High Humidity After Home Energy Retrofit
I’m a contractor in south-central Wisconsin (Climate Zone 6). I have a client that purchased a 50’s ranch two years ago that had gone through a deep energy retrofit right before the sale. The retrofit was done by a company that is funded through federal and state grants. Since the homeowner has moved in there have been alarmingly high humidity levels. It rarely drops below 50% even in the winter. There is LOTS of water condensing on all the windows and signs of the mold and mildew growing. The homeowner has been running stand-alone dehumidifiers which helps but they are constantly running.
I looked around the space and found that they have installed 2″ XPS on all the basement walls and air-sealed the rimmed joist but there is no vapor barrier under the slab so you can see the moisture being drawn up. They blew in cellulose in the wall cavities and attic. The attic insulation is roughly R60. I was not able to confirm that they air-sealed the ceiling but it seems that they did based on the IR camera.
They did not install any form of ventilation system.
I’m looking for any advice on how to get their humidity levels under control. I thought about installing a central dehumidifier into the HVAC but it runs so infrequently that I don’t think it would be very effective. I’ve also thought that an HRV should have been install at the time the retrofit was done but I’m worried that will do enough to lower the humidity either.
Any advice on solving this problem would be greatly appreciated.
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