Thermal performance of steel embedded in foam
The company Legalett out of Canada offers an EPS panel system (Thermalwall) designed to make installing thick exterior foam both easier and with less thermal bridging at screw heads. Its made for both ICFs and wood frames walls. They do this by embedding a steel channel 3 inches inside each foam panel that has a foam insert that is replaced after installing screws. I have attached a photo from their marketing that shows this. Here is a link to their product page. http://www.legalett.ca/eps-foam-panel-wall-insulation-passive-house-zne-leed-nzeb-thermalwall-ph.html
My main concern relates to the steel that’s embedded in the foam. While the company claims an 8″ panel provides R-32 with virtually no thermal bridging (since the screws are buried in foam), I still am left wondering if the steel inside the panel will have any effect on the total R value of the wall due to the poor thermal properties of steel. I have read elsewhere on green building advisor about the thermal perils of using steel studs, I just am unsure if the same principles would apply here. Maybe someone more intelligent than I in the subject of thermal dynamics can weight in.
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