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Community and Q&A

Frost in Attic and Wet Exterior Wall

user-1152396562 | Posted in General Questions on


I’m located in Northern WI and we have had a challenging winter of deep freezes and then warm temps. 

My house is a cape cod style home with an unfinished/unconditioned attic that we want to finish one day. The space to access the attic is through what looks like a closet. I’m wondering if they built homemade stairs? 

Last year I had an insulation contractor out to air seal and add insulation. We did a blower door test which showed some improvement. The company spray foamed at the soffits and dense packed the roof side the rafters. I wanted them to prep it for finishing however we had some personal issues which stalled the project/finishing of the attic. 

Fast forward to this winter season I’ve noticed on one specific exterior sidewall of my house there’s moisture stains. When I went up in the attic and felt the wall under the insulation there was frost which I assumed melted on the warm day and seeped through. 

I checked the attic humidity and it was incredibly high at 64%. As a temporary measure I’ve placed a dehumidifier up there which has cut it down to 30%. It got up to 46 degrees today which is unseasonably warm for early Feb and my attic was 72 degrees. Usually on days it’s been in the teens and 20s my attic is no warmer than 52 degrees. 

Since I paid for air sealing I started pulling up the insulation on the floor and it seems the company got most places I checked. (They did miss a pretty big spot) which I’ve since sealed up. I am unsure if they did the wall bypasses though which I’ve read should be sealed.

I wanted to ask what an ideal temperature is up there and what everyone thinks is causing the issue? Is it warm moist air? It’s strange because it never did this last year after they finished the project. We have started cooking a lot more than last year. We have a bath vent that vents to the exterior and unfortunately no kitchen vent. The side with the biggest water stain is the directly above the kitchen.xx

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