I am currently building a house with an unvented crawlspace, SE Tennessee, hot humid 3 seasons. The construction is as follows: Engineered wall system (concrete with embedded metal studs, insulated) with a 2″ concrete slab through the crawlspace, with barrier installed under slab. No openings to the outside, access to the crawlspace located in the partial basement. 4′ tall walls. In other words, the crawlspace is built like a 4′ tall basement connected to an actual basement.

I am currently weighing my ERV/HRV/air mixing options. I need to decide what the best approach is to dealing with the crawlspace air. Since it is constructed as a mini basement, do I treat this as a good source of air and encourage mixing this with the house in order to dehumidify the crawlspace air? Or is it best to separate this air as its own thing?

One option I have considered is supplying fresh air to the crawlspace through an ERV and exhausting air from the master bathroom. Then providing open registers from the crawl to several locations in the house above. As the house is ventilated (hopefully) it will draw the fresh air from the crawlspace into the house and condition. I am thinking this will take care of humidity issues in the crawl through conditioning with the house, create an easy way to distribute fresh air throughout the house, and hopefully provide a known source of makeup air as negative pressure is created from the exhaust.

The flipside is, would drawing this air from the crawlspace have a negative effect and actually draw moisture and humidity from the ground and create a constant battle with this in the house. In other words, I can’t decide if this crawlspace is a “good” or “bad” source of air. Thoughts?