Building America 

Partnership for Improved Residential Construction (BA-PIRC) to develop a new High 

Performance Manufactured Home (HPMH) specification, prove its feasibility through 

prototyping of individual measures, and support its adoption in the marketplace. The project 

team consists of Northwest Energy Works (NEW), working with the manufactured housing 

(MH) industry, the relevant in-plant primary inspection agencies, the plants’ design approval 

primary inspection agencies (DAPIA), retailers, industry associations, Florida Solar Energy 

Center, the Northwest Energy Efficiency Alliance’s (NEEA) NW Ductless Heat Pump Project, 

Pacific Northwest National Laboratory (PNNL), the Northwest Power and Conservation Council, 

Washington State University Extension Energy Program (WSEP), and regional utilities.

The project’s first phase progress report (Hewes and Peeks 2013) covered the project team’s

work with the MH industry in the Pacific Northwest region (Idaho, Montana, Oregon, and 

Washington) to develop the HPMH specification and obtain approval for its use as a measure in

utility energy efficiency programs. The project’s overall goal is to help the industry build homes

that incorporate a package of readily available and proven energy efficiency measures not 

currently being used in the MH industry. The potential annual savings for the HPMH are about

8,000–10,000 kWh for each home produced and sited, depending upon siting location. This 

represents potential annual energy savings of 50% over a typical baseline manufactured home 

produced today in the Pacific Northwest region. 

In this project’s specification development phase, the HPMH energy modeling, package cost and 

benefit/cost analysis was presented to the Regional Technical Forum (RTF) at its April 2012 and 

May 2012 meetings. The HPMH specifications and energy use modeling were reviewed by the 

RTF, and the body concurred with the project team’s findings. As analyzed using the RTF’s 

methodology, the HPMH constitutes a cost-effective measure package with benefit/cost ratios 

ranging from 1.8 to 2.5, depending upon climate zone. Consequently, the HPMH specification 

received Provisional Unit Energy Savings (UES) approval, with the requirement that research be 

performed to confirm that the heat pump water heater (HPWH)-crawlspace interaction modeling 

results hold up in real-world applications, especially in cold climates. Provisional UES approval 

makes it possible for Northwest utilities to develop incentives in support of the HPMH 

specification. The full presentations made by NEW and Ecotope can be found at the following 

links:

www.nwcouncil.org/energy/rtf/meetings/2012/04/HPMH_Proposal_v4.ppt

www.nwcouncil.org/energy/rtf/meetings/2012/05/HPMH_Proposal_20120515_v2a.ppt

The current prototyping project phase focused on building and installing five of the individual 

measures called for by the HPMH specification. Research involved assisting the plants with 

obtaining engineering approvals for the new construction methods. Before each measure was 

built, it had to be accepted by the plant’s DAPIA. Except for the exterior foam sheathing, it was 

the first time most of the construction methods or equipment were included online in the plants. 
2

The experiences of building the prototype measures into homes assisted the project team in 

developing the initial construction processes plants used to incorporate the measures in future 

homes.

Construction methods developed through this project might well be readily adopted as best 

practices in new and retrofit work. The measures developed for the HPMH specification also 

have appreciable applicability to existing manufactured homes, especially measures that affect a 

home’s structure and heating system.

The project team worked with manufacturers, DAPIAs, and in-plant primary inspection agencies 

to develop the specific details of how various measures included in the HPMH specification 

could be implemented. The details worked through included how to meet structural and other 

code requirements, optimize cost efficiency in implementing measures, and ensure consistent 

outcomes when installing the measures. 

The project team asked for volunteers from the MH industry to build prototypes of some of the 

equipment (e.g., ductless heat pump—DHP, and heat pump water heater—HPWH) and building 

materials such as foam sheathing and windows in a few of its new NEEM homes to ensure 

correct operation. NEW purchased materials or equipment in some cases, and the homebuyers

purchased equipment such as the DHP. Prototyping shell and mechanical innovations in the 

plants included drawing new details or floor plans and working with suppliers to gain access to 

new equipment and materials.

To gauge the reaction of the industry, NEW staff met regularly with key groups, such as state 

MH associations, to bring the industry up-to-date on measure development and prototyping 

progress with the different shell and mechanical systems measures. Positioning the HPMH

concept in Northwest markets was discussed with financial institutions, building code officials, 

and industry leaders at their quarterly association meetings.

The resultant HPMH specification was then analyzed using Seasonal Energy and Enthalpy 

Model (SEEM) for its energy savings and cost-effectiveness potential, and the energy modeling 

results were presented to the Northwest Power Conservation Council’s RTF. Electric energy 

savings ranging from about 8,000 kWh/yr up to nearly 11,000 kWh/yr over today’s regional 

baseline home are possible using the HPMH specification. Gaining RTF concurrence with costeffective energy savings attributable to the new specifications was a necessary step to permit the 

Bonneville Power Administration (BPA) and the region’s utilities to consider moving forward 

with developing a program around the HPMH.

The list of HPMH measures developed in the prior phase of this BA-PIRC project is included in 

Table 1, below. Table 1 compares current NEEM program requirements and the HPMH 

measures.
3

Table 1. Detailed HPMH Specifications

Component NEEM (Base) HPMH

Ceiling R-40 R-49 (R-45 net) 

Floor R-33 R-38

Wall R-21 R-26 (with R-5 foam)

Window U = 0.35 U = 0.22

Door R-5 R-5

Duct Leakage 6% of supply No ducts

Target Uo 0.054 0.040

Heating System Electric forced air furnace

DHP/electric residential 

hybrid zonal

Lighting 1.4 W/ft2 0.7 W/ft2 (almost all are 

CFL or LED)

Infiltration 0.25 ACH (natural) and cfm50

targets 0.21 ACH (natural)

Ventilation Whole-house fan, 32 W 

continuous (0.1 ACH added) HPWH (0.14 ACH added)

DHW (EF) 0.93 2.0 (HPWH)

Appliances and 

Miscellaneous

Standard refrigerator, 

ENERGY STAR® dishwasher

ENERGY STAR 

refrigerator and 

dishwasher/low-flow 

showerheads and faucet 

aerators

Notes: Uo, U overall (average hourly conductive heat loss for the building envelope on a ft2 basis); CFL, compact 

fluorescent lamp; LED, light-emitting diode; ACH, air changes per hour; cfm50, cubic feet per minute at 50 Pa; 

DHW, domestic hot water; EF, energy factor

1.1 Mathematical Modeling—BEopt

BEopt V2.0 was used to model energy savings of a two-section home, which is the most 

commonly built product in the region, including the HPMH specification energy features. 

Modeling was performed in accordance with the December 2012 Addendum to the Building 

America House Simulation Protocols of October 2010. The HPMH specification resulted in just 

under 29% savings over the Building America Benchmark in a western Washington state marine 

climate location. Figure 1 illustrates the BEopt-modeled energy consumption by end use.

