Can you use polyiso insulation on the exterior of a wall behind cedar siding on the west coast?

Iain Matheson Published: Jan. 28, 2020, 10:38 p.m.Last updated: Jan. 29, 2020, 9:11 p.m.

At what point/temp & to what extent does polyiso board loose its thermal properties?  Does it go below R4.5 per inch?  Is it usless at -15C ?  or equal to XPS  ?

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