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Field Demonstration of Alternative Wall Insulation Products - 11/11/2004 - House Energy Efficiency Insulation

Summary of Report: Field Demonstration of Alternative Wall Insulation Products

Tests of completed homes performed by the NAHB Research Center studied the impact of three alternative wall insulation materials and a variety of air sealing techniques on air leakage rates in new single-family homes.Conducted for the U.S. Environmental Protection Agency, the study found that:

The alternative wall insulation products were routinely installed with an integrated air sealing package that would be expected to produce a tighter building envelope. Once the impact of the air sealing package was accounted for, blow-in-blankets (BIBs) and spray cellulose did not measurably reduce envelope leakage in the houses studied. Low-density polyurethane foam insulation appeared to reduce air leakage in some cases, but the effect was quite variable.
Two air sealing practices that had the shortest payback periods were (1) a standard air seal that included caulking or gluing double studs and plates, applying foundation sill sealer, chinking windows with fiberglass and installing air barrier tape at windows, and (2) an additional air seal of window rough openings with foam, caulk or construction adhesive.
The alternative wall insulation products cost the builders 70% to 150% more than fiberglass batts, and took over 2.5 times longer for crews to install.
Fewer installation defects were observed with the alternative products than with fiberglass batts, but defects for the batts were nearly as low as those for alternative products when the insulator knew the homes would be tested. This suggested that quality audits or performance incentives may improve installation quality and overall insulation performance.

Four production builders each provided a group of nearly identical homes for the study. Two homes from each builder represented the builder’s typical practice and provided an estimate of construction variation. The homes were all two-story colonials with basements; other house designs were not studied. Some of the measurements and observations taken for the study included house air tightness, total labor time, initial insulation moisture content, installed density, and installed quality. Infiltration and energy savings were estimated and compared to installed costs to calculate simple paybacks.

Prior to this study, many researchers and others speculated that the newer alternative systems provided a tighter construction. This study found that, at least for wall insulation, the real benefits in reducing air leakage appeared more closely related to the caulking and sealing of joints than to the type of cavity insulation material. Results indicated that homes with batt insulation as well as alternative insulation materials achieve reduced air leakage through careful attention to sealing joints in the building envelope. Builders offering incentives or paying for improved air sealing can get improved performance for modest cost.

What does this mean for you? Do your installation crews pay careful attention to details and workmanship in creating a tight building envelope, especially when caulking or sealing around windows, doors, plates and other penetrations in the building? You may want to consider developing and implementing a quality control program to decrease installation defects.

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