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Hpac 1270 Insulation

Report: Insulation Performance Dependent on Installation, not Material

Aug. 31, 2015
According to the report, when walls are constructed to the same R-value and properly air-sealed, all insulation types essentially perform the same.
Photo by Justin Sullivan/Getty Images

A new study from Building Science Corp. demonstrates that all insulation products perform equally well when properly installed and air-sealed.

“Thermal Metric Summary Report” concludes a multiyear collaborative research project that examined how walls insulated with different materials performed with air at temperatures between 144°F and -18°F moving through them. 

A preliminary version of the report released in the fall of 2013 contained the results of tests on walls insulated with fiber-glass batts, cellulose, closed-cell spray foam (ccSPF), and foam sheathing. The results of a test conducted on an open-cell-spray-foam (ocSPF) wall were not included because the wall had defects, including large voids, and the thermal performance of the wall was significantly less than expected. A second wall insulated with ocSPF was tested; the results of both the first and second tests are contained in the recent update of the report. The new report also includes the results of testing on walls that were air-sealed and insulated with R-15 fiberglass batts and R-15 dense-pack fiberglass loose fill (similar to blown-in blanket systems). The air-sealed R-15-fiberglass-batt wall performed better than the R-13 ocSPF wall and the R-12 ccSPF wall. 

Among the report’s findings are:

  • When walls are constructed to the same R-value and properly air-sealed, all insulation types essentially perform the same.
  • Air sealing is required for all insulation types to provide optimal performance.
  • During decommissioning of the ocSPF wall, the researchers confirmed there were areas where the foam did not adhere to the oriented-strand-board sheathing, resulting in large voids. These gaps can affect performance. 
  • Energy losses attributed to thermal bridging occur with and have the same effect on all insulation types.
  • The R-15 fiber-glass-batt wall was among the better-performing assemblies tested. All of the fiber-glass walls with air-sealing were among the top performers. 
  • All of the insulation materials showed temperature-dependent thermal performance (i.e., changes in insulation R-value with changes in mean temperature).

The research project was funded by a group of industry partners, including NAIMA (North American Insulation Manufacturers Association).

To download the report, go to