Closing Crawl Space Vents in the Winter – Myth #11

This week’s myth is one we hear all the time: “Well, I’m gonna open my vents in the summer and close them in the winter in order to control humidity.” At this point in the series, I think you know where this is going…

When To Close Crawl Space Vents

So, is that true? Should you open your vents in the summer and close them in the winter?

Well, think about this for a moment. When is the humidity the most outside? More often than not, it’s in the summer. If you open your crawl space vents in the summer, you’re actually allowing more humidity into your crawl space and creating an environment conducive to mold growth.

When is the humidity lowest outside? In most cases, like in our area in East Tennessee, it’s in the winter. If you close the vents in your crawl space, you’re actually keeping the dry air out.

Now, most people close their crawl space vents in the wintertime to keep the cold out so that the cold air doesn’t freeze the pipes under the house. That’s understandable. But when you add humidity to the equation, this is a very poor decision for the overall health of your crawl space and home because it doesn’t have any effect at all on controlling humidity.

How to Control Crawl Space Humidity

So what should you do? Well, we recommend sealing the crawl space vents and controlling the humidity with a dehumidifier year round.

This will keep your crawl space cooler in the summer and warmer in the winter, so you don’t have to worry about freezing pipes, and you won’t have to worry about remembering to open or close your vents each season.

All in all, opening and closing vents during different times of the year doesn’t really do anything for humidity, so we call that a big myth. We’ve got two more myths to cover in this series, so stay tuned!

And lastly, we have everything you need to tackle sealing your crawl space vents available on our DIY Store. Check out our crawl space vent covers, spray foam kits, ventilation fans, and top of the line dehumidifiers.

4 thoughts on “Closing Crawl Space Vents in the Winter – Myth #11”

  1. Hi, Kayla.

    I was going over your blog again and had a question regarding sealing the crawl space vents.

    When you guys say seal them, do you mean block them off properly i.e. removed and replace with block?

    Apologies for my confusion.

  2. The HVAC system is located in my crawl space. There are two vents in the runs off the main trunk. Therefore cool air is pumped in during the summer, and warm air during the winter. Should these vents remain open or should they be closed? I also have a dehumidifier set at 50%.

    1. Hello Art, great question but I would ask your local HVAC professional to do a load test on your unit. If the HVAC system is calculated to include the crawl space then closing the vents could oversize your unit for the rest of the home. If it is not calculated to include your crawl space then closing the vents would be ideal in order to make sure your HVAC is properly cooling your home. The dehumidifier, if properly sized, should address the crawl space humidity either way. Hope that helps, thanks for the comment.

Leave a Comment

Your email address will not be published. Required fields are marked *

Would love to help you with your next project! Schedule your Free Assessment today!

Scroll to Top