Insulating shed floor from outside
I am remodeling a shed and would like to insulate the floor. Its a 12×16 shed with metal joists that are spread 24in apart and are 6 inches in height. I could insulate from the inside but could not go more than 1/2 inch in thickness. My plan would be to go on the outside as shed sits about 8 to 12 inches above ground. To make my installation easier my plan is to use 1×4 treated lumber to raise the insulation up to the OSB flooring. The insulation will be cut 24 in wide and will have an 8 ft on the center with 2ft long pieces on the edges. That way I can reach the seam and tape it.
I will use a sheet that is 1/2in and then a 2 in sheet below it so the 1×4 keeps the foam tight to the floor. The metal joists have a lip on the bottom that will hold the 1×4 during installation and I can eventually screw the 1×4 to the joist to make a more solid installation
My question is where to use Owens Corning NGX which is polystyrene or use Rmax Polyiso with aluminum facers. I prefer the Rmax but getting it on 2 inches thick is very difficult. I only need 6 sheets or 4×8 insulation. I live in Austin, Texas so our winters are pretty mild and go around low 30’s sometime and high 30’s most of the time.
Which way should I go polystryrene or polyiso?
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Replies
Luigi,
You know your local conditions better that I do, but here in the PNW unprotected foam on the underside of a building would get eaten by pests, or tunneled into to give access to the joist bays. You might consider gluing plywood or some other facer to the foam sheets before installation.