Project Overcoat—An Exploration 

of Exterior Insulation Strategies 

for 11⁄2-Story Roof Applications in 

Cold Climates

Cindy Ojczyk, Garrett Mosiman, Pat Huelman,

Tom Schirber, Peter Yost, and Tessa Murry

NorthernSTAR

April 2013
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its endorsement, recommendation, or favoring by the United States government or 

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iii

Project Overcoat—An Exploration of Exterior Insulation Strategies for 

1-1⁄2 Story Roof Applications in Cold Climates

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: 

Cindy Ojczyk, Garrett Mosiman, Pat Huelman, 

Tom Schirber, Peter Yost, and Tessa Murry

NorthernSTAR Building America Partnership

University of Minnesota 

2004 Folwell Avenue 

St. Paul, MN 55108 

NREL Technical Monitor: Stacey Rothgeb 

Prepared under Subcontract No. KNDJ-0-40338-00 

April 2013 
iv

Acknowledgments

This report was prepared for the U.S. Department of Energy Building America Program. 

Funding for this work was provided by the National Renewable Energy Laboratory under 

contract KNDJ-0-40338-02. Additional funds were provided by the University of Minnesota and 

the Initiative for Renewable Energy and the Environment. 

The primary authors were Cindy Ojczyk, owner, Simply Green Design; Garrett Mosiman, 

research fellow, University of Minnesota; Peter Yost, principal and director, Residential 

Services, BuildingGreen, Inc.; Pat Huelman and Tom Schirber, Cold Climate Housing Program, 

University of Minnesota; and Tessa Murry, Cocoon Solutions Inc. 

These authors would like to acknowledge the following contractors and builders who gave their 

time to answer many questions related to this report:

• Steve Schirber, Cocoon Solutions, Edina, Minnesota 

• Steve Mindel, Mindel and Morse Builders, Dummerston, Vermont 

• Paul Eldrenkamp, Byggmeister, Newton, Massachusetts

• Ben Southworth, Garland Mill Timberframes, Lancaster, New Hampshire

• Alex Cheimets, Synergy Construction, Leominster, Massachusetts

• Curt Stendel, Panelworks Plus, St. Francis, Minnesota 
v 

Contents

Acknowledgments ..................................................................................................................................... iv

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

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

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

Executive Summary..................................................................................................................................... i

1 Introduction ........................................................................................................................................... 2

2 Literature Review of Four Exterior Roof Insulation Strategies...................................................... 12

2.1 External Thermal Moisture Management System .............................................................14

2.2 Structural Insulated Panels .................................................................................................18

2.3 Over-Roofing .....................................................................................................................19

2.4 Spray Foam ........................................................................................................................19

2.5 Alternate Processes and Materials for Exterior Overcoat ..................................................20

3 Overcoat Impact Study ...................................................................................................................... 21

4 Contractor Interviews......................................................................................................................... 22

4.1 General Comments From Contractor Interviews ...............................................................24

4.1.1 Solution Generation Phase .....................................................................................24

4.1.2 Construction Phase.................................................................................................24

4.1.3 Post-construction Phase .........................................................................................25

4.1.4 Sales and Marketing ...............................................................................................25

4.2 Noteworthy Comments From Contractor Interviews ........................................................25

4.2.1 Garland Mill Timberframes ...................................................................................25

4.2.2 Synergy ..................................................................................................................26

4.2.3 Byggmeister ...........................................................................................................26

4.2.4 Mindel and Morse Builders ...................................................................................27

4.2.5 Cocoon ...................................................................................................................29

4.2.6 Panelworks Plus .....................................................................................................33

5 Conclusions and Further Work......................................................................................................... 37

5.1 Energy Efficiency and Ice Dam Prevention/Durability .....................................................37

5.2 Indoor Environmental Quality ...........................................................................................38

5.3 Constructability ..................................................................................................................38

5.4 Affordability ......................................................................................................................38

5.5 Assessment Strategies ........................................................................................................39

5.6 Overall Conclusions and Further Work .............................................................................39

6 References .......................................................................................................................................... 41

Appendix A. Project Overcoat Contractor Interview Template ............................................................ 44

Appendix B. Project Overcoat Contractor Interview—Garland Mill Timberframes............................ 47

Appendix C. Project Overcoat Contractor Interview—Synergy Construction.................................... 50

Appendix D. Project Overcoat Contractor Interview—Byggmeister ................................................... 53

Appendix E. Project Overcoat Contractor Interview—Mindel and Morse Builders Problem 

Statement: ........................................................................................................................................... 56

Appendix F. Project Overcoat Contractor Interview—Cocoon ............................................................ 60

Appendix G. Project Overcoat Contractor Interview—Panelworks Plus ............................................ 63
vi 

List of Figures

Figure 1. How an ice dam forms................................................................................................................ 2

Figure 2. Fully vented pitched attic assembly for highest R-value and durability............................... 4

Figure 3. Details for ETMMS roof overcoat approach............................................................................. 5

Figure 4. Details of ETMMS exterior overcoat retrofit on 11⁄2-story home............................................. 6

Figure 5. Details of spray foam exterior roof overcoat approach.......................................................... 7

Figure 6. Details of an unvented SIP retrofit ............................................................................................ 7

Figure 7. Details of a vented SIP retrofit................................................................................................... 8

Figure 8. Details of an over-roofing approach ......................................................................................... 8

Figure 9. Two-plane, two-gable roof ......................................................................................................... 9

Figure 10. Two-plane, two-gable roof with gable dormers ..................................................................... 9

Figure 11. Two-plane, two-gable roof with shed dormers ...................................................................... 9

Figure 12. Four-plane, three-gable roof.................................................................................................. 10

Figure 13. Three-plane, two-gable roof................................................................................................... 10

Figure 14. Established neighborhood in Minneapolis displaying various roof typologies and 

obstacles ............................................................................................................................................. 11

Figure 15. Exterior overcoat approach for roof retrofits....................................................................... 14

Figure 16. BSC Sears Roebuck house DER details............................................................................... 16

Figure 17. Venting a compact roof to prevent ice dam formation ....................................................... 17

Figure 18. Exposing rafter cavities to prepare for spray foam insulation .......................................... 27

Figure 19. Foil-faced foam between rafter framing ............................................................................... 28

Figure 20. Dormers wrapped in foam...................................................................................................... 28

Figure 21. Finished roof ........................................................................................................................... 29

Figure 22. Removing the soffit for an ETMMS approach illustrated by superimposing a drawing of 

the process over a photograph of the home ................................................................................... 30

Figure 23. Insulation, air barrier alignment, and soffit construction illustrated by superimposing a 

drawing of the process over a photograph of the home................................................................ 31

Figure 24. Installing the air/vapor barrier over existing roof decking................................................. 32

Figure 25. Transition where new insulation meets eave wall and new soffit ..................................... 32

Figure 26. Ventilation of ETMMS ............................................................................................................. 33

Figure 27. SIP retrofit panel installation ................................................................................................. 34

Figure 28. SIP retrofit panel installation over dormer........................................................................... 35

Figure 29. SIP retrofit panel installation with double fascia................................................................. 36

Unless otherwise noted, all figures were created by NorthernSTAR.

List of Tables

Table 1. Contractor Overview .................................................................................................................. 23

Table 2. Types of Ice Dam Mitigation Strategies Employed by Contractors ...................................... 24

 

Unless otherwise noted, all tables were created by NorthernSTAR.
vii 

Definitions

BA Building America

BSC Building Science Corporation

Btu British thermal unit

cfm Cubic feet per minute

DER Deep energy retrofit

DOE U.S. Department of Energy

EIFS Exterior insulation finishing system

EPS Expanded polystyrene

ETMMS External thermal moisture management system

FMS Force measuring sensor

ft2 Square foot

HRV Heat recovery ventilator

MLS Multiple Listing Service

NYSERDA New York State Energy Research and Development Authority

PERSIST Pressure Equalized Rain Screen Insulated Structure 

Technique 

pc/L Picocuries per liter

REMOTE Residential Exterior Membrane Outside Insulation Technique

SIP Structural insulated panel

SPF Spray polyurethane foam

Sqft Square feet

XPS Extruded polystyrene
i 

Executive Summary 

Interior approaches to energy loss and ice dam mitigation have been favored by contractors and 

homeowners because of the perceived lower cost and ease of application. Interior approaches to 

preventing energy loss through roofs can be effective if detailed protocols for aligning air 

barriers and applying adequate levels of insulation are followed. The rise in winter-storm-related 

insurance claims in 2010, however, indicates that a more reliable approach is needed. Millions of 

older homes with complicated roof structures, like the 11⁄2-story Cape Cod, remain vulnerable to 

heat loss and ice dams caused by hurdles that prevent thorough insulation and air sealing from 

the interior. 

The NorthernSTAR Building America Partnership team was interested in exploring more robust 

solutions for older homes at risk for heat loss and ice dam formation. This three-part exploration 

was focused on identifying an exterior approach for the roof portion of 11⁄2-story homes with the 

potential to provide cost-effective, long-term, scalable solutions. In part one, the team conducted 

a literature review to examine four exterior insulation and air sealing techniques to determine 

which solution appears most effective. In part two, a limited study of the Multiple Listing 

System in the Minneapolis area was used to broadly estimate the number of existing homes in 

cold climates that could be improved through an exterior insulation approach. In part three, the 

NorthernSTAR team interviewed a sampling of contractors who have participated in ice dam 

mitigation projects to gain baseline knowledge on how they sell, design, and construct ice dam 

solutions. 

This exploratory study found that research favors an exterior approach to deep energy retrofits 

and ice dam prevention in existing homes using the external thermal moisture management 

system technique. But this technique has been mainly documented for whole-house deep energy 

retrofits, leaving a void in data for roof-only applications and durability, constructability, and 

cost. Contractors interviewed for this report indicated an understanding that exterior approaches 

are most promising for mitigating ice dams and energy loss and reported being able to sell these 

strategies to homeowners.

Results from this research can help direct future Building America research activities in efforts to 

create information for professionals, homeowners, and insurance companies. Such information 

will allow them to make decisions about roof-related energy improvements and ice dam repair 

and prevention. 
2 

1 Introduction

A key durability concern for existing homes in cold climates is ice dams resulting from heat loss 

through the roof. In areas of the country that experience snow accumulations, ice dams and 

melted snow can cause significant premature roofing failure, wet insulation, soffit/fascia 

deterioration, paint failure on claddings or interior surfaces, interstitial and interior mold growth, 

structural decay, and further exacerbation of rot and water damage. In addition, ice dams pose 

safety risks from falling ice, structural collapse of roof overhangs, and shearing of deck 

assemblies from ice and snowfall. 

Figure 1 from Larson and coauthors (2010) demonstrates how heat loss can promote ice dam 

formation and reduce building durability as well as energy efficiency. 

Source: Larson et al. 2010

Figure 1. How an ice dam forms

O’Rourke and colleagues (2010) found the size of an ice dam to be a function of snow load, roof 

R-value, indoor temperature, and effective eave to ridge distance. Complex roof geometries such 

as roof valleys and dormers, by adding surface area opportunities for snowmelt, have a further 

impact on the size of the ice dam. The horizontal extent of the ice dam was found to be a 

function of the slope of the roof, with low-slope roofs exhibiting greater horizontal extent. As 

horizontal extent increases, the potential for water seepage and wetting of interior surfaces also 

increases. The application of this research is limited because it only studied the impact of indoor 
3 

temperature on ice dam formation. Estimating that the impact of air leakage would exacerbate 

predicted ice dam formation, the NorthernSTAR team recommends expanding the research to 

include the impact of air leakage. 

Ice dams can require expensive removal or can lead to expensive repair. This problem becomes 

an even greater frustration when homeowners who have invested in energy efficiency 

improvements to address ice dams one year continue to experience heat loss and ice dam 

formation in subsequent years. There are limited data to calculate the extent of residential ice 

dam re-formation after an attempted mitigation, but a report by Lstiburek ( 2008) and anecdotal 

reports in the media and within the building industry indicate that it does occur frequently. 

According to the Insurance Information Institute (2012), losses resulting from water damage and 

freezing have increased significantly from 14.60% of all claims in 2005 to 23.7% in 2009. These 

claims were the second most claimed loss behind wind and hail. Iowa Insurance Institute 

Communications (2011) reported that winter storms accounted for 7.4% of catastrophic losses 

nationwide from 1991 to 2010, or an average of $1.3 billion per year. In 2010, more than $1 

billion in claims for damage caused by winter storms were filed on the East Coast alone (Air 

Worldwide 2011). 

