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n0c7 03-04-2013 09:08 AM

Detached garage insulation
I'm going to be building a 20x22 detached garage heated with a natural gas ceiling mounted furnace. For the most part the temperature will be turned down just enough to keep things from freezing and when I want to work in it I'll crank it up to room temperature.

Question is - For the size and purpose of the garage is it worth the effort to upgrade from 2x4 to 2x6's to take advantage of the additional insulation?

joecaption 03-04-2013 09:11 AM

In your zone I would.

handyman_20772 03-04-2013 09:20 AM

I would, the walls will have a minimum of R-19 batt insulation or you can spray foam and you can either frame it 16 inch on center or 24 inch on center, it is a much stronger building in my opinion and most of all your comfort level will increase.

HomeSealed 03-04-2013 09:59 AM

I'd have to agree. Up in Canada you probably want as much insulation as you can get.

hammerlane 03-04-2013 10:26 AM


Originally Posted by n0c7 (Post 1129627)
For the size and purpose of the garage is it worth the effort to upgrade from 2x4 to 2x6's to take advantage of the additional insulation?

what is the cost difference in using 2x4s instead of 2x6s. Have your figured that out yet? Whats needed about 60 studs?

Gary in WA 03-04-2013 02:03 PM

So many variables to meet your requirements; type of siding, type of insulation, any exterior insulating sheathing foam board, vapor barrier, vapor retarder, wet vehicles being parked to add moisture, propane furnace adding how much moisture to room air, etc. R-19 (made for floors) is the lowest density fiberglass cavity insulation (lose R-1 just installing in 5-1/2" space) you can use in a 2x6 wall and is inherent with convective loops, and add the thermal bridging of the studs, 16"o.c. (R-1.25 per inch of thickness = R-7-) equals the whole wall R-value of R-13.7 (28% reduction). A 2x4 whole wall R-value is R-9.8 (11% reduction). So you lose with the price for the extra thick studs, the thermal bridging loss and the insulation loss if using foamboard on the exterior to raise the dew-point of the cavity against condensation. 2x4 is good to 12' high in the States, check w. your local AHJ.


ddawg16 03-04-2013 02:42 PM

I used 2x6 in my garage...

A 2x6 is maybe $2/ most.......

I'm still trying to digest what Gary was explaining regarding the insulation. I do know that my 2x6 walls cut down better on if I'm doing some sawing at one hears it.

One other point....2x6 studs are typically going to give you a straighter wall. While doing the construction on my 2-story addition...I've had more than one 2x4 that needed to be replaced because it bowed in or the family room where I have 9' walls....all the walls are 2x6 and I have no issues with bowing.

ryanh 03-04-2013 03:57 PM

How warm are you planning on keeping your garage?. Here in Wpg I have 2x4 walls with R12 and R20 in the ceiling and with the insulated door the coldest I have ever seen it (with it being -40 outside) was -8 inside. I have a 4000watt garage heater and bring the place to 0 in 15-20 minutes.

You could also frame with 2x4 and r12 insulation and use rigid foam boards on the exterior.

n0c7 03-04-2013 04:39 PM

Working on price quotes atm.

ryanh - When I want to work in it I want to bring it up to 22C. When I'm not in there and just parking cars, no higher than 5C I would say.

vsheetz 03-04-2013 10:38 PM

A layer of spray foam, to really seal it up tight - then insulation. This whether you go 2x4 or 2x6. And plenty of insulation in the ceiling.

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