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Community and Q&A

Condensate moisture around window frames

Myrtleboone | Posted in GBA Pro Help on

I am in the process of foaming and taping the spaces between my interior window frames and boxes. I have noticed that after sealing the gap with tape (after foam has cured) that I begin to have slight moisture on the tape surface only on the bottom section of the window frame. I didn’t notice it after I foamed and before I taped; only after taping. I have also noticed it under my exterior door, on the interior side, despite proper sealing of the door frame on the sill (It’s certainly not water from the exterior making its way in). Important to note that my new house is very tight, and the weather has gotten cold and damp (30F and snowing). My air exchange unit is not working yet and the Sheetrock is being mudded with a bit of heat from electric heaters. Probably a high humidity problem (No humidity numbers to report)? If it’s not, how do I eliminate the condensation that will eventually be covered up by window trim and on the bottom of the exterior door? I plan on holding off on finishing the window boxes with wood trim for the winter to see how it goes and will start running a dehumidifier ASAP (until my air exhange unit is up and running). Thanks for your time.

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  1. davidmeiland | | #1

    You have my unconditional money-back guarantee that it's a construction humidity phenomenon. Taping drywall in cold weather in a minimally heated new house is a sure-fire way to get condensation on lots of interior surfaces, including some (like plywood sheathing) where it may just soak in and be hard to detect. The surface of the tape is a place where it won't soak in. Heat / dehumidify and carry on.

  2. GBA Editor
    Martin Holladay | | #2

    David is right.

  3. Richard Beyer | | #3

    Sir you answered your own question... "My air exchange unit is not working yet". Turn it on and bingo your problem is resolved.

    I ran into this problem with a builder last winter in zone 5a who never built a tight home in his building career. He desperately tried to blame the window manufacturer for his sweating windows. In fact the new small house was so tight when his wife showered she never turned the bathroom fan on. Then the windows really fogged up.

    To make matters worse there was no HRV or ERV installed in the home. He was furious his HVAC tech never informed him one was needed. He told his wife to use the bathroom fan and installed an HRV... problem gone!

  4. Myrtleboone | | #4

    Thanks. That is what I expected, however, why am I only noticing the moisture after I tape the gap underneath the window and not before (when it is just foam)? Humidity should be present regardless, whether the gap is just foam or when tape is added after?

  5. Myrtleboone | | #5

    Also, I am not turning on HRV yet. Uneasy about using it when it's still dusty inside. Sheetrock finishing (and spraying primer after) still happening. Using a dehudifier since last night. Will keep it running continuously.

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