It is difficult to isolate the amount of homeowner claims resulting from ice dams because that 

information is part of total winter storm claims. But it can be assumed from a review of 

insurance company websites that ice dam prevention is an important issue. Most insurance 

companies offer ice dam prevention information on their customer websites (State Farm 

Insurance 2012; Insurance Institute for Business and Home Safety 2012). These websites, 

however, offer generic information on ice dam formation, but little detailed information on 

proper prevention strategies. 

Energy research has shown that improving the building envelope can have a significant impact 

on comfort, building durability, and energy bills. The question is how to properly incorporate 

energy strategies without compromising the integrity of the building envelope. The Building 

America Special Research Project: High-R Roofs Case Study Analysis (Straube and Grin 2010) 

states that the consensus in the research community is that fully vented, pitched attic assemblies 

are the lowest cost and provide the highest R-value, most durable roofs in all climate zones when 

no ductwork or major air leakage are above or in the ceiling plane. Figure 2 demonstrates the 

strategies that must be combined to achieve optimal R-value and durability with this interior 

approach. 
4 

Source: Straube and Grin 2012

Figure 2. Fully vented pitched attic assembly for highest R-value and durability

Figure 2 highlights the insulation, air sealing, and ventilation strategies considered optimal for 

fully vented, pitched attic assemblies, but it is truly focused on new construction where the 

strategies can be incorporated into a home design before construction. Additionally, these 

strategies are relevant only when the attic will remain unconditioned and will not be used for 

living space. 

Existing homes do not always have the flexibility of design necessary for optimizing energy 

efficiency and durability because of barriers to effective air sealing, insulation, and ventilation. 

One hurdle in existing homes is the inability to change the truss structure to make it deeper or 

longer (refer to Figure 1), which prevents the application of appropriate insulation depth. Lack of 

industry consensus on when roof venting should be employed may lead to the creation of 

unvented roof decks that should be vented. The presence of ceiling penetrations, such as those 

from recessed lighting, limits opportunities for effective air sealing. If the trio of strategies 

cannot be done extremely well, top building researchers have recommended an exterior 
5 

insulation overcoat approach to prevent ice dam formation (Lstiburek 2008) in existing homes 

with unconditioned attics. 

Existing homes where homeowners wish to live in the attic space pose additional challenges to 

insulation, air sealing, and roof ventilation necessary to prevent ice dam formation. Finished 

walls, shallow rafter bays, roof pitch, major and minor valleys created by dormers and 

architectural details, lack of raised heel energy truss, obstacles, and penetrations all encumber the 

application of the trio of strategies, indicating that an exterior overcoat approach may be the best 

solution for energy efficiency and ice dam prevention. 

The NorthernSTAR Building America Partnership team was interested in exploring more robust 

exterior roofing solutions for existing 11⁄2-story homes. This three-part exploration was focused 

on identifying an exterior approach with the potential to determine cost-effective, long-term, 

scalable solutions. In part one, the team conducted a literature review to examine four exterior 

insulation and air sealing techniques used in new construction, deep energy whole-house 

retrofits, and roof-only applications. The literature review was undertaken to determine which 

solution appears most effective in preventing heat loss through the roof and ice dam formation. 

The following exterior insulation strategies have been used in the cold-climate markets for 

energy improvements and ice dam mitigation and were investigated in this exploratory research: 

• External thermal moisture management system (ETMMS) 

• Spray foam 

• One-sided structural insulated panel (SIP) overlay (often called a “retrofit” panel)

• Over-roofing. 

Figure 3 depicts the basic details for the ETMMS roof overcoat approach.

Figure 3. Details for ETMMS roof overcoat approach
6 

The figure demonstrates the air/vapor membrane layer between the existing roof decking and the 

rigid insulation. Ventilation is designed into the system using sleepers attached through the 

insulation. Roof sheathing and underlayment are similar to standard roofing practices. 

Figure 4 demonstrates the layering of the materials in the ETMMS approach. 

Figure 4. Details of ETMMS exterior overcoat retrofit on 11⁄2-story home 

(Courtesy of Cocoon) 

Figure 5 is similar to the ETMMS rigid insulation approach, but closed cell spray foam is 

substituted for the rigid insulation. 
7 

Figure 5. Details of spray foam exterior roof overcoat approach

Figure 5 demonstrates the use of wood sleepers attached with standards to the existing roof 

framing to create a cavity that contains a continuous layer of closed cell foam. Care must be 

taken to ensure that the foam does not reach the front edge of the sleeper. This maintains a 

natural ventilation area between the face of the foam and the new roof sheathing. 

Figure 6 shows the SIP retrofit panel where the panel is manufactured with a structural panel on 

one side only and the exposed foam face is placed directly atop an air barrier applied over the 

existing roof decking. The sheathing of the SIP provides the roof decking for the new roof 

material. Figure 6 also depicts an unvented, hot roof application that is commonly seen in the 

marketplace.

Figure 6. Details of an unvented SIP retrofit
8 

Figure 7 illustrates a vented SIP retrofit type that is being created by a few SIP manufacturers in 

the marketplace. Creating grooves in the foam may reduce insulation value of the complete 

system but does allow some heat to escape between a soffit and roof ridge.

Figure 7. Details of a vented SIP retrofit 

Figure 8 illustrates an over-roofing approach in which a vented roof insulated with batt insulation 

is applied directly to the existing roof decking. 

Figure 8. Details of an over-roofing approach

Because of the added wood sheathing and materials associated with these overcoat strategies, 

cost is a large barrier in bringing any of these to market in a scalable manner. For homeowners 

fighting recurring ice dams or those seeking to expand living space into an unfinished attic, 

however, the combination of energy improvement and ice dam prevention may be the incentive 
9 

that overcomes the cost. Alternative materials were also investigated whenever possible to 

uncover opportunities to lower overcoat costs and to make them more competitive with interior 

insulation. 

In part two of the exploratory study, the Multiple Listing System (MLS) in the Minneapolis area 

was used to roughly estimate the number of existing homes in cold climates that could be 

improved through an exterior insulation approach. 

In part three of the study, a sampling of contractors that have participated in ice dam mitigation 

projects were interviewed to gain baseline knowledge on how they sell, design, and construct ice 

dam solutions. The NorthernSTAR team was also interested in learning about the ease of 

installation of each exterior insulation strategy on different 11⁄2-story roof typologies. Figure 9, 

Figure 10, Figure 11, Figure 12, and Figure 13 represent the most common 11⁄2-story roof 

typologies and were used in interviews with the builders.

Figure 9. Two-plane, two-gable roof 

Figure 10. Two-plane, two-gable roof with gable dormers

Figure 11. Two-plane, two-gable roof with shed dormers
10 

Figure 12. Four-plane, three-gable roof

Figure 13. Three-plane, two-gable roof

Another common roof typology, not illustrated here, is a two-plane, two-gable roof with both 

gable and shed dormers. 

In addition to predicting how easily each exterior insulation type can be installed on the different 

roof typologies, it was important to learn if rooftop obstacles such as valleys, chimneys and 

vents, skylights, soil stacks, and architectural/structural details at the eave presented hurdles to 

the overcoat approach. Figure 14 illustrates the variations in obstacles and roof typology from 

house to house. 
11 

Figure 14. Established neighborhood in Minneapolis displaying 

various roof typologies and obstacles 

(photo from maps.google.com)

Although energy efficiency and ice dam prevention were critical elements to investigate, the 

NorthernSTAR team explored other key performance attributes of the various exterior overcoat 

strategies during the literature review and contractor interviews. Durability was considered by 

evaluating potential impact on interior and exterior moisture control and moisture storage and 

drying potential. Indoor environmental quality was explored by evaluating the impact of changes 

to the building envelope and potential combustion safety issues. Team members reviewed the 

literature for information on indoor air quality issues potentially linked to exterior materials and 

installation methods. Constructability was assessed by evaluating exposure time, subcontractor 

skill versus technical requirements of installation, and material availability. Affordability was 

investigated by comparing insulation material costs as well as costs with and without new 

roofing materials, where possible. Additionally, pre- and post-assessment opportunities for 

evaluating the feasibility of the exterior overcoat method were explored. 
12 

2 Literature Review of Four Exterior Roof Insulation Strategies

A large body of research exists to define the strategies for making new homes more energy 

efficient, durable, and cost effective. Usually the strategies encompass a whole-house, systems 

approach that looks at the integration of design, materials, and installation. The Building 

America (BA) Builders Challenge Program and the Environmental Protection Agency’s 

ENERGY STAR Program are just two examples where integrated design is used to maximize 

overall performance of new homes and deliver energy savings of 20% or more. Strategies such 

as SIPs, exterior insulation finishing system (EIFS), and ETMMS seek to maximize energy 

efficiency through unique building envelope designs such as reduced thermal bridging (SIPs) and 

insulation located on the exterior of the building envelope (EIFS and ETMMS). Several 

departments at the University of Minnesota have worked directly with the ETMMS to test this 

whole-house overcoat system on 24 affordable townhomes in one project and 4 single-family 

homes in another project. 

Although the lessons learned from new homes can offer valuable insight into potential strategies 

for existing homes, the opportunities to address whole-house improvements or even the complete 

building envelope at one time are limited and not yet practical at a scalable level. The deep 

energy retrofits (DERs) documented by the New York State Energy Research and Development 

Authority (NYSERDA) highlight the extra costs that can be incurred when existing materials are 

removed to ready a structure for an upgrade or preconstruction testing indicates additional 

measures for energy and occupant safety (Pedrick et al. 2010). Roof decks, sheathing, framing, 

and sill plates may need repair or replacement if they have experienced water damage. Windows 

and doors with lead paint need to be addressed according to new regulations. Large obstacles, 

such as chimneys, may need to be removed. New siding, roofing, and mechanical equipment add 

additional costs above the energy improvement. The four NYSERDA whole-house overcoat 

projects were able to achieve a commendable 69% to 81% reduction in air leakage, but the 

project costs, which include implementation of deferred and critical repairs along with the deep 

energy measures, ranged from $96,200 to $144,000. 

Researchers continue to examine whole-house DER strategies and ways to reduce costs. Energy 

improvement for existing homes has been focused on cost-efficient “packages” of options. When 

installed in existing homes, these packages produce energy savings of 15% or more, motivating a 

homeowner to action with improved return on investment and comfort. The BA document

Energy Savings Measure Packages: Existing Homes (BA 2011) uses the Building Energy 

Optimization energy modeling software to predict energy savings from packages of strategies 

applied to a reference home design in a variety of climates.1

 A contractor or homeowner can use 

the information to choose strategies most likely to produce various levels of energy savings for 

their particular home, geographic location, and fuel type. The strategies listed, however, are 

limited to sealing air leaks and adding additional ceiling insulation from the interior. They do not 

address exterior roof retrofit options for problematic attics (those that cannot completely meet 

the trio of strategies to prevent ice dam formation).

There are also countless magazine and Internet articles, websites, and blogs on the methods for 

improving energy efficiency of existing homes through roof and attic strategies. Much of the 

 

1 For more information on the Building Energy Optimization software, see http://beopt.nrel.gov/
13 

information is coming from field experience of individual contractors, code mandates, 

manufacturer marketing information, and industry experts. Even though some of the information 

is based on building science principles and new construction best practices, the lack of 

consistency in approach, as well as the lack of climate-specific, research-supported data, presents 

confusion in the marketplace. 

No building code for existing homes requires a test-in/test-out process to determine if the home 

has been left in a safe manner for the occupants or if the measures were installed to perform as 

designed, so little attention to safety and long-term performance is required of product 

manufacturer, distributor, installer, or homeowner. Yet research-supported guidelines, such as 

Attic Air Sealing Guide and Details (Lstiburek 2010), stress the importance of understanding 

changes to the home as a result of air sealing techniques. Occupant safety needs to be considered 

along with energy design. 

To begin the process of developing research-based packages of solutions for roof energy loss and 

ice dam prevention in existing homes, the NorthernSTAR team focused this exploratory study on 

11⁄2-story homes with conditioned living space on the upper floor. This type of housing was 

chosen because it is a common fixture in cities and towns in cold climates and finding a cost and 

energy effective solution can affect millions of homes. 

Most 11⁄2-story homes were built in an era when energy efficiency was neither sought nor 

understood. Homeowner desire to expand living area into unused attic space, however, has 

resulted in less than optimal conditions for energy efficiency, comfort, and long-term durability. 

