Mineral Wool Rigid Insulation Price
I’m planning on building a cabin in the next few months and would like to have a 3 inch layer of semi-rigid mineral wool on the exterior. Even though R-values are a little less compared to rigid foam, I think its a superior product given it’s breathable, is insect resistant, mold resistant, and r-values don’t drift over time. I also like that its a green product and doesn’t contain any blowing agents or formaldehyde.
It seems that Roxul Comfortboard 80 is the go to product for exterior applications in the residential market, but it’s very expensive. I’ve talked to local building suppliers that have quoted around $1.25/sqft for the 2 inch version. It looks like big box stores are selling the 1.5 inch version at about $1/sqft. I could probably negotiate those prices down, but it’s still considerably more than foam. I’ve found 2 inch XPS at $0.60/sqft and I can probably improve on that.
Does anyone recommend alternative suppliers or would like to share their experience with mineral wool? Is there a general market cost per square foot I should have in mind for mineral wool? I used to see older posts that praised the affordability of semi-rigid mineral wool compared to XPS, but that seems to have reversed in recent times.