Has anyone in climate zones 5 thru 8 ever used Rockwool Comfortboard80 as CEI on roof? Here’s why we ask: We live in a leaky ancient house near NH-VT-MA intersection. We were planning to find a contractor to replace our wooden clapboards (in horrid shape) with vinyl siding, and our asphalt shingles (20+ years old) with standing seam metal. Since there is practically no existing housewrap, we were going to have said contractor apply fully adhered vapor permeable membrane to walls and roof, then use Rockwool Comfortboard80 as continuous exterior insulation on both surfaces as per attached detail from manufacturer. (We cannot seem to source the denser Comfortboard110). Anyway, a contractor considering the job pointed out that, with respect to the roof, it’s tough to hit the (hopefully straight) rafters with (necessarily) long screws: in his experience, wood grain in the strapping (2×3 on end per detail) is liable to re-aim the drill bit and screw; furthermore, if the rafters are at all sagged, the contact patch and compression come out irregular. He also expressed concern re: compression of Rockwool Comfortboard80: specifically, given its compressive strength of 439 psf at 10% compression, if the roof were to ever have a load of 50 lbs per sq ft (not far-fetched during our snowy months!), then the 1.5 in wide strapping (rafters are spaced 16 o.c.), would bear a load of 3.7 lbs per square inch, which is > 10% compression. Assuming roof CEI is 5 inches thick, this means > half an inch compression (excessive in contractor’s estimation). I shared the contractor’s concerns with the Rockwool Tech Services Dept which, interestingly, is headquartered in a colder climate than ours and presumably gets more snow than we do. Nonetheless, their response was: “It may be best to have a structural engineer assess the max loads your roof is expected to experience and the compressive resistance of ROCKWOOL Comfortboard 80. If this does not meet your requirements, then consider rigid foam.” We were hoping to avoid rigid foam because we understood that vapor permeable CEI (eg, rockwool) was less risky than vapor closed (eg, foam). If you have ever executed rockwool as CEI on pitched roof in cold climate, can you please share details? We were attracted to rockwool CEI not only due to its vapor permeability, but also its superior resistance to fire, moisture, bugs. Plus, we liked the quote a nearby lumberyard gave us. But the concerns of this contractor re: rockwool’s suitability as roof CEI have given us pause…any input would be much appreciated. Thank you.