Assessing Foundation 

Insulation Strategies for the 

2012 International Energy 

Conservation Code in Cold 

Climate New Home Construction 

E. VonThoma, C. Ojczyk, and G. Mosiman

NorthernSTAR

April 2013
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iii

Assessing Foundation Insulation Strategies for the 2012 International 

Energy Conservation Code in Cold Climate New Home Construction

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: 

E. VonThoma, C. Ojczyk, and G. Mosiman

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 

March 2013 
iv

Contents 

List of Figures ............................................................................................................................................ iv

List of Tables .............................................................................................................................................. iv

Definitions .................................................................................................................................................... v

Executive Summary................................................................................................................................... vi

Acknowledgments ..................................................................................................................................... vi

1 Introduction ........................................................................................................................................... 1

1.1 2012 International Energy Conservation Code and Impact on Foundation Insulation ........1

1.2 Insulation Considerations for Basements in Cold Climates ................................................1

2 Minnesota as a Case Study for Code Change................................................................................... 5

2.1 Builders Association of Minnesota Energy Code and Housing Summit .............................6

2.2 Minnesota Building Performance Association Energy Forum—Spring Edition .................7

3 Baseline Foundation Insulation Strategies of New Home Builders in Minnesota ...................... 13

4 Conclusions and Further Work......................................................................................................... 15

References................................................................................................................................................. 17

List of Figures

Figure 1. Illustration of exterior foundation insulation from the DRAFT Builder’s Foundation 

Handbook created by Oak Ridge National Laboratory for the U.S. Department of Energy.......... 4

Figure 2. Cast-in-place concrete foundation wall with integral rigid insulation................................... 9

Figure 3. Concrete masonry foundation wall with exterior rigid/semi-rigid insulation..................... 10

Figure 4. Cast-in-place concrete foundation wall with insulated concrete forms.............................. 11

Figure 5. Cast-in-place concrete foundation wall interior closed cell spray foam insulation .......... 12

Unless otherwise noted, all figures were created by NorthernSTAR.

List of Tables

Table 1. Builder Responses to Proposed Foundation Insulation Code Change Questions ............. 14

This table was created by NorthernSTAR.
v 

Definitions 

BA Building America

BAMN Builders Association of Minnesota

BCAP Building Codes Assistance Project

ft Foot

ft2 Square foot

ICC International Code Council

IECC International Energy Conservation Code

in. Inch

IRC International Residential Code

MBPA Minnesota Building Performance Association

NREL National Renewable Energy Laboratory

WSP Water separation plane
vi 

Executive Summary

Even though the International Energy Conservation Code 2012 (International Code Council 

2012) is a model code now available for adoption by individual states, only two cold-climate 

states have adopted it as their new home energy code. Understanding the resistance to adoption is 

important in assisting more states to accept the code and engage in deep energy strategies 

nationwide. This three-part assessment by the NorthernSTAR Building America Partnership was 

focused on foundation insulation R-values for cold climates and the design, construction, and 

performance implications. In Section 1, a literature review and attendance at stakeholder 

meetings held in Minnesota were used to assess general stakeholder interest and concerns about 

proposed code changes. Section 2 includes drawings of robust foundation insulation systems that 

were presented at one Minnesota stakeholder meeting to address critical issues and concerns for 

adopting best practice strategies. In Section 3, a sampling of builders participated in a telephone 

interview to gain baseline knowledge on insulation systems used to meet the current energy code 

and how the same builders intend to meet the new proposed code. 

In general, most builders expressed interest in being able to deliver greater energy efficiency to 

their customers. Concerns were voiced, however, about the costs compared to the energy 

savings, constructability, and durability risk resulting from increased foundation insulation Rvalues. When solutions for building robust foundation wall systems were presented to 

stakeholders, they did express interest in learning the details of the strategies. There was, 

however, continued interest in proof of cost, payback, and hygrothermal performance. Builders 

who participated in the interview were more confident in being able to meet the new 

requirements. This might have been a result of these respondents already using more advanced 

techniques for foundation insulation. 

This insight gives Building America an opportunity to engage the industry with existing research 

and practice measures that can address constructability and durability concerns at the proposed 

code levels. It also indicates that builders are interested in more specific information on cost, 

energy savings, and overall hygrothermal performance. Filling these voids could yield the 

supportive data needed to enhance building industry confidence and engage more states in the 

adoption of 2012 International Energy Conservation Code for new homes. 

