Bath Fan and Range Hood Dripping During High Outside Humidity
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| Posted in Energy Efficiency and Durability on
We recently had record dew points in Minnesota (86 degree) and I had several callbacks from homeowners who all had the same issue with water dripping from their bath fans, range hoods, and self-vented gas fireplaces. I attributed this to condensation from the warm moist air traveling down the ducts and hitting the cold surfaces of the fans/hoods/fireplaces.
Homes are spray foamed with Icynene (walls/lids) and have HERS scores in the low 50s. Any insight how to prevent or at least help the homeowner manage? The dripping stopped when we operated the bath fans.
Thanks for any insight here.
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Replies
Scott,
It sounds like these homes are depressurized with respect to the outdoors. This can happen if their HVAC systems are leaky or unbalanced. For example, if a forced-air system has ductwork outside of the conditioned envelope, and the supply ducts are leaking air, the house can become depressurized.
If the house is depressurized, outdoor air can be drawn down bath exhaust ducts or range hood ducts.
You should have a home-performance contractor test the homes to see if they are depressurized under normal operation.
Martin:
Thanks for this information. In my mixed hot/cold climate, do you think homes should be slightly pressurized in summer and slightly depressurized in winter?
Thanks agin.
Scott,
In my opinion, a home should be neither pressurized nor depressurized. But if you're having problems attributable to depressurization, then slight pressurization might solve your problems.
What type of mechanical ventilation systems do these homes have?