Close the vents in a crawlspace or not? Add small exhaust fan?
Hi. I’ve read on this website (in an article about sealing crawlspaces) that it is wise to close the vents in a crawlspace despite what code says to help eliminate moisture and odor/mold issues.
I have a crawspace under part of my house (below an addition) that I’m thinking about sealing as the article suggested. My crawlspace however is reasonably clean and dry (never see any wetspots ) I just smell a mustiness that sometimes permeates the house/room above. This crawlspace has about a 3′-4′ clearance and the floor is concrete not dirt. The walls are block walls.It has two vents on one wall, those standard ones you see in many homes.
Should I close off these vents as the article suggests. I believe code says they are required. The author of the article explained that in his decades of experience, closing them does more good than bad. Will I be causing a problem if I do close them off?
Also, there was a small article by a contractor on this website a while ago that showed how to make a small vent fan (purchased from Grainger) to use instead of a de-humidifier that the author claimed worked better than a de-humidifier and was much much less costly to operate than a de-humidifier. I was thinking of doing that as an option in the crawspace possibly (closing one vent off and running this fan out the other vent).
What do you all think? Thanks
Replies
In the summer. the vents draw in warm but really moist air into the cool crawl space where it can condense. just the opposite of what you are trying to avoid by having them in the first place.
In the winter you are drawing in very cold air which is generally dry but it is cooling all of the surfaces where warm moist air from the house is leaking out. Again, the opposite of what you want.
If i had a crawl with concrete, I would seal the vents, insulate the walls/rim joist and throw a dehumidfier down there to keep and moisture coming in through the walls/floor in check.
crawlspace vent
Thanks. To insulate the rim joist I guess I would fill the spaces between the floor joist with rigid foam at the rim joist. Is that Ok and up to code? If so I'll do that there.
How do u insulate the short block wall? I was going to get in there and paint it with Dry Lok (had great success with that in the past ,it's all about surface prep)