Working from the “Ground Up” to Renovate Your Air Quality
We’ve written quite a few articles about how crawl spaces have a lot of input on our homes’ air quality. Unless the crawl space has been encapsulated or built as a “conditioned” area, it will “communicate” with your home’s air: air from your nicely conditioned home will seep into the crawl space, and moist, moldy air from the crawl space will seep into your home. Yuck.
If you have an unconditioned crawl space and really want to improve the air in your home, just take a peek at the crawl space (I won’t even recommend going in it) and then watch this video. I think you’ll be convinced that the crawl space should be one of your top priorities!
The title of the video, The Truth About Crawl Space Retrofits: Labor, Moisture & Air Quality, was the hook that got me in. I thought, is there a “hidden downside” of encapsulating a crawl space? It turns out, the only downsides are in the title: there’s a reason they’re called a “crawl space” and laboring in them amounts to laboring on your knees, stomach or back, on the dirt, in the trash that was left over from when they were built or whatever animal made their home there. Trust me, I had plenty of experience in my former house! And that’s where the downsides end: if you can bear to do it yourself, or afford to pay someone else to do it, the rewards to your air quality are going to be very worthwhile.
What exactly are you or your hired team doing down there in the dirt? The video mentioned above was in conjunction with a renovation of the entire house, so they were doing additional work to the HVAC, plumbing and electrical. But in general, when focusing on the crawlspace itself, you’re righting the “wrongs” of the dirt floor, walls and ceiling (subfloor of the house). Following are some major steps in the work; they’re not all consecutive, so read all the way through and plan the job thoroughly before starting!
-
Check for radon: Radon is a colorless, odorless gas that seeps naturally from certain underground rocks and can permeate basement walls and foundations, as well as contaminate ground or well water. Because radon is radioactive, it can cause cancer (it’s estimated by the EPA to be the #1 cause of lung cancer among non-smokers). If you live in an area known to have high levels of radon in the soil (you can check this map to see if you live in the red or orange zones), then you’ll want to have a contractor come in to install a radon mitigation system BEFORE you place a vapor/air barrier on the floor of your crawl space, because it’s designed to suction out gases from the soil before they make it into your home. You can find qualified professionals from the links on this page.
-
“Even out” the earth so that a vapor and air barrier can be laid down. If there are all kinds of hills and valleys under the home, it’s not easy to lay down this barrier and seal the edges to themselves and to the walls (only very small homes will not require more than one width of material and therefore no sealing it together in the middle of the floor). The team in the video removed trash, raked out the high spots as much as possible, and used scrap insulation (rockwool, which doesn’t absorb moisture and thus is adverse to mold formation) to fill in the remaining valleys before covering the floor with a vapor barrier. If you really want to make the home more thermally comfortable, you can install a continuous layer of rigid foam on the earth as a thermal break below the vapor barrier. (See our article on Concrete-Free Slabs).
-
Addressing the HVAC and other systems: If the ductwork, plumbing and electrical under the home are in bad shape, you may want to consider replacement or repair of all these systems right after grading the dirt floor, to avoid contractors tearing up the vapor barrier while working later. The reason it’s a good idea to do this now, is that if you have an old cast iron drain pipe, it’s only a matter of time before it cracks and spews sewage all over your “new” crawl space. You also don’t want to contaminate the “new” space with deteriorating fiberglass or asbestos insulation (very common to have asbestos tape at least) or asbestos wire insulation (electrical wire was covered in asbestos insulation from the 1920s through the mid 1980s). It’s best to bite the bullet now, while the renovation is going on, and remove all of these pollutants from your home. In the case of the ductwork, you’ll at least need to check and seal all the joints while you’re down there, to make it a closed system.
-
Addressing the walls: I like the position the builder used to shoot the video, because it showed the bare concrete block walls before work was complete. You can see that the bottom 2 rows, and even part of the third row of block were saturated with water. That is WAY too much water to just apply water-resistant coatings and a combination insulation-air barrier (the builder isn’t going to apply a vapor barrier to the walls so the dehumidifier can “dry to the inside” or pull remaining moisture out of the block). As the builder rightly stated, they will need to investigate reducing the water from the outside. They will check the gutter situation to make sure they are not clogged and directing water away from the house, and look at grading the soil to help with water runoff as well. If the home is built on the side of a hill and water is running down the hill into the foundation, then they could excavate the dirt next to the wall, install a drain at the bottom next to the bottom of the wall, and fill the trench with gravel so that all of the water is directed to the drain. While the wall is excavated, it would be wise to apply exterior insulation rated for ground contact to the wall. All of these steps will reduce the load on the dehumidifier that will be installed in the crawlspace. It’s the same as we recommend in the home: in order to stop mold, you need to get rid of the moisture.
-
Addressing the underfloor: Now’s the time to seal all the cracks and holes in your subfloor. You really don’t know if there are gaping holes that are letting air through until you (or your team) visualize them. See our article (with photos) on how to get the job done!
-
Install a dehumidifier: Sealing up and insulating your crawl space is like closing the lid on a portable cooler (the kind you use to carry cold drinks). Even though it’s clean and empty, without dehumidification, it’s just a matter of time before mold will start to form on the walls inside. This is because the insulation and lack of air flow allows moisture from the air to condense on the walls, and mold spores are everywhere. It only takes a little moisture and a few spores to form mold (in a few weeks to months). This is inside an insulated cooler, which is more airtight and insulated than you can get a crawl space to be. The daily fluctuation of temperatures and ample supply of food (on wood joists, for example) will easily support mold if dehumidification is not installed.
As the builder stated at the end of the video, it’s a lot of work if your access hole(s) is small or the crawlspace has a low ceiling and is cluttered…but it’s worth it. If you plan to do it yourself, check out your crawl space and watch this other short video to make SURE you can finish what you start. Plan out your job, including all the materials and related tasks (installing drainage, replacing aged drains, ducts and wires), and consult the extensive (free) online library and resources at the following:
-
Crawlspaceninja.com (also check out their DIY store)
-
What Supplies Will I Need to Encapsulate My Crawl Space? By Stego, the manufacturer of the vapor barrier used in the first video
-
Crawlspaces - Either In or Out: If you are a fan of dry humor and common sense, you’ll appreciate this article with helpful construction details by building science expert Joe Lstiburek.
Photo by Chelsey Marques on Unsplash
