The hot topic for the fall is, what is the proper way to insulate a crawlspace? There are really two ways to get the most bang for your buck: one is adding insulation in the crawl space in the proper place in the proper way and the other is to close the foundation vents that let in the outside air.
Let’s talk about proper installation first. The new idea behind insulation in crawl space is to insulate between the inside and the outside of the home rather than insulating between the house in the crawl space. By preventing the cold air from entering the homes envelope you can better protect your home from heat loss. Installing insulation on the foundation walls will get you the greatest result for the cost and effort. With that being said, it is my recommendation that you use extruded rigid polystyrene insulation rather than spray foam polyurethane insulation. The biggest reason I recommend rigid foam over spray foam is because of the amount of moisture the insulation will absorb. Rigid foam absorbs far less moisture than spray foam does. This means, better results for a longer period of time. The Achilles’ heel of all insulation is moisture. This is why fiberglass insulation should not be used in a moist environment like a crawl space, unless of course your crawl space is not a moist environment. The bottom line is everyone has an opinion. My opinion is backed by over 20 years in the building industry and seeing every other way to insulate a crawl space fail miserably.
Now, let’s talk about the other way to insulate your crawl space. Well maybe insulate isn’t the proper way to say it. It’s more of a preventative then it is a procedure. If you’re air-conditioning your home and you want to keep the cool air inside you won’t open all your windows. The same is true in the opposite, if you’re heating your home you don’t open the windows and let the cold air in. When it comes to insulating a crawl space or preventing your crawl space from getting colder than you want the most effective way, even more than crawl space insulation, is to prevent the cold air from entering the crawl space. It is becoming well known and well excepted that the crawl space foundation vents cost far more harm than they were ever meant to prevent. Closing the event is simply not enough. The vent must be sealed in order to prevent the outside cold air from entering the crawl space. In fact, the best place to insulate in a crawl space is the foundation vents.
Properly insulating a crawl space and properly handling the foundation vents is critical to saving hundreds of dollars a year in heating costs. Choosing the proper insulation will give you years of effective service. Correcting the problem with the foundation vents however, carries a much larger commitment. Your choices are: to seal your foundation vents before the winter every year and undo that work every spring or you seal the entire crawl space, permanently close the foundation vents, condition the crawl space and treated it as part of the house. It’s your house and you always have final say, but the facts are in and a conditioned crawl space is far more efficient than one that is not.