Dear Mr. Energy,
What is a closed crawl space? Do I need one?
–Crawling around in Chapel Hill
A closed crawl space is a crawl space (the area found underneath your house and which is typically floored with dirt and vented to the outdoors) that has been air-sealed. A closed crawl can provide moisture control, help mitigate pest problems, provide safety measure for combustion appliances, radon, and potential fire hazards, and can make homes more energy efficient.
Think of what your crawl space is made of: dirt, primarily, but also insects, insect body parts, rodent excrement, and who knows what else. If you have any leaks in your ductwork, this is what’s blowing in your house. If you have any leaks in the part of your house that separates your crawl from your living space, this is the air that’s being drawn into your house. And the crawlspace naturally contains moisture, which evaporates from the ground into your house every minute of every day. Sealing the crawl keeps all of that from coming into the conditioned living space of your home.
For many years it was believed that the crawl space needed to be vented in order to “breathe” – especially in a humid climate like we have in North Carolina. But research in building science has actually shown the exact opposite – that if the living space of the home is on top of space that has been sealed off, if will actually make the house last longer, make its residents more comfortable, and make the house easier to heat and cool. Mr. Energy has installed many closed crawl spaces and he can attest to their benefits for homeowners.
Now, as to your second question, whether or not you should get one: how would Mr. Energy know the answer to that question without actually visiting your home and doing a thorough energy audit? He is not about to start flinging around recommendations that everyone needs this or that (although he does believe that everyone needs a professional energy audit and practically everyone needs their ducts sealed. But that’s just based on personal experience). But he can tell you this: if you are worried about your crawl space and worried that it’s causing health, safety, or energy efficiency problems, then it may be something to consider.