Further investigation into how BEopt models the DHP hybrid heating system and the HPWH 

unit drawing air from the crawlspace is warranted, and future work on this project will explore 

the subject further. Also worthy of note is that the Building America Benchmark includes gasfueled space and water heating, which diminishes the apparent value of HPMH reductions in 

electricity use for these end uses in the home on a source fuel basis. The assumption that gas is 

available as the baseline fuel choice is not valid for many locations where manufactured homes 

typically are sited in the Pacific Northwest region. Smaller communities and rural areas—where 

manufactured homes constitute a larger percentage of the housing stock—often do not have 

natural gas infrastructure in place. Many homes being sited in existing manufactured home 

communities in larger towns also do not have gas available to them, as many communities
4

predate the arrival of gas to the area, and the cost to install gas is prohibitive to the community 

owners.

Figure 1. BEopt V2.0 modeled annual consumption by end use
5

2 Results of Prototyping the Measures

All of the shell improvements and energy-efficient mechanical technologies proposed for 

inclusion in the HPMH package are buildable with readily available equipment and materials, 

but they may require revisions to floor plans and/or factory construction processes. The project 

team focused its efforts on prototyping the five measures that involve the most significant 

changes to current practices in the plants. The following sections describe the measures, the 

construction processes developed by the project team, and the plants to implement the measures, 

the challenges faced during the prototyping process and the outcomes from the efforts. The 

research questions posed by the project team and the individual measures were prototyped and 

put through the design approval process for this project phase. Appendix A contains the full 

construction processes developed by the project team.

2.1 Continuous Exterior Rigid Foam Wall Insulation

New wall assemblies with reduced thermal bridging (e.g., exterior rigid foam sheathing, 

structural insulated panel construction, etc.) – Research questions: shear implications? Transport 

issues with lap siding being held off from sheathing? Would there be DAPIA engineering 

approval difficulties?

Through discussions with plant personnel, the project team determined that an improved wall 

assembly with exterior rigid foam sheathing added to reduce thermal bridging could be 

implemented with modest impact on plant production processes, provided that siding would be 

able to be installed directly over the foam using a nail gun. The project team worked with the Kit 

Homebuilders plant in Idaho to prototype this wall assembly. The project team assisted with any 

technical information needed to secure DAPIA engineering approvals before the prototype home 

was built (which did not prove to be an issue, as all materials were installed in accordance with 

manufacturer specifications), participated in the installation in the plant to develop appropriate 

job processes, and observed the home on site to assess any discernible problems that transport 

may have caused.

The project team supplied R-5 foam sheathing (3⁄4-in.-thick polyisocyanurate) for installation on 

the exterior walls of a single-section home. Members of the project team were on hand to 

monitor both the time implications for the added process and any potential impacts on building 

durability or insulation effectiveness. The team used the experience gained from the prototyping 

exercise to develop initial work processes to guide installation of this measure.

The prototype home wall assembly consisted of 1⁄2-in. gypsum board on the interior, 2 × 6 stud 

walls on 16-in. centers, 1⁄2-in. oriented strand board sheathing, building wrap, 3⁄4-in. foam board 

sheathing, and 3⁄8-in. lapped siding. See Figure 2 for wall cladding detail. The Northwest plants’ 

home designs typically do not count upon the exterior cladding for shear strength, so adding 

exterior foam sheathing did not prove to alter the home’s structural design. 0.092-in. diameter by 

21⁄2-in. siding nails were used to fasten the siding to the framing through the foam. This is the 

longest fastener the plant was able to locate that was not also of a heavier gauge than its typical 

siding nail. Larger diameter fasteners are reported to cause unacceptable levels of damage to the 

siding during installation. The thicker 5/4-in. trim pieces were attached with larger fasteners, as 

this material is not adversely affected by thicker fasteners. Windows were installed outboard of 

the foam sheathing and sealed to the foam. Following this plant’s process, windows would be 
6

installed outboard of sheet good siding products and sealed to the siding, as currently is done by 

all plants with their conventional wall systems.

Figure 2. Wall cladding with exterior foam sheathing

The home selected for the prototyping exercise arguably constitutes a “worst case” test for how 

this insulation detail might impact the production line. First, a single-section home (most homes 

built in the Pacific Northwest region are multi-section) has the most exterior wall to be treated

per floor section, and any additional work required at this stage of construction has the potential

to hold up the production line. Second, the prototype home was of a modern design with tall 

sidewalls, and it had multiple changes in the wall plane for architectural detailing (see Figure 3). 
7

Figure 3. Exterior foam installed

The task of installing the rigid foam sheathing took about 6 person-hours for the entire home. 

The workers became significantly more proficient as the work progressed, and the project team 

estimates that the same work might be done in about 4 person-hours. Each section of a simple 

two-section home might be done in less than 2 hours, once workers become familiar with the 

process. The installation rate appears to vary directly in response to workers’ being allowed to 

waste some of the foam material. In the beginning of the installation process, the workers very 

carefully trimmed each piece of foam and utilized most of each sheet of material by carefully 

laying out cuts on the foam sheets. Each cut involved carrying foam over to a table saw, marking 

the cuts, sawing the foam, and returning to the home to install the cut piece. Later in the exercise, 

workers were instructed to install whole sheets of foam on the wall and trim it around window 

cutouts, which caused the installation rate to increase significantly. Waste increased, but the total 

amount of wasted material appeared to be acceptable, and there likely are opportunities to utilize

some of the foam elsewhere in the production process. Simpler home designs with fewer window 

openings very likely would result in less waste as well. The prototype home required 48, 4 × 8 ft. 

foam sheets.

Plant staff members expressed concerns about how the home would travel with foam between 

the siding and the wall framing. The prototype home traveled from Caldwell, Idaho to Eugene, 

Oregon—a trip of more than 400 miles. The project team went to see the home on site as it was 

being installed, and no sign of siding shifting or window movement was evident. Figure 4 shows 

the home being installed on site.
8

Figure 4. Exterior foam-sheathed home after transport

The project team also worked with another plant to explore how foam sheathing might be 

incorporated into its construction processes. The second plant found that the 21⁄2-in. length 

limitation for siding nails left insufficient nail penetration into the wall framing for the wall 

assembly to meet the siding manufacturer’s warranty requirements. The fastener supplier 

confirmed that longer nails were available only in heavier gauge fasteners. The solution for this 

plant may be to use 5⁄8-in. thick R-4 polyisocyanurate foam sheathing and look at other tradeoff 

opportunities in the home’s thermal package. 

2.2 Triple-Glazed Windows

High performance windows – Research questions: gas-filled dual pane versus triple pane. 

Transport implications for heavier units? What’s the best cost to performance point? 

Triple-pane R-5 vinyl windows are available in the Pacific Northwest. The company that 

currently supplies the majority of the region’s MH window market is not building R-5 windows.

Two window manufacturers supplying a minority of the region’s MH industry are producing R-5 

windows, though not in product lines currently purchased by the industry. Members of the MH 

industry expressed general concern about the increased cost and weight associated with triplepane windows, fearing that the heavier units might have a greater tendency to shift and get 

torqued out of square during transport and that the additional weight could push homes to where 

they require an additional axle to carry the home. 
9

The HPMH specification calls for triple-glazed low-e windows with a U-value of 0.22 or better. 

