Back in the early 2000s, Canadian scientists dealing with a consortium of spray polyurethane foam (SPF) producers and contractors started studying how air leakage affects the thermal efficiency of wall assemblies. The effort ended up being known as the Wall Energy Rating (WER) system.The research study team was based at the National Research Council of Canada’s Institute for Research in Construction(NRC-IRC). Using a modeling tool referred to as hygIRC-C(a 3D hygrothermal design ), the group evaluated various wall assemblies to better understand how air movement interacts with heat flow. A paper published in 2010 offers an in-depth take a look at that work.The SPF industry has long argued that separating R-value and airtightness into two independent metrics stops working to capture real-world assembly performance. WER was an attempt to deal with that problem by combining thermal resistance and air leakage into a single performance-based approach.According to the researchers, the goal of the WER research study was to develop a system that could”be used as a simple tool for constructing designers and construction specialists,”and potentially support compliance with current or future energy codes.In practical terms, the research study raised the possibility that spray foam assemblies might potentially achieve comparable real-world performance with lower small R-values than other code-compliant assemblies. If accepted by code, that might decrease the amount of insulation needed in specific applications and improve spray foam’s cost competitiveness.What did the research show?The NRC-IRC work showed that it is possible to design the combined impacts of heat transfer and air leakage with affordable precision. The results revealed excellent arrangement in between
simulations and laboratory testing.
However translating that research into a usable metric proved difficult.WER depends on modeling to forecast efficiency, and results vary depending on climate conditions and pressure differences. Just as crucial, there’s no obvious method to lower … Weekly Newsletter Get building science and energy efficiency advice, plus special offers, in your inbox.< img src="https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/gba-prime-white.png" alt="GBA Prime"/ > Sign up for a free trial and
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