Thickness of XPS Siding Underlayment
Hi GBA Community,
Zone 5, new construction. The siding team wants to use this XPS siding underlayment from Kingspan to furout the walls a little bit to install the siding. There is a watertable installed at the bottom where the first row of siding is not installing well because the starter strip is being installed over the watertable trim. (https://www.kingspan.com/us/en/products/rigid-insulation/fanfold-insulation/greenguard-q350/) This 3/8″ insulation is thick enough to bring the rest of the siding out a bit so there isn’t this “flaring out” that is currently happening.
From what I understand thinner foam can be considered be risky, because the R-value isn’t enough to keep my plywood sheathing dry during the winter. The greenguard is “Perforated to allow moisture vapor to escape”. Is this small amount of exterior insulation alright? Are there any risks?
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