This house type has been constructed with a variety of rooflines that can be simple or 

complicated. There are older 11⁄2-story homes (from the 1950s) that were built with finished 1⁄2-

story spaces and have similar issues. One and one-half story homes suffer from frequent ice 

dams because of one or more shortcomings, including the following: 

• Difficulty in adequately insulating vaulted ceilings with shallow rafter depths 

• Difficulty in preventing thermal bridging of interior heat to the roof deck even with high 

R-value foam insulation in a vaulted ceiling 

• Difficulty in venting the roof deck of vaulted ceilings in high snow load regions 

• Challenges in properly venting the roof deck with multiple valleys 

• Roof obstructions and penetrations such as chimneys, vent and soil stacks, and skylights 

• Failure to maintain air barrier continuity at the wall to roof transition at soffit

• Failure to maintain air barrier continuity at the roof to wall transition at dormers

In addition to homeowners attempting to address ice dams with increased insulation and air 

sealing on the inside, many have also tried heat tapes, heat panels, and metal snow/ice belts at the 

eaves, full replacement standing seam metal roofing, de-icing materials, and hand raking the 

eaves. Although these methods can reduce the risk of ice dam formation, they do not attempt to 

improve the energy efficiency of the home. Their effectiveness also decreases when melting or 

removing the snow becomes complicated by frequent snow events and accumulations. 
14 

The roof “overcoat” concept follows principles developed for new construction building 

envelope overcoat methods. Examples are the Canadian whole-house overcoat method known as 

the Pressure Equalized Rain Screen Insulated Structure Technique and the Alaskan wall-only 

overcoat method known as REMOTE (Residential Exterior Membrane Outside Insulation 

Technique). In these systems, a continuous air, moisture, and thermal barrier is applied on the 

outside of the building envelope for improved overall performance. The continuous insulation 

promotes a reduction in thermal bridging that could further reduce energy consumption. 

2.1 External Thermal Moisture Management System

A study by Building Science Corporation (BSC) for BA on high R-value roofing assemblies for 

new construction indicates that the exterior overcoat approach to roofing can also be applied in 

retrofit situations (Straube and Grin 2010). The approach promoted in the study for cold climates 

includes unvented, R-60 roof insulation achieved by combining two layers of 2-in. rigid 

polyisocyanurate foam on the exterior of the roof sheathing with netted fibrous fill blown into 

the rafter bays. Figure 15 presents the complete details. 

Figure 15. Exterior overcoat approach for roof retrofits 
15 

BSC has created numerous case studies of DER projects in which a whole-house overcoat, not 

just a roof overcoat, process was undertaken. But valuable information for roof retrofits can be 

understood through examples. Lstiburek (2011) outlines the process of upgrading a 11⁄2-story 

Cape Cod house built in 1953. The roof was fairly simple in that the shed dormer on the back of 

the house was increased during the remodel to encompass the whole width of the building and 

add living space for the homeowners. There were no overhangs on the roof, which proved to be 

both good and bad. The lack of overhangs made the process of aligning the air barrier and 

insulation of the walls to the roof easier. The lack of overhangs, however, led to extensive water 

damage to the wall sheathing (hidden behind the vinyl siding) that needed to be fixed before 

energy improvements could be installed. A continuous air barrier was adhered to the new wall 

and roof sheathing. Two 2-in. layers of polyisocyanurate, seams staggered and sealed, were 

applied over the wall and roof air barrier. High-density spray foam was added to the rafter bays 

to yield an R-60 roof. The roof was unvented. The Building Energy Optimization analysis of the 

applied strategies indicated a source energy use savings above 50%. 

BSC was involved in the DER of an original Sears Roebuck home, a 3,600-ft2

, four-square, twostory home with a finished attic (Pettit 2009). This process was similar to the 11⁄2-story home 

retrofit, featuring a whole-house overcoat with two 2-in. layers of polyisocyanurate, seams 

staggered and sealed, over the air barrier. Again, high-density spray foam was added to the rafter 

bays, yielding an R-60 unvented roof. The roof of this home, however, was much more 

complicated than the previous one. The hip roof was interrupted by four hip dormers and deep 

overhangs. The existing rafter tails were extended and the soffit widened to accommodate the 

exterior insulation. The large overhangs were detailed with crown molding to accommodate the 

extra thickness of the exterior foam. Gas utility costs after the retrofit indicated that the wholehouse retrofit had been successful; gas usage was reduced by nearly two-thirds. Figure 16 

illustrates the details for the overcoat process on the home. Note the removal of the existing attic 

flooring at perimeter to allow for installation of spray polyurethane foam (SPF) to seal the top 

plate and align the insulation layers of the roof and wall. 
16 

Figure 16. BSC Sears Roebuck house DER details
17 

To develop guidelines for other users of the exterior overcoat strategy, BSC worked with the BA 

to create comprehensive design and installation details for integrating exterior moisture 

management and insulation on wall assemblies for DERs (BSC 2009). Drawings include window 

and door head/jamb/sill/trim, exterior light fixture, electric box, and vent pipe/duct penetration 

details. Installation sequences for windows and doors are also included. 

The BSC information provides guidance on creating whole-house overcoat retrofit assemblies 

with unvented roofs, which the authors call “compact roofs” (BSC 2009). Researchers at BSC, 

however, have noted the necessity of venting the upper roof deck in certain situations (Lstiburek 

2008). If the snow load is less than 50 lb/ft2 and the thermal resistance is greater than R-50, the 

compact roof can be used. If the ground snow load is greater than 50 lb/ft2, the roof should be 

vented. As the snow load increases, so does the R-value of the snow, insulating the roof deck 

from above and elevating its temperature above freezing. 

Venting the upper roof deck may also be necessary when overhangs are present. Wall claddings 

can absorb solar radiation and release heat that can get trapped under the overhang. This heat, 

even though produced on the exterior of the building, can melt snow and result in ice dam 

formation. The vented air space allows the roof deck to be cooled. Figure 17 shows the vented 

compact roof. 

Figure 17. Venting a compact roof to prevent ice dam formation
18 

A small case study from the University of Alaska Southeast (George 2012) found that adding 

10.5 in. of extruded polystyrene to the exterior of the roof (no other energy strategy employed) of 

a home built in 1930 resulted in an air leakage reduction from 4,897 cfm to 691 cfm and a Btu 

per hour reduction of 70,422 Btu/h to 36,791 Btu/h. The total change went from 27.7 Btu/h/ft2 to 

14.5 Btu/h/ft2 (both at winter design temperature).

The NYSERDA (Pedrick et al. 2010) DER case studies present whole-house overcoat strategies 

for four existing homes that follow a similar assembly process as BSC. The layering of materials 

consisted of a water resistive ice and water shield over the sheathing, two layers of 2-in. 

polyisocyanurate foam with the edges staggered and sealed, and 1⁄2-in. nail base material over the 

foam to anchor the siding and roofing materials. Roof ventilation was included if there was a 

high exposure to wind-driven rain, a heavy snow risk, or a complex roof typology. A roof was 

left unvented if the building envelope was considered airtight, no interior vapor barrier was 

present, and the roof insulation value was a true R-40. Successful implementation of the overcoat 

process was driven by comprehensive installation drawings included in the report (Pedrick et al. 

2010). 

The Cold Climate Housing Resource Center in Fairbanks, Alaska, promotes an exterior wall 

overcoat system using the REMOTE process. REMOTE is an insulation and moisture 

management system applied to the exterior of a house wall system that is combined with a 

conventional, unconditioned attic. Although the process itself does not address roofs, the 

REMOTE manual (Cold Climate Housing Research Center [CCHRC] 2009) contains numerous 

detailed drawings and methods for installation of various cladding systems including stucco and 

lap siding, cladding systems that might be present on the dormers of 11⁄2-story homes. It also 

includes details on working around obstacles such as windows, decks, bays, and cantilevers, 

some of which may be present in the upper level of a 11⁄2-story home. The manual does include a 

short disclaimer on using REMOTE for retrofit situations. It urges caution and consideration on a 

case-by-case basis because of the limited opportunities to align the exterior moisture 

management system with the interior vapor barrier system and to apply adequate insulation.

As a follow-up to the REMOTE manual and numerous inquiries from Alaskan property owners, 

the CCHRC (Craven and Garber-Slaght 2012, 2010) has been conducting laboratory wall 

studies. The goal of these studies is to understand the effects of varying levels of interior and 

exterior insulation combined with exterior vapor retarder of the REMOTE wall system in the 

presence of existing interior vapor barrier. These investigators found that the presence or absence 

of an interior vapor barrier in the local climate was not of great significance if there was thick 

exterior insulation—when 65% of the total wall R-value was to the exterior—even when the 

interior vapor barrier was not perfectly applied. 

2.2 Structural Insulated Panels

There is a growing use of SIPs for roof retrofit applications. SIP manufacturers are also 

modifying their products by removing one layer of sheathing so the foam face can be applied to 

existing roof sheathing. These revised panels are often called nailbase panels or retrofit panels. In 

response, classes are available to teach proper installation methods, including effective air 

sealing, along with post-construction air quality and combustion safety. One example is an 

upcoming SIP school class where the nailbase panel is used for roof overcoat retrofits 

(SIPschool.org 2012). 
19 

A simple example of a DER using SIPs was documented on a one-story home. The SIPS roofing 

(121⁄4 in. at R-60) and walls and exterior expanded polystyrene foam foundation insulation 

enabled a Massachusetts home to achieve a 70% energy reduction (R-Control 2011). 

2.3 Over-Roofing 

No documented research could be found for over-roofing as a means of improving energy 

efficiency or for ice dam remediation.

2.4 Spray Foam

The internet is filled with spray foam companies and contractors offering their products and 

services as solutions for energy inefficiency and ice dam problems. A homeowner uneducated in 

building science would have a difficult time separating the fact from the fiction because so many 

websites claim they are the ones to offer the solution. As noted in Section 1, fixing ice dams 

from the interior may or may not be successful. Problematic roof structures may limit the ability 

to effectively apply the trio of solutions—insulation, air sealing, and ventilation—especially in 

11⁄2-story homes and homes with cathedral ceilings. 

Research on the commercial/industrial building industry indicates that SPF is used quite 

frequently on the exterior of flat roof systems to overcoat existing roofing. Two-pound closed 

cell foam has an R-6.5 per inch. Three-pound density foam used frequently at the commercial 

building level has an R-7.14. Costs were estimated from $2.50/ft2 installed (Kohls Foam Systems 

2012) to $5.00/ft2 installed (Tucker and Knowles 2012). An elastomeric coating or gravel is used 

over the dried foam for added durability and solar protection.

One research report (Lstiburek 2011) did discuss the use of SPF as exterior insulation for wall 

assemblies. The initial focus was for use behind brick walls. Attention to detail is critical for 

successful implementation. Windows and doors require a transition assembly between the 

glazing systems and the wall assembly similar to that of an extended “buck” to ensure that the 

window or door can be removed if needed instead of being integrated with the foam. Design 

details show a window filet made of SPF that is applied prior to the rest of the foaming to 

prevent gaps at the junction of the buck and the wall foam. Brick works well because installation 

naturally requires masonry ties and drainage planes. The gap between brick and foam 

accommodates the unevenness of the foam. Other claddings will require some type of furring 

system that will maintain a level surface for installation. The downside to a furring system is it 

can reduce R-value because of thermal bridging from furring to sheathing. This is most true for 

“z” girt systems. There are, however, some manufactured and field-implemented systems 

(fasteners with stand-offs) that can largely avoid thermal bridging. 

A DER using combined rigid foam and SPF on the exterior walls of a 100-year-old home 

demonstrates the SPF technique previously described but with furring strips held from the block 

wall with metal brackets (Yost 2009). This allowed 3.5 in. of closed cell SPF to be applied to the 

original block while minimizing thermal bridging. The foam will not fully expand to the front 

edge of the furring strip, leaving an air gap and drainage plane behind the new cladding. 

Foam-Tech (a division of Building Envelope Solutions) is a company in Vermont that focuses its 

business primarily on commercial and industrial applications (Building Envelope Solutions 

2012). The company’s website, though, provides case study information relevant to anyone 
20 

contemplating spray foam technology as an interior insulation and air sealing strategy to prevent 

ice dams. To understand what caused the problem and where to focus solutions, the company 

begins all of its remediation with on-site testing and data collection. It is also interesting to note 

that the company has a formal plan to provide post-work temperature monitoring, infrared 

testing, and visual inspection to determine if applied strategies were functioning or what 

solutions are necessary to fix the attempted mitigation. 

2.5 Alternate Processes and Materials for Exterior Overcoat

The ETMMS solution recommends using an air barrier membrane between the foam and roof 

sheathing. A liquid applied membrane could be a possible alternative to the typical peel and stick 

membrane. In the Midwest, liquid applied membrane costs are roughly $0.60/ft2 for product and 

installation (Schirber 2012). This compares to peel and stick that is roughly $3.26/ft2 for product 

and installation (based on product at $125 for a 99-ft2

 roll and labor at $2/ft2).

An alternate material to rigid foam exterior insulation would be the use of mineral wool board. In 

2009, the New York City area prices were around $0.25 ft2 for 1-in.-thick boards (approximately 

R-4.2 per inch) up to $1.00 ft2 for 2-in.-thick, foil-faced boards (Ehrlich 2009).