The leading supplier of the region’s MH window market (Kinro) is not building this grade of 

window, so the plants do not have access to windows that meet the HPMH specification. The 

project team was able to gain experience with installation of triple-glazed windows through its 

participation in PNNL’s Manufactured Home Laboratory research team. For one of the PNNL 

laboratory homes, Jeld-Wen built a complete set of triple-glazed low-e windows with an

improved foam-filled vinyl frame design with a U-value of 0.20. The project team was on hand 

for the installation of the windows and worked with the Jeld-Wen representatives to develop and 

implement a best practice installation of the windows that would be applicable to the factory 

setting. The windows were able to replace the existing window packages without significant 

design impacts in the PNNL laboratory home. 

The plants typically install sheet siding products and set the windows outboard of the siding, 

relying upon butyl putty or caulking to provide a weather-tight seal to the siding. Trim is 

installed to cover the window nail fins, and additional caulking between the trim and siding 

provides an additional barrier against water intrusion. The weight of the window is borne by 

fasteners through the nailing fins. 

The key differences in the window installation process developed by the Jeld-Wen factory 

representatives for the triple-glazed windows, compared to typical window installation 

procedures used by the plants, were that flexible flashing was used to create a window sill pan, in 

addition to the conventional sealing at the window nailing fins (see Figure 5), and the weight of 

the window was supported by shims placed between the window and sill. Backer rod and 

caulking were used to create an interior air seal, as can be seen in Figure 6. The plants’ present 

window installation processes rely solely upon sealing windows to the cladding at the nailing fin 

and supporting the weight of the window with fasteners installed into wall framing through the 

nailing fin. The Jeld-Wen representatives used a rigid pan flashing under sliding glass doors as a 

best practice that currently is not being done by the plants. Figure 7 shows the pan flashing in 

place, with flexible flashing being installed to create an end cap for the pan.
10

Figure 5. Flexible flashing window sill pan

Figure 6. Backer rod and caulking as secondary air seal
11

Figure 7. Sill pan for sliding glass door

2.3 Improved Ceiling Thermal Performance

Improved attic insulation strategies – Research questions: do changes to rooflines and trusses 

hold promise for improved ceiling insulation? Can new insulation approaches improve thermal 

performance with existing trusses? 

The project team’s discussions with industry personnel confirmed that improving attic thermal 

performance has limited opportunities without making major changes to the home construction 

process. Switching to trusses with greater heel heights often would result in taller home sections 

and cause transportation issues. New roof insulation strategies can achieve improvement to 

current practice without changing the roof trusses being used. The primary improvement that 

appears to be feasible for implementation involves increasing insulation levels in the eave area 

where limited attic depth prevents typical loose-fill insulation application from achieving

acceptable insulation levels. Compressing full-width R-38 fiberglass batts under baffles and 

dense packing loose-fill insulation under baffles could prove to be two low-cost, easily 

implemented strategies that offer higher R-values per inch of depth than today’s standard 

practice of using loose fill insulation exclusively. Another plant expressed interest in exploring 

the use of spray foam for its attic assemblies, but the change proved too expensive from both 

capital and product cost perspectives for them to implement at this time.

The target performance for the vaulted ceiling assembly is U = 0.026, which results from 

achieving an area-weighted average R-45 insulation value in the ceiling. The current standard 

reference assembly for the NEEM program is a nominal R-40 with a resulting U = 0.029 for 

vaulted ceilings insulated with loose-fill stabilized cellulose, based upon common rafter 

geometry that has a 51⁄4-in. heel height and a king post height of at least 17 in. The project team

prototyped and gathered cost-related data for changing the ceiling insulation details with trusses 
12

typically used by two plants—one using a truss with a heel dimension of 51⁄4 in., and the other 

using a truss with a heel dimension of 7 in.

The new roof insulation strategies for conventional trusses included using a 24-in. wide R-38

fiberglass batt in place of blown-in loose fill insulation in the area extending from the eave above 

the top wall plate—where the batt is compressed using a baffle but still has a higher R-value than 

loose fill fiberglass insulation—and inward for 4 ft (see Figure 8), where the attic depth is

sufficient to transition to blown-in insulation for the rest of the attic (see Figure 9). The full 

width batts effectively fill in between roof truss members to prevent insulation voids. The 

insulation baffles selected for this application have 1-in. wide side flanges that are stapled onto 

the truss top chords to create the required ventilation space, and they have a tail that is stapled 

onto the outer edge of the wall top plate to further stiffen the baffle against the compressed batt 

and prevent wind washing of the insulation. The batt and baffle installation took about 20 

person-minutes to complete a 40-ft long attic, and insulation blowing used 11⁄2 fewer bags of 

insulation per 10 ft of attic length. For the prototype home, this represented a 25% reduction in 

loose fill insulation and blowing time. Since the fiberglass batts and the baffles were purchased 

retail by NEW for the exercise, it is not possible to give an accurate measure of the full cost 

implications, but the detail likely adds about $140 to the cost to insulate a 40-ft long two-section 

home.

Figure 8. Compressed R-38 batts with baffles at eaves
13

Figure 9. Transition to blown-in insulation for deeper attic cavity area

The second attic assembly prototyped used dense-packed loose-fill insulation at the eave area. 

The same baffles that were used for the fiberglass batt detail proved to work effectively for this 

application. Dense packing insulation at the eaves can be used to improve the thermal 

performance of almost any attic system being insulated with loose-fill insulation where space is 

constrained near the eaves. 

For the dense packing prototype assembly the lower half of the roof assembly was blown with 

insulation. Then, baffles were installed at the eaves and secured to the truss top chords and wall 

top plate. Insulation from the area inboard from the baffle was then raked toward the eave and 

compressed into the cavity formed by the ceiling and the baffle. Afterward, additional insulation 

was blown in to fill the ceiling’s inboard area. Consistent density was obtained by pushing 

insulation into the cavity until the baffle bowed up in the center by nearly 1 in., after which the 

baffle was pushed downward until it returned to its flat position. Figure 10 shows a baffle in 

place. Core sampling from the dense-packed area (see Figure 11) showed the density of the 

fiberglass insulation to be a little more than 2.5 lb/ft3

, which yields approximately R-4.1/in. of 

thickness (compared to the manufacturer’s listed value of R-3.5/in. at 0.9 lb/ft3 installed 

density—an increase of 17%). Dense packing the eave area required approximately one extra 30-

lb bag of loose fill insulation per 10 ft of attic length.
14

Figure 10. Baffle retaining compressed loose-fill insulation near eave

The current loose-fill insulation practice being used at the plant where the prototyping exercise 

was performed often results in the eave areas being underinsulated. Much of the eave area 

typically is blown with greater than a 1-in. airspace, and core sampling indicated that insulation 

was being installed at less than the manufacturer’s required density. Weighed samples showed 

that insulation was being installed at 0.68 lb./ft3 versus the manufacturer’s specified minimum 

density of 0.9 lb./ft3

. The insulation density improved sufficiently in the roof areas where it was 

installed at greater depth. Consequently, the plant’s current process is causing approximately a 

25% reduction from the expected R-value of the insulation near the eaves.
15

Figure 11. Core sampling of dense-packed insulation

2.4 Heating, Ventilation, and Air Conditioning System

Ductless heat pumps with zonal heating in secondary zones – Research questions: can in-plant 

installation of DHP be reliably accomplished in a way that travels well to site? For all floor 

plans? One DHP or two? What type(s) of supplemental zonal heat are needed?

