Closed Crawl Space

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Closed Crawl SpaceA closed crawl space is one that was built without foundation Vents

Within the last few years the building code has allowed homes built on a crawl space to be built as a “closed crawl space”. This means foundation vents are not required as long as other requirements are met. This type of crawl space is more energy efficient than an open crawl space.

Sealing the crawl space is also known as crawl space encapsulation. Encapsulating crawl spaces ensures that the outside moisture is sealed outside and you reduce the moisture levels within the crawl space. Afterward, a crawl space dehumidifier can be used to lower the moisture levels even further.

The crawl space still needs ventilation

If a crawl space is built without foundation vents it is still required to have ventilation. The two most common configurations are:

  1. Ventilation using the air from the home- via openings in the floor


  1. Ventilation using the forced air (furnace) system of the home

Continuous vapor barrier on the floor

There needs to be a continuous vapor barrier, rated at less than 1 perm, laid on the floor with all seams lapping at least 12?.


There are two insulation methods allowed in a closed crawl space:

  1. Insulating the perimeter foundation wall


  1. Insulating the floor joists (crawl space ceiling)


  1. Generally, the vapor barrier is loosely installed preventing proper moisture control from the earth floor.
  2. There is no moisture protection from the crawl space walls.
  3. Odor can still be a problem with a closed crawl space