Crawl Spaces and Cold Floors

Crawl spaces and cold floors is all too common of a problem during the heating season - which you may not be thinking about right now, as summer is just around the corner. But in fact, now is the best time to be thinking about your crawl spaces and cold floors, because now is the best time to fix it. The problem with crawl spaces and cold floors is that the temperature in your home will be comfortable, but your home's floors are cold to the touch. This happens when whatever is underneath your floor is not properly insulated. Additionally, missing/inadequate insulation can increase your heating costs.

The type of floor insulation you need depends on what your floor sits above, whether it's a garage, basement, or more commonly for this problem, a crawl space.


If your floor sits above your garage, it's recommended to use blown-in insulation (use dense-pack cellulose if your garage ceiling is finished with gypsum board) to fill the space between floor joists.


If your floor sits above your basement, make sure to air-seal and insulate any rim joists. You can do this with two-part spray foam, or with a combination of spray foam and rigid foam insulation. You can also use rigid foam wall insulation.

For basement floor insulation, you should avoid wood subflooring during the insulation process in order to avoid problems with moisture or mold damage. Instead, you can use a special thermal dry subflooring, which is made from waterproof rigid foam and composite board. This special type of subflooring provides a thermal break for the floor while supporting the finished flooring you want on top.

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Crawl Spaces:

For crawl spaces and cold floors, you should insulate your crawl space, which means sealing rim joists and insulating the walls and floors.

The most successful way to avoid cold floors means using insulation that both seals and insulates the foundation of your subfloors. Use spray foam or install rigid foam board panels that is caulked at the edges, but beware that the joist bays located overhead in a crawl space usually host plumbing valves, ducts, and electric junctions. Also keep in mind that insulating just the floor will not help to fix your crawl space moisture issue, if you have a moisture issue. The crawlspace will continue to be a damp, wet place that's conducive to rot, rust, and insect infestation. HVAC ducts will still be traveling through a cold space, losing some of the heat they are supposed to be delivering to your living space; and your plumbing pipes will still be vulnerable to freezing.

Sealing a crawl space involves more material and effort but can be a much more effective solution to fixing your crawl space and cold floors than trying to insulate the subflooring. Sealing a crawl space usually includes the installation of a tough polyethylene membrane over the crawl space walls and floors. Any and all seams are sealed up with a special tape, outside vent covers are used to seal existing vents, and hatchways are fitted with airtight entry systems. Gaps that may be found along with rim joists are carefully sealed, and rigid board insulation could be used in combination with the liner while a flexible insulation mat is laid underneath the liner.

Once your crawl space is encapsulated, it becomes a part of the conditioned space of your home, meaning it responds to heating and cooling. Because of this, the temperature in the crawl space becomes similar to the rooms above it, meaning your floors stay warmer in the winter. Additionally, because heating ducts will lose less heat, your pipes should no longer freeze.

What Causes Crawl Spaces and Cold Floors?

If your crawl space isn't sealed, it's easy for warm, humid summertime air to find its way through hatchways, vents, and smaller gaps found in the framing on top of foundation walls. As this moisture-thick air cools and reaches its dew point, then condensation forms on your cool crawl space surfaces. Gaps then open up that lead directly to the subflooring.

Fixing Crawl Spaces and Cold Floors

While sealing your crawl space may not seem like a particularly complex task, it is a task that needs to be done correctly the first time - otherwise, it will most likely cause more problems than it solves. For example, if you have a water leak, that should be addressed before the encapsulation work starts. And if your waterproofing requires a sump pump, then the basin needs to be carefully fitted to the liner and covered with an impermeable lid.

Be sure to contact a crawl space service expert may be necessary to solve your issue. 

More info? For more information about common places for moisture in your home, check out our related post: Crawlspace Moisture Problems

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