Some rigid foam board manufacturers make their products with built-in furring strips that could 

be customized to extend beyond the face of the foam board. This would result in a built-in 

ventilation area between foam board and roof sheathing (DF 2012). 
21 

3 Overcoat Impact Study

The MLS (2012) and the U.S. Census Bureau (2010) were used to estimate the number of 11⁄2-

story homes that exist in Minnesota. From this information, a rough estimate was created to 

define the number of homes that could be potentially improved with an overcoat approach. 

The Minneapolis MLS website represents all listings in the state of Minnesota registered by 

state-licensed real estate brokers. Although the MLS does not include properties being sold 

directly by owners, it is the number one source in the state for locating homes for sale. The site 

was queried to get some preliminary data about the proportion of 11⁄2-story homes, relative to 

other house types, in Minnesota (MLS 2012). On February 27, 2012, there were 15,463 singlefamily homes for sale. Of those, 2,178 (14.1%) were listed as 11⁄2-story houses. 

The Census Bureau provides statistical data on housing by type (e.g., single-family detached and 

single-family attached among others (U.S. Census Bureau 2010). A query of this website found 

there are 1,571,436 single-family detached housing units in Minnesota. As a crude estimate of 

the number of 11⁄2-story houses that could potentially benefit from an exterior roof insulation 

overcoat strategy, 14.1% of 1,571,436 results in a figure of 221,572 homes in the state of 

Minnesota alone. 

This study was limited to the Minneapolis MLS. This number, though, is expected to be 

representative of other cold-climate cities in other states, bringing the total number of 11⁄2-story 

homes that could benefit from an overcoat approach into the millions. 
22 

4 Contractor Interviews

The NorthernSTAR team conducted interviews with six contractors from two cold-climate 

regions in the United States, the Midwest and the Northeast. The contractors have experience 

with installing exterior roof insulation and a known or stated focus on roof retrofits, particularly 

in response to ice dam problems. The goal was to gain field insight into problems and solutions 

for scalability related to material availability and cost, contractor training, and construction 

technique. Each contractor was provided with a script of questions from which they could 

prepare for the telephone interview (see Appendix A for the actual contractor interview 

template). A follow-up phone interview was employed to ask further questions. Key interview 

questions covered the following: 

• Scope of company services including range of energy and ice dam solutions offered 

• Cost, ease of construction, durability, and hygrothermal performance of energy and ice 

dam solutions offered 

• Pre- and post-assessment process

• Overall design issues and approach to critical details

• Material and labor costs

• Marketing strategies for energy efficiency and ice dam services.

The contractors were also asked for their opinions on what single change could significantly 

promote a complete exterior insulation roof retrofit in comparison to other potential solution sets 

for ice dam problems in existing homes. 

Table 1 gives an overview of each company, its location, and its experience with ice dam 

retrofits.
23 

Table 1. Contractor Overview 

Contractor Garland Mill 

Timberframes

Synergy 

Construction

Byggmeister Mindel and 

Morse Builders

Cocoon Panelworks 

Plus

Location New Hampshire Massachusetts Massachusetts Vermont Minnesota Minnesota

Years in 

Energy 

Retrofit

25 3 20 30 4 10

# Ice Dam 

Retrofits in 

Past 5 Years

4–5 as part of 

whole house 

overcoat

2, roof only 20–25 2–3 112 5

Type of Case 

Study Provided

NA NA Interior Retrofit Interior Retrofit ETMMS SIP Roof 

Retrofit Panel

Cost per 

Square Foot 

for Case Study 

Provided

NA NA $16.00 for 

materials and 

labor 

$21.74 for 

materials and 

labor 

$12.00 for 

materials and 

labor 

$5.60 for 4-in. 

panel and labor
24 

Table 2 summarizes the types of strategies employed for addressing ice dams.

Table 2. Types of Ice Dam Mitigation Strategies Employed by Contractors

Exterior Roofing Strategy Number of Companies 

That Use Each Strategy

Ice Belt 2 

Metal Roof 1 

Interior Air Sealing and Insulation 4 

SIP and Nailbase SIP 2 

Exterior Strapping and Spray Foam Insulation 1

Exterior Strapping and Rigid Foam Insulation 1 

ETMMS-Like Approach 4

Roof Geometry Modification 1

4.1 General Comments From Contractor Interviews

4.1.1 Solution Generation Phase

Before starting a construction project, all the participating contractors engage in some type of 

process that helps them determine which solution to offer for ice dam or energy efficiency 

improvement, or both. All the contractors cited building details, client budget, and other planned 

work as key determinants. Additional information may come from the use of a pre-assessment 

form, photographs, and visual inspection. A few contractors have even been involved in some 

form of preconstruction testing. Only two builders consistently use a blower door test to uncover 

air bypass routes, but a few builders received this information through the project architect or 

building scientist. These contractors have come to recognize the value of the information as a 

way to create more effective ice dam strategies and stated their intention to hire this test on their 

next projects.

Those builders that engage in preconstruction testing on a regular basis believe that the 

information uncovered during this critical phase helps educate clients on the real causes of ice 

dams and energy loss. This exchange of information seems to be critical to moving potential 

customers from band-aid approaches to true solution sets. 

In regards to actual construction concerns when using an overcoat approach, the participating 

contractors that have experience cite deeper and taller roofs as requiring more time and greater 

cost. This may deter other contractors from seeking this solution for their clients. 

4.1.2 Construction Phase

Of the concerns expressed by the contractors using an overcoat approach, how and when to vent 

an assembly appears to be the most confusing. The remodelers are uncertain about when the 

assembly should be vented and if the roof assembly or the cladding should be vented. Although 

the literature review sheds some light on these issues, the research is not always in agreement 

and the lack of conclusive understanding in the industry is evident in the contractors’ responses. 
25 

4.1.3 Post-construction Phase

It is interesting to note that there is a general understanding among the contractors interviewed 

about the importance of post-construction review of a project. Two of the contractors always use 

blower door performance testing; the majority of the remaining contractors have been involved 

in projects where post-construction testing was completed. The important nature of postconstruction testing has led two contractors to purchase their own blower door equipment. 

There was, however, a shared understanding of the impact of tightening a home on occupant 

ventilation. As a result, five of the six contractors have recommended the use of a heat recovery 

ventilator (HRV) or other mechanical ventilation in some or all of their projects. What is not 

widely understood is the “house as a system” approach. Occupant ventilation was a concern for 

most contractors, but only two were concerned about moisture and carbon monoxide issues that 

can result from tightening a home. These two contractors calculate heating needs as a result of 

the energy improvements and recommend heating replacement as part of an energy upgrade. One 

consistently tests for post-construction radon levels and combustion safety. The other frequently 

uses temperature and moisture monitoring before and after retrofits. 

4.1.4 Sales and Marketing

All the contractors interviewed have experienced competition from other contractors that sell 

band-aid approaches to ice dam mitigation. A few contractors have responded to the competition 

by providing such approaches to keep a client. Yet the contractors with a more sophisticated 

approach to performance testing seemed to have an equally sophisticated approach to marketing 

and greater success with offering more advanced solutions. They often used collateral pieces or 

websites, or rely on their reputation for ice dam solutions. These contractors also cited building 

science experts when talking with clients about ice dam formation and solutions. Two of the 

cited experts include Lstiburek (2008) and Rose (2005, p. 113). 

One of the final contractor interview questions asked contractors what they believed to be the 

single most important or influential change that would significantly promote a complete exterior 

insulation roof retrofit in comparison to other potential solution sets for ice dam problems. There 

was no consensus in response. Half the contractors, though, believe that using metrics, 

especially information from diagnostic testing, is important to help clients understand how ice 

dams are formed and what that means for long-term solutions. Deferred maintenance, owner 

desire to stay in the homes, education, and carbon tax were also cited as important considerations 

for improving homeowner buy-in. 

4.2 Noteworthy Comments From Contractor Interviews

4.2.1 Garland Mill Timberframes

Ben Southworth, president of Garland Mill, stated that they work with both BSC and Marc 

Rosenbaum, an energy engineer/building scientist, on DER projects to ensure that their building 

assemblies are high performance. The company, however, prefers to work on homes with flat 

ceilings and vented roofs because of the ease, cost, and opportunities for long-term success. 

Garland Mill has developed a system in which their experts follow behind their air sealing 

contractor with a can of spray paint to highlight areas where foam is installed incorrectly. The air 

sealing contractor has to correct the spray-painted spots. 
26 

Garland Mill has a unique way to address super-tall fascia when topside new roof framing is 

used. The existing soffit assembly is removed, eave walls are plumb cut flush, and then a 

traditionally sized eave soffit is built. This essentially increases the total height/appearance of the 

eave wall. The drawback to this approach is that it changes the aesthetic of the height of the wall 

over eave wall windows. 

This company tends to avoid SIPs because of problems related to product quality and air sealing. 

The most influential factors affecting proposed solutions are budget and exterior architectural 

details.

4.2.2 Synergy

Synergy has participated in many whole-house DERs using the ETMMS approach through the 

National Grid Program. Synergy’s success with the process has led them to aggressively promote 

the ETMMS solution. The decline in National Grid whole-house funding, though, has led 

Synergy to promote smaller projects, such as roofs, using the ETMMS approach. Although 

performance testing was managed by outside consultants on whole-house overcoat projects, 

Synergy representatives sees their company moving into the use of performance testing to guide 

their solutions development process. 

4.2.3 Byggmeister

Byggmeister’s experience with nailbase SIPs cites excess waste with complex roofs as a reason 

to discontinue using the approach. The optimal exterior retrofit approach includes rigid 

insulation with access to the roof framing cavities to increase insulation opportunities and to 

prevent excess thickness of exterior foam from complicating the installation. 

Paul Eldrenkamp, president of Byggmeister, cites building details and client budget as key 

factors that drive solutions development. Age or newness of the roof cladding may not prevent a 

homeowner from pursuing an exterior insulation solution, especially if it promises to be the best 

solution. 

Figure 18 illustrates a project in which the historical relevance of the home and complexity of the 

roof indicated that exterior overcoat would not be the optimal solution. Instead, the existing roof 

decking was removed and rafter cavities were sealed and insulated with medium density spray 

foam (R-5). New roof sheathing was installed and the new roof was left unvented. 
27 

Figure 18. Exposing rafter cavities to prepare for spray foam insulation 

(Courtesy of Byggmeister)

The estimated cost for this type of project was $30,000 or $16/ft2. 

Byggmeister often uses an OmniSense monitoring system (www.omnisense.com) to monitor 

before, but most often and most importantly, after the retrofit. The company uses a 12-sensor 

force measuring sensor (FMS; about $800) and its wireless Internet access ($20/month) to gather 

relative humidity, temperature, and moisture content from within assemblies. The 

preconstruction testing helps drive solutions that are offered to homeowners in a comprehensive 

report.

Byggmeister always tests in and out for radon, but they have never had a project where their 

work moved the home from below to above the EPA action level, 4 pc/L. 

4.2.4 Mindel and Morse Builders

Mindel and Morse Builders has been involved with several projects using nailbase SIPs. 

Complexity of the projects ranged from simple two-plane roofs to six total dormers. If dormers 

were present, they were wrapped with exterior rigid foam or rebuilt entirely of SIPs. Adding 

dormers made of SIPS during a roof retrofit was deemed easy. SIPS were seen as a tighter and 

less expensive solution to exterior retrofit. 

The company reported that exterior approaches are often driven by homeowner desire to 

maintain an interior aesthetic. 

Figures 19, 20, and 21 show an ice dam mitigation project constructed by Mindel and Morse 

Builders that did not use exterior insulation approach because the homeowner was concerned 

about the aesthetics of the thickness of the foam. It did, however, include six dormers that were 

wrapped with exterior rigid foam. The main roof rafter cavity was filled with 7-in. of foil-faced 

foam rough cut in layers to fill the spaces. This insulation system can be constructed by company 
28 

crews instead of hiring spray foam contractors. Foam edges were sealed from the exterior using 

spray foam. The standing seam metal roof cladding was vented. 

Figure 19. Foil-faced foam between rafter framing 

(Courtesy of Mindel and Morse Builders)

Figure 20. Dormers wrapped in foam 

(Courtesy of Mindel and Morse Builders)
29 

Figure 21. Finished roof 

(Courtesy of Mindel and Morse Builders)

The six-dormer project covered 27 squares. The job cost for expenses related to the roof 

insulation was $58,700, or $21.74/ft2. The new windows and dormer insulation expenses added 

another $8,000. The standing seam metal roof expenses totaled $22,600. 

