What is a Foundation Vent?

Estimated reading time: 3 minutes, 26 seconds

Proper foundation vent

Proper foundation vent

Foundation vents are a common device found in most forms of residential construction. They are a necessity but usually obscured by mature shrubbery and are never accentuated.

In fact, you could have lived in your home for over 50 years and have never noticed them.

What are they?

Foundation vents are rectangular metal vents situated in the stem wall just above the dirt line on the exterior around the perimeter of home. They are often operable with a little lever that causes a hinged flap inside your crawlspace to operate. Just  (Pull to shut), and Vice versa.

Foundation vents are not sexy; they are designed to create some passive airflow into the crawl space. If you have “slab on grade” construction, you do not have or need these vents.

Why does your crawl space need to breath?

You might ask. Well it all boils down to the current trends in building science, and building codes, which change every three years or so.

  • The crawl is usually separated from your home’s envelope and the floors are insulated.
  • We used to turn off water to spigots well inside the home, and drain them to prevent freezing. Now we have frost-proof faucets and don’t give them much thought, (Other than removing the hose in winter).
  • Several years ago, it became popular to insulate the rim board and stem walls on the inside and omitting insulating the floor.
  • Then it became popular to condition the crawl space so it was actually heated and cooled with a dedicated vent blowing down there.

Building Science is evolving

better protection

Better protection with a metal vent well

Is there a right way? Who knows? The point is that if you have a home with operable vents, they should be closed in the fall (Thanksgiving) and open in the spring (Easter).

One neighbor with non-operable vents had me make some wooden covers that I would screw into place for the winter. In fact it is a good time to shut them right now! as part of your fall preventative maintenance checklist.

Using foundation vent wells will help discourage water from entering foundation vents that have been installed at or below grade. The other option is to fix the grade which likely changed over the years.

Problems with foundation vents

  • Spiders and other creepy crawlers can come in.
  • Water can come flowing in when builders put the building too low in the ground (or landscapers add too much soil). Vents must be protected if placed below grade.
  • They let cold winter air in and can be responsible for freezing pipes in your crawl space.

 Good things about foundation vents

  • Radon gas can escape.
  • Some cross ventilation can occur to dry out a moist crawl space.
  • They are one more way that combustion air can come in for your gas appliances and exhaust fans.
  • In a recent situation we added a humidity controlled, temperature limited powered foundation vent.

Where the insulation in your crawl space is has a lot to do with how well the foundation vent system works. Insulation placed between the floor joists works well. In many of the vintage homes I go in, there is no insulation in the crawl space at all. Closing vents in this case is even more important.

Why is this important information?

Although you might think everyone in the remodeling industry understands the importance of these devices, I assure you they do not. Obviously, lack of foundation ventilation, or location of the vents can be responsible for all sorts of problems in a home. We put a premium on understanding how all of the systems and components of a home work together or not… This makes Levco the go-to contractor for all of your remodeling needs.

Your comments are welcome. To ask questions or get more information about remodeling, click here to email me directly, or call 208-947-7261

If you or someone you know is considering remodeling or just wants to speak to a trustworthy remodeling contractor please contact me, you’ll be glad you did.


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