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 authors also acknowledge Pat Huelman and Tom Schirber, Cold Climate Housing Program, 

University of Minnesota, for technical guidance, project development, and coordination. 
1 

1 Introduction

Changes to the national model energy code for cold and very cold climates are represented in the 

newly adopted 2012 International Energy Conservation Code (2012 IECC).1 The new code is 

inclusive of strategies to meet the U.S. Department of Energy Building America (BA) Program 

goals for new homes to achieve 30% improvement in energy savings over the 2006 IECC. 

Communities and states across the United States are in the process of reviewing the code 

changes and discussing how to integrate the 2012 IECC into their own energy codes. Stakeholder 

acceptance of the stated benefits is an important tool in creating a smooth transition from the old 

code to the new code and ensuring compliance that leads to measured energy savings. Although 

energy efficient, comfortable, safe, healthy, and durable homes are the goal of the BA program, 

many stakeholders who also desire these outcomes are concerned about potential cost increases 

and unknown risks that might accompany a change as compared to the known costs and risks of 

their current building practices.

1.1 2012 International Energy Conservation Code and Impact on Foundation 

Insulation

A definition of the foundation insulation requirements of 2012 IECC by component can be found 

in note “c” of the 2012 International Residential Code (IRC) table N1102.1.1 (R402.1.1). For 

cold-climate zones 5, 6, 7, and 8, the note states the following: 

“15/19” means R-15 continuous insulation on the interior or exterior of the home or R-19 

cavity insulation at the interior of the basement wall. “15/19” shall be permitted to be met 

with R-13 cavity insulation on the interior of the basement wall plus R-5 continuous 

insulation on the interior or exterior of the home. 

These changes were designed to achieve 30% increase in energy savings compared to the 2009 

IECC—a goal in line with the BA program’s desire to achieve 30% energy savings over IECC 

2009 while also promoting building durability, indoor air quality, and occupant safety and 

comfort.

1.2 Insulation Considerations for Basements in Cold Climates

Building foundations are complicated systems that are easily misunderstood and strategies for 

energy improvement are often oversimplified. In the cold-climate building regions of the United 

States, it is not uncommon to experience annual frost depths of 3 to 6 ft. Foundation walls 

typically extend 4 ft or more below grade to protect the foundation from frost heave. As a result, 

full basements have become a common construction practice. Although it was once typical to 

find only mechanical equipment, plumbing systems, and stored items located in these spaces, 

homeowner desire to use a basement as living space creates urgency for reliable information on 

best practice strategies for foundation insulation systems. 

The principal drawback to basement spaces that are surrounded by soil and experience both 

above grade and below grade conditions is hygrothermal durability. Foundation walls almost 

 

1 Note that complete citations for all International Code Council (ICC) codes mentioned in this report are given in 

the References list.
2 

always experience variations in temperature and drying potential from the top (above grade) to 

the footing (below grade), from season to season, and from wall to wall depending on solar 

orientation, soil conditions, and design (Huelman et al. 2012). It is common to find full wall, 

lookout wall, and walkout wall designs in the same basement area. Lack of soil slope, foundation 

wall waterproofing, capillary breaks, and drainage at the footing create further risk for increased 

moisture stress resulting from rainwater and groundwater intrusion. Ueno and Lstiburek (2010) 

note that even though bulk water control adds negligible energy benefit, it should be a base 

requirement for any high performance house because it is critical for building durability, indoor 

air quality, pest management, and the creation of acceptable living conditions within or above the 

foundation space. 

Although soil contact prevents the below grade foundation wall from drying to the exterior, 

interior insulation and the presence of vapor impermeable materials can reduce the opportunity 

for the foundation wall to dry to the interior. This can create continually wet insulation and 

building materials. Temperature differences from the top of walls to the bottom can also 

exacerbate the movement of water vapor toward the sill and rim, especially in hollow core 

masonry block (Goldberg 1999). This can lead to deterioration and rot of the building structure 

components, loss of energy efficiency, and decreased comfort, as well as the opportunity for 

mold growth and resultant poor indoor air quality. 