4.2.5 Cocoon

Cocoon bases its approach to ice dam solutions on pre-work testing and inspection, the condition 

of existing roof cladding, the roof complexity, and the client’s budget.. The company explores 

the possibilities as they pertain to achievable solutions and work with the homeowner on crafting 

a good, better, and best approach while trying to align their decision with the measurable 

outcomes, financial cost and performance benefits. Their goal is to market “to the pain” but to 

sell “solutions,” not products. 

Cocoon also actively engages in post-work performance testing and thermal imaging, ventilation 

measurement, combustion safety, and radon measurement. The company wraps all this 

information into a customer job report, with recommendations for additional considerations for 

improved home performance and/or remaining issues. The post-work report to the customer 

almost always includes HVAC recommendations or considerations.

Steve Schirber, president of Cocoon, indicated that an interior air sealing and insulation approach 

can be quite challenging. Although attending to the details necessary for long-term durability can 

be challenging, it can be done in a relatively short period of time and is much less expensive than 

ETMMS. Interior air sealing is often low in cost and the spray foam is easy to install, but the 

lack of data on hygrothermal performance of this approach is the reason Cocoon prefers exterior 

insulation whenever possible for mitigating ice dams. The ETMMS is the more expensive option 

but it offers the most durable and best hygrothermal solution for ice dams. Because it involves 

exterior access to eaves and even sometimes top of eave walls, it is a much more invasive 
30 

process, although it has little impact on day-to-day activities of the occupants. Figure 22 

illustrates the process of removing the soffit for access to the eave wall and accommodation of 

the added thickness of the exterior insulation. 

Figure 22. Removing the soffit for an ETMMS approach illustrated by superimposing 

a drawing of the process over a photograph of the home 

(Courtesy of Cocoon)

The open eave allows spray foam insulation to be added at the eave wall to align wall insulation 

with the exterior insulation plane. Figure 23 illustrates the rigid board insulation over the new 

air/vapor barrier on the roof sheathing, the new soffit, and the framing lumber placed over the 

foam to ventilate the roof and support the new roof decking. 
31 

Figure 23. Insulation, air barrier alignment, and soffit construction illustrated by superimposing a 

drawing of the process over a photograph of the home 

(Courtesy of Cocoon)

Figure 24 demonstrates the first protective strategy in an overcoat approach with the use of an 

air/vapor barrier over the entire roof surface.
32 

Figure 24. Installing the air/vapor barrier over existing roof decking 

(Courtesy of Cocoon)

Figure 25 illustrates the transition at the eave wall where the new rigid insulation meets the new 

vented soffit. 

Figure 25. Transition where new insulation meets eave wall and new soffit 

(Courtesy of Cocoon)

Figure 26 illustrates the method Cocoon uses to ventilate the roof decking to enable continuous 

ventilation at the valley. 
33 

Figure 26. Ventilation of ETMMS 

(Courtesy of Cocoon)

Cocoon representatives believe that there are several circumstances under which homeowners 

are more likely to consider an ETMMs approach. These include deferred maintenance such as 

roofing, siding, and windows already in need of repair/replacement; the desire of the homeowner 

to stay in the house long term; and the homeowner’s ability to understand the complexity of 

building performance and the risk of not completing the project correctly. 

4.2.6 Panelworks Plus

At Panelworks Plus, the builders believe that the increased ice dam occurrence during the winter 

of 2010 is driving the surge in requests for roof retrofits. The lack of snow during the winter of 

2011, however, is preventing opportunities to examine the effect of ice dam mitigation efforts 

from 2010. 

A recent project using 4-in. retrofit panels (R-16) that was considered medium in complexity 

incurred costs of just over $3.00/ft2

 for materials and $2.60/ft2 for installation. Figure 27 shows 

the beginning stages of the retrofit application with several panels in place.
34 

Figure 27. SIP retrofit panel installation 

(Courtesy of Panelworks Plus) 

Thicker R-value SIP retrofit panels make the installation more complex. The presence and 

number of valleys have more of an impact on the complexity of the installation than any other 

roof feature. Other roof features that heighten complexity include steep pitches and dormers. 

Figure 28 highlights the more complex process of detailing dormers. 
35 

Figure 28. SIP retrofit panel installation over dormer 

(Courtesy of Panelworks Plus) 

The company addresses the increased fascia height of exterior SIP installation with a double 

fascia. Or, if the depth of panels precludes the double fascia, the existing soffit will be plumb-cut 

to the eave wall and a new soffit will be built, essentially making the eave walls one or more 

courses of wall cladding “taller.” Figure 29 demonstrates the double fascia combined with 

standing seam metal roof cladding. 
36 

Figure 29. SIP retrofit panel installation with double fascia 

(Courtesy of Panelworks Plus) 

Curt Stendel, president of Panelworks Plus, indicated that increasing panel thickness will add 

around $0.45 to $0.50/ft2 for each additional 2 in. of foam thickness. Labor costs are driven by 

the complexity and the size of the roof with cost estimates ranging from $2.00 to $3.00/ft2

. 

A second project installed in 2010 using 4-in. retrofit panels is realizing a 15% savings on 

natural gas for heating over the previous year. 

The SIP retrofit panel method used by Panelworks Plus does not use an ice and water membrane 

over the existing roof decking. Panels are carefully sealed to each other to prevent air leakage, 

but no perimeter air sealing of the panels to the existing structure is undertaken.
37 

5 Conclusions and Further Work

This exploratory study found that the majority of information on exterior overcoat strategies for 

DERs and ice dam prevention in existing homes has focused on the use of the ETMMS 

technique. In this technique, continuous air, moisture, and thermal barrier systems are applied on 

the outside of the building envelope for improved overall performance. The ETMMS research 

data has been mainly documented for whole-house, DERs, which has left a void in information 

for roof-only applications. 

Some SIP manufacturers and installers are also promoting a SIP retrofit panel as a solution to ice 

dams. Installation techniques vary and do not always include the use of continuous air and 

moisture barrier systems. The SIP retrofit panel system, however (sheathing and insulation) is a 

component of an ETMMS approach and could easily be promoted as part of an ETMMS 

protocol if installed accordingly. 

5.1 Energy Efficiency and Ice Dam Prevention/Durability

A fair amount of information found during the literature review discussed the energy efficiency 

opportunities, or R-value capabilities, of exterior whole-house overcoat approaches. Roof 

insulation values of R-60 and above were possible when new roof cavity and overcoat insulation 

could be applied together. Case studies reviewed by the NorthernSTAR team indicate that 

exterior insulation systems can produce significant reductions in energy use. But there is little 

information on expected energy performance when new and old systems and materials are 

combined for roof-only applications. 

Very little research could be found that documents roof, wall, and/or foundation wall durability 

and post-construction hygrothermal performance. It is not known whether the subjects of the 

case studies are performing as predicted in preventing ice dams or interior moisture 

accumulation. The contractor interviews, though, indicated that there is an understanding among 

high performance contractors in the industry that exterior overcoat strategies have the best 

potential to address energy efficiency, durability, and ice dam prevention in existing homes. 

Overcoat would be their preferred method of roof insulation in most situations. 

Only one study, George, M. (2012), looked at the impact of adding overcoat measures to existing 

insulation and vapor barriers in wall systems. Further research would be needed to make 

conclusions about the performance impact of new overcoat measures combined with existing 

roof insulation type and R-value. There are also other issues besides the installed R-value of the 

existing insulation including insulation condition, contamination, presences of vapor retarders, 

and venting in the existing assembly. 

The BSC studies (Straube and Grin 2010, Lstiburek 2011, Pettit 2009, Lstiburek 2008) present 

optimal strategies for achieving DERs where insulation levels between roof rafters and the 

exterior insulation levels are optimized for snow load. Not all exterior roof retrofit projects will 

be able to improve interior insulation or add enough exterior insulation to meet the optimal levels 

described by BSC. Further research will be needed to study the performance impact of varying 

the levels of new exterior insulation in the presence of existing rafter insulation. 
38 

Additional research on roof ventilation for overcoat practices would help clarify when roof 

ventilation should be applied. Although some research (Lstiburek 2010) suggests that roof 

ventilation is not needed when R-values meet or exceed R-60, other research (Lstiburek 2008) 

suggests that it is still necessary in areas of high snow loads and for houses with large roof 

overhangs and dark claddings. It is not known if there are any existing conditions such as vapor 

barriers or certain types of insulation that would also preclude the necessity for a vented roof. 

5.2 Indoor Environmental Quality

No information was found in the literature review that linked any of the products or systems for 

exterior overcoat roof insulation to indoor air quality issues, except for research that linked a 

tighter home with the need to address combustion safety (Lstiburek 2008). There are no data 

measuring how many contractors that do energy improvements address health and safety, but the 

lack of consistency in post-construction performance testing, as noted in the contractor 

interviews, suggest that contractors should be educated about combustion safety. 

5.3 Constructability 

No studies were found that addressed issues related to specific roof typologies. Nothing could be 

located in the literature that indicated one roof typology was favored over another or that a 

specific roof typology could not be addressed through an overcoat approach. The literature 

review, in fact, indicated that complex roof structures—even those of 11⁄2-story homes with 

varying typology and obstacles—are capable of receiving exterior insulation if planned and 

designed well. 

BSC (2009) has created numerous cross-section details to furnish the information that design 

professionals and contractors will need for successful installation of rigid foam overcoat 

strategies. These details, though, are focused on whole-house integration where the new roof 

insulation and membrane are tied to the new wall insulation and membrane and all existing 

insulation is removed. No research could be found that addresses details for aligning new 

insulation and air/water barriers in the roof with existing insulation and air/water barriers in the 

walls. 

The BSC research and contractor interviews indicate the need for training and construction 

oversight to ensure that insulation and air barriers are aligned correctly.

5.4 Affordability

The cost information that was found for whole-house overcoat projects was inclusive of 

additional remodeling strategies needed to bring a house up to code, to repair damaged structural 

elements, and to add energy efficiency strategies such as new windows or mechanical systems. 

The cost for the overcoat components and labor were not isolated. As a result, the NorthernSTAR

team could form no conclusions about cost for overcoat measures from the literature. 

The contractor interviews found a wide range of costs for ice dam mitigation strategies. The 

approach applied by each contractor varied, making direct cost comparisons difficult. The 

contractor interviews, however, did offer some insight into costs. This information indicated that 

ice dam mitigation in 11⁄2-story homes via an interior approach is not always less expensive than 

exterior approaches. Increased cost in either approach is driven by the complexity of the roof and 

the need to maintain architectural or historical features.
39 

The overall consensus from the contractor interviews, however, indicates that budget is a key 

consideration but does not always drive the decision-making process. Changes to architectural 

and historical features are often determinants for which solution is most appropriate. Home 

improvements such as new windows, wall cladding, and roofing, or the addition of large dormers 

in a livable attic provide opportunities for energy retrofits and ice dam mitigations that favor 

exterior approaches over interior methods. 

In terms of cost, some materials not traditionally used for roofing—such as liquid applied 

membrane and mineral wool insulation— could lower the overall cost for an overcoat approach. 

Because these materials are not being used for roofing, constructability and durability would 

have to be researched before the materials could be recommended as replacements for products 

currently used in the marketplace.

5.5 Assessment Strategies

Some of the contractors interviewed use a pre-assessment process to determine which strategy is 

best for mitigating ice dams and improving energy efficiency. Those same contractors often 

begin their assessment with an energy audit using a blower door test and infrared camera scan to 

determine where air is leaking. These same contractors often include a post-construction blower 

door test and infrared camera scan to determine that the air sealing measures have been installed 

correctly. Only one contractor addressed combustion safety and tested for carbon monoxide postconstruction. 

Only one report in the literature review (George, M. 2012) addressed issues that might occur 

with preexisting vapor barriers in walls. Because newer 11⁄2-story homes constructed with vapor 

barriers may experience ice dams, understanding issues related to the presence of these vapor 

barriers is critical. If further research determines that a home with a vapor barrier requires special 

consideration for exterior overcoat applications, this would be a good pre-assessment question 

for a contractor to ask a homeowner. 

5.6 Overall Conclusions and Further Work

The BA website addresses best practice strategies for the roof component of new construction 

and references interior insulation and air ceiling for flat ceilings of existing homes.2 The website, 

however, lacks comprehensive information on roof insulation techniques for existing homes in 

cold-climate regions with complicated roof structures. Results from this research can help direct 

future BA research activities in efforts to create information for professionals, homeowners, and 

insurance companies to make decisions about more robust strategies for ice dam prevention.

Construction details that would help a designer or contractor understand how to align new and 

existing air barriers and insulation when employing an overcoat approach on an existing home 

are an important component missing from the literature. It is also unknown how beneficial an 

overcoat approach is for mitigating ice dams and improving energy efficiency because ETMMS 

studies have not been isolated to roof-only projects. Further research would be necessary to truly 

understand the costs associated with a roof overcoat approach and whether or not alternate 

materials and processes can be put in place to lower costs.

