GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Humidity Control in Cold, Humid Climate

brad17 | Posted in General Questions on

We have a 1000 SF vacation home in coastal Maine that is experiencing humidity problems. We have no mechanical ventilation in the house. In the summer, it needs no AC and the windows are kept open. In the winter, we rely on hydronic radiant heat. Humidity is very high year round (about 80%), but a major concern in winter when we see significant condensation on our windows. We are considering installing an ERV unit but would love feedback on the simplest way to add both fresh air and humidity control, mostly in winter.

Thank you!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    DCcontrarian | | #1

    Air at 72F and 80% RH has a dew point of 65F. I can guarantee you that no place in Maine regularly has a outside dew point of 65 in the winter, because no place in Maine has outdoor temperatures that high in the winter, and the dew point can never be higher than the temperature.

    What that means is that humid exterior air leaking in does not account for the humidity you are experiencing in winter. I can think of two other possibilities: one is that something inside the house is generating excessive humidity. The other is that there is moisture leaking into the house somewhere, probably either in the basement or through the roof.

    Tell us more about the house: how old is it, what is the construction like? Is it well insulated? Is it tight or drafty? What's the basement like?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |