insulate garage ceiling


Old 06-20-01, 07:05 PM
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Building bedroom above attached garage in Michigan. I've heard several opinions about whether or not to insulate garage ceiling. One is that heat rises so you won't lose any heat through floor so you don't need any insulation on garage ceiling. The other is to insulate ceiling of garage. I tend to agree with insulation in ceiling because if heat rises, in summertime it's going to rise to the ceiling....not to mention in wintertime the floors in room above will be cold. Not insulating doesn't make any sense to me , but i would like to hear some other opinions or facts.

Thanx in advance, Bill
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Old 06-20-01, 07:32 PM
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You must insulate the probably won't even pass inspection if you dont... Put the maximun amount of insulation in the area (R-38 would be ideal if you have at least a 2" x 10") with the heated space above... Material will cost you max 1.00 per square foot in the detroit Metro area... Install with vapor barrier up towards heated space..

Bonus Rooms over garages are notorious for having cold floors.... Here is also what I would do If it were my home.

Install R-13 Kraft batts in walls of Bonus Room.
Most Bonus rooms have a sloped portion of the ceiling .
Install styrofoam vents in every truss space, Then install the maximum R-value into this area that you can..

If they are only 2x6's then i would add on a 2 x 2 on top and then install a high density R-21 minmum batt in the sloped areas..

In the flat ceiling area I would install again R-38 Batt.

I would then install 6" R-19 Kraft insulation in the balance of the garage ceiling area.

Caulking or foam sealing along the bottom plate will help

also any electical outlets on the outer walls, I would foam seal. If there is no exterior sheating in the kneewall areas i would install a small piece of plywood behind the out and foam seal those also..

Insualtion is a minimal cost compared to the price...To do it right the first time will make you alot more satisfied.

I work in the Detroit Metro area and can direct you to the best places to buy insulation for do it yourselfers..

Good Luck


Old 06-21-01, 05:30 PM
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WOW!!!!!! Now THAT is an answer !!! One of the best , if not the best reply to a post i've gotten. Thanx a million.
My builder is supplying my insulation at his cost so i'm guessing he was trying to keep the tab down !
Couple questions :
1) Getting insulation via builder through Home Depot and they don't carry 24" r-38 , at that location, in stock. However I have 24" r-30. Would poly barrier on ceiling (garage side)opposite kraft face help out ? Have to do it this weekend (and Drywall) in 24x24 garage for occupancy , so I can't wait for special order.
2) What I do have is r-30 for whole garage ceiling , r-30 for flat part of room ceiling , and r-19 for sloped ceiling and knee walls.My sloped part is 2x6 , so I will have to ad depth. Don't recall seeing high density r-21 at Home Depot. If they don't have it , should I stick with r-19 or is there something better ?

Again , thanx for your input !
Old 06-21-01, 09:58 PM
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You can buy R-38 and R-21 from Insulation Sales located in Ferndale, Michigan.. Probably can buy all the insulation cheaper than at Home Depot and I am sure they most likely have it in stock....

their phone is 248-398-7200 ask for Greg

Let them know I sent you

Also do not put the poly in the garage ceiling that will give you a double vapor barrier which is a no no...

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