We live in a 2 level home with basement in central washington. The winters average 20-36 degrees Fahrenheit with humidity levels of 70-99%. Summers are fairly warm to hot with lower RH.

Our issue is condensation on our vinyl double pane windows upstairs. All of the windows upstairs have condensation and subsequent mold buildup which is becoming concerning to us. The issue does not happen downstairs where we have a wood stove. The humidity downstairs is usually 30% and upstairs is 50-60%.

We have vent fans in the bathrooms, and also heat with central furnace most nights when the stove burns out. The air return for the furnace is on the main level (between the basement and upper level), and there is no return on the upper level.

It seems to be an above average tight house built in 1997 but we haven't done any air tests on it to know for sure.

My question is: What would be a good option to mitigate some of this excess moisture on the upper level? The windows are fine, not excellent but not interested in replacing those. We just need to decrease the humidity on the whole upper level.

From my research, it seems like a HRV air exchanger may be the best option. I could install in the attic and duct to each room to get some air exchange. We do out best to limit moisture producing things, I think its just a catchment for the moisture in our house in general.

Thoughts? Whole house dehumidifier? ERV? HRV? Something different entirely?


  • You might try running the fan (only) on the central furnace while you are heating with wood to get some air circulation - it's easy to try and does not require anything more than (typically) flipping the switch from "fan auto" to "fan on."
    – Ecnerwal
    Jan 13, 2021 at 14:14
  • 1
    If you don’t have a return air duct upstairs there is nothing to really circulate the air or enough to balance the humidity. A dehumidifier upstairs at a central location would provide best results. Remember in bedrooms while you are sleeping you exhale moisture with each breath so removing the moisture will be the only way to stop this with no intake or return up stairs a whole house system for dehumidification would be a waste, yes the rooms would see dryer warm air supplied but so would the entire house and not much to remove the moisture upstairs. Add a dehumidifier in a common area first.
    – Ed Beal
    Jan 13, 2021 at 15:14
  • I wonder what would happen if you opened the attic access and left it open. You would lose hot air to the attic and with it moisture. You would need to spend more on heat. Could that be enough?
    – Willk
    Jan 13, 2021 at 16:48
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    Update: Thanks for your input so far! Here is what we have done: The external cold air intake for the furnace was closed, so we weren't bringing is any external air to the system, so I opened that fully. Can adjust if needed. We also set the fan to run 15 mins every hour, and are keeping the doors open. No condensation on windows this morning. removed all trim and casings and ensured mold wasn't penetrating and all looks good. Thanks again! I'll update in a couple weeks with final results after some cold spells. Jan 13, 2021 at 20:41


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