Garage Insulation Options

[mattthegorby]

Originally Posted by skidderman

Are you suggesting that if one had a perfect seal then air circulation is not required? Was told that as well but don't know what to think.

I do not have a technical knowledge of sprayfoam insulation, so I would not want to speak with too much confidence. My understanding is that spray foam, like foam paneling, is totally sealed with no internal airspace so condensation cannot form inside of it.

Batt insulation on the other hand is full of air space so condensation is a risk and needs to be allowed to breathe. As it is sealed on the inside with vapor barrier, the outside cannot be flush against a roof because unlike tyvec the roofing materials do not breath. With the roof you also get the risk of ice dams depending on the construction and need that air flow.

Sent from my SM-G920W8 using Tapatalk

[spazzy]

It is 2x4 trusses and im thinking spray foam is the only way to go ill do the walls my self and get some quotes on the spray foam . At this point i might have to just shhet the ceiling and do blow in attic insulation

[Tungsten,]

Haven't read all the posts so it may have been suggested already.Your cement walls will also need some insulation as there is almost no R value in cement.

[Kim473]

Originally Posted by CaberTosser

Ahh Mulie, I just noticed it was you that made that comment about putting rigid foam board up against the bottom of the roof sheathing, letting the shingle nails hold it up. I'm not sure if you were kidding there or not, so I'll note that the insulation can't go right to the bottom of the roof sheathing. There needs to be an airspace there for airflow to keep the roof sheathing dry. Problems arise if no airflow exists there, some of which can be ice damming and the sheathing rotting, among others.

If you were kidding. HaHa, carry on.

And your shingles will have 1/2 life or so. Air space is needed as said.