Insulating 15x27x8 garage

[The_Auto_Tech]

Figured I'd just start another thread regarding insulation in my garage. It's approximately 15x27x8. Currently just has OSB walls with no insulation and open rafters. We replaced the roof sheathing and shingled the roof about 6 years ago. I use the overhead space to store stuff. It's been nice to leave it open so I can fit larger items through the rafters up there. I'm debating what I'd like to do about insulating the place. I'm not wanting to drywall the ceiling or the walls as I like having OSB walls to hang various things on, plus I don't have to worry about damaging it since this is a shop space.

From what I read I don't want to insulate at the sheathing because the roof needs to "breathe" otherwise it'll create moisture on the sheathing and roof and rot the roof. From what I understand I'd need to insulate at the rafters. I'm curious about maybe just using foam board on the ceiling, that way I can still use the overhead area as storage. I guess I could maybe screw paneling to the ceiling and then insulate on top of that between the rafters and then lay OSB on top of the rafters so I can maintain my storage area, but that seems like a lot of work as well.

I just know that the ceiling right now is the most important place to insulate as the heat is rising and going through the roof. What would you guys recommend?

 

[astroracer]

I used foil backed 1/2" foam for the ceiling and put 6" batt on top of it. I don't store anything up there though.
Mark

 

[Radix2]

Get the roof spray foamed, then everything is the same as now, but you have insulation.

Closed cell foam right on the roof sheathing is used all the time these days.

 

[The_Auto_Tech]

I used foil backed 1/2" foam for the ceiling and put 6" batt on top of it. I don't store anything up there though.
Mark

Yea, if I put batts in I'd have to lay something over it so I could still use the top for storage. It's nice to have that storage for boxes (in case I need to warranty something), winter sleds, summer toys, extra building materials, extra car parts, etc. Stuff that only gets touched maybe twice a year and would otherwise be in the way. I've heard the only issue with using foam on the ceiling is it's against fire code but I think that's only if it's attached garage? It would be nice to have something on the ceiling as it would help keep the heat in the workspace instead of in the storage space.

Get the roof spray foamed, then everything is the same as now, but you have insulation.

Closed cell foam right on the roof sheathing is used all the time these days.

You think that would insulate good without creating moisture issues? I agree that would be nice as I could retain my storage area easily.

 

[Radix2]

You think that would insulate good without creating moisture issues? I agree that would be nice as I could retain my storage area easily.

Yes, definitely.

The reason it is not done all the time is that spray foam is expensive.

 

[The_Auto_Tech]

Yes, definitely.

The reason it is not done all the time is that spray foam is expensive.

Yea, that's what worries me. This garage may not be nice enough to warrant using it. I just asked a contractor friend about doing it and he said it would most likely cost around 3500 to do it. That's way beyond what I'm willing to spend on this garage. It seems my best option is going to be to just insulate the trusses. It seems like insulating against the roof sheathing is just going to cause issues with rotting the roof out.