# Vents from the outside of the house into the crawl space. How to use them? **URL:** \ **Category:** Factual Questions\ **Created:** [April 18, 2010, 9:03pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558 "2010-04-18T21:03:40Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\ **Post date:** [April 18, 2010, 9:03pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/1 "2010-04-18T21:03:40Z")
Our house has a crawl space under the entire house and there are vents from the outside into the crawl space. These vents can be open or closed. How to I utilize them? When do I open them and when do I close them? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [April 18, 2010, 9:08pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/2 "2010-04-18T21:08:27Z")
depends on your environment and if you are heating or cooling. also is the floor insulated and do you have a vapor barrier on the earth. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [April 18, 2010, 9:21pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/3 "2010-04-18T21:21:24Z")
I only close the foundation vents during the winter. Keeps the pipes from freezing. Vents must be open in the summer because we have a lot of humidity in the South. I normally go around the house and close them in November and open them again in April. ---
**Author:** ![Autolycus](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Autolycus](https://boards.straightdope.com/u/Autolycus)\ **Post date:** [April 19, 2010, 4:09am UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/4 "2010-04-19T04:09:58Z")
When you’re gassing people in your crawlspace, you close them. Otherwise, leave them open. ---
**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\ **Post date:** [April 19, 2010, 8:10pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/5 "2010-04-19T20:10:36Z")
There is a vapor barrier on the earth. The floor has only wall-to-wall carpeting with some sort of a sub-carpet. High desert with cold winters and hot summers. ---
**Author:** ![Lunar\_Saltlick](https://avatars.discourse-cdn.com/v4/letter/l/977dab/32.png) [@Lunar\_Saltlick](https://boards.straightdope.com/u/Lunar_Saltlick)\ **Post date:** [April 19, 2010, 8:26pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/6 "2010-04-19T20:26:47Z")
You’ll never get a definitive, unanimous answer. I know I couldn’t. Everyone has a different notion of how moisture moves under your house and what its effects are. Ultimately, if you believe the people at [buildingscience.com](http://buildingscience.com) (and they seem to generally know their stuff), crawl spaces should be completely closed and sealed, with no venting, and should be conditioned. They should be a mini-basement. [http://www.buildingscience.com/documents/information-sheets/5-thermal-control/crawlspace-insulation/?searchterm=crawlspace](http://www.buildingscience.com/documents/information-sheets/5-thermal-control/crawlspace-insulation/?searchterm=crawlspace) Not likely at my place. Humidity isn’t a big issue where I live, but I vent in the summer. I’ve recently closed up a lot of, uh, unintentional venting in the crawlspace walls, so I guess I will essentially be closing venting pretty much completely for the first time this winter. Might make a small difference in my heating bill. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [April 19, 2010, 11:51pm UTC](https://boards.straightdope.com/t/vents-from-the-outside-of-the-house-into-the-crawl-space-how-to-use-them/536558/7 "2010-04-19T23:51:28Z")
it would make sense to close them during winter. during summer you might monitor the crawl space and keep closed if the space is cooler than outside and open it if the moisture builds up. you could monitor the temperature with a remote reading thermometer.