The hybrid zonal system eliminated the existing electric forced-air furnace and duct system from 

the home altogether, which allows for more floor insulation where the ductwork was located. A 

single DHP was connected to one or two indoor heads and was sized to meet the majority of the 

home’s heating load. Electric wall or baseboard heaters were located throughout the house so 

that each room has an independently controlled supplemental source of heat. The project proved 

that a DHP can be reliably installed and commissioned on the production line, ready for transport 

to the homebuyer’s site. This eliminated the need for aftermarket heat pump installation. With 

technical support from NEW, staffs at three plants were able to design and install the DHP and 

the supplemental zonal heating systems appropriate for all Pacific Northwest climate zones. As a 

result of the project, the team and industry identified three installation options, presented in 

Table 2, below. In all but the DHP Ready option the factory determines the size of the DHP, and 

in all cases the factory installs the zonal electric resistance heaters and runs a dedicated electrical 

circuit to a disconnect box near where the DHP compressor will be located. 
16

Table 2. DHP Installation Approaches

Option Description Key Requirements

Factory 

Turnkey 

DHP

Factory installed system by properly 

trained factory staff or outside heating, 

ventilation, and air conditioning 

(HVAC) technician. In-factory 

commissioning before home shipment.

Factory wholesale DHP equipment 

purchase, and inventory of 

installation items at the factory. 

Warranty by factory or partner 

HVAC contractor.

Field 

Finished 

DHP

Factory staff installs the indoor head, 

prepares any building envelope 

penetrations and runs DHP electric 

circuit/disconnect. Home ships with 

the outdoor unit shipped loose in the 

home. A certified field contractor 

installs and commissions the system 

after the home is installed on site.

Factory wholesale DHP equipment 

purchase, reduced inventory of 

installation items at the factory. 

Warranty by partner HVAC 

contractor. Onsite permit and 

inspection for DHP placement and 

electrical connections to disconnect.

DHP Ready

Factory staff installs DHP electric 

circuit/disconnect. Retailer hires 

HVAC contractor to install DHP on 

site.

No factory inventory. Warranty by 

local HVAC contractor. Onsite 

permit and inspection for DHP 

placement and electrical connections 

to disconnect.

The team also teamed up with NEEA’s NW Ductless Heat Pump Program, retailers and 

interested local utilities to begin planning and promoting “show and tell” events. At an event in 

Sequim, Washington, in response to an announcement placed in the local newspaper 20 people 

attended to hear about the DHP manufactured home on the retailer’s sales lot. There was a good 

90 minutes of questions and answers after the DHP presentation. The Sequim event promoted

DHPs as both an upgrade to existing heating systems and as the best option for new 

manufactured homes. Most attendees were interested in the retrofit potential for the DHP 

systems. 

The alternative HVAC system, based on a DHP, combined with zonal electric heaters in each 

bath and bedroom, replaces the electric forced-air furnace and duct system. The system is called

a hybrid DHP zonal electric heating system, because while the DHP provides most of the home’s 

space conditioning needs, the electric wall heaters or electric baseboard units (sizes range from 

500 W to 2.0 kW depending on the climate and room size) located throughout the house give 

occupants the ability to obtain additional comfort heating in individual rooms. 

The high-efficiency DHP is located in the central living area, but it is sized with sufficient 

capacity to meet the entire home’s cooling load and its heating load under most conditions, 

especially if interior doors are left open. The DHP includes one or two wall-mounted indoor 

heads in the central space that operate nearly continuously, ramping up and down the fan speed 

in proportion to the amount of heating or cooling being performed by the unit. The continuous 

operation of the indoor head blower thoroughly mixes the room air to the point that air 

throughout the house gets turned over and conditioned by the DHP. Figure 12 shows a DHP 

indoor head located in the main zone of the home. Remote rooms will be conditioned indirectly 

most of the time, with the backup electric resistance wall heaters supplementing as needed, 
17

especially in extreme conditions. Installing ceiling fans in secondary zones may help evenly cool 

the home, especially if secondary zones have significant southwest-facing glazing. Additional 

research is needed to give guidance for designing systems that ensure adequate home cooling 

performance in areas with hotter summer conditions.

Figure 12. DHP indoor head mounted in main zone

The project team was able to prototype the hybrid DHP zonal electric heating system in six 

homes built at three different plants. In order to achieve a complete turnkey DHP installation at 

the plant (achieved in four homes), both the DHP indoor head(s) and the outdoor compressor 

must be mounted on the same home section. Four homes were prototyped with this approach. 

Not all floor plans lend themselves to locating the entire DHP system on a single home section, 

so the team also explored ways to ship the home with a complete zonal electric resistance heating 

system and perform DHP installation on site. One option the team explored was to have the plant 

purchase the DHP equipment, install the indoor head, drill all necessary holes through the 

building envelope, supply an equipment electrical disconnect near where the outdoor unit was to 

be installed, and arrange for a refrigerant technician and electrician to complete the DHP 

installation on site (done for one home). A second option field DHP installation was simply to 

ship the home with the zonal electric resistance heating system installed with an equipment 

electrical disconnect near where the outdoor unit was to be located on site. The home retailer 

then arranged for an HVAC contractor to install the DHP system (done for one home). All three 

approaches proved viable, but each presents a different set of challenges and requirements for 

achieving successful integration into the home and into the factory building process.

Factory-installed DHP systems require that the home have a suitable mounting location on the 

rear wall of the floor section receiving the DHP equipment (see Figures 13 and 14). Even with 

the longest trailer tongue installed on the home, a DHP compressor mounted on the hitch end of 
18

the home proved to be vulnerable to damage by the transport rig. Sidewall mounting presents 

similar vulnerabilities, and over-width considerations further limit the potential applicability of 

this mounting strategy. Many homes built in the Pacific Northwest are sited in western Oregon 

and Washington—areas with a marine climate. For such applications, using a DHP that has 

published capacity data for lower temperatures than the U.S. Department of Energy-specified 

17°F rating temperature can allow the heating system to be designed without installing 

supplemental heating in the main zone of the home in many cases, because the DHP still has 

ample capacity at the mild heating design temperatures common in the marine climate zone—a 

cost savings and a possible perceived benefit from an aesthetic perspective. 

Figure 13. DHP compressor on end wall with indoor head on 

other side of wall—“up and in” installation

Figure 14. DHP mounting location integrated into home design
19

Limitations to factory installation include optimal indoor head location, which can be difficult to 

achieve (due to the need to locate both compressor and indoor head in the same floor section).

Wall mounting of the outdoor compressor may present a noise issue when mounted on a 

bedroom wall, and installation may involve particularly long refrigerant line runs.

Approaches that involve installing or completing installation of the DHP in the field can expand 

the range of floor plans that lend themselves to DHP integration, as there are more options for 

equipment location in the home. Field-installed DHP approaches require that the home have a 

zonal electric resistance heating system installed in the plant that serves the entire home and has 

sufficient capacity to meet heating loads at design conditions, because the home is required to be 

complete at the time it leaves the factory. It is possible to ship a home that has elements to be 

completed on site, but this requires the home to have an “alternative construction” letter and an 

additional on-site inspection by an In-plant Primary Inspection Agency representative. 

