Building a Tight Storage Shed
A variation of this option is to replace all of the EPS/XPS with Rockwool Comfortboard and install a poly vapor barrier on the interior side of the walls, roof, and ceiling.
Similar to the above, 2*8 walls, rafters and joists.
However, with this option there will be no external insulation. Instead, I will install 2*4 strips perpendicular to the studs, rafters, and joists on the interior side and then another layer of Rockwool batts.
On all six sides of the building, the core assembly will be (from inside to outside):
– 5/8″ plywood
– 2*4 with cavities insulated by Rockwool
– Structural 2*8s perpendicular to the 2*4s insulated by Rockwool batts
– 5/8″ plywood
Roof: I would then just put tar paper and shingles
Walls: Furring strips and siding
Floor: Nothing additional
With this option, I would not install a vapor barrier.
Because there is no vapor barrier on the inside, the roof can still dry into the shed if needed.
A nice thing about this option is that I only need to buy a few packages of the 3.5″ thick Rockwool batts. I can use two layers in the 2*8 section and one layer on top in the 2*4 section.
It also greatly simplifies the exterior details and that is important to me because those take a lot of time and I need to think about making the building pest proof.
I’d appreciate any and all feedback.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part