How much insulation?

[go4donuts]

I'm getting ready to insulate my garage and was wondering how much insulation I should put in the ceiling. The garage is 24x24 wood frame, truss rafters, 8 foot ceiling, located in Saskatchewan (cold!). While the garage will be heatable with an electric construction heater for now, and possibly natural gas later, I plan to heat it only for 'project days' and avoid heating in extremely cold weather.

My question: is R14 - 4" insulation enough, or should I go with R22 - 6" insulation. There appears to be a couple hundred buck saving by going with the thinner insulation.

 

[buzz4041]

As much as your pocketbook can afford.

 

[Scott H in Wheaton]

R49 - R60 on top of the ceiling, but then you would have no storage up there.
This is the amount suggested by the US Dept of Energy.
International Energy Code calls for R49 in attics.
Fit whatever you can in the ceiling joists if you are trying to use the attic space for storage

 

[Gary S]

You don't say if your walls are 2x4 or 2x6. If 2x6, use the R19 blankets. If 2x4, use the R13 blankets. Fill the walls up. It costs so little.
Walls are not your big heat loss site, so either one will work just great. Your ceiling should be around R40 if you want to retain heat.
If you put R13 in the walls and R40 in the ceiling, almost all your heat loss will then be the doors and windows.

 

[f150skidoo]

I would do a minimum of a double layer of R22. First layer in the joists then the second going opposite direction on top of the rafters.

 

[mechanic217]

Insulation is a one time cost put in as miuch as you can afford , you will not regret it

 

[Sureshot]

Blow in to an R40. If it is attached the heat from the attached wall and door opening will keep it decent in Sask terms, maybe not for our Florida friends.

 

[NUTTSGT]

My question: is R14 - 4" insulation enough, or should I go with R22 - 6" insulation. There appears to be a couple hundred buck saving by going with the thinner insulation.

That savings with the thinner insulation will cost you more in the long run with heating costs. Insulation is an investment, it will continue to pay you back during it's lifetime.

 

[Chuck Farley]

Once upon a time I lived in Sask, so I know how c-c-c-c-cold it can get. Now I live in SW BC, and even so I put R20 in my walls and R40 in the ceiling of my shop. Heating costs ain't gonna go down any time soon!

 

[justanengineer]

Dam, and I thought I was cold blooded after living in AK. Im in a fairly warm climate and ONLY have R30 batts. Not sure about Canada, but down here the cost isnt any huge expense, ~$400 (US) to do the job well.

 

[Moose97]

If trying to conserve attic space, use foam insulation on your rafters. Will be more initial cost but will pay you back in the long run. R-13 walls and R-30 ceiling at a minimum if no foam. R-19 walls and R-49 ceiling better.

 

[SlappyWhite]

Insulation and R value is interesting at most, a joke at worst. Air infiltration is much more interesting! Basically a leaky building will undo r value all day long. Seal up the building, make sure the furnace draws outside air for combustion so there i no vacuum... Then worry about r value.....

6mil vapour barrier is a joke. Closed cell spray foam is way better at sealing the building. Any insulation you put on top is a bonus....

 

[go4donuts]

Insulation and R value is interesting at most, a joke at worst. Air infiltration is much more interesting! Basically a leaky building will undo r value all day long. Seal up the building, make sure the furnace draws outside air for combustion so there i no vacuum... Then worry about r value.....

That's very good point, because this IS a garage, with a double garage door, which, even though it's new and in good condition and seals relatively well, will bleed heat like crazy compared to the rest of the building envelope.

A few years ago I had a single garage with one of those old one-piece un-insulated steel doors. Talk about a heat-sink in minus 30 degree weather! When I was doing a project in the winter, I would cover the door with a big heavy painter's drop sheet and staple it around the edges. It made a big difference in the comfort level in the garage.