Roxul or polyisocyanurate?
I am putting together the design/spec for a deep energy retrofit of a 60’s bungalow in Calgary, Alberta. I will be applying an insulation product to the exterior of the sheathing to eliminate as many thermal bridges as possible.
As a big part of the retrofits intentions are for environmental reasons, I want to use as benign materials as is possible and fiscally reasonable. With regard to exterior insulation I am debating on either 4″ Roxul RockBoard 80 (R16.4) or 4″ of polyisocyanurate board (R24).
Issues I see with Roxul are: less R value, uses a “cured urea extended phenolic formaldehyde binder”. My issues with polyisocyanurate is it has a halogenated flame retardants. Any thoughts on which way to go?