Bonderized metal /paint grip siding over mineral wool
![](https://secure.gravatar.com/avatar/2279fb389eb47d10a5ac6e2763a7e811?s=52&d=https%3A%2F%2Fimages.greenbuildingadvisor.com%2Fapp%2Favatars%2F200x200%2Fg.png&r=g)
Hello,
Looking for advice on how to install horizontal bonderized steel siding over Rockwool Comfortboard 80. Location is climate zone 3a warm-humid (north central Texas)
The assembly we’re considering is the following:
2×6 @ 16” OC walls insulated with Rockwool batts (R-23), Zip sheathing
Roxul Comfortboard 80 – 1.5” (R-6), bonderize metal (paint grip) siding running horizontally.
Rockwool doesn’t have information online on how to make this assembly possible, but I submitted an inquiry earlier. In the meantime, I was wondering if anyone has tried the wall configuration mentioned above, or what would be other exterior insulation options to consider, accounting for the weight of the metal cladding.
Thanks
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb1.png)
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb2.png)
Replies
side_oats_grama,
Metal siding (with maybe the exception of corten steel) is relatively light. Any strapping detail that works for other claddings like cement-based ones or wood, will work for metal.
Try to include a rainscreen gap between the siding and the exterior mineral wool, using vertical furring strips. It shouldn’t add a tremendous amount of cost and will make the entire assembly last longer.
Also, seeing as you’re from Texas like me, consider foil-faced polyiso as your exterior insulation instead of mineral wool. It will double as a radiant barrier (your metal siding will give you some radiant barrier benefit already too), it has a higher R-value per inch, it’s cheaper and it’s more environmentally friendly. The radiant barrier benefit will only work with a rainscreen gap though, keep that in mind.