Additionally, a local electrician and heating contractor are needed to install and commission the 

DHP, which adds cost and complexity to the system. Also, if the plant supplies the DHP 

equipment, there are warranty issues in terms of which party takes responsibility for the 

equipment once installed. On-site installation also makes it more difficult to ensure uniform 

quality in DHP system performance.

2.5 Domestic Hot Water System

Heat pump water heaters – Research questions: supply air from home or outdoors? Tied into 

central ventilation system? 

The HPMH specification requires that HPWH equipment meet Tier 2 of NEEA’s Northern 

Climate Heat Pump Water Heater specification, plus have the ability to fully duct the process air. 

The project team examined three key elements: exhaust air ducting, quiet operation, and defrost 

capability to permit operation in colder temperatures. For ready integration into MH applications, 

the HPWH would be designed to draw air from the home’s crawlspace, transfer its heat into the 

DHW tank, and then exhaust the resultant cool air via an exhaust duct to the outside. Appropriate 

products with sufficient availability are only now beginning to arrive in the market. Having the 

ability to use the HPWH as a key component in a whole-house heat recovery ventilation system

remains very attractive to the project team, but there is no appropriate equipment available at this 

time. Further HPWH research and product development are warranted to help improve and 

increase the range of applications in which this technology can be used.

Changing to an HPWH will significantly improve the efficiency of the DHW system, relative to 

a conventional electric tank water heater. Several products have been demonstrated in the Pacific 

Northwest over the past several years, and a few units have shown good performance 

characteristics in both laboratory tests and home installations. One manufacturer, AirGenerate, 

produces equipment compliant with Tier 2 of the NEEA Northern Climate Heat Pump Water 

Heater Specification, and has reportedly secured Underwriters Laboratories approval for a unit 

that is capable of fully ducting both intake and exhaust air streams.

The project team worked with AirGenerate to arrange installation of a fully ducted unit in a 

customer-sold home, but the equipment ultimately proved to be unavailable in time for use in the 

project’s prototyping work. Without a commercially available fully ducted HPWH on the 

market, the project team turned to PNNL for assistance with prototyping, using the manufactured 
20

home laboratory as a surrogate for an actual prototype home built in the factory. The PNNL 

laboratory homes are equipped with General Electric (GE) HPWH units that are not designed for 

ducted operation. The project team sponsored additional research testing at the PNNL facility, 

wherein one of the GE HPWH units was modified to accept duct fittings, and an inline fan was 

added to generate appropriate airflow through the ductwork. As modified, the HPWH was set up 

to pull air from the home’s crawlspace and exhaust it to outdoors. Figure 15 shows the screened 

air intake in the crawlspace, and Figure 16 shows the exhaust ducting with inline fan fitted to the 

HPWH. The laboratory’s monitoring and control equipment is being used to detect HPWH 

compressor operation and energize the inline fan in response.

Figure 15. HPWH screened inlet located in vented crawlspace
21

Figure 16. HPWH modifications to allow fully ducted operation

The project team is pushing to prototype a HPWH configuration that draws air from the house

crawlspace, transfers heat into the DHW tank, and then exhausts the resultant cooler air to the 

outside, because this configuration has no impact on indoor air temperature or home ventilation 

systems, which greatly simplifies the home’s mechanical systems. While this configuration can 

be expected to suffer a reduction in HPWH efficiency compared to one that makes use of indoor 

air, the project team finds this outcome acceptable when compared to attempting to obtain nearterm deployable solutions to the challenges of introducing up to 200 CFM of makeup air into a 

home that is relying upon indirect conditioning of secondary zones to maximize the DHP’s 

heating contribution or working with equipment manufacturers to develop new control strategies 

that permit interaction between HPWH, DHP, and home ventilation equipment.
22 

3 Discussion

This project phase incorporated in-plant prototyping and preliminary construction process 

development for five measures that constitute the core components of the HPMH specification. 

This project will continue in subsequent years with prototyping of complete homes incorporating 

the full complement of HPMH specifications. Should the region’s utilities choose to fund a 

coordinated program, then the subsequent years’ work could involve a significant number of 

homes. Given that four of the five measures prototyped in this project phase have direct 

applicability to existing manufactured homes, other activities in subsequent years would include 

preparation of specifications or guidelines for use by programs retrofitting manufactured homes. 

Through the first two phases of this Building America project the project team determined:

• The project successfully scoped the technological challenges at the plants involved with 

measure implementation for four of the five most challenging measures in the HPMH 

specification. 

• This project phase demonstrated that the HPMH measures can be built as described by 

the specifications developed during this project’s prior phase, so the anticipated electric 

energy savings ranging from greater than 8,000 kWh/yr up to nearly 11,000 kWh/yr over 

today’s regional baseline home are supported. The actual measure costs will be 

determined on a plant-by-plant basis in the next Building America project phase that will 

build HPMH prototype homes. A few obstacles remain in terms of HPWH equipment 

availability and the extent to which appraisals might fail to value the option package. 

• Given the lack of suitable HPWH unit availability, the HPWH measure’s development 

has lagged behind other elements of the HPMH package. NEW staff and BPA met with 

AirGenerate personnel to discuss installing a unit to prototype in a NEEM home. The 

AirGenerate HPWH is currently the only HPWH that meets all the NEEA Northern 

Climate Spec Tier 2 criteria and is capable of fully ducting intake and exhaust air 

streams. AirGenerate’s new fully ducted unit has not become available as anticipated. 

NEW, PNNL, and BPA are currently conducting testing on the GE HPWH at the PNNL 

home laboratory. Once the AirGenerate fully ducted HPWH becomes available, NEW 

plans to prototype the unit in a factory built home. 

• The hybrid DHP zonal space conditioning system has performed very well in the first 

prototype homes, with retailers and homebuyers reporting that the homes have been 

comfortable in both heating and cooling seasons. The project team has very limited 

experience with DHP systems in climates with significant cooling loads, and more 

research into how well a single indoor head can be expected to cool homes with various 

floor plans is needed. It also is not known the extent to which ceiling fans in bedrooms 

might be able to increase air circulation throughout the home to effectively extend 

cooling into these zones. The project team anticipates that a home incorporating the full 

HPMH specification will prove even more able to be cooled well from a single, centrally 

located indoor head. 

• The attic insulation improvements prototyped proved able to produce a marginal 

improvement to the attic’s overall thermal performance, and they promise the ability to 

significantly improve the quality of insulation detailing in the attic eave area. The cost 
23 

involved with implementing this measure appears to be modest, especially since it also 

solves a common NEEM program compliance issue. The plants where the measures were 

prototyped responded positively to the results, as the improvement in insulation detailing 

was readily apparent.

• MH industry leaders have said that the appraisers will not give added value to the HPMH 

measures and will use simple $/ft2 numbers to value even the HPMH. Low appraised 

values could cause a problem for anyone applying for a loan on a HPMH home. NEW 

staff will be working with Robin LeBaron of the Fair Mortgage Collaborative, to educate 

appraisers and banks to account for the value of the efficiency upgrade in the home 

valuation (Hewes and Peeks 2012). The HPMH specifications and measures have relative 

market acceptance/value from the perspective of MH industry leaders at the plants and 

retail home centers. The industry is eager to find ways to position its homes such that 

they will appeal to buyers looking for a more modern home and to take advantage of the 

positive momentum being generated by “Prefab” and “Factory-built” home media 

coverage. 

