SKINNER
Well-known member
What R-value should I use on the ceiling of my garage? I am located in Southern Indiana and plan on installing R13 in the walls....R30 is really pricey...any suggestions?
SKINNER said:What R-value should I use on the ceiling of my garage? I am located in Southern Indiana and plan on installing R13 in the walls....R30 is really pricey...any suggestions?
jerry j said:Skinner; "R-30 is pricey" So is the fuel to heat our spaces..
I've been an insulation contractor for 30 years..
What I would do is: install R-19 batts and then blow 8" Cellulose (R-30)
over the batts. This will give you a total R-Value of 49.. This will also seal anywhere that heat could escape with just batts only...I know it sounds like overkill but fuel prices are not going to go down any significant amount, and this is one job that you don't want to do over again... If you heat on a regular basis you should save enough to pay for the extra insulation in a very short amount of time..
SKINNER said:Jerry,
What's needed to blow-in insulation on a 4/12 vaulted ceiling? Does one have to build up supports or firring?
What is the benefit of using batts then blown in Cellulose vs. just using the blown in, assuming you ended up with the same R value?jerry j said:What I would do is: install R-19 batts and then blow 8" Cellulose (R-30) over the batts. This will give you a total R-Value of 49..
jerry j said:Skinner;
Whoops..... Now everything changes.... Your Limited.....
Everything depends on the size of the truss material.. 2x4, 2x6, 2x8, etc.
You are limited to the amount of space.. Also there should (must) be some sort of air space, after insulation is installed, from the underside of the roof to the insulation, to remove any moisture on the underside of the roof..
If you want, you can call me tomorrow as I'm leaving shortly.....

Itzkwik said:What is the benefit of using batts then blown in Cellulose vs. just using the blown in, assuming you ended up with the same R value?[/QUOT
Good Question. Basically the only real benefit would be the Vapor Barrier..
Although if you have E N O U G H ventilation then a vapor barrier is not needed..But you must have ENOUGH.. I know, there isn't a lot of moisture in a garage, but there is...or could be..
The idea behind R-19 W Vapor Barrier is then you don't have to spend all day in the attic blowing in the cellulose and or laying visqueen as a vapor barrier.. (pain in the a**) (Doesn't work)
Special55 said:Like Jerry said, make sure you have an air space running from your soffets to your roof vents. You can get plastic or styrofoam troughs that staple to the underside of your roof sheeting at Lowes/Home Depot. I used these when I built my greatroom addition and they are a no brainer
If you are going to have an inspection I would be leary of the rigid foam. I remember hearing something about it releasing toxic fumes when exposed to flames. For that reason it probably wouldn't pass code.JMURiz said:Thread resurection:
I'm in the same boat, vaulted ceiling that I'd like to put insulation in. Would the rigid foam or something like double-bubble foil insulation stapled to the rafters work best (while leaving ~4" space from the insulation to the roof)?
Foil ~ 9 R-value up
2" rigid foam =10 R-value