Where to exhaust conditioned crawl space
torreyho
| Posted in General Questions on
I live in SW Colorado, climate zone 5. I have an approximately 600 sq ft crawl space, which is adjacent to a basement/garage, which is outside of the house’s envelope. I am in the process of changing the crawl space from a vented to conditioned, bringing it inside the house’s envelope.
My question is, since I need to air exchange in the crawl space, I was planning on having a low powered fan to depressurize it. Can I exhaust the fan into the basement(outside the envelope) or does it need to exhaust into the house(inside the envelope?) Any recommendations on a fan that can do 20CFM or so?
Thanks
Chris
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Replies
Have you tested for radon? The result may inform your next step.
Chris,
How are you conditioning the space? Where would the make-up air for the crawlspace come from?
The options are in the IRC, section R408.3: https://codes.iccsafe.org/content/IRC2018P4/chapter-4-foundations#IRC2018P4_Ch04_SecR408.3
I have tried or been otherwise involved with all of these approaches. With what I know now, I would opt for a dehumidifier and a heat source. Anything else either wastes energy or is hard to get tuned correctly.
I have an ongoing radon testing device, and it reports consistently <0.5 picocurie. I will also be venting "soil gas" to the outside with a sub-vapor barrier pipe, that isn't powered but could be.
As far as make up air, that is the question about vents. Since the subfloor, to the living space above, isn't air sealed, is that good enough or so I need to cut in a register?
Thankfully I don't need a dehumidifier, as the soil is dry and I live in the high desert.
What kind of heat source would be the best?
What do you mean basement outside the envelope? It is very hard to have a basement separated from the house. Usually with this type of crawl, the wall to the basement is opened up connecting the two spaces and then you install a small electric baseboard to heat it.
If the house ducts run through this space (these are almost always un-insulated up here), there is enough heat from it that the baseboard heater never runs.
Bonus is to put down some patio pavers once done and you can use the space as junk storage. Not fun to get in/out and usually a lot of swearing but does work.
The basement is really a garage or a walk out basement with a very large, very leaking and uninsulated door.
Is there a temperature range at which heat is needed?