I was wondering if it would be worth adding insulation above my garage. Currently, there is no insulation in there, but the garage is connected to the house. Also, the attic is one big attic, so you can see to the front of the house when you're in the attic above the garage.

I'm getting ready to lay down some plywood in there to give me some storage space for boxes and stuff like that, but thought it might be a good idea to do some blown in insulation between the joists before I lay down the plywood.

Is it worth the effort even though the garage isn't heated/cooled? I feel like it'll just make the garage hotter in the summer with the cars in there.

What are everyone's thoughts?

We put r30 in the attic above our attached garage. It made it much more climate controlled. I didn't think it would be worth it, and got differing opinions from alot of people online, but eventually spoke to one of the best homebuilders in Houston and was told that they do it and it is worth the small cost.

Why not use batts vs blown in? If the rafters are exposed, unrolling batts will probably be cheaper and easier. Face mask, box cutter, pipe to compress the material, and Ou are ready to go.

Home depot has unfaced Owens Corning r30 for about $17 for a 15 inch x 25 feet.

Also, make sure not to cover or block out any ridge vents or softfit vents.

It wouldn't be a bad idea if you think the cost to do so is reasonable. I'd use batts tho, since you got a blank slate, should be easy. Blow in shouldn't be hard either if you prefer to go that way.

How many sq ft? We did 3/4 of the attic space over the garsge for around $150 after all materials including mask, gloves, and cutter, and tyvek.

I forgot to mention that we only insulated around the deck that was built by the previous homeowner. We are going to fill those cavities with blown in fiberglass when we are able to start the main insulation project as the area under the deck space is only ~150 sq ft.

It's about 300 sqft. I'm looking at getting this stuff since my joists are about 26" on center.

http://www.homedepot.com/Building-Materials-Insulation-Fiberglass/h_d1/N-5yc1vZbay7/R-202585900/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

I've actually got 2X10's up there, but figure for an "unconditioned" space, R19 should be fine.

Next question...should I try to put any ventilation in there? If so, what kind? It just seems like this will actually keep heat in from the cars as opposed to keeping it cooler.

I know this is odd, but we were instructed by one of the top homebuilders in Houston to use unfaced insulation above the attic if the space is not heated or cooled. Plus, you can get the unfaced R 30 for cheaper per sq ft from home depot than the faced r 19

[This message has been edited by CSTXAG2015 (edited 7/17/2011 5:53p).]

So this stuff?

http://www.homedepot.com/Building-Materials-Insulation-Fiberglass/h_d1/N-5yc1vZbay7Z1z0zycl/R-202689769/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

Id get the 15 x 25 and trim it. The 15 x 25 are 15.99 vs 39.77. Im sorry, but I call that a screw job. As long as you have a decent piece of rebarb or wood to put down when you are making cuts, id get the 15 inch and save the money. You could even do alot of ~25 inch cuts and lay it horizontal if you dont feel comfortable splitting the sheet in the middle. Maybe use some of the saved cash on a good respirator, suit, and gloves.

Ok...one other question.

Do I need to worry about putting down a vapor barrier? If so, should it go down before the insulation or put it on top?

Thanks for all the help!

If you use the 15 vs the 23, you will save ~$130 after tax (171.5 vs $300) or ~45% from a the base price of $300.

http://www.homedepot.com/Building-Materials/h_d1/N-5yc1vZaqns/R-202585906/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

Sounds good. Guess that means we'll be doing lots of cutting. But they'll all be the same size, so it shouldn't be too hard to knock out.

My house in Phoenix had a west facing garage that was attached and uninsulated.

I bit the bullet and blew in insulation over the garage, and it made a world of difference in terms of sound and on my electric bill.

Heat is going to transfer - it will go from the garage to the attic and eventually to the rest of the house. Physics and all of that.

I personally wouldn't mess with batt insulation - you can blow 300 square feet in there in about 20 minutes for probably cheaper than you can buy, unroll, trim, and install the batts, and you'll get better overall coverage than you will with batts.

Where are you located travelag? If you are close to BCS, I can help you for a case or beer or bottle of bourbon.

If it is a one man job, use batts. If you have someone that can help and you dont mind throwing a little more down on respirators etc, then blown in might make sense.

Batts will be easier than blown in if you have decently standard splits for the rafter and will keep you from having to deal with installing baffles if they arent there. The biggets thing Ive seen with friends that use blown in vs batts is that those that use blown in [if they arent experienced] end up covering lights etc)

Have you insulated your garage door too?