Paper presented at 1990 ACEEE Summer Study on Efficiency in Buildings Conference
Paper Dated: 1990
By: Michael Blasnik
In order to verify the attic model and quantify the performance of attic insulation, six occupied houses were instrumented to monitor hourly averages of temperatures, pressure differences, humidity, and heating system status for 1-2 winters each. Wood moisture content was also periodically measured.
Each of the instrumented attics was given a series of treatments consisting of a combination of bypass sealing, insulation and venting. The performance of the treatments at three of the sites was analyzed with the attic model. The model performed well overall and provided reasonable estimates of attic performance.
The study demonstrates that the performance of common flat roof insulation methods falls short of standard predictions because of substantial air leakage from the house below. The effectiveness of and difficulties inherent to, several approaches for sealing bypasses in limited access flat roof attics is presented.
When significant bypasses are present, effective treatment can dramatically and cost-effectively improve attic retrofit performance. But the most cost-effective strategy is site specific. Evidence is also presented that standard passive roof ventilation is often ineffective, unnecessary, and counterproductive in these houses, leading to potentially significant additional heat loss. An attic airtightness test is described which can help estimate the impact of insulation, bypass sealing and venting strategies.
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