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Energy Penalties of a Dirt Crawl Space

A home with a dirt crawl space costs more to heat and cool. Houses with dirt crawl spaces have damp air. Damp air is more difficult to heat and cool, requiring more energy and more cost. Damp air puts a "latent" (hidden) load on the HVAC system. A ductless air conditioning system is an option to consider.  Everyone knows they need to run their AC more on a humid day. But what about humidity from inside the building? Same thing. Removing humidity from your crawl space, saves money on heating and cooling costs.

How much money? You could save 15% to 35%! Which over the years, adds up. Of course there are variables, such as, how many vents you have, whether you live in a one or two story home, if you have ducts in the crawl space, how big your crawl space is, etc.

The penalties from living with, and the savings from fixing the dirt crawl space problem are real, and proven. Advanced Energy, a private non-profit organization funded by both public and private funds, has done studies to measure these effects. The results can be found on their web site, advancedenergy.org.

In fact, the energy loss is so substantial in a home with a vented dirt crawl space with ducts, that you may as well ignore all other ways to save energy and make your home more comfortable, until you fix the crawl space problem. Caulking around a window, or weather-stripping a door, would be like patching a tiny hole in a rowboat, and ignoring the foot-wide round hole on the other side.

Controlling air infiltration is the key to energy conservation in a building. Closing up those giant holes in your crawl space walls, and eliminating the "reason" (exposed damp earth) why they were there in the first place must be top priority.

In one Advanced Energy study, the organization experimented with 12 identical new homes in a Habitat for Humanity subdivision. Some of the homes had vented dirt crawl spaces, and others were sealed. By sub-metering the heat pumps, they found that the homes with the vented dirt crawl spaces cost $28 more to cool in a single month (June 2003).

crawl space insulationThere are a few catches. First, the homes were small. If the homes were twice as big, we might expect twice as many dollars saved in energy costs in the same one month. Second, the ones with a "vented dirt crawl space" had two things going for them that the average house with vented dirt crawl spaces does not. They had a 6 mil plastic ground cover down on the floor, and they had their ducts sealed. In a 100 house study in 1994, Bruce Davis, from Advanced Energy, determined that the average house has more than 300 cubic feet per minute of duct leakage, of which these comparison homes did not have.

If this control group of houses was more like the millions of real homes across the country we see out there, the difference in energy use would be even more dramatic.

Nevertheless, it doesn't take long before the numbers add up to serious money. Add to that the benefits of preserving your home's value, and eliminating rot repairs and mold remediation, and you see that fixing your crawl space is one home repair you canít afford not to make.

Spread across the 26 million homes with dirt crawl spaces, it is estimated that with just a 15% energy savings, homeowners in the U.S. would save 7 billion dollars annually.

US Department of Energy - Crawl Space Insulation

US Department of Energy - Crawl Space Moisture Control

Energy Star - Recommended Levels of Insulation for Crawl Spaces

North American Insulation Manufacturers - FAQs About Home Insulation