Of the four foundation wall insulation approaches—exterior, interior, both interior and exterior, 

and in the middle—the most common insulation approach for new homes has been to insulate on 

the interior because it is the least expensive. Lstiburek (2006) notes, however, that interior 

insulation is the most risky insulation system because the foundation wall remains cold as a 

result of being in contact with below grade soil. It is imperative to keep warm, moist interior air 

from condensing on the cold wall. To do this, the interior insulation assembly must be built 

airtight. It must also be built to dry inward (Building Science Corporation 2009) with the 

insulation layer built vapor-semi-impermeable (greater than 0.1 perm), vapor-semi-permeable 

(greater than 1.0 perm), or vapor-permeable (greater than 10 perm). As the permeance increases, 

the inward drying potential rises and the risk of excessive moisture accumulation lowers. Highly 

permeable interior materials, though, will increase the outward wetting potential during the 

heating season in cold climates. To achieve the proper permeance, the following insulation 

products were recommended by Lstiburek: “Up to two inches of unfaced extruded polystyrene 

(R-10), four inches of unfaced expanded polystyrene (R-15), three inches of closed cell medium 

density spray polyurethane foam (R-18) and ten inches of open cell low density spray foam (R35) meet these permeability requirements.” The use of vapor-impermeable materials to control 

air flow adds undue risk because they prevent foundation walls from drying inward. 

Contrary to the published information just cited, though, a recent presentation given by Lstiburek 

and summarized by Holladay (2012) indicates that Lstiburek has reconsidered and suggests that

the concrete does not have to dry to the inside. 

Huelman and coauthors (2012) also note that managing moisture is critical. Any additional 

moisture from groundwater entry, construction moisture, and capillary rise through the footing 

could be trapped in the foundation system. This creates opportunities for mold growth, building 

material degradation, and effective insulation value reduction. If interior insulation is used, the 

foundation should be very dry and include quality damp/waterproofing. Capillary breaks at 
3 

critical junctions should be included. Basement dehumidification should be installed. Attention 

to effective interior air barriers is important.

Fugler (2002) reports on the occupant health risks and building durability risks associated with 

finishing or adding insulation to the interior of a basement with moisture problems. Those risks 

include toxigenic or pathogenic mold growth potentially harmful to occupants (especially 

children). Fugler estimates that, in Canada, 20%–50% of basements visited had moisture 

problems. He advises that the interior basement walls of existing homes should be left unfinished 

in a cold climate because, among other factors, “there is too much risk in disturbing the moisture 

and temperature environment that has maintained this foundation for decades.” Fugler notes, 

however, that “if the homeowners are also prepared to add exterior drainage and insulation, 

interior finishing would pose no problem.” 

A foundation wall can also be insulated by placing the insulation in the center of the foundation 

wall. Although this approach is considered ideal, it is also the most expensive and most difficult 

to construct (Lstiburek 2006). 

Lstiburek also notes that exterior insulation and insulation located on both the exterior and the 

interior constitute an optimal approach for moisture control. The hurdle to using either are the 

increased costs associated with the need for an additional layer to protect the exterior insulation 

during backfill and over the life of the home, insect control in termite areas, and heat loss with 

brick veneers (Lstiburek 2006). 

Yet applying insulation to the exterior of the foundation during new home construction and 

implementing proper groundwater and rainwater management strategies greatly reduce the risks 

related to water/vapor flow and foundation wall temperature differential. The results of this 

approach indicate a more comfortable, durable basement environment. Figure 1, created by Oak 

Ridge National Laboratory, highlights the key elements for exterior insulation and water 

management on the foundation wall that will help achieve the BA goal of improved energy 

savings combined with improved building durability, indoor air quality, and occupant safety and 

comfort.
4 

Note: o.c., on center

Figure 1. Illustration of exterior foundation insulation from the DRAFT Builder’s Foundation 

Handbook created by Oak Ridge National Laboratory for the U.S. Department of Energy
5 

2 Minnesota as a Case Study for Code Change

According to the Building Codes Assistance Project (BCAP 2012a) map of codes per state, the 

2012 IECC has been adopted by only one state, Maryland, to date. Although not referenced on 

the BCAP map, the state of Illinois has also adopted the code (Illinois Department of Commerce 

and Economic Opportunity 2012). All other states and their various stakeholders have the option 

to adopt the 2012 IECC as is or use it to help build their own state energy codes. 

The NorthernSTAR BA team, led by the University of Minnesota, has the opportunity to 

observe the conversations happening within the new home building industry about proposed 

code changes. Minnesota is an important state to study because it has not yet adopted the code 

but is on track to do so. Adoption, though, has brought about much discussion and resistance by 

stakeholders in the industry. Understanding how the state proceeds and the industry responds 

may be helpful in moving other cold-climate states toward adoption of the 2012 IECC and 

greater reductions in energy use. 

