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We built a "pretty good house" in Jefferson NH this year and are getting condensation on the interior of the windows.

We have 3 layers of 2.5" XPS with staggered and sealed seams on the walls and 4 layers on the roof. So 7.5" and 10" respectively. The interior stud cavities have been left open and empty. The windows are set as "outies" and the doors as "innies" and space between the studs/plywood boxes and the doors/windows were filled with cans of window and door spray foam. The house is heated by two mini splits and has been performing very well to date. It is a vacation home and when we come back after a week plus away there is condensation at the bottom of the glass of the window. We have yet to install the HRV, it is going in next week, but we are concerned that it will not remedy this issue. Do you think it will remedy this issue, and if not is there another tact we should consider?

Asked by james magner
Posted Thu, 12/12/2013 - 12:35


2 Answers

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Your question is the second question this week on the topic. If you want to read the other thread, here is a link: Why are my windows wet?

There are only two ways to address condensation on windows. You can either raise the temperature of your windows, or you can lower the indoor humidity. In your case, high indoor humidity is probably to blame.

This type of condensation is fairly typical during construction or when a house has just been closed in. Your house is humid because of construction moisture from the concrete foundation and drywall mud. After 6 or 12 months, everything will dry out and stabilize.

Installing and running your HRV will help lower the indoor humidity. Once the ventilation system is installed, the indoor air should begin to dry out.

For more information, see Rating Windows for Condensation Resistance.

Answered by Martin Holladay, GBA Advisor
Posted Thu, 12/12/2013 - 12:45
Edited Thu, 12/12/2013 - 12:46.

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Thank you!

Answered by james magner
Posted Thu, 12/12/2013 - 12:57

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