In Toronto, ON and I'm finishing my attached double garage (20x20) in hopes of setting up a woodworking shop.

It's not currently heated or cooled but I plan on using it year-round so heating is definitely coming and I may get a portable AC too in the future. Replaced the 2 garage doors with insulated ones. There is no living space above the garage, just the garage attic (not connected to house attic). I will be installing 1 (or 2?) vents in the garage roof (this one: homedepot.ca/product/master-flow-50-nfa-black-roof-louver-aluminum-square-top/1000405504), soffit vents exists already on 3 sides.

The house is 33 years old.

It's coming along well but I want to do it right and have a few questions:

  • The attached (shared) wall is concrete block. I have already installed 2x4 framing in front of it and plan to use batt insulation, vapor barrier, and drywall. I'll also be filling any gaps with gap filler foam. Do I need a vapor barrier here since the finished inside house wall should have a vapor barrier? I've read not to install a vapor barrier on both sides of a wall as it will trap moisture. But I've also read you want to block all gas/fumes from the garage.
  • I have already finished 1 side wall with batt insulation and poly vapor barrier (no drywall yet). I learned afterwards that I should have used vapor boxes around my electrical boxes (metal). Is it worth it to cut the vapor barrier, redo the electrical boxes with the vapor box, and tape everything back up?
  • What is the proper application of acoustic sealant around the vapor barrier? I've seen it done only on the bottom, on all 4 sides of the wall, and even on every stud.
  • Once the garage is sealed and insulated, how do I dead with the trapped moisture? I am thinking ventilation fan? Will that be inefficient in terms of blowing out heated air?

Thank you!

  • How often do you plan to heat it up? – Harper - Reinstate Monica Aug 20 '19 at 22:09
  • Get a small heat pump, cost around 1k your moisture problem is totally gone when cooling as the condensate is drained outside. This also takes care of your heating needs and there are some out there that can be done diy. For a 2 car garage you will probably want 18k or 24k btu but depending on your climate zone and insulation a 12k unit might work. Just something to think about. – Ed Beal Aug 20 '19 at 22:16
  • Is insulating the garage from the outside an option here? – ThreePhaseEel Aug 20 '19 at 23:51
  • @Harper, during the cold months, I'd like to maintain the temperature at 10 degrees celcius and increase it to a comfortable temp when I'm working in the garage, probably 2 to 3 days a week to start. – hhrahman Aug 21 '19 at 17:36
  • @EdBeal, thanks for the idea. I will look into heat pumps. – hhrahman Aug 21 '19 at 17:38

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