• Housing Authorities, Habitat for Humanity, the U.S. Department of Agriculture, Indian 

tribes, and utilities are interested in the outcome of the HPMH project. The Housing 

Stock Upgrade Initiative in Oregon is interested in the project. This program incentivizes 

and induces the replacement of rural substandard housing, specifically obsolete 

manufactured homes, in a systematic manner and with a simplified approach for 

homeowners. The Housing Stock Upgrade Initiative is a broad-based and far-reaching 

initiative that intersects several important community and economic realms: local, 

regional and state economies; home building, home rehabilitation, green-building, and 

housing-related industries; job creation and retention in established industries; new 

business in leading-edge industries; employment skills and education; public health and 

public safety; energy use and efficiencies; preserving the environment. NEW has been 

working with the Governor’s Regional Solutions Team for SW Oregon and partnering 

with Curry County to identify priority projects with positive economic and human 

outcomes. The Housing Stock Upgrade Initiative is a priority project for Curry Co. Three 

homes have been replaced with energy-efficient manufactured homes in the last 5 

months. 
24

4 Conclusions/Lessons Learned

1. Electric energy savings ranging from more than 8,000 kWh/yr up to nearly 11,000 

kWh/yr over today’s regional baseline home are anticipated using this package across the 

entire region. The actual cost will be monitored in the next phase of this project where 

each plant will build an HPMH prototype home.

2. The higher cost of the HPMH home package could affect regional adoption of HPMHs in 

the Pacific Northwest. This cost factor could make it more difficult to secure mortgages,

affecting customers’ ability to finance homes. The utilities might be willing to incentivize 

the HPMH up to a level that could make the make the HPMH affordable. Affordability

will be the focus of the next phase of the project.

3. The fully ducted HPWH is not available for purchase. The project team tried to prototype 

a home with an early release of a fully ducted HPWH, but the manufacturer was unable 

to make available the appropriate equipment.

4. Feedback from retailers about home sales indicates that the hybrid zonal DHP system is 

now being requested by some homebuyers. Retailers and customers can now order new 

homes with hybrid DHP systems installed in the factory. One retailer is selling more than 

90% of homes to its customers as hybrid DHP-ready, with the zonal system installed in 

the factory and a DHP circuit wired to a disconnect outside the home, greatly simplifying 

DHP installation once the home is sited. One plant reports having installed nearly 50 

DHP units. The DHP is a measure that has been accepted by the industry.

5. The hybrid zonal DHP system can be adapted to many manufactured home floor plans.

The noise reduction might be a significant benefit of DHPs compared to typical 

manufactured home forced-air systems. Further work is needed to develop DHP 

installation approaches that rely upon work performed on site. It will be important for the 

NEEM program and local utilities to be able to track and be assured of quality 

installation. 

6. Installation of exterior foam sheathing adds additional labor at a point in construction 

where most plants already experience production bottlenecks, so reconfiguring plant 

workstations might be required. The foam installation proved to be straightforward, and 

the modest material thickness appears to avoid the problem of siding fasteners missing 

framing members that other research efforts have reported with thicker foam layers being 

incorporated into the wall system. While it is too soon to be certain, the prototype home 

built for this project endured a 400-mile transport without any issues apparent at the time 

of setup or subsequently reported by the homeowner. The plants appear to recognize the 

thermal benefit from this measure, but they have not embraced it as yet. Additional 

prototyping on a simpler home might help prove to the plants the ease of implementation 

of this measure.

7. Triple-pane windows do not appear to present any significant technical challenges

beyond the possibility that the additional weight of the windows might require some 

home models to be built with an additional axle under the home sections, but adoption of 
25

the technology will require a window manufacturer to step forward and begin producing 

a value-oriented window line that incorporates the thermally improved extrusions and 

glazing units that together can achieve U-0.22 or better. More information on weight, 

transport, and cost issues will be needed to ensure this measure is durable and saleable.

8. Marginal improvement to attic insulation proved to be possible using commonly 

available materials. The prototyping effort also succeeded in demonstrating common 

deficiencies in current insulation practice, so the industry might be persuaded to adopt 

these improvements as a way to correct their current process.
26

Bibliography

Baechler, M.; Hadley, D; Sparkman, R; Lubliner, M. (2002). “Pushing the Envelope: A Case 

Study of Building the First Manufactured Home Using Structural Insulated Panels.” Presented at 

the 2002 ACEEE Summer Study on Energy Efficiency in Buildings Conference, Pacific Grove, 

CA.

Baylon, D.; Larson, B.; Storm, P.; Geraghty, K. (2012). Ductless Heat Pump Impact & Process 

Evaluation: Field Metering Report. Prepared for Northwest Energy Efficiency Alliance. Seattle, 

WA: Ecotope, Inc.

Baylon, D.; Davis, B.; Hewes, T. (March 2009). Summary of NEEM Manufactured Home Field 

Data and Billing Analysis. Seattle, WA: Ecotope, Inc.

Baylon, D.; Davis, B.; Palmiter, L. (1995). Manufactured Home Acquisition Program: Analysis 

of Program Impacts. Prepared for the Bonneville Power Administration. Seattle and Olympia, 

WA: Ecotope, Inc. and Washington State Energy Office. 

Baylon, D.; Lubliner, M.; Davis, B.; Kennedy, M. (1990). Manufactured Homes Cost Data 

Analysis Report. Prepared for the Bonneville Power Administration. Seattle and Olympia, WA: 

Ecotope and Washington State Energy Office.

Code of Federal Regulations. (2001). “Manufactured Home Construction and Safety Standards.”

Title 24, Part 3280.

Eklund, K. (2008). Residential Heat Pump and Air Conditioner Research, Demonstration, and 

Deployment Improving Pacific Northwest Utility and State HVAC Programs—Project Report. 

Prepared for the National Association of State Energy Offices. Boise, ID: Idaho Department of 

Water Resources, Energy Division.

Eklund, K.; Gordon, A. (2011). “Cost Assessment for Manufactured Homes.” Prepared for the 

Bonneville Power Administration. Olympia, WA: Washington State University Extension 

Energy Program. 

Eklund, K.; Gordon, A.; Lubliner, M. (January 31, 2011). Strategic Recommendations to 

Improve Energy Efficiency in Manufactured Housing. A Report to the Bonneville Power 

Administration. Olympia, WA: Washington State University Extension Energy Program.

Greer, R.; Hewes, T.; Peeks, B. (2004). Northwest Energy Efficient Manufactured Housing 

Program In-plant Inspection Manual. Salem, OR: Oregon Department of Energy.

Hewes, T.; Peeks, B. (December, 2012). High Performance Manufactured Home Project: Final 

Project Report. Prepared for Bonneville Power Administration. Corvallis, OR: Northwest 

Energy Works.
27

Hewes, T.; Peeks, B; (January 2013) “Northwest Energy Efficient Manufactured Housing 

Specification Development” Prepared for the U.S. Department of Energy Building America 

Program under contract to Florida Solar Energy Center. Corvallis, OR: Northwest Energy 

Works.

Hewes, T.; Peeks, B. (2011). Field Monitoring of Two Manufactured Homes in the Pacific 

Northwest. Prepared for the U.S. Department of Energy Building America Program under 

contract to PNNL. Corvallis, OR: Northwest Energy Works.