Foundation insulation requirements in the 2012 IECC for cold and very cold climates represent a 

significant departure from existing codes and current practices. In Minnesota, for example, 

builders currently follow the 2009 Minnesota Energy Code adopted from the 2006 IRC. The 

current Minnesota Energy Code, which went into effect on June 1, 2009, includes 1322.1102 

IRC Section N1102.2.6, Building Thermal Envelope, Foundation wall insulation 

prescriptive option and N1102.2.6.12 Foundation wall insulation performance option 

(Minnesota Administrative Rules 2009). These sections include details for basement 

foundation walls, crawlspace walls, slab on grade, and basement walkout foundation walls 

with exceptions listed for the southern zone of Minnesota. The following wording is specific 

to the foundation wall and rim joist area: 

N1102.2.6.4 Foundation wall and rim joist area thermal insulation requirements. The 

foundation wall system and rim joist area shall have an insulating layer with minimum 

thermal properties as required in this section. The insulation layer must be a minimum 

R-10 in accordance with Table N1102.1. 

The 2012 IECC increases the R-value requirement from R-10 (or R-5 in southern Minnesota

with appropriate trade-offs) found in the 2009 Minnesota Energy Code to a minimum of R-15 

(continuous)/R-19 (cavity) for the entire state. 

With pressure from the Builders Association of Minnesota (BAMN), the state is keenly aware of 

the need to ensure that the new insulation levels and language will include a solid approach to 

long-term moisture durability and indoor air quality. The current Minnesota Residential Energy 

Code incorporates specific performance criteria and prescriptive requirements governing 

foundation insulation, including the incorporation of a water separation plane (WSP). In general, 

the code stipulates that the interior side of the WSP must have a stable annual wetting/dry cycle 

with limited net accumulation of ice or water, prevent conditions for mold growth, and prevent 

liquid water rundown. The current code proposal developed at the state’s request includes a 

definition and properties for the WSP as follows (Goldberg 2012): 
6 

 A single component or system of components creating a plane that effectively resists 

 capillary water flow and water flow caused by hydrostatic pressure and provides a water 

 vapor permeance of 0.1 perms or less to retard vapor flow by diffusion. 

BAMN has expressed that an undesired outcome of the code change would be a reduction in the 

number of builders currently using exterior foundation insulation strategies (BAMN 2012). What 

is not known is whether builders will change their current building strategies to avoid cost 

increases or the design details required of thicker exterior insulation. As described in a BA report 

(Building Industry Research Alliance et al. 2006) “the residential construction industry is highly 

risk-intolerant and first-cost sensitive. Development of new systems and corresponding changes 

in design and the relatively low level of R&D investment further complicate construction 

practices by the housing industry.” Today, the challenges remain substantially the same. This 

could result in a shift in the performance of new homes away from BA program goals described 

previously. 

2.1 Builders Association of Minnesota Energy Code and Housing Summit

On April 3, 2012, BAMN hosted an Energy Code & Housing Summit as an open forum to 

discuss issues related to the adoption of the 2012 IECC (BAMN 2012). Ed Von Thoma, a 

member of the NorthernSTAR Building America Partnership Research Team, attended the event 

and disseminated notes from the presentation (Von Thoma 2012). 

The overall concern presented by BAMN is that the R-value increase may pose potential 

challenges to design and construction as well as create a potential resistance to acceptance by the 

industry and the home buying markets. The three main issues of concern include durability, 

constructability, and cost of meeting the 2012 IECC. One of the key issues that surfaced at the 

BAMN meeting was whether the investment required of the home buyer is justified by the 

energy conservation methods and resultant energy savings. 

Carey Becker, of Becker Home Building and Remodeling and a Department of Labor and 

Industry Residential Energy Code Advisory Committee member, presented a case study 

evaluating the cost to comply with the 2012 IECC. Becker provided cost data for a home he built 

in Minneapolis to be marketed to new home buyers. He supplied projected costs for complying 

with the 2012 IECC and actual costs for complying with the current code. The original home of 

540 ft2

 built in 1900 was torn down and a new 1,688- ft2 home was built to match the look and 

size of neighboring houses. Becker presented data indicating that meeting the 2012 IECC would 

increase the home cost by $7,307 with a payback on energy savings of 48.3 years based on 

REMRate analysis. Of the $7,307 cost, $4,000 was allocated to meeting the R-value for above 

grade wall insulation, which includes exterior insulation. Less than $1,000 was allocated to 

meeting the R-value for foundation wall insulation.

