The Money Mustache Community
Learning, Sharing, and Teaching => Ask a Mustachian => Topic started by: gillstone on March 09, 2017, 10:08:56 AM
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We have a 1950’s home with an attached, unheated garage. Due to a roof leak across the entire exterior wall (this winter sucked and so did the roof) we had to pull the sheetrock and insulation that was there.
We plan on eventually converting the garage into living space, but for now we want to add just enough heat to keep it above 40F in winter and use it as a basic workshop and workout space.
The wall studs are 2x4s. What is the best insulation option for the walls? Is it possible to double the insulation layers?
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Closed cell foam is the best. It's expensive, though, and can create moisture problems if your wall isn't set up correctly.
Cellulose is also really good and DIY. Better if you can pack it.
https://buildingscience.com/documents/insights/bsi-043-dont-be-dense
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Seeing that you live in Montana and only have 2x4 studs, closed cell foam is probably your only option. If you are seriously thinking about converting it to living space and want to insulate it for that ahead of time, I would take this opportunity to extend it out to 2x6 so you don't have to redo it all later on.
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A good resource for all things insulation is the Cold Climate Housing Research Youtube channel. One method I have seen would be to put R-13 fiberglass in the 2x4 wall, then a normal 6 mil vapor barrier, then use 2x2 furring strips horizontally on 2' centers to support 1 1/2 inch foam board on the inside of the wall. This would give you roughly R-20 depending on what type of foam you use, but a higher effective R value than a 2x6 wall because the foam layer prevents thermal bridging through the studs. You would need to hang 5/8 sheet rock vertically to finish the wall out. If you are doing the work yourself this would definitely be cheaper than hiring a spray foam contractor.
As far as moisture management is concerned, the rule of thumb I have heard is at least 2/3 of the total wall insulation should be on the cold side of the vapor barrier, and the remaining 1/3 inside.
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A good resource for all things insulation is the Cold Climate Housing Research Youtube channel. One method I have seen would be to put R-13 fiberglass in the 2x4 wall, then a normal 6 mil vapor barrier, then use 2x2 furring strips horizontally on 2' centers to support 1 1/2 inch foam board on the inside of the wall. This would give you roughly R-20 depending on what type of foam you use, but a higher effective R value than a 2x6 wall because the foam layer prevents thermal bridging through the studs. You would need to hang 5/8 sheet rock vertically to finish the wall out. If you are doing the work yourself this would definitely be cheaper than hiring a spray foam contractor.
As far as moisture management is concerned, the rule of thumb I have heard is at least 2/3 of the total wall insulation should be on the cold side of the vapor barrier, and the remaining 1/3 inside.
Interesting. Certainly more work than just slapping fresh insulation in, but might be worth it for the long run.
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A good resource for all things insulation is the Cold Climate Housing Research Youtube channel. One method I have seen would be to put R-13 fiberglass in the 2x4 wall, then a normal 6 mil vapor barrier, then use 2x2 furring strips horizontally on 2' centers to support 1 1/2 inch foam board on the inside of the wall. This would give you roughly R-20 depending on what type of foam you use, but a higher effective R value than a 2x6 wall because the foam layer prevents thermal bridging through the studs. You would need to hang 5/8 sheet rock vertically to finish the wall out. If you are doing the work yourself this would definitely be cheaper than hiring a spray foam contractor.
As far as moisture management is concerned, the rule of thumb I have heard is at least 2/3 of the total wall insulation should be on the cold side of the vapor barrier, and the remaining 1/3 inside.
I like the looks of that.
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There was an OLD thread on here about "DIY Foam insulation for a fraction of the cost!", and that thread still exists....
BUT... the LINK in the story leads to a dead blog page.
Since the BLOG PAGE had all the details, I dug that up from the WayBack machine:
https://web.archive.org/web/20150611003351/http://www.thegrowinggreen.com/diy-foam-insulation-construction-cost-saving-measures/ (https://web.archive.org/web/20150611003351/http://www.thegrowinggreen.com/diy-foam-insulation-construction-cost-saving-measures/)
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If you have an unheated garage, check the attic space, too. You need an insulated, vented attic, or spray foam directly on the underside of the roof (if no venting). No cold dead space over an insulated heated area below, as you will invite all sorts of moisture problems.
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If you have an unheated garage, check the attic space, too. You need an insulated, vented attic, or spray foam directly on the underside of the roof (if no venting). No cold dead space over an insulated heated area below, as you will invite all sorts of moisture problems.
The attic was its own special nightmare. Prior owner couldn't decide if it should be a warm attic or a cold one so there was insulation everywhere including over the soffit vents.