Hewes, T.; Peeks, B. (2011). State of the Industry Report. Prepared for the Bonneville Power 

Administration. Corvallis, OR: unpublished report.

Hewes, T.; Peeks, B. (January 18, 2012). Personal communication with Robin LeBaron, Deputy 

Director of Fair Mortgage Collaborative. 

Lubliner, M. (October 2000). “WSU Energy House.” Automated Builder Magazine.

Northwest Energy Efficiency Alliance (NEEA). (November 7, 2011). “A Specification for 

Residential Heat Pump Water Heaters Installed in Northern Climates, Version 4.0.” Portland, 

OR: NEEA.

NEEM. (2011). Northwest Energy Efficient Manufactured Housing Program Database. 

Corvallis, OR: Northwest Energy Works. 

Northwest Power and Conservation Council. (2010). Sixth Northwest Conservation and Electric 

Power Plan. Portland, OR: Northwest Power and Conservation Council.
28

Appendix A: Outline of Construction Processes

Improved Attic Construction Practice

Option 1. Dense-packed loose fill insulation near roof eaves

Applicability: Flat or vaulted ceiling roof cavities insulated with blown-in fiberglass

Additional Materials Required:

• Insulation baffles, cardboard 32 × 24 in. with 1-in. side tabs and “tail” at least equal in 

length to truss heel height.

Installation procedure:

1. Prepare roof assembly and insulate ceiling as is typically done, except with the target 

insulation depth being the value determined by the specific truss geometry. See Table 3

and Table 4 for insulation target depth for commonly used roof trusses.

Table 3. Cellulose Loose Fill Insulation in Attic

Eave Insulation 

Strategy

Heel 

Height

(in.)

King Post 

Height 

(in.)

Insulation 

Target Depth 

(in.)

AreaWeighted 

R-Value

Loose Cellulose 5.25 22.25 18.25 45.6

Fiberglass Batt 5.25 22.25 18.25 45.6

Loose Cellulose 5.25 37.4 13.9 45.2

Fiberglass Batt 5.25 37.4 13.9 45.0

Loose Cellulose 7 23 14.8 45.0

Fiberglass Batt 7 23 14.8 44.7

Table 4. Fiberglass Loose Fill Insulation in Attic

Eave Insulation 

Strategy

Heel 

Height

(in.)

King Post 

Height

(in.)

Insulation 

Target Depth

(in.)

AreaWeighted 

R-Value

Dense-Pack 5.25 22.25 21 45.4

Fiberglass Batt 5.25 22.25 21 45.6

Dense-Pack 5.25 37.4 14.3 45.4

Fiberglass Batt 5.25 37.4 14.3 45.0

Dense-Pack 7 23 15.5 45.1

Fiberglass Batt 7 23 15.5 44.7

2. Install baffles, if not installed for initial insulation blow, stapling the side tabs and the tail 

to framing members so as to create an even 1-in. airspace along the truss top chords and 

completely enclose the wall top plate under each baffle.

3. Rake insulation down ceiling toward eave, packing it into the cavity formed by the 

ceiling and insulation baffles until the center of the baffles are deflected upward by 

approximately 1 in.
29

4. Push down on baffles, further compressing the insulation and returning the baffles to a 

flat shape.

5. Reblow insulation to fill the void created by raking insulation toward the eave, anticipate 

needing one 30-lb bag of insulation per 10 ft of attic length (depending upon specific 

truss geometry). 

Option 2. Compressed fiberglass batt insulation near roof eaves

Applicability: vaulted ceiling roof cavities insulated with blown-in fiberglass or stabilized 

cellulose

Additional Materials Required: 

• Insulation baffles, cardboard 32 × 24 in. with 1-in. side tabs and “tail” at least equal in 

length to truss heel height

• R-38 fiberglass batts, 48 × 24 in.

Installation Procedure:

6. Install fiberglass batts in eave area, ensuring proper fit of batt:

• completely cover wall top plate

• split insulation around wiring, framing, plumbing vents, etc. to keep insulation in full 

contact with attic floor

7. Install baffles, compressing the batts, then stapling the side tabs and the tail to framing 

members so as to create an even 1-in. airspace along the truss top chords and completely 

enclose the wall top plate under each baffle

Prepare the roof assembly and insulate ceiling as is typically done, except with the target 

insulation depth being the value determined by the specific truss geometry and considering the 

thermal performance of the compressed fiberglass batt for the given heel height of the truss. 

Anticipate saving about 11⁄2 30-lb bags of loose fill insulation per 10 ft of attic length (depending 

upon truss geometry). See Table 3 and Table 4 for insulation target depth for commonly used 

roof trusses.
30

Wall With Exterior Foam Sheathing Construction Practice

Applicability: all conventional wood-framed walls

Additional Materials Required:

• 5⁄8-in. thick R-4 polyisocyanurate foam sheathing, 4 × 8 ft sheets

• 0.092 × 21⁄2-in. collated siding nails (for use with 3⁄8-in. thick cement or composite board 

siding, other fasteners may be needed for different siding types)

• Doors ordered with 5⁄8-in. deeper jams to allow for the walls’ added thickness, or

• 5⁄8-in. thick moulding stock to add between door jamb and casing.

Recommended Additional Materials:

• Building wrap, or (if suitably faced foam is used)

• Sealing tape designed for use to face-seal foam sheathing and create a water resistive 

barrier

Installation Procedure:

1. Construct and install exterior walls as is typically done, up to the point of siding the 

walls.

2. Install building wrap, if not face-sealing foam sheathing.

3. Staple rigid foam to wall assembly, taking care to tightly butt joints of foam sheets.

4. Cut out window and door openings where foam may have been installed over said 

openings.

5. Measure and mark stud locations as needed to ensure fasteners strike framing through 

foam.

6. Face-seal foam with special tape, if applicable, and seal any damaged areas on foam 

facing.

7. Install siding and corner trim.
31

Triple-Pane Window Installation Practice

Applicability: all homes

Additional Materials Required:

• U-0.22 or lower windows

• Shims, wood or plastic, for supporting window on sill of rough opening

• Backer rod and caulking, or

• Spray foam, soft formulation for use with windows and doors

Recommended Additional Materials:

• Flexible adhesive window flashing

Installation Procedure:

Note: each window manufacturer will supply installation instructions specific to its products. 

While these recommendations are intended to describe quality installation practices, window 

manufacturer’s instructions take precedence, as they constitute requirements for obtaining 

warranty coverage. 

1. Apply flexible adhesive flashing to window sill, ensuring that the material:

• Laps over foam sheathing and adheres to the rough opening sill

• Extends down foam sheathing at least approximately as far as the window nail fin 

covers

• Wraps up the sides of the window opening by at least 2 in.

