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Infrared thermographic scans of the walls of 79 homes in Spokane, Washington, were made during the winter of 1983 as a means of observing the installation quality of retrofitted wall insulation. A special attempt was made to determine quantitatively the amount of void area that is typical in insulated walls since it can have a significant impact on thermal performance. Valid results were obtained for 30 of the test homes in this study, and the average uninsulated or void area was 9%, with a range of 1 to 35%. This result is in excellent agreement with those from other studies. For a 9% uninsulated area, estimates of the increase in heat loss relative to a fully insulated wall vary from a low of about 9% to as high as about 40%.
As suggested by the wide range in results, some of the retrofit wall insulation jobs were excellent and some were extremely poor. The newer installations were generally poorer. The important point is that it is clear from these results that wall insulation can be properly installed with little or no void area. Improved quality control on the part of the installers is certainly possible and needed. The fact that the average installation quality is relatively poor and the range in results is very large indicates that some kind of inspection program is advisable.
During this thermographic study, an assessment was also made of blown-in wall insulation installation problems. A number were observed, most of which could be eliminated with proper care and attention on the part of the installers. In addition, an effort was also made to locate high heat loss areas. One notable finding is that often the exposed portions of heated basement walls were uninsulated and therefore exhibited relatively high heat loss.
thermal insulation, quality control, retrofit, thermography, weatherization
Professor of mechanical engineering, Portland State University, Portland, OR
Energy consultant, Olympia, WA