Open cell spray foam

We just had our tank filled today. The first in two years. $1.75/gal.
 
@RJSakowski stated it 100% correctly.

If you use open-cell spray foam in a cold climate, you MUST install a vapor barrier on the warm side of the wall/ceiling, and it must be installed correctly. We have 15" or so of closed cell foam in our living room vaulted ceiling. We also have five inches in the walls. No vapor barrier is required in the entire structure.

BTW, $1.65 for propane on contract for this winter.
 
I used closed cell foam on my 17x36 shop. I then put 3/4" plywood over the first 10 feet of a 17' height. I live in central Texas so keeping cool is much more important that keeping warm. I have been very happy with the results so far. I choose closed Cell mostly due to the higher R Factor. Buy once / Cry once philosophy.
 
Scruffer said:
Closed cell has an R value of 7 per inch. Open cell has an R value of 3.8 per inch.
Click to expand...
So you need double the thickness of open cell to match closed in insulating value. So the economics are easy to calculate for heat flow. Next is moisture control. On one side you want to stop it, on the other side you want to get rid of it. It takes very little moisture at cold temperatures to condense and become water. Water brings with it mold, rot and loss of insulating value. Some way of stopping moisture from getting into the insulation is needed and if it does get in a way out before damage can occur. Where I live it gets moderately chilly in winter (at worst only -15F) so an interior vapor barrier is used. The assumption being that the outside of the wall or roof will be less moisture tight than the inside. There are places where the climate and direction of heat & moisture flow may be different. Closed cell foam is about as good of moisture stopper as you can get. Fiberglass batts have pretty good barriers but they are not continuous, seams, electrical outlets, poor installation ... Plastic sheeting is probably better but still leaks around electrical outlets a little.

The video was very good. Especially the part about what happens when a very steep roof hits the valley of a lower pitched one.
 
Living in Wisconsin, we experience extreme cold in winter and high heat and humidity in the summer. Vapor barriers are installed on the warm side of the insulation which creates a dilemma for air conditioned homes as the vapor barrier is typically installed inside of the insulation. . Closed cell foam solves that dilemma as it is a vapor barrier in itself.

Edit: @Larry$ posted as I was typing.
 
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