2. Apply caulking sealant to window nail fins on four sides of the window, leaving a few 

small gaps on the bottom fin

3. Install window into rough opening, using shims to set window square in the opening 

support corners of window and interior edges of glazing units on horizontal sliders

4. Install fasteners through nail fins in accordance with window manufacturer instructions, 

ensuring that smooth window operation is maintained

5. Install adhesive flashing over vertical side nail fins, then install over head of window, 

lapping over side pieces

6. Trim window as is typically done

7. Install appropriate diameter backer rod between window and rough opening on all four 

sides, apply caulking to complete the seal

8. Finish interior window trim as typically is done, noting that the depth of the window 

opening may be different as a result of the foam sheathing adding thickness to the wall 

assembly and the triple pane window possibly extending further into the window opening
32

Ductless Mini-Split Heat Pump Hybrid Electric Zonal Heating System

Applicability: Most one- and two-section homes, many three-section or larger homes with open 

floor plans and low to moderate cooling needs

Additional Required Materials and Equipment:

• Ductless mini-split Heat Pump equipment

• Electric resistance heaters

• Refrigerant lineset

• 14-2-G cable suitable for indoor/outdoor use, tray cable recommended, UF-rated cable 

also acceptable—for interconnection between compressor and indoor head

• Condensate piping/tubing, size and material selection depending upon application

• Compressor wall-mounting brackets (consider keeping at least one set of rail-hung 

brackets in inventory to facilitate installation in the event of wall framing errors or 

construction change orders fail to deliver wall studs and/or blocking in the necessary 

locations

• Vibration isolator pads

• Stainless steel fasteners for mounting brackets to wall and compressor to brackets

• Equipment electrical disconnect on a circuit sized for the equipment load or fused to 

provide the necessary protection for the DHP equipment

• Flexible weather-tight conduit, fittings and securing clamps

• Lineset cover with various terminus, weather head and corner fittings

• UV and weather resistant tape for lineset protection and dress-up

• UV resistant low-expansion foam sealant 

• Self-drilling concrete/metal screws (#10 or #12 by 1⁄2-in. to 1-in. long) and plumber’s 

strapping or clamps for securing lineset along chassis, if applicable

Installation Procedure:

Note: The following is not an exhaustive job process description, as specific applications will 

vary in the specific actions required for proper installation of the DHP and the supplemental 

electric resistance heaters. DHP equipment has model-specific requirements for clearances, 

electrical connections, etc. that must be considered when planning for equipment location. Inplant training of all personnel involved with designing, drafting, installing, supervising, and 

inspecting should be considered a necessary pre-requisite to incorporating DHPs into the 

plant’s homes. A properly licensed refrigeration technician is required to evacuate and release 

refrigerant into the system, and it is highly recommended that the same individual make all 

refrigerant connections. DHP systems completed in the field also will require a licensed 

electrician to make the connections between the equipment disconnect, indoor head and the 

outdoor compressor. The following job process outline is for a DHP system completely installed 

in the plant.
33

1. Before construction begins, perform heat loss calculations for the home using design 

temperatures appropriate to the home’s potential siting destination. 

a. Select appropriate DHP equipment. Primary considerations include appropriately 

sizing indoor head to the space where it is to be located. A unit that is too large 

may result in the indoor head delivering high airflow close to where people likely 

will be sitting, and a unit that is too small may require more electric resistance 

heating in the main zone of the home.

b. Determine DHP equipment placement. Primary considerations include locating 

indoor head and outdoor compressor on the same home section to facilitate 

complete installation at the factory and placing the indoor head where it will be 

able to mix air within the main zone of the home. Avoid placing the indoor head 

near heat-producing appliances. Whenever possible, locate the indoor head on an 

interior wall that backs up to a closet or on an exterior wall to facilitate access to 

the indoor head’s lineset connections. Include wall framing and/or blocking in 

locations where equipment will be mounted to the home. This is most critical for 

the outdoor unit, as its mounting brackets must be fastened into framing members.

c. Determine electric resistance heater locations. If supplemental heating is required 

in the home’s main zone, locate it away from the DHP and close to heavily glazed 

areas in the zone, if possible. Bedroom heaters require a 31⁄2-in. deep wall cavity 

for mounting, and locating heaters on a closet wall can minimize the amount of 

wall that must be framed with 2 × 4 studs. 

2. Prepare indoor head mounting and holes for lineset routing. 

a. Tack wall mounting bracket in place, ensuring each end of the bracket is the same 

distance up the wall from the floor (level). Using bracket as a template, mark 

locations of mounting holes on the wall. Install drywall anchors in locations near 

attachment tabs on mounting bracket that are not backed by wall framing or 

blocking. Install mounting bracket to wall. 

b. Using guides on mounting bracket locate center of hole to accommodate 

refrigerant and condensate lines and power cable. Drill pilot hole through wall, 

taking care to drill perpendicular to wall. Use pilot hole as the center of larger 

hole to be sawed on the side of the wall with the indoor head and as the top of the 

hole on the opposite “backside” of the wall to ensure that the condensate line will 

get a good drop out of the indoor head.

c. If indoor head is being mounted on an interior wall, saw hole through floor deck, 

directly adjacent to the backside wall (so lineset cover will cover the hole) to 

accommodate condensate line and, if routed under the home, refrigerant lines and 

electrical cable. If lineset and electrical cable are to be routed through the attic, 

drill hole through ceiling directly adjacent to the backside wall.

d. Install back half of lineset cover and fittings to wall(s)

3. Working outside the home, unroll refrigerant lineset and tape it together with electrical 

cable every few feet to facilitate routing through the home’s attic, along the chassis or in 

lineset cover mounted on the exterior of the home. 
34

4. After the home is sided and painted, bore hole through gable end wall into attic or 

through floor rim joist near the outdoor compressor, or trim siding that hangs below 

bottom of rim joist for routing lineset against bottom of rim joist (also requires including 

setup instructions for notching skirting or perimeter foundation at the location where 

lineset passes through).

5. Route lineset and electric cable from outside the house to the inside head location, taking 

care not to kink the copper lines. Bends in the lines must be made gradually and with 

proper support given to the inside of the bend. Be certain ends of lineset remain tightly 

closed at all times, and leave enough extra length at both ends to allow for making tubing 

flares and connecting the lines to the DHP equipment.

6. Mount outdoor unit. For applications where the outdoor unit will be mounted to the end 

wall, locate framing members installed to accommodate mounting brackets. Measure to 

ensure level bracket mounting, drill pilot holes, apply caulking to the holes and install 

brackets with stainless steel lag bolts. 

7. Mount outdoor unit with stainless steel bolts to brackets, using vibration isolators 

between unit and brackets. 

8. Make electrical connections from the indoor head to the interconnecting cable and install 

indoor head onto mounting bracket, pulling slack cable toward the outdoor unit as the 

head is installed. Take care to ensure the condensate drain line is located at the bottom of 

the bundle of lines and tubes as the head is installed onto the bracket.

9. Make electrical connections to the outdoor compressor, running wiring in flexible 

weather-tight conduit wherever it exposed outside of the home. Secure conduit to home 

with clamps as necessary.

10. Connect condensate drain tubing to indoor head’s stub out. Run tubing through floor 

decking and transition to pipe to carry condensate outside the home footprint. Plumb the 

piping in the same manner as is done for high efficiency gas furnace condensate drain 

piping.

11. Refrigerant technician can now cut lineset tubing to length, flare the tubing ends, make 

connections to the indoor head and outdoor compressor, flush the system with nitrogen, 

check for leaks, evacuate the system, check for leaks, release refrigerant, and test system.
buildingamerica.gov

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