Even though the cost of meeting the 2012 IECC for foundation insulation was only $1,000, there 

was considerable discussion about the foundation wall requirements in the new code. The main 

resistance and ensuing discussion centered on the code allowance of an insulation assembly 

consisting of a framed wall with R-19 batt insulation installed on the interior side of the 

foundation wall. The concern was the potential for moisture to be trapped within the framed 

wall. The current Minnesota Energy Code has additional requirements for this type of assembly 
7 

to reduce the potential for moisture problems. BAMN noted, however, that a builder using batt 

insulation and following the process to reduce moisture risk incurs added expense. The 

consensus was that BAMN and its stakeholders would prefer to have any language that could 

create nondurable systems be removed from the code. BAMN also commented that it wished to 

see a new code that would address the building science of both winter and summer conditions 

and seasonal impact on drying potential. 

In regards to the R-15 requirement, BAMN expressed concern about the impact on design when 

creating a thicker exterior foundation wall and the concern that a split process of exterior/interior 

insulation to meet the R-value would reduce drying potential to the inside. 

BAMN also contended that the foundation insulation requirement of R-15 continuous insulation 

does not provide sufficient energy savings for the cost. Association members cited a report from 

the University of Minnesota conducted in 2005, which determined that, based on thermal 

requirements, optimal foundation insulation is R-10 (Goldberg and Huelman 2005). An audience 

member questioned whether this optimal level would also apply to the above grade foundation 

walls more commonly seen in lookout and walkout foundation configurations. It was not known 

if any studies have been done for these configurations. 

BAMN also noted a conflict in the BCAP (2012b) analysis for new single-family homes in 

Minnesota and the 2012 IRC Section R702.7.1, where the modeled wall assembly would not be 

code compliant. Association representatives also contended that BCAP analysis overestimated 

the energy savings and underestimated the cost of the energy upgrades. BCAP estimates that the 

proposed code changes would add only $2,682–$3,959 to the cost of a typical home in 

Minnesota (in comparison to the $7,307 from the BAMN builder study) and produce energy 

savings of between $848 and $925 per year, shortening the payback to 8 to 14 months (in 

comparison to the 48.3 years from the BAMN builder study). BAMN has requested details of the

modeling assumptions from BCAP in order to study the discrepancies and differences between 

the BCAP work and the Minneapolis case study findings. 

There were numerous audience comments throughout the BAMN presentation. Several builders 

suggested that different methods could have been used to meet the foundation insulation 

requirements and yield a significantly lower cost to achieve the code, thus reducing the payback. 

Some builders also challenged the assumptions used to compute building costs and expressed 

concerns that numbers were inflated. 

Although the BAMN meeting has stimulated industry conversation and further efforts to 

understand costs, benefits, and risks, a number of media representatives invited to the BAMN 

meeting presented their view of the outcome with article headlines reading “Local View: If New 

Building Codes Arrive, Prices Will Rise” (Duluth Tribune News 2012); “Builders Balk at Cost of 

Proposed Code Changes” (Johnson 2012); and “Minnesota Builders Warn Energy-Code Changes 

Would Raise Prices of Homes” (Dornfield 2012). 

2.2 Minnesota Building Performance Association Energy Forum—Spring Edition

On June 12, 2012, the Minnesota Building Performance Association (MBPA) hosted the MBPA

Energy Forum—Spring Edition to discuss the 2012 IECC and its impact on the residential 
8 

building industry. Cindy Ojczyk, NorthernSTAR Building America Partnership Project Team 

member, attended the forum and disseminated notes from the event (Ojczyk 2012). 

The goal of the MBPA meeting was to extend the stakeholder conversation that BAMN began by 

presenting additional cost estimates, energy savings calculations, and case studies of successful 

projects that meet the 2012 IECC. 

The forum began with a presentation by Isaac Elnecave of the nonprofit Midwest Energy 

Efficiency Alliance, which represents 13 midwestern states. His presentation highlighted the 

recent adoption of the 2012 IECC by Illinois, making it the second state to adopt the new energy 

code. The adoption of the 2012 IECC by Minnesota would be important for influencing the other 

11 midwestern states that either have no state energy code or follow codes from 2009 or earlier. 

Minnesota is also unique to follow because it covers two climate zones and has adapted the 

energy code in the past to account for temperature differences across the state. Elnecave 

reiterated that the 2012 IECC does require a blower door test be performed in every new home, 

and each new home must meet an air leakage rating of less than 3 air changes per hour at 50 

Pascals. This requirement for a blower door test is also seen as a hurdle because it adds an 

additional cost (estimated $150) to the project as well as additional time for scheduling.

