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Spray Foam Insulation Questions.

288 Views 12 Replies 8 Participants Last post by  Akcabin
Hi all

I will be doing spray foam insulation in my 1.5 car garage soon as part of a major man cave/garage mahal overhaul.

In addition to the insulation, I plan on having a mini-split heat pump to keep it comfortable in there year-round.

I've had several quotes from reputable installers. All quoted 2" for the walls, but some quoted 2" for the roof deck and others have quoted 3".

I live in Michigan where it can be very hot or very cold. What are your suggestions regarding whether it's worth going for the extra inch?
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· Naildriver
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Pay me now, or pay someone else (POCO) later. Spray foam, IMO, is the best insulation you can hope to get in your situation. I had a client who spray foamed an addition in the back of her garage. I went over to check something out, and my truck thermometer read 100 degrees F. I unlocked the room, and with no air movement at all, it was a comfortable 80 degrees on her wall thermostat/garage door opener.. I turned on the window unit and within about 15 minutes, I heard the compressor kick off and it was 70 degrees. Amazing stuff.
 

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Discussion Starter · #4 ·
Pay me now, or pay someone else (POCO) later. Spray foam, IMO, is the best insulation you can hope to get in your situation. I had a client who spray foamed an addition in the back of her garage. I went over to check something out, and my truck thermometer read 100 degrees F. I unlocked the room, and with no air movement at all, it was a comfortable 80 degrees on her wall thermostat/garage door opener.. I turned on the window unit and within about 15 minutes, I heard the compressor kick off and it was 70 degrees. Amazing stuff.
Absolutely. We had my wife's shed spray foamed and it makes a huge difference.
 

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I would go a minimum of 3 inches on all surfaces and probably at least 4 in the ceiling. 2" is definitely not enough. As mentioned previously you want to go closed cell foam because it provides a vapor barrier also.
 

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You mention Michigan are you in an area that has building codes. Once you make that a living space they may require code level r-values.

Bud
 

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Discussion Starter · #7 ·
I would go a minimum of 3 inches on all surfaces and probably at least 4 in the ceiling. 2" is definitely not enough. As mentioned previously you want to go closed cell foam because it provides a vapor barrier also.
3 In is the most I will be able to do basically anywhere in it. The alternative would be adding additional 1x2s everywhere to make the cavities deeper, but I'm not really interested in that. It's not that big of a garage to begin with.

I may have them quote me for 3 inch everywhere though just to see what that does to the quotes.
 

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Thickness depends on the type of foam, closed cell or open cell.
Michigan gets pretty cold so I would be leaning towards closed cell and at least 3 inches or fill the void.
 

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Discussion Starter · #9 ·
Thickness depends on the type of foam, closed cell or open cell.
Michigan gets pretty cold so I would be leaning towards closed cell and at least 3 inches or fill the void.
It will definitely be closed cell. I've asked the vendors to provide updated quotes to do 3" for the walls instead of 2".

I wonder why they wouldn't have recommended that from the beginning. It'd be more money for them....
 

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99% of vendors will quote their bottom dollar price. A few will offer suggestions/additions.

If your walls are 2x4's have them bring the foam out flush and cut the foam off even with the studs. Have everything done before they show up. Closed cell is a bugger to remove.
 

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I wonder why they wouldn't have recommended that from the beginning. It'd be more money for them....
Could be that they are approaching the maximum thickness of sprayfoam that can be done in one pass.

The curing of polyurethane sprayfoam is exothermic, which means it creates heat as it cures. And because it is very good insulation, the heat has difficulty escaping. Spray it too thick, and it can overheat and catch fire while curing.

 

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Discussion Starter · #12 ·
Being that I saved almost $4K doing the framing myself, deciding to splurge and do 3" all around on the insulation. It's too much work to do to get it all done and have the insulation not perform when I could have added an extra inch.
 

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I would do 2" of closed cell to seal all holes that will allow air movement, moisture. Then 3-1/2" rockwool sound n fire.
The rockwool has a better r value. R4 compared to around r3 for foam. Sound n fire resistant insulation helps a lot. Cheaper n easy to do yourself. Very easy n no itching. Spun wool.
You will not use a vapor barrier over the walls interior before installing sheetrock. The closed cell is a vapor retarder. But really not much moisture can move through it. You do not want 2 barriers. Sounds like a great project
 
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