Sunday, December 13th, 2020 by CJ Garcia
Is the floor or room over your crawl space colder than the rest of the house? This is a common problem in homes built over a dirt crawl space or with a basement that’s unheated and not insulated.
If you’ve been researching how to make the floors over your crawl space, or basement warmer, then you know there is a lot of information on the best solution. The key takeaway from the research is that to make cold floors and uncomfortable rooms over these areas warmer, you need a continuous air barrier and proper insulation in place to stop cold air. We’ve put together this guide to explain what causes cold floors (and rooms) over the crawl space and basement as well as solutions for making them warmer.
In the winter, the warm air inside the house is lighter than the cold air outside. As the warm air rises through the house and escapes out through leaky windows, the attic and roof, this draws cold, dense air from outside into the basement, crawl space, garage, and first-floor windows. To add to the problem, most basements and crawl spaces either don’t have insulation at all or don’t have proper insulation. If nothing is stopping the cold air from reaching your floors and the rooms above, it’s no wonder they are cold.
Insulation works by trapping pockets of air that slow the flow of heat out of the house in the winter (and into the house in the summer). The R-value of the insulation is an indicator of how well the insulation resists this movement; the higher the R-value, the more effective it is at lowering heating and cooling costs and maintaining comfort.
Fiberglass batts are inexpensive and quick to install, which is why they are the most common type of insulation. However, challenges with properly installing fiberglass batts make blown-in insulation or rigid foam a better choice for insulating the ceiling in unconditioned basements and crawl spaces.
What you should know
Adding spray foam or rigid foam board insulation to the underside of the floor can help warm up the floor and rooms above the crawl space. However, this approach makes it difficult to access plumbing and electrical wires when the need arises. Another common mistake that homeowners make when repairing the crawl space is adding plastic (or a vapor barrier) to the underside of the floor joists in an attempt to make their floors warmer in the winter, but doing so can trap moisture that can lead to mold and rot.
The best approach
Sealing or “encapsulating” the crawl space involves more material and the help of a professional, but it’s a much more effective solution than insulating under the floor. Covering the ground with a crawl space vapor barrier reduces moisture and sealing the rim joist and crawl space vents keep out cold air during the winter, which will make the floors above feel warmer. Additionally, crawl space encapsulation and insulation can prevent cold ducts and frozen pipes.
If you’re worried about how your unheated basement or crawl space is impacting your home’s comfort and energy efficiency, check out our tips to winterize your basement or crawl space. You can also always contact TerraFirma for a free evaluation of your home's crawl space!