Paul Morin of MPBA reviewed data computed by two Minnesota home builders that compared 

the savings and costs to meet the 2012 IECC in one home with two basement options—a walkout 

and a full basement. The total cost for the upgrades to meet the 2012 IECC in the home with the 

walkout option was computed to be $2,122 for an annual energy savings of $280. The total cost 

for the home with the full basement option was $2,362 with an annual energy savings calculated 

at $270. 

Pat Huelman, team lead for the NorthernSTAR Building America Partnership, presented four 

drawings of foundation insulation systems that represent robust methods that would meet the 

2012 IECC and potentially comply with the foundation performance criteria in the 2009 

Minnesota Energy Code. These four drawings were based on best practice building science 

information from research conducted at the University of Minnesota as well as best practice 

measures promoted by BA. The goal of the presentation was to address the durability concerns 

expressed at the BAMN meeting by offering best practice solutions to increasing R-value while 

attending to building durability, air quality, insulation quality and performance, and 

constructability. The four solutions also represent the four foundation wall insulation approaches 

– exterior, interior, both interior and exterior, and in the middle - while indicating the best 

methodology to reduce risk. 

These four solutions, however, do not represent all of the possible foundation wall insulation 

strategies that could be conceived based on the code. Because the energy code does not include 

or exclude specific materials or dictate where insulation must be placed on the foundation wall, 

many more solutions exist to meet the R-value requirements of the code. Yet not all systems are 

equally robust and will not equally minimize building durability risk while maximizing energy 

performance. And given that the moisture performance requirements for the proposed Minnesota 

code were still under development, only the most robust systems were presented to the MBPA 

audience.
9 

Huelman also mentioned that Louise Goldberg, a NorthernSTAR Co-principal investigator with 

the University of Minnesota, is under contract with the Minnesota Department of Labor and 

Industry and the State of Minnesota to conduct a “due diligence” review of the proposed code 

language. Goldberg’s task is to evaluate the entire range of foundation insulation materials and 

strategies to ensure compliance with the original performance criteria set out in the 2009 

Minnesota Energy Code. 

Figure 2 shows the first solution presented by Huelman. It is a foundation wall with insulation in 

the center, which is considered ideal, but most difficult to construct. Achieving the required Rvalue for the 2012 IECC is a matter of increasing the thickness of the insulation. Because the 

concrete on the exterior foundation serves as the protective barrier to the insulation, no further 

protection is needed. The additional elements that make this strategy robust—waterproofing, 

perimeter drainage systems, capillary break, slab drainage, air sealing, vapor and moisture 

management, sloped grade, and flashing—maximize building durability. 

Figure 2. Cast-in-place concrete foundation wall with integral rigid insulation

Figure 3 is a foundation wall with insulation on the exterior. Huelman stated that it is considered 

one of the most universal systems because it can work for both cast-in-place concrete and 
10 

concrete masonry foundation walls. Achieving the required R-value for the 2012 IECC is a 

matter of increasing the thickness of the insulation. The exposed insulation on the exterior 

foundation requires a protective board or coating to maintain the integrity of the exterior 

insulation. The additional elements that make this strategy robust—waterproofing, perimeter 

drainage systems, capillary break, slab drainage, air sealing, vapor and moisture management, 

sloped grade, and flashing—maximize building durability. The details for aligning above and 

below grade insulation, which address the constructability concerns expressed by the builders in 

the BAMN meeting, are also given in Figure 3. 

Figure 3. Concrete masonry foundation wall with exterior rigid/semi-rigid insulation
11 

Huelman noted that a foundation wall with insulation on the exterior and interior has been made 

possible and easier to attain using insulated concrete forms where the structural concrete is 

poured in between the insulation as shown in Figure 4. A protective board or coating is needed to 

maintain the integrity of the exterior insulation and a thermal barrier is usually required on the 

interior for fire safety. The additional elements that make this strategy robust—waterproofing, 

perimeter drainage systems, capillary break, slab drainage, air sealing, vapor and moisture 

management, sloped grade, interior finishes, and flashing—maximize building durability. The 

details for aligning above and below grade insulation are also shown in Figure 4. 

Figure 4. Cast-in-place concrete foundation wall with insulated concrete forms

A robust foundation wall system with insulation on the interior can be achieved by following 

very specific air sealing and moisture management details to reduce the risk of moisture 

migration that can result in building rot, loss of integrity, or mold growth. Huelman presented 

Figure 5 to show how a cast-in-place concrete foundation is used to minimize bulk water 

movement through the walls. Exterior and interior waterproofing, perimeter drainage systems, 

capillary break, slab drainage, air sealing, vapor and moisture management, sloped grade, 

interior finishes, and flashing maximize building durability by attending to bulk water and vapor 

management. Closed cell spray foam insulation applied along the full height of the wall and the 

rim maximizes R-value and air sealing opportunities. A hollow-framed wall allows for air flow 
12 

behind the paperless drywall to enable any drying to the interior. In some cases, the foam 

thickness may need to exceed the R-15 thermal requirement to successfully meet the vapor 

permeability requirements in the Minnesota code. 