 

2 For more information, see Building America 

http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/26450.pdf
40 

The lack of pre- and post-construction blower door depressurization, infrared thermal imaging, 

and combustion safety testing also gives BA an opportunity to evaluate methods that improve 

performance outcome and reduce contractor risk by addressing occupant safety. 

Because most of the existing research and supporting strategies for exterior overcoat are based 

on the ETMMS whole-house approach, this is the most logical process to study. Monitoring 

actual ETMMS field installations of multiple roof projects would yield more robust cost, 

constructability, durability, and performance data that could lead to scalability opportunities for 

the millions of 11⁄2-story homes in snowy regions of the country. 
41 

6 References 

Air Worldwide (2011). Air U.S. Severe Storm Models: Severe Thunderstorm and Winter Storm 

Models. Boston, MA: Air Worldwide. 

BA (2011). “Energy Savings Measure Packages: Existing Homes.” Golden, CO: National 

Renewable Energy Laboratory. Accessed February 8, 2012: 

http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/energy_savings_meas

ures.pdf. 

Building Envelope Solutions. (2012). “American Ski Company: Ice Dam Case Study.” Accessed 

February 5, 2012: www.foam-tech.com/case_studies/asc_air.htm. 

BSC (2008). Building Science Corporation, “Building Science Insights: Dam Ice Dam”. Joseph 

Lstiburek. Accessed February 5, 2012: http://www.buildingscience.com/documents/insights/bsi046-dam-ice-dam. 

BSC (2011). “Cold Climate: National Grid Deep Energy Retrofit Pilot Program—Millbury 

Cape.” BSC. Accessed January 12, 2012: https://www.buildingscience.com/documents/casestudies/cold-climate-national-grid-deep-energy-retrofit-millbury-cape. 

BSC (2010). “Cold Climate: Bedford Farmhouse High Performance Retrofit Prototype.” 

Accessed January 12, 2012. https://www.buildingscience.com/documents/case-studies/coldclimate-bedford-farmhouse-retrofit-case-study. 

BSC (2009). “Deep Energy Retrofit Details.” Accessed January 24, 2012: 

www.buildingscienceconsulting.com/services/documents/file/20100312_Deep_Energy_Retrofit_

Details.pdf . 

CCHRC (2009). REMOTE: A Manual. Accessed February 9, 2012: 

www.cchrc.org/docs/best_practices/REMOTE_Manual.pdf . 

Craven, C.; Garber-Slaght, R. (2012). “Safe and Effective Exterior Insulation Retrofits: Phase 

II.” Accessed February 9, 2012: www.cchrc.org/docs/reports/MTL2_final.pdf. 

Craven, C.; Garber-Slaght, R. (2010). “Safe and Effective Exterior Insulation Retrofits: Phase I.” 

CCHRC. Accessed February 9, 2012: www.cchrc.org/docs/snapshots/RS_2010-

03_Exterior_Insulation.pdf. 

Ehrlich, B. (2009). “Product Review: Mineral Wool Residential and Commercial Insulation.” 

Buildinggreen.com. Accessed February 4, 2012: 

www.buildinggreen.com/auth/article.cfm/2009/9/25/Mineral-Wool-Residential-andCommercial-Insulation/?&printable=yes. 

George, M. (26 January 2012). Internal email. University of Alaska, Southeast. 
42 

Insurance Information Institute (2012). “Homeowners and Renters Insurance: Causes of 

Homeowners Insurance Losses.” Accessed January 22, 2012: 

www.iii.org/media/facts/statsbyissue/homeowners. 

Insurance Institute for Business and Home Safety (2012). “Preventing and Removing Ice Dams.” 

Accessed February 24, 2012: http://disastersafety.org/freezing_weather/preventing-ice-dams-onhomes. 

 

Iowa Insurance Institute Communications (2011). “Is Your House Properly Winter-Proofed?” 

Accessed January 22, 2012: http://www.iowains.org/homeowners-and-rentersarticle.aspx?id=12&Is+Your+House+Properly+Winter-Proofed%3F+ 

Kohls Foam Systems, Inc. (2012). “Spray Foam Insulation and Roofing.” Accessed February 6, 

2012: www.sprayfoamminnesota.com/about-spf-roofing.html.. 

Larson, T.; Hendricks, L.; Huelman P. (2010). “Ice Dams.” University of Minnesota Extension. 

Accessed February 8, 2012: 

www.extension.umn.edu/distribution/housingandclothing/DK1068.html#causes. 

Lstiburek, J. (2011). “Exterior Spray Foam.” BSC. Accessed February 6, 2012: 

www.buildingscience.com/documents/insights/bsi-048-exterior-spray-foam/?searchterm=spray 

foam exterior.

Lstiburek, J. (2010). “Guides and Manuals: Attic Air Sealing Guide and Details.” BSC. Accessed 

February 8, 2012:

www.buildingscience.com/documents/guides-and-manuals/gm-attic-air-sealingguide/view?searchterm=guide to attic air sealing.

Lstiburek, J. (2008). “Building Science Insights: Dam Ice Dam.”. BSC. Accessed February 8, 

2012: 

www. , 

MLS (2012). Minneapolis MLS. Accessed February 27, 2012: http://msp.themlsonline.com. 

O’Rourke, M.; Ganguly, M.; Thompson, L. (March 2010). “Eave Ice Dams.” Journal of 

Architectural Engineering (16:1); pp. 11–19. 

Pedrick, G.; Hamilton, B.; Rosenbaum, M.; Schneider, P.; Young, L.L. (2010). NYSERDA Deep 

Energy Retrofit Contractor Training. Accessed February 8, 2012: 

www.nyserda.ny.gov/~/media/Files/EIBD/Residential%20Buildings/der-contractortraining.ashx?sc_database=web. 

Pettit, B. (2009). “Cold Climate: Concord Four Square Retrofit.” BSC. Accessed January 12, 

2012: www.buildingscience.com/documents/case-studies/cs-climate-concord-four-squareretrofit/?searchterm=Concord. 
43 

R-Control SIPs (2011). “Deep Energy Retrofit Project Profile: Tudor Residence, Centerville, 

MA.” Accessed February 8, 2012: www.r-control.com/projects/tudor-retrofit.asp. 

Rose, W.B. (2005). “Chapter 4: Roofs and Facades.” Water in Buildings: An Architect’s Guide 

to Moisture and Mold. Hoboken, NJ: John Wiley & Sons. 

Schirber, T. (28 January 2012). Internal email. University of Minnesota. 

State Farm Insurance (2012). “Ice Dams and Attic Condensation.” Accessed February 24, 2012: 

http://learningcenter.statefarm.com/residence/maintenance/ice-dams-and-attic-condensation. 

SIPschool.org (2012). “Deep Energy Retrofit with Nailbase Panels (SIPs 175).” Accessed 

February 8, 2012: http://sipschool.org/classDetails.asp?article_id=1428&class_id=58. 

Straube, J.; Grin, A. (2010). “Building America Special Research Project: High-R Roofs Case 

Study Analysis.” BSC. Accessed January 24, 2012: 

www.buildingscience.com/documents/reports/rr-1006-ba-high-r-roofs-case-study-analysis. 

Tucker, R.; Knowles, M. (2012). “Closed-Cell Spray Foam to Offer Significant Benefits to Metal 

Buildings.” Accessed February 6, 2012: 

www.sprayfoam.com/newsarchives/archivedetails.cfm?id=256. 

U.S. Census Bureau (2010). “Selected Housing Characteristics.” Accessed February 27, 2012: 

http://factfinder2.census.gov/faces/tableservices/jsf/pages/productview.xhtml?pid=ACS_10_1Y

R_DP04&prodType=table. 

Yost, P. (2009).”Deep Energy Makeover: One Step at a Time.” GreenBuilding Advisor.com. 

Accessed February 10, 2012: www.greenbuildingadvisor.com/homes/deep-energy-makeoverone-step-time. 
44 

Appendix A. Project Overcoat Contractor Interview Template

Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name: 

2. Interviewee Title: 

3. Company Name: 

4. Location of Business: 

5. Complete scope or range of company services: Energy retrofits to solve comfort, utility 

bill and ice dam problems

6. Years in energy retrofit business: 

7. Number of “ice dam” retrofits completed in last 5 years:

Questions: 

When a potential client comes to you to with an ice dam problem: 

1. What information do you need before proposing solutions to the client? 

a. Assessment/inspection form

b. Pre-work testing (blower door, infra-red imaging, etc.) 

c. Client financial “aptitude”

2. What is the full range of ice dam solutions your company provides? 

3. How would you rate each of the above based on: 

a. Relative cost

b. Ease of construction/feasibility

c. Durability

d. Hygrothermal performance (combined energy and moisture management 

performance)

4. What resources do you use to explain the phenomenon of ice dams to your clients? 

5. What are the factors that drive which solutions you propose? 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)

b. Client budget 
45 

c. Sequenced or planned previous or future work 

6. Check out the 5 common roof types on the last page of this questionnaire:

a. Is there one or two that you most commonly deal with in ice dam work? 

b. Is there any relationship between roof type and which solution you propose? 

7. What sort of post-job evaluation or results do you gather? 

8. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)?

9. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g., heat tape, roof raking, installing a standing seam metal roof—complete or 

just the eaves)?

10. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR [infrared])

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.)

11. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes? 

2 plane, 2 gable 

2 plane, 2 gable with gable dormers 
46 

 2 plane, 2 gable with shed dormers 

4 plane, 3 gable 

 

3 plane, 2 gable 
47 

Appendix B. Project Overcoat Contractor Interview—Garland Mill 

Timberframes

Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name: Ben Southworth

2. Interviewee Title: President

3. Company Name: Garland Mill Timberframes (www.garlandmill.com/ ) 

4. Location of Business: Lancaster, NH

5. Complete scope or range of company services—mainly new construction and some 

DERs, including company purchase of foreclosed homes for major renovation and then 

rental

6. Years in energy retrofit business: DERs for 5 years, energy efficient new construction 

and retrofit for 25 years 

7. Number of “ice dam” retrofits completed in last 5 years: 4—5 DERs in which ice dams 

were a part of the puzzle

Questions: 

When a potential client comes to you to with an ice dam problem: 

1. What information do you need before proposing solutions to the client? 

a. Assessment/inspection form - no 

b. Pre-work testing (blower door, infra-red imaging, etc.)—blower door and fogging 

c. Client financial “aptitude”—yes, always 

2. What is the full range of ice dam solutions your company provides? 

a. Interior air sealing and insulation 

b. Exterior SIP and air sealing

c. Exterior strapping/framing with spray foam or more typically, cellulose cavity fill

d. Exterior rigid insulation (almost always using salvaged rigid insulation purchased 

from Conigliaro Industries)

3. How would you rate each of the above based on: 

a. Relative cost

b. Ease of construction/feasibility

c. Durability
48 

d. Hygrothermal performance (combined energy and moisture management 

performance)

Southworth follows the building science recommendations created by Building 

Science Corporation and Marc Rosenbaum of South Mountain Company. Of the 

techniques listed in #2 above, the least expensive approach tends to be c, air seal with 

foam and then topside new roof framing cavity filled with cellulose. 

NOTE: an innovative way that Garland Mill deals with the super-tall fascia when 

topside new roof framing is used: plumb cut flush the eave walls (remove existing 

soffit assembly) and then rebuild a traditionally sized eave soffit, essentially 

increasing the total height/appearance of the eave wall. This does change the aesthetic 

of the height-of-wall over eave wall windows, though. 

Southworth tends away from SIP products because of ongoing concerns about PBTs 

[polybutylene terephthalate] in the fire retardants and high GWP [global warming 

potential] of the different foams used in SIPS. Will limit use of these foams until 

there is more information is available to make better decisions on use. 

4. What resources do you use to explain the phenomenon of ice dams to your clients? Uses 

Joe Lstiburek’s newsletter on ice dams from 2011 

(www.buildingscience.com/documents/insights/bsi-046-dam-icedam/?searchterm=ice%20dams ).

5. What are the factors that drive which solutions you propose? 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)

b. Client budget 

c. Sequenced or planned previous or future work 

The most influential factors affecting proposed solutions are budget AND exterior 

architectural details (namely eave and gable overhangs and whether or not the 

overhangs remain or will be removed and rebuilt). 

Also, Garland Mills has a strong preference for working on homes with flat 

ceilings/vented, unconditioned attics because it is so much easier and cheaper to air 

seal and insulate a flat ceiling rather than a cathedral or cathedralized attic. Typical 

home they can air seal and insulate (2 feet of cellulose) an attic for $3,000. 

