Crawl Space Insulation

Crawl Space Insulation Tips

“What is the proper way to insulate a crawl space?” has to be one of the most frequently asked questions we get each year, as we head into the cooler months. The answer is "by simply completing a couple of tasks." There are really two tasks you’ll need to complete to get the most bang for your buck. The first is to install insulation in the crawl space in the proper place in the proper way. The other task is to close the foundation vents that let in the outside air.

To start, it will be helpful to look at the similarities and differences between a crawl space and a basement. Basements may have windows, whereas crawl spaces have foundation vents. Basements are below the home, and crawl spaces are as well. Most basements have a vapor barrier liner underneath a concrete floor for comfort and moisture control, but most crawl spaces do not. Most basements need some sort of dehumidification in order to control moisture, as most crawl spaces do as well. Due to basements being located below the house, they are often much cooler than other areas of the house, just as crawl spaces are as well. It's quite obvious that these two spaces are very similar, and yet they continue to be seen very differently. So the question is, why is that?

Why Are They Viewed So Differently?

The answer is, it all comes down to that green stuff. The greatest difference between the crawl spaces and basements is their impact on a home’s monetary value. Crawl spaces hold far less value in a home's price tag. It is not considered living space, and therefore it is not conditioned with the rest of the home. This fundamental difference is where the devaluing of crawl spaces began. However, those of us pioneering the crawl space repair industry began to wonder what could happen if we transformed the crawl space by giving it more of the attributes of a basement.

Basement windows are typically closed, so we began closing the foundation vents in crawl spaces. Basements have moisture control in the floor system, so we began installing a vapor retarder or vapor barrier liner onto the floor of the crawl space. Basements most often need a dehumidifier, so we began implementing them in crawl spaces. Basements are colder because of their location, and yet no basement has insulation in the ceiling. In fact, it is code in almost every city and town in America to insulate the foundation walls of a basement prior to making it a conditioned space. So we began looking into insulating the walls of crawl spaces as well.

Installing Crawl Space Insulation

We began researching the most effective ways to insulate crawl spaces. The newest idea in crawl space insulation is to insulate between the inside and the outside of the home rather than insulating between the house and the crawl space. This follows all of the best practices of building envelope energy efficiency. By preventing the cold air from entering a home's envelope, the better the home is protected from heat loss. Installing crawl space insulation on the foundation walls will get you the greatest result for the cost and effort, just like in a basement.

Following thorough research and after conducting many applications, we recommend the use of extruded rigid polystyrene insulation rather than spray foam polyurethane insulation. The most important reason we recommend rigid foam over spray foam is because of the amount of moisture it absorbs. Rigid foam absorbs far less moisture than spray foam does. This will mean better results for a longer period of time. The fact is, moisture is the Achilles’ heel of all insulation. This is the primary reason that fiberglass insulation should never be used in a moist environment like an unconditioned crawl space.

In addition to installing the insulation in the crawl space, there is also a preventative measure that has to be addressed as well, in order for the insulation to really be its most effective. If you’re air-conditioning your home and you want to keep the cool air inside, you wouldn’t open your windows for ventilation; you would do what is necessary to keep any of your cool air from escaping your home. The same would be true if you were heating your home; you wouldn’t open the windows and let cool air infiltrate your warm air inside. When it comes to insulating a crawl space to better control the temperature inside, especially to prevent your crawl space from getting colder than you want in the winter months, the most important measure you can take is to do whatever you have to do to prevent cold air from entering the crawl space. Being mindful of that and of the fact that simply closing the vents is just not enough to prevent cool air from seeping in, it becomes clear that the only solution has to be a more secure, closer-to-permanent closure of the vents. The vents must be closed and sealed off completely in order to really prevent the cold outside air from seeping into the crawl space. In fact, it turns out that the number one thing a crawl space homeowner can do to lower their winter heating bills is to close the foundation vents.

Proper Crawl Space Insulation

Proper insulation and closure of the foundation vents in a crawl space are essential to saving hundreds of dollars a year in heating costs. If you choose the right insulation and simply install it properly, it will give you years of effectiveness and the best return on your effort and cost. Correcting the problem of the foundation vents will be a bit more complicated and require you to decide on how much you want to commit to the solution. As in, you’ll have to choose between sealing your foundation vents prior to winter each year, then undoing that work each spring OR sealing the entire crawl space permanently, which will allow the foundation vents to remain closed all year. Though you have to keep in mind that permanent sealing of the vents will require that you also then condition the crawl space by installing a dehumidifier and possibly encapsulating the crawl space to begin treating it as part of the house, much like a basement.

At the end of the day it comes down to this: homeowners will have to make the best decision for their homes based on their own unique situations. Nevertheless, the facts remain; a conditioned crawl space makes a home far more energy efficient than one that is not.