Can I Insulate Foundation Walls of Vented Crawl Space?

When is it best to insulate the foundation walls of your crawl space? Can you insulate the walls of a vented crawl space? Recently, we received this question on our Ask-a-Ninja page. If you have a question, please let us know.

Q: What would be the problem if we did wall insulation and kept some vents open and left the batt insulation? Thanks so much for your time. – Amanda, Newnan, GA

Crawl Space Insulation

There are many ways to insulate the crawl space. Unfortunately, many contractors do not emphasize insulation in crawl space encapsulation. Most of the quotes we see from our competition completely leave out insulation. Does this mean that crawl space insulation is not important? The crawl space and basement are the second most important areas of your home to insulate. The attic is the most important.

Crawl space insulation can be accomplished via the foundation walls or subfloor. There are many types of insulation to use as well. Spray foam, foam board, batt fiberglass, Rockwool, insulation vapor barrier, cellulose, and more. Although each type can be applied to many areas of the crawl space, how you insulate your crawl space is based on whether it is vented or sealed.

Foundation Insulation for Open Crawl Space

If your crawl space is open or vented, it probably has subfloor insulation. This is because the outside air is able to freely enter the crawl space. Once the air enters, the subfloor insulation becomes a thermal break. This thermal break is important between the crawl space and the living space. Studies have shown that subfloor insulation is extremely effective in the winter versus the summer compared to foundation wall insulation.

A: The problem is that foundation wall insulation in a vented crawl space is pretty much useless. It would be like you insulating the walls of your living space and leaving the windows open all the time. How effective can wall insulation be when outside air can enter freely?

Contact Crawl Space Ninja for Basement Waterproofing and Encapsulation

Please contact us to schedule your assessment to fix your crawl space, basement issue. 


Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, foundation repair, basement waterproofing, or controlling humidity in your crawl space?

If you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, or Kentucky, Crawl Space Ninja can help!


Also, let us know in the comments below if you have an idea for a new blog topic.

DIY Crawl Space Repair

Perhaps you’d like to tackle your own crawl space repair. Visit our DIY Store.

Join Crawl Space Ninja as an Owner

Learn about Crawl Space Ninja Franchise opportunities.


Michael Church’s Crawl Space Repair Myths-Busted book was written to help you Avoid Bad Advice, Bad Decisions, & Bad Repairs.

“This book is the Cadillac for crawl space information and Michael Church is your experienced driver. What can I say? It’s just an amazing read.” 5.0 out of 5 stars The real deal.

4 thoughts on “Can I Insulate Foundation Walls of Vented Crawl Space?”

  1. I have a house that was built in 1885, it has dirt basement floor, it is dry, has a stairs that go down to it with large opening, I would like to use for storage but i’m afraid that walking vapor barrier would damage it. Is there ballast that work?

    1. We did a video about that a while back and a lot of people like using that workout foam that you would put over a garage floor in order to create a space to store things on. You can place it directly on the vapor barrier.

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