6. Check out the 5 common roof types on the last page of this questionnaire: 

a. Is there one or two that you most commonly deal with in ice dam work? Two-plane 

and doghouse dormers 

b. Is there any relationship between roof type and which solution you propose? See 

response above #5. 
49 

7. What sort of post-job evaluation or results do you gather? Blower door with targeted 

result.

An interesting quality control item that Garland Mill conducts is following behind their air 

sealing contractor with a can of spray paint, highlighting areas where the foam is deficient, 

rolled over on itself, or misapplied. The insulation/air sealing contractor has to go back and 

attend to all the spray painted spots, essentially covering the paint with their corrected work.

8. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)? Changes in heating unit (typically boiler) almost never. Addition of whole 

house mechanical ventilation (an HRV) always.

9. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g. heat tape, roof raking, installing a standing seam metal roof—complete or 

just the eaves)? N/A—Garland Mill does virtually NO ice dam-driven energy retrofits. 

10. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR)

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.)

Ben is considering providing info on one of their projects, but cannot by the 

January 31 deadline. 

11. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes? 

Metrics—increasing his company’s depth and capabilities in building performance 

measurements.
50 

Appendix C. Project Overcoat Contractor Interview—Synergy 

Construction

Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name—Alex Cheimets

2. Interviewee Title—VP, Sales and Marketing

3. Company Name—Synergy Construction (http://synergy-green-builders.com/ ) 

4. Location of Business—Leominster, MA

5. Complete scope or range of company services: high performance new homes and 

deep energy retrofits

6. Years in energy retrofit business—real push to high performance in last 3 years

7. Number of “ice dam” retrofits completed in last 5 years—plenty of bids but only two 

roof-only retrofits

Questions: 

When a potential client comes to you to with an ice dam problem: 

1. What information do you need before proposing solutions to the client? 

a. Assessment/inspection form - no 

b. Pre-work testing (blower door, infra-red imaging, etc.) - no 

c. Client financial “aptitude”—yes 

2. What is the full range of ice dam solutions your company provides? ETMMS primarily; 

Synergy has done a lot of DERs within the National Grid Program 

(https://www.powerofaction.com/der/ ) but that money is really drying up right about 

now, so more of the work Synergy is bidding is NOT whole-house deep energy retrofits 

but more “piece” work like roof retrofits. 

NOTE: one recent project, a very complicated slate roof, forced Synergy to do an interior 

roof retrofit: detailed air sealing with cellulose fill. This is not the preferred approach for 

Synergy because only the topside rigid insulation gives the thermal bridging solution and 

superior air seal.
51 

NOTE: Synergy has done a number of retrofits from inside the attic. Synergy believes 

that the best retrofit is from exterior, but most of their projects, including those with 

exterior insulation, include an interior attic component. 

When the roof is new, or slate, or for economic reasons, Synergy will suggest all the 

work be interior. Because of NGrid and NStar, though, many of Synergy’s projects need 

exterior insulation to reach utility program R-levels (R-60).

Synergy believes that the mix between exterior and interior will become more balanced. 

3. How would you rate each of the above based on: 

a. Relative cost

b. Ease of construction/feasibility

c. Durability

d. Hygrothermal performance (combined energy and moisture management 

performance)

The ETMMS solution is all that Synergy does. They feel it is the best solution, 

but although they have a very aggressive marketing program for this approach, 

they have lost quite a few bids of late based on cost and the dwindling of the 

National Grid DER program. 

4. What resources do you use to explain the phenomenon of ice dams to your clients? n/a 

5. What are the factors that drive which solutions you propose 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)

b. Client budget 

c. Sequenced or planned previous or future work 

See 2 above: essentially, Synergy works from the exterior unless some condition, 

like a slate roof that has to stay, precludes this approach.

6. Check out the 5 common roof types on the last page of this questionnaire: 

a. Is there one or two that you most commonly deal with in ice dam work? No, all 

types. 

b. Is there any relationship between roof type and which solution you propose? No, 

not really, even complicated roofs can be handled effectively and efficiently with 

ETMMS—see http://synergy-green-builders.com/concord-partial-retrofit-newroof/ . 

7. What sort of post-job evaluation or results do you gather? On the National Grid projects, 

Building Science Corp is the consultant and always does pre- and post blower door 

testing. Never thermal imaging. On non-National Grid projects, no testing currently, and 

certainly not for roof-only projects (Cheimets was surprised to hear, but then understood, 

that roof-only projects can give air tightening results worth capturing quantitatively). But 
52 

with the apparent ending of the National Grid Program, Cheimets stated that gaining 

performance measurement capability was really important.

8. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)? With DERs, required, but not for roof-only work. 

9. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g. heat tape, roof raking, installing a standing seam metal roof—complete or 

just the eaves)? Free consultation approach to selling high performance solutions: 

http://synergy-green-builders.com/request-quote/ . 

10. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR)

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.)

Alex would not commit to providing a project, but I am working on him to 

provide more info on recent ice-dam bids they have won/lost and to provide cost 

info for the one roof-only project they have on their website: http://synergy-greenbuilders.com/concord-partial-retrofit-new-roof/ . 

11. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes?

As the marketing guy at Synergy, Alex seemed very interested in connecting 

performance metrics to their marketing, particularly with the National Grid work fading.
53 

Appendix D. Project Overcoat Contractor Interview—Byggmeister 

Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name: Paul Eldrenkamp

2. Interviewee Title: President

3. Company Name: Byggmeister (www.byggmeister.com/index.shtml ) 

4. Location of Business: Newton, MA (5600 HDD [heating degree days]) 

5. Complete scope or range of company services: Exclusively remodeling, high 

performance retrofits

6. Years in energy retrofit business: 20

7. Number of “ice dam” retrofits completed in last 5 years: 20—25 roof retrofits (does about 

30—40 projects per year) 

Questions: 

When a potential client comes to you to with an ice dam problem: 

1. What information do you need before proposing solutions to the client?

a. Assessment/inspection form—no, visual inspection plus info/photos from client 

b. Pre-work testing (blower door, infra-red imaging, etc.)—sometimes, depends on 

if the project has “mysteries” or not

c. Client financial “aptitude”—absolutely, always competing against “band-aid” 

approaches 

2. What is the full range of ice dam solutions your company provides? 

a. Interior air sealing and insulation

b. Exterior only (rigid insulation or something close to the ETMMS) 

c. Ideally, exterior with access to roof framing cavities 

NOTE: Paul mentioned that the complexity of his roof projects means they never use 

nailbase panels—just too many cuts and different thicknesses of insulation required 

so from a cost and waste perspective, always does rigid insulation.

NOTE: if after all is said and done the customer wants to go with a band-aid 

approach, Byggmeister won’t do it and sends the client somewhere else. 
54 

3. How would you rate each of the above based on: 

a. Relative cost

b. Ease of construction/feasibility

 c. Durability

 d. Hygrothermal performance (combined energy and moisture management performance) 

Best solution is (c) from hygrothermal/durability perspective, but also the most expensive. 

(b) is challenging architecturally and the deeper the exterior insulation approach, the tougher 

(and more expensive) more-complicated roofs become.

4. What resources do you use to explain the phenomenon of ice dams to your clients? 

Generally, just verbal BUT if the client seems to want or need a resource (Paul’s company 

reputation means that they generally defer to his professional judgment quite a bit), the best 

one is in Bill Rose’s book, Water in Buildings, Chapter 4, Roofs and Facades, pg. 113, Ice 

Dams).

5. What are the factors that drive which solutions you propose 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)

b. Client budget 

c. Sequenced or planned previous or future work 

All of the above, but a and b are paramount and related, often. Paul mentioned that 

the age or newness of the roof cladding was not quite as important or influential as 

you might think—sometimes the problem means tearing off a perfectly good roof 

cladding because the solution requires it. 

6. Check out the 5 common roof types on the last page of this questionnaire:

a. Is there one or two that you most commonly deal with in ice dam work? 

b. Is there any relationship between roof type and which solution you propose? 

Paul proposed that all of his projects would require Figures 6—12; his projects tend 

to have very complicated roof configurations and architectural details. 

NOTE: the complicated details are existing conditions; Byggmeister strives to 

simplify roof details as a design policy in their work. 

7. What sort of post-job evaluation or results do you gather? 

a. Blower door 

b. IR imaging 

c. Monitoring

Paul uses an OmniSense system (www.omnisense.com/ ) as often as he can with 

clients to monitor before but most often and most importantly after the retrofit. He 

uses a12-sensor [force measuring sensor] (about $800) and then their wireless 
55 

internet access ($20/month) to gather RH [relative humidity], temp, and moisture 

content from within assemblies.

8. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)? About 10% of the time. On the low end, Paul will recommend a FanCycler 

system and on the high end an HRV. Byggmeister always tests in and out for radon, but 

they have never had a project where their work moved the home from below to above the 

EPA action level, 4 pc/L. 

9. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g., heat tape, roof raking, installing a standing seam metal roof—complete or 

just the eaves)? Byggmeister does not target market their roof retrofits; high performance 

is at the heart of all their marketing/company positioning.

10. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR)

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.)

Paul will do his best to provide us with one of his projects. The good news is he 

has been doing performance testing and monitoring on two recent projects. The 

bad news is that they are roof retrofits from last year, so he does not really have a 

full winter (this winter) of “after” data. He has promised the Journal of Light 

Construction [JLC] “first dibs” on this roof retrofit and monitoring work but will 

share with us what he can as long as we don’t in any way “scoop” JLC.

11. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes? Carbon tax to drive the 

economics of truly high performance solutions. Yes, exterior roof retrofits are more 

expensive, but if the cost of energy reflected all of its true costs, the economics would 

support the higher performance solutions. Right now, the “best” solutions—exterior roof 

retrofits—move the cost from about $10k to $60k. That is a tough sell. 
56 

Appendix E. Project Overcoat Contractor Interview—Mindel and

Morse Builders Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name: Steve Mindel

2. Interviewee Title: President

3. Company Name: Mindel and Morse Builders 

4. Location of Business: Dummerston, VT 

5. Complete scope or range of company services—full service renovation and new 

construction company 

6. Years in energy retrofit business—energy efficient construction for 30 years (began using 

exterior rigid foam on walls in 1981) 

7. Number of “ice dam” retrofits completed in last 5 years—2, and 3 including roof retrofit 

(longer than 5 years ago: 2—3 more)

Questions: 

When a potential client comes to you to with an ice dam problem: 

1. What information do you need before proposing solutions to the client? 

a. Assessment/inspection form - no 

b. Pre-work testing (blower door, infra-red imaging, etc.)- no (but should—need to 

gain the capability in-house) 

c. Client financial “aptitude”—not really

2. What is the full range of ice dam solutions your company provides? 

a. Ice belt (“band-aid” approach, admittedly) 

b. Standing seam metal roof (“band-aid” approach, admittedly) 

c. Exterior rigid insulation w/ strapping 

d. Cavity fill and air sealing

e. Nail base

Green River project (6 sloped roof doghouse dormers)—dormers wrapped with 

exterior rigid foam with main roof: cavity foil face, rough cut in layers to fill 

spaces, edges spray foamed as air seal, blow cellulose, “hot roof” (unvented roof 

framing cavities) with roof cladding ventilation topside (current project). No 
57 

exterior rigid foam topside because of overall project cost concerns and impact on 

exterior aesthetic.

On the following projects, nailbase SIPs were used on the roofs with doghouse 

dormers either wrapped with exterior rigid foam or dormers rebuilt entirely from 

SIPs. In each of the three, an exterior approach was driven by client’s desire to 

maintain interior aesthetic of exposed framing and underside of roof board 

sheathing. 

f. Baker Brook project (simple—two planes) 

g. Newfane project (one doghouse dormer—wrapped with SIPs)

h. Guilford project (6 doghouse new SIPs)—SIPs on top with blown cellulose in 

sleeper cavity essentially as a fire stop (has added this detail due to concerns that 

having a dead air space in the middle of the new roof assembly would allow a fire 

to stay “hidden” in this space).

i.

Note: The Newfane project with the single dormer is where we filled the sleeper 

space.

Eave detailing - foamed eave 

SIPs were tighter and less expensive (nailbase)

Interesting phenomenon with skylights, particularly on north slope; differential 

melting around skylight—solution is to rake below skylight 

Special Note: adding dormers in a roof retrofit constructed of SIPs is really easy

3. How would you rate each of the above based on: 

a. Relative cost

b. Ease of construction/feasibility

c. Durability

d. Hygrothermal performance (combined energy and moisture management 

performance)

Solving the heat and air loss problem means taking the whole roof system apart. Any 

of the external systems work at this point in the process, the cost and “convincing” is 

all about taking the roof apart, from the outside. So, most expensive solution is the 

most durable and best hygrothermal performance. 

