Hello There:

I live in climate zone 5A – we’re in a northwest suburb of Chicago. I experienced condensation on the interior of some walls & a portion of the ceiling in my garage, and I am curious for opinions on how I might prevent this in the future.

A few details about the space/house:
1. The home was constructed in 1988. It is a 2×4 wood framed home with 1/2 XPS rigid insulation as the exterior sheathing. The home is insulated with R13 craft paper fiberglass insulation with the paper facing the interior of the home.
2. The garage in question is attached to the home. It is partially insulated–any wall/ceiling adjacent to living space is insulated with the same R13 paper faced batt insulation.
3. This summer, I made a few modest improvements to the garage with the hope of using one bay as a workshop. I had the concrete floor coated with a polyaspartic floor coating, and I added power to install a King electric heater.
4. I also replaced the garage door with an insulated door.
5. I installed a dehumidifier sized for the space to ameliorate excess humidity associated with drying cars, etc..

Throw on a fresh coat of paint, and I thought I was in business…

The Issue:
However, last night with the rapid drop in temperatures, I woke up to a partially frozen ceiling/walls on the uninsulated section. Interestingly, the heater barely kicked on last night. I had it set to 40 degrees to simply keep any liquids in the garage from freezing, but nevertheless I have a bit of a pickle on my hands today. I am surprised at how much condensation occurred.

Solutions?
My understanding is that the warm interior of the garage coupled with the extreme cold outside caused condensation to form on the inside of the walls/ceiling, and it froze in some of the coldest uninsulated areas of the garage. I drilled a hole and verified that the backside of the drywall is not wet.

Couple questions:
1.What is the best short term dry out solution. Do I crank up the heat to dry it out – once dry, shut the heat off and open the door to stabilize the temperature to the outside?
2. Aside from tearing walls down and adding spray foam, is there any solution to prevent this from occurring so I can use the garage heater at times? Blown in cellulose? Any other short term options?

Thanks for your thoughts on this one.

John