Figure 5. Cast-in-place concrete foundation wall interior closed cell spray foam insulation

At the end of the MBPA program, time was allocated to address questions from the audience. 

One audience member was interested in seeing cost data for building a home with the four robust 

foundation insulation strategies presented by Huelman. Several additional audience members 

requested access to the foundation insulation strategy drawings. There was a question about 

design details when using exterior foundation insulation and the transition where above grade 

materials meet below grade materials. Huelman referred back to the slides showing exterior 

insulation to point out the details. Another question centered on insulation grade requirements in 

the code. Elnecave answered that although the code does not require insulation installation to 

meet a certain grade, how well or how poorly insulation is installed could affect the final blower 

door test and might have an impact on occupant comfort, putting a builder at risk for a callback. 

When asked why batt insulation is still allowed in the code, the audience was reminded that the 

energy code does not and cannot recommend or exclude specific products. It only makes 

provisions for R-value. 
13 

3 Baseline Foundation Insulation Strategies of 

New Home Builders in Minnesota

The BAMN discussion on the risk of using batt insulation to meet the code highlights the shifting 

stakeholder attitudes about insulation. There is a greater understanding that energy efficiency and 

building durability are affected by factors beyond the R-value of the insulation. Efforts by the 

building science community to communicate the benefits of exterior foundation insulation have 

resulted in more cold-climate builders adopting an exterior approach. There is a risk, however,

that the builders using exterior insulation strategies will return to interior foundation strategies if 

they feel that material costs or design challenges will become greater as the R-value increases. 

There is also a risk that perceived cost increases and difficulty of design integration will keep 

other builders from moving to exterior insulation practices. 

The NorthernSTAR Building America Partnership team was interested in gauging the attitudes 

of new home builders in Minnesota on the proposed code changes. Specifically, the team was 

interested in knowing how the 2012 IECC foundation changes for cold and very cold climates 

would affect decisions of residential builders with respect to foundation insulation type and 

insulation location. Market-ready solutions improve efficiency only when they are adopted by 

the industry and accepted by consumers. The builder questionnaire given in Table 1 was 

intended to promote conversation and identify issues related to the residential construction 

industry’s willingness to embrace advances in construction processes and practices. 

 

NorthernSTAR industry partners selected 18 contractors to participate in a telephone 

questionnaire. These 18 were predominantly high-end custom builders already following abovecode building practices. Ten builders were able to give answers, and Table 1 presents the results. 

The answers indicate a movement away from fiberglass batt insulation to continuous foam board 

products installed on the interior, exterior, or a combination of interior and exterior. No builders 

reported that they would change the location of their insulation as a result of the increased Rvalue requirement. All builders reported being satisfied with their current foundation insulation 

strategy and said they would prefer to continue using it. It should be noted, though, that several 

of these current practices meet the prescriptive language in the current 2009 Minnesota code, but 

they may not meet the moisture performance criteria in the current or proposed code language. 

Only two builders were concerned with design details that might arise when exterior foundation 

insulation is increased to meet code. These builders, however, would still prefer to apply 

insulation on the exterior instead of the interior.

The concerns about code changes were consistent with those raised at the BAMN meeting. The 

builders that responded to the questionnaire were concerned that other builders in the state could 

continue to use batt insulation and experience moisture and durability issues as a result. It is 

important to note that the sample size of 10 builders is small compared to the number of licensed 

builders in the state. 
14 

Table 1. Builder Responses to Proposed Foundation Insulation Code Change Questions 

Builder

What is your 

current 

foundation 

insulation and 

waterproofing 

strategy?

If code changes

require continuous R15 (interior, middle, 

or exterior) or R-19 

cavity, what would be 

your likely insulation 

approach?

Why? 

Are you in agreement 

with this possible code 

change? If not, what are 

your concerns about it?