4. What resources do you use to explain the phenomenon of ice dams to your clients? 

Verbal explanation—new JLC cover article on ice dams – planning on using that. 
58 

5. What are the factors that drive which solutions you propose? 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)—all factors. Valleys and hips and dormers are hard to insulate 

and vent 

b. Client budget – biggest 

c. Sequenced or planned previous or future work 

Because things are currently pretty slow, Steve’s company generally prefers solutions 

that keep his crews working rather than more fully engaging a subcontractor, like 

spray foam. Steve’s company also favors insulation systems with better 

environmental profiles (rigid insulation—blowing agent is pentane—low global 

warming potential; closed-cell spray foam blowing agent is high GWP). 

6. Check out the 5 common roof types on the last page of this questionnaire:

a. Is there one or two that you most commonly deal with in ice dam work? Simple 

and doghouse 

b. Is there any relationship between roof type and which solution you propose? No, 

largely driven by other factors (aesthetics)

7. What sort of post-job evaluation or results do you gather? None at this point, but wants to 

use performance pre- and post-testing.

8. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)? Added spot ventilation and radon in some cases, based on need. None with 

balanced systems; just too hard to add the proper ducting—some 24/7 exhaust. 

9. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g. heat tape, roof raking, installing a standing seam metal roof—complete or 

just the eaves)?

Steve’s company does not do any real marketing. They have been in business long 

enough in the Brattleboro area that word-of-mouth and referrals is how they get just 

about all their work, including any ice dam projects. They are always trying to address 

the cause, not the symptom but not always successful.

10. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR)

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.)
59 

Possibly, on one project: Green River. We stripped 2 layers of shingles and a 

layer of plywood, then removed the old roof boards. We removed fiberglass batts 

and filled the cavities with 7 in. of foil-faced polyiso, foaming gaps throughout. 

We installed 3⁄4-in. plywood, deck armor paper- breathable, then standing seam 

roofing with backer rod down the center of the roof panels to create an air space. 

i. The job was 27 squares and cost $66,700 ($24.70/ft2

).

ii. (less $8,000 for window replacement)

11. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes? 

Diagnostic testing—blower door and infrared
60 

Appendix F. Project Overcoat Contractor Interview—Cocoon

Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name: Steve Schirber/Tessa Murry

2. Interviewee Title: President/Lead Researcher

3. Company Name: Cocoon 

4. Location of Business: Edina, MN 

5. Complete scope or range of company services: energy retrofits to solve thermal comfort, 

utility bill and ice dam problems 

6. Years in energy retrofit business: 4

7. Number of “ice dam” retrofits completed in last 5 years: 112

8. Questions: 

9. When a potential client comes to you to with an ice dam problem: 

10. What information do you need before proposing solutions to the client? 

a. Assessment/inspection form - Yes

b. Pre-work testing (blower door, infra-red imaging, etc.)—Blower door and IR 

imaging, combustion safety, ventilation, radon 

c. Client financial “aptitude” - Yes

11. What is the full range of ice dam solutions your company provides? 

a. Basic air sealing 

b. Cavity fill and BIB [blow-in blanket] insulation 

c. Roof ventilation 

d. Roof geometry modification 

e. Interior insulation and air sealing

f. Exterior insulation and air sealing

g. Exterior foam and false deck overlay

h. ETMMS

i. Ventilation - HVAC system design and install 

12. How would you rate each of the above based on: 

a. Relative cost
61 

b. Ease of construction/feasibility

c. Durability

d. Hygrothermal performance (combined energy and moisture management 

performance)

Basic air sealing 5 5 5 1

Cavity fill and BIB insulation 4 5 3 1

Roof ventilation 3 3 3 2

Roof Geometry modification 2 2 5 2

Interior insulation and air sealing 4 3 4 3

Exterior insulation and air sealing 2 2 4 3

Exterior foam and false deck overlay 2 2 4 4

ETMMS 1 1 5 5

1=worst, 5=best

ETMMS is the more expensive option but it offers the most durable and best 

hygrothermal solution for ice-damming. Since it involves exterior access to eaves 

and even sometimes top of eave walls, it is a much more invasive process, 

although it has little impact on day-to-day goings-on of the occupants. 

The interior air sealing and insulation approach is quite challenging for the 

installers, but it can be done in a relatively short period of time and is much less 

expensive than ETMMS.

13. What resources do you use to explain the phenomenon of ice dams to your clients? 

Cocoon has extensive information resources for the general public and its clients on its 

website: http://cocoon-solutions.com/about-you/resources-for-you/ . These, of course, 

include reputable information on ice dams, causes and solutions. 

14. What are the factors that drive which solutions you propose 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)

b. Client budget 

c. Sequenced or planned previous or future work 

Cocoon bases its approach on the pre-work testing and inspection, the condition 

of existing roof cladding, the roof complexity, and the budget of the client. In 

general, we explore the possibilities as it pertains to achievable solutions. From 

there we work with the homeowner on crafting a good, better, best approach and 

try to align their decision with the measurable outcomes, financial cost and 

performance benefits.

15. Check out the 5 common roof types on the last page of this questionnaire: 
62 

d. Is there one or two that you most commonly deal with in ice dam work? All of the 

above 

e. Is there any relationship between roof type and which solution you propose? All 

approaches apply to all shapes and each have their pros and cons. The decision 

making process highly depends on what is inside. 

16. What sort of post-job evaluation or results do you gather? 

 Cocoon not only does post-work performance testing and thermal imaging, 

 ventilation measurement, combustion safety and radon measurement, but wraps 

 all this information into a customer job report, with recommendations for 

 additional considerations for improved home performance and/or remaining 

 issues. 

17. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)? See above—the post-building envelope work to the customer almost 

always includes HVAC recommendation or considerations. 

18. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g. heat tape, roof raking, installing a standing seam metal roof—

complete or just the eaves)?

The Cocoon website is a model of how to present information and high 

performance solutions in comparison to band-aid superficial approaches that do 

not really solve the underlying causes of ice dam problems. We market to the 

“pain” and sell “solutions,” not product (i.e. insulation) 

19. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR)

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.) 

(was not able to supply photo before completion of report) 

20. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes? 

Deferred maintenance. By this I mean, items like the roof, siding, windows and mechanical 

systems are already in need of repair/replacement. This factor is highly leveragable. I would 

also add the desire of the home owner to stay in the house long term, and their ability to 

understand the complexity of building performance and the risk of not doing it right.
63 

Appendix G. Project Overcoat Contractor Interview—Panelworks 

Plus

Problem Statement:

Ice dams are a huge problem in existing homes in cold, snowy climates. We are evaluating just 

how retrofit contractors and their clients select a solution, particularly for story-and-a-half 

homes. We are especially interested in the conditions, methods, cost, and marketing of exterior 

insulation roof retrofits in the context of effectively solving ice dam problems. 

Background Info: 

1. Interviewee Name: Curt Stendel

2. Interviewee Title: President

3. Company Name: Panelworks Plus, Inc. (PWP) (http://panelworksplus.com/index.html ) 

4. Location of Business: St Francis, MN

5. Complete scope or range of company services: SIPs for new construction and retrofit; 

Panelworks Plus is an independent dealer/distributor of SIPs and retrofit panels 

manufactured by Extreme Panel Technologies, Inc. of Cottonwood, MN

(www.extremepanel.com) working with homeowners, builders and remodelers, often 

providing full panel installation or on-site training to ensure proper installation.

6. Years in energy retrofit business: 10 years (since 1999 residential; incorporated 2001 

with Extreme Panel). Panelworks Plus was incorporated in 2001 based on Curt’s 

background of working with SIPs in agricultural, commercial and residential applications 

since 1980. To date, work is almost equally divided between DIY homeowner/contractors 

and licensed general contractors.

7. Number of “ice dam” retrofits completed in last 5 years: the ice dams of 2010-2011 is 

driving PWP’s recent surge in roof retrofits—5 last year alone

Questions: 

When a potential client comes to you to with an ice dam problem: 

1. What information do you need before proposing solutions to the client? 

a. Assessment/inspection form - no 

b. Pre-work testing (blower door, infra-red imaging, etc.)—sometimes, when 

working with a home performance contractor/consultant, but not on his own 

(Curt).

c. Client financial “aptitude”—not really; they come to PWP because they have heard 

that they work

2. What is the full range of ice dam solutions your company provides? PWP only does 

retrofit panels, either two-sided or one-sided nail base panels.
64 

3. How would you rate each of the above based on:

a. Relative cost

b. Ease of construction/feasibility

c. Durability

d. Hygrothermal performance (combined energy and moisture management 

performance)

Curt believes that retrofit panels are competitive on all fronts with any other roof 

retrofit or ice dam solution. I am following up with Curt to see if he can give us a 

single estimate or range for installed cost per square foot of his retrofit panels.

Curt is just starting to keep track of the reduced energy bill impacts of his roof 

retrofits. He is calculating therm usage based on heating degree days. So far, an 

estimate of the impact of his work is about a 15% reduction in gas use for space 

heating. He wants to add information on any reduction in electrical use for space 

cooling. 

Two important notes on Curt’s work on roof retrofit panel installations:

1. PWP pays very close attention to perimeter air sealing anywhere that our panel 

installation is in contact with the existing structure as well as between the 

individual panels. 

2. Curt deals with the increased fascia height of exterior panel installation on roofs 

with a double fascia or, if the depth of panels precludes the double fascia, he will 

plumb-cut existing soffit to eave wall and rebuild new soffit, essentially making 

the eave walls one or more courses of wall cladding “taller.”

4. What resources do you use to explain the phenomenon of ice dams to your clients? 

Just verbal so far; ice dam roof retrofits are a new line of business for PWP and they are just 

starting to develop information and marketing resources targeting this work. 

5. What are the factors that drive which solutions you propose 

a. Building details (roof complexity, extent of the ice dam problem, age of roof 

cladding, roof pitch)

b. Client budget 

c. Sequenced or planned previous or future work 

The thicker the panel, the more complex installation is; the presence and number of 

valleys also affects installation, more than any other roof feature.

i. Panel cost will vary with the thickness of the panel but the bigger issue of

cost is driven by the complexity of the roof. Since panels are cut to fit on 

site, the panel cost will not change much but labor to install panels on 

steeper roof pitches, valleys, dormers will impact the total retrofit project 

cost.
65 

6. Check out the 5 common roof types on the last page of this questionnaire: 

a. Is there one or two that you most commonly deal with in ice dam work? 

b. Is there any relationship between roof type and which solution you propose? 

Quite a bit of PWP’s work to date has been cabin-type upgrades, often with fairly 

simple roof configurations, but including plenty of valley work. 

a. Our work to date has included rather simple 4/12 pitch roof planes to a very 

complex 12/12 pitch roof with valleys, transitions, both gable and shed dormers 

and a porch roof with both a hip and a valley on a 130 year old farm-house. 

7. What sort of post-job evaluation or results do you gather? 

Nothing yet, unless PWP’s work happens to be with a performance contractor/consultant. 

Only one project has involved any sort of pre- and post-work performance testing and this 

one was just an abovegrade wall retrofit, not involving the roof. 

But PWP strongly recommends to their clients that they start and end by working with a 

home performance contractor.

8. How often are mechanical system changes/retrofits associated with your building 

envelope work (adding spot exhaust ventilation, whole-house ventilation, or radon 

mitigation)?

This is not part of PWP’s business model or expertise. But PWP does, however, strongly 

recommend that their clients add a home performance contractor to their projects.

9. How do you specifically market your ice dam/roof retrofit solutions, especially in the 

context of what you consider to be the competition for effectively solving ice dam 

problems (e.g. heat tape, roof raking, installing a standing seam metal roof—complete or 

just the eaves)?

Just now working on a marketing 2-pager on ice dam roof retrofits and Curt has offered 

to send this to us just as soon as the copy is finalized. Extreme Panel also has a new flyer 

out regarding retrofit panels.

10. Can you provide documentation for one or more of your recent ice dam-driven roof 

energy retrofits:

a. Inspection/assessment

b. Before/after images (digital/IR)

c. Construction details 

d. Pre-/post-testing results

e. Cost details (labor/materials/profit; bid/cost-plus contract, etc.)

Curt is working on getting us details, including photos and cost, for his David 

Miller project.
66 

11. What do you think is the single most important or influential change that would 

significantly promote a complete exterior insulation roof retrofit in comparison to other 

potential solution sets for ice dam problems in existing homes? 

Education! Curt is convinced that work such as this project (the NorthernSTAR overcoat 

project, and conferences like the upcoming Duluth Energy Conference 

(www.duluthenergydesign.com/), at which Curt will be presenting on his retrofit panel 

projects.
DOE/GO-102013-3751 ▪ April 2013

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