Data is coming back from an ongoing test neighborhood built in Midland, Mich. by Cobblestone Homes and Dow in late 2011. The Twelve Energy Efficient Test Homes (TEETH) subdivision was specifically designed to generate data on home energy efficiency based on whole-house insulation, air sealing, and real-world living conditions. For the project, three homes of similar floorplans were built to each of four different design standards ranging from baseline 2006 International Energy Conservation Code to exceeding current 2012 Energy Conservation Codes Results. Appropriate levels of insulation were used in each installation, including batts, spray polyurethane foam, and Dow's Styrofoam exterior continuous insulation.
"For more than 60 years, Dow has worked hand-in-hand with the global building industry to address their evolving needs through our building science expertise," says Jim Morey, residential market manager of Dow Building Solutions. "Most recently, our series of test homes building science projects - including TEETH - is filling a critical information gap in whole-house energy efficiency data. The results will enable builders to make a stronger case to homeowners and potential buyers that high-performance solutions can cost-effectively maximize home value and comfort while lowering homeownership costs."
Key Insights
A chart outlining specific construction approaches for each home is below. Based on these specs, first-year results show that homes using continuous insulation and closed-cell SPF show a 30% improvement in air leakage over the homes built to 2006 standards with batts and housewrap. Homes built to the highest current standards (in the 2012 Outperformance group) achieved warmer above-grade walls with less potential for condensation within the walls, and below-grade walls also proved to be dryer and warmer than those built to basic 2012 standards (in the 2012 Energy Performance group).
Dow also noted that improving home performance cost less for these homes than many builders and remodelers might expect. Using the Home Energy Rating System (HERS), homes in 2006 IECC Baseline Performance Group achieved a HERS score of 77. With an investment of about $5,000, builders were able to meet 2012 IECC best practices in the Outperformance Homes group, and the HERS rating dropped by 30% to a score of 54.
| Baseline Performance | 2012 Energy Performance | 2012 Outperformance Homes | Beyond Code: Renewable Ready | |
|---|---|---|---|---|
| Goal | Meet 2006 IECC at lowest possible price point | Meet 2012 IECC at lowest possible price point | Meet 2012 IECC building science best practices | Exceed 2012 IECC |
| HERS Index (plan) | 82 | 57 | 57 | Mid-40s |
| HERS Index (as built) | 77 | 59 | 54 | 48 |
| Cost of Construction | ||||
| Somerset Model (ranch) | $25,166 | $26,416 | $30,639 | $40,644 |
| Kendall Model (two-story) | $27,467 | $29,018 | $32,889 | $43,042 |
| Preston Model (ranch) | $27,314 | $29,350 | $33,902 | $43,194 |
| Below-Grade Insulation Used | ||||
| Under-Floor Slab | None | None | None | R-10 XPS |
| Rim Joist - Interior | R-19 fiberglass bat | R-19 fiberglass bat | R-16 closed-cell SPF | R-16 closed-cell SPF |
| Rim Joist - Exterior | None | None | R-5 XPS | R-10 XPS |
| Basement Wall - Interior Finished | R-13 fiberglass batt | R-19 fiberglass batt | R-5 XPS | R-10 XPS |
| Basement Wall - Interior Unfinished | R-10 fiberglass vinyl-faced | R-15 fiberglass vinyl-faced | R-5 PIR | R-10 PIR |
| Basement Wall - Exterior | None | None | R-10 XPS | R-10 XPS |
| Above-Grade Insulation Used | ||||
| Stud Dimensions | 2x6 | 2x6 | 2x4 | 2x6 |
| Interior | R-19 fiberglass batt | R-19 fiberglass batt | R-16 closed-cell SPF | R-31 closed-cell SFP |
| Exterior | Housewrap | Housewrap | R-5.5 SIS | R-5.5 SIS and R-5 XPS |
| Ceiling | R-38 dry blown cellulose | R-49 dry blown cellulose | R-49 dry blown cellulose | R-12 2-inch closed-cell SPF and R-49 dry blown cellulose |
| Compression of Air Leakage | 2.8 | 3.1 | 2.2 | 1.8 |
