My house has a partial basement and a crawlspace. The forced air furnace is in the basement, and ducts run through the crawlspace to distribute air to the house. In the summer, when we don't use the furnace, our living room, where the cold air return is, starts to smell like dirt. Like the crawlspace. I think the issue is that certain atmospheric conditions will cause a pressure or temperature differential that makes air flow up and out of the crawlspace via the cold air return.
This must be an issue for other houses with crawlspace duct work. Is there a standard way that HVAC pros mitigate this? Would it help to add more ventilation to my crawlspace (it has very poor ventilation currently)?
The easiest solution would be to block off the cold air return when it's not in use, but I'm the kind of moron who would probably forget about it and turn on the furnace while it's still blocked.