Saturation & frost outside above grade foundation
Hi everyone,
We moved into a newly built house 13 months ago and when Winter hit, we started getting freezing/frost on the outside of the exterior wall.
The parged portion is poured concrete and the brick portion is the framed section.
Concrete below grade has exterior rigid foam. Concrete above grade has rigid foam on interior + fiberglass insulation + vapor barrier. Framed portion has wrap, rigid foam, fiberglass insulation and vapor barrier.
After consulting a few people, they came to the conclusion that it was the concrete releasing moisture and freezing. It’s been 18 months since the concrete was poured (poured in May/June). It’s happening again this year now that winter has started.
The base of the interior of the garage wall on this side becomes saturated/wet to the touch and freezes/frosts up. Running a ventilation fan in the garage has helped with this. The saturation starts at the back of the garage and wicks towards the front. The back of the garage is where the first step down on the foundation.
Under the garage is unexcavated, after the first step down is a finished basement room.
Using an infrared camera inside the house in the room that’s in the lower right, there’s nothing that looks too out of the ordinary behind the wall.
I’m not sure where this moisture is coming from. The exterior infrared image seems darkest where the basement room is finished. The unexcavated isn’t as frozen. The first image (wall.jpg) is from last year, the remaining ones are from today. It’s not as bad as last year yet, but still early on. We’re at about 34% RH indoors.
I’m not sure what to do / how to source the issue, but would love to know what’s going on and hopefully solve it. Has anyone seen this happen / have any ideas?
I’m also trying to figure out when it happens – it’s possible that the saturation happens when it gets a bit more mild out and then wicks up. It was hovering between just above freezing and just below freezing the past 24 hours after a fairly good cold snap. I looked up the historical weather from last year when I took that photo and it looks like the same. This could be coincidental, but in case it helps.
Thanks in advance
Replies
Sounds like the water on the outside of the concrete wall is just condensation. Since the concrete wall is insulated on the interior with both rigid foam and fiberglass insulation, the exterior wall face remains cold because little heat from the interior reaches it. Since you indicated there is a vapor barrier between the concrete and the interior insulation, there is little worry of inward vapor drive. However, it's possible that interior moisture attempting to migrate to the exterior, if the interior rigid foam insulation is not air sealed, is reaching the cold vapor barrier and condensing on the inside of vapor barrier. The thermal image seems to pick up more moisture on the exterior than interior, but that may only be due to drying from indoor heat.