Spray foam insulation

I think your math is way off. That kit will produce 43cu ft, which comes out to about 12 sq ft. At 850.00/kit that is $69/sq ft. Also, I can guarantee that you will not get the volume they claim out of those kits.

Edit: Apparently my math is way off, disregard this post

I’m interested in this for a very small job

Will it affect the existing drywall? I’m concerned with walls bowing

Anyone have a situation like mine:
I have a front porch and a rear porch that are under the main roof with blue vinyl-non-perforated-soffit-like material. There are 3 dormers (part of interior rooms) and quite a bit of attic on one side
The back porch actually has almost a whole bedroom on top of it.


Do they spray over that? Or does that screw up the building envelope so much that it becomes not worth sealing the top?

I can’t give you a cost since I used spray foam on my house 8 years ago. I sprayed foamed my exterior walls, laundry room walls for soundproofing, and a couple of inches in the attic floor to seal ceiling penetrations. I used blown cellulose over the bottom 2” in the attic to obtain desired R-values.

Couple of things I learned:

1. There needs to be fresh air introduced into the duct system.
2. For new construction, the spray foam will expand beyond the studs. They uses a milling machine to mill off the excess so as to be flush with the studs. But the spray foam can push out wiring or PEX so that this milling machine will damage it, Care shall be used while milling.

I had the underneath of my raised house sprayed with 2in of closed cell (1800sf) for $2/sf.

As others have said, closed cell on walls and below raised floor, but open on underside of roof deck.

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I think your math is way off. That kit will produce 43cu ft, which comes out to about 12 sq ft. At 850.00/kit that is $69/sq ft. Also, I can guarantee that you will not get the volume they claim out of those kits.

Edit: Apparently my math is way off, disregard this post

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As the first response to my thread, I was really disappointed with myself until I saw your edit. I got a laugh.

Thanks for the responses and tips about closed cell in walls and open cell on roof. The site didn't really go into detail on that.

ETA: I am in Texas West of Fort Worth (Weatherford).

First of all I’ve seen at least 2 times that experienced contractors ( not foam guys, but people that have been in construction for years ) didn’t spray it correctly and the foam caught on fire. It’s a chemical reaction.
And second it’s a science on how a house should be insulated, if done incorrectly it can and will cause mold and mildew issues..
That’s just my two cents, if you do decide to do it yourself do as much research as you can.

For those who added open cell to roof of existing construction, did you seal the entire attic or keep the same ventilation?

To do it right the existing insulation on the ceiling needs to be removed and the entire attic needs to be sealed.