Insulating Your Crawl Space

A crawlspace that is insulated properly will contribute to an overall savings in utility costs in your home. The goal of a thorough insulation job is to ensure that all air is sealed out, and the moisture levels are properly maintained either through water removal, dehumidification or both.

When considering an insulation job for your crawlspace, make sure you obtain information about insulation products and materials that may be available, as well as any installation guides or instructions. Some products require special equipment and/or training to install properly.

You may find that your crawlspace is vented. This is a common requirement by building departments in the construction of a home or addition with a crawlspace, as they are installed to allow moisture to evaporate and keep the crawlspace from developing moisture