Unventilated Crawl Space

An Unventilated Crawl Space is a Warm and Dry Crawl Space

By Mark J. Donovan

Unventilated crawl spaces offer benefits over a traditional vented crawl space. An unventilated crawl space is similar to a basement in that it is reasonably warm and dry and can thus be used for storing items that could be affected by cold or hot temperatures. An unventilated crawl space is also less apt for causing cold floors and freezing pipes in the winter time. Finally, an unventilated crawl space will have less moisture problems compared to a ventilated crawl space.

For decades, building codes have required that crawl spaces be vented to allow moisture laden air to escape the crawl space area. The moisture in the crawl space is caused from moisture in the damp soil that permeates up into the crawl space.

Unfortunately crawl space vents never seem to really do a sufficient job of removing moisture from crawl spaces, and sometimes they are more of a problem then they are a help. On hot, sultry days humid outside air has the tendency to only make a crawl space even more humid.

To create an unventilated crawl space three components need to be incorporated into the crawl space; a vapor retarder, insulation and some conditioned air (heat).

These three components are exactly what are found in basements that typically do not require ventilation.

To create an unventilated crawl space start by installing a vapor retarder, aka vapor barrier, on the floor of the crawl space.

Typically a 6 mil plastic will work just fine. Just make sure it laps up the sides of the crawl space walls by about a foot. Tape the vapor retarder to the sides of the crawl space walls to properly seal it.

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Finally apply sand and gravel over the vapor retarder to allow you to walk/crawl around the crawl space without the threat of damaging the vapor retarder.

Next, install batt or rigid foam insulation on the walls of the crawl space and in-between the floor joists near the band joists.

Then, introduce some heat into the crawl space area. You may need to contact a heating contractor to help with this.

Finally, make sure the existing vents are closed and that the doorway entrance to the crawl space is also tightly insulated.

Crawl space vapor barrier

With these steps taken, your newly created unventilated crawl space should be warm and dry all year round.

For more help on Basement Additions, see HomeAdditionPlus.com’s Basement Remodeling Bid sheet. The Basement Remodeling Bid Sheet will help ensure that your hire the right contractor so that your basement remodeling project is done correctly and you get the project finished on time and budget.

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