Dehumidifier in an unvented crawl space
Hi all,
In Martin Holladay’s article about unvented crawl spaces he says there are 2 code approved ways to ventilate an unvented crawl space (supply conditioned air from the HVAC system or exhaust air to the outside with a fan). In Allison Bailes article on 5 ways to ventilate a crawl space he lists these same 2 ways to ventilate but also lists a dehumidifier as an option. My question is, can you install a dehumidifier INSTEAD of an HVAC supply or vent fan ? I’m not asking for code compliance necessarily, just whether this is a good idea or not. I’ve got an unvented crawl space in south alabama with no ventilation. I recently cleaned it out and sealed some big holes (critter problems) and am looking to install a vapor barrier or encapsulate. The encapsulation crew wants to install a dehumidifier so I wanted to ask if this is a good idea or not. If it helps you answer, the house has no insulation anywhere (probably won’t ever get any), has ductless mini-splits for heat/air, and is seldom occupied (so the mini-splits don’t run often).
Thanks for any feedback you can provide.
Jennifer
https://www.greenbuildingadvisor.com/article/building-an-unvented-crawl-space
https://www.greenbuildingadvisor.com/article/five-ways-to-deal-with-crawl-space-air
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Replies
Yes, if you install a dehumidifier then you don't need an HVAC supply or an exhaust fan. Martin probably didn't mention the dehumidifier option because it was a later addition to the building code.
Thank you, that makes sense. I know the article Martin wrote is several years old.
In general, do you think it makes sense to encapsulate a crawl space in a house that doesn't have heat/air on very often and will likely not have any insulation in the near future? I like the idea of the encapsulation because it will seal the crawl space including the rim joist which should help with general comfort and critter control but I don't want to create new problems with the encapsulation.
Thank you.