I'm wanting to insulation my shop with spray foam. I will have about 7in of space between the metal and the interior wall. Should I fill the whole cavity with open cell or just use close cell and leave a air gap? Should I use any vapor barrier? I live in Oklahoma and I'm open to suggestions.
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Insulation questions
- Thread starter Dspurlo81
- Start date
Ross/Kzoo
Well-known member
Have you priced it out yet? It's expensive. You may want to to put in 4-6" of rigid foam board and fill the rest with spray foam.
LX-Markham
Well-known member
facing a similar problem with spray foaming my garage.
thanks for the ideas guys!
thanks for the ideas guys!
Many people will put in a couple inches of closed cell then fill the rest of the cavity with wet sprayed cellulose. Cheaper and nearly as effective as filling the whole cavity with foam. If you have electrical or plumbing in a cavity and ever need to tear your wall apart down the road, having the entire cavity in spray foam will be a nightmare. I'd say leave a gap or fill the remaining with cellulose.
So put closed cell then cellulose? What's wet sprayed cellulose?
Just an installation method. They spray it in wet to get it to pack/stick in the cavity then they let it dry before drywall or wall covering. Some do it dry with netting stapled to the wall but may not work well in a cavity already half filled with foam.
Here's a video that shows what I'm referring to:
Also just noticed that you are in Oklahoma so you're in a pretty mild area. 2" of closed cell foam on your wall would probably be enough. If you fill your 7" cavity with foam/cellulose, that's a lot of insulation for a wall (especially a garage) in Oklahoma. If you were farther North, I'd fill it but not sure it would be worthwhile for you.
Voi
Well-known member
Here's a video that shows what I'm referring to:
Interesting that they used foam for the exterior roof and wall sheathing and they sprayed an inch of foam on top of it, at least on the walls.
Any idea why they did this? Is it a green/eco thing where they don't want to use OSB?
Ross/Kzoo
Well-known member
Interesting that they used foam for the exterior roof and wall sheathing and they sprayed an inch of foam on top of it, at least on the walls.
Any idea why they did this? Is it a green/eco thing where they don't want to use OSB?
I wouldn't think tat the 2 x 4 wall would have any structural rigidity with just 1" foam board and 1" spray foam.
Interesting that they used foam for the exterior roof and wall sheathing and they sprayed an inch of foam on top of it, at least on the walls.
Any idea why they did this? Is it a green/eco thing where they don't want to use OSB?
It is possible to get away without OSB or plywood sheathing on the walls if the use diagonal strapping, let-in bracing or corner shear sheathing reinforcement. He could have just forgot to mention that there is OSB sheathing and there is foam insulation installed on top of that. The roof would have to have some sort of wood or steel sheathing. I think what they mentioned was a hybrid wood/foam sheathing on the roof.
Voi
Well-known member
It is possible to get away without OSB or plywood sheathing on the walls if the use diagonal strapping, let-in bracing or corner shear sheathing reinforcement. He could have just forgot to mention that there is OSB sheathing and there is foam insulation installed on top of that. The roof would have to have some sort of wood or steel sheathing. I think what they mentioned was a hybrid wood/foam sheathing on the roof.
Yeah I watched some of his other videos. On the roof they use a panel sort of like half a SIP. OSB bonded to one side of 1.5" or 2" thick foam.
For the walls the exterior foam is how they meet insulation code for 2x4 wall construction in Texas.
They also install the siding over the foam with an air gap so the foil face can act as a radiant barrier. Makes sense but I wonder how long that radiant barrier stays effective?
Voi
Well-known member
I wouldn't think tat the 2 x 4 wall would have any structural rigidity with just 1" foam board and 1" spray foam.
I always hear how much spray foam adds the structure of a wall. I guess 1" is enough?