A Thermax R-10 Continuous interior

Like the 

performance and 

installation of 

interior insulation

Going backward with 

cavity insulation, potential 

moisture issues

B Thermax Continuous interior Doesn’t like 

fiberglass Condensation on the poly

C Thermax Continuous interior

Too hard to 

manage backfill 

on exterior

Durability/moisture if 

using batts

D Warm and dry 

basement Continuous exterior Prefer to insulate at exterior

Prefer to insulate at 

exterior

E 

Warm-n-Dri R-10,

with 2-in. foam on 

interior

Will use current system 

- interior

Warm and dry 

basement None

F Warm and dry 

basement Continuous exterior Easier to install on exterior

Moisture issues with cavity 

insulation

G R-10 rigid foam 

exterior Continuous exterior Prefer to insulate at exterior

Detailing where foundation 

insulation meets exterior 

wall

H 

10 R-value 

exterior 

continuous and 10 

R-value interior 

rigid foam board

Continue with current 

practice, if this doesn’t 

meet code will consider 

insulating concrete 

forms

Provides value to 

clients None

I 

5 R-value exterior 

continuous rigid

foam

Continuous exterior Prefer to insulate 

at exterior

Detailing where foundation 

insulation meets exterior 

wall

J 

Exterior liquid 

applied 

membrane, 

capillary break at 

footing, exterior 

drain tile, exterior 

rigid insulation 

R-10

Exterior

Cost and 

performance is 

optimal

No. Changes are intended 

to achieve a particular 

result and the results 

desired are not completely 

related to the code change. 

There are other factors that 

are more complex related 

to foundations and 

insulation that require a 

more comprehensive 

approach to each situation. 

Testing and verification 

are needed.
15 

4 Conclusions and Further Work

As the BA program targets greater energy efficiency levels in homes, builders are interested in 

being able to deliver greater energy efficiency to their customers. Yet adoption of the 2012 

IECC—designed to deliver the increase energy efficiency in homes—has met resistance in coldclimate states: only two states have embraced the new code. The conversations being held by 

stakeholders in Minnesota indicate that builders have a variety of concerns about adopting the 

new code. In regards to foundation insulation, cost versus energy savings, constructability, and 

durability are the top three issues. 

The durability concerns indicate a misunderstanding about the role of energy code. Stakeholder 

resistance to code change has centered on batt insulation and potential moisture issues. Builders 

are unaware that code cannot mandate or exclude products, nor does it address all building 

science strategies to ensure a safe, durable building. The stakeholder meetings indicate that there 

is a general lack of awareness about resources available to help builders and design professionals 

integrate code mandates with strategies to ensure building durability. This gives the BA program 

an opportunity to promote its existing best practices and measure guidelines for durable 

foundation wall systems. The survey of builders also shows that once a builder moves to a higher 

level of performance, they grasp an understanding of the benefits that makes reverting to 

previous strategies undesirable. 

Code recommendations need to be framed in the context of the building culture and climate. 

Many cold-climate homes, especially those in the Midwest, are not just full-depth foundation 

wall systems. Some have lookout walls, walkout walls, and combinations. It is not known how 

the presence of two or more wall types affects effective R-value, hygrothermal performance, and 

durability. Although exterior insulation strategies could effectively address concerns, moving 

builders toward adopting them might require proof of effectiveness and detailed information on 

how to construct exterior insulation in a low-risk, cost-effective manner. 

Builders are also seeking strategies to protect foundation walls from both summer and winter 

conditions. Exterior insulation strategies may be the recommended strategy from a building 

science perspective, but builders are looking for proof that the process will be effective and 

deliver the energy savings for the added costs. The BA program could help alleviate 

constructability concerns by making available detailed foundation insulation drawings that would 

help builders understand how to address design impacts of thicker wall insulations under varying 

insulation strategies.

The greatest concerns for adoption of the code, as voiced by stakeholders, center on proof of 

actual energy performance, costs, and payback. Minnesota stakeholders are seeking to 

understand the value of embracing proven cost-effective advances in product and process 

technologies before they sell this value to home buyers. The current energy code is based on R10 (or R-5 with trade-offs in southern Minnesota) foundation insulation and builders are seeking 

data to prove that increasing to R-15 will provide cost-effective energy performance. The BAMN 

case study produced different cost/payback data than the BCAP and MBPA case studies, further 

enhancing the confusion in the industry. 
16 

BA has many opportunities to help builders over the hurdles of understanding durability, 

constructability, and cost versus energy performance for foundation insulation in regards to the 

2012 IECC. BA data and expertise can help offset the negative media reports that surfaced after

the industry summits. Disseminating supportive data and detailed drawings will help to build 

industry and consumer confidence and engage more states in the adoption of the 2012 IECC for 

new homes.
17 

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DOE/GO-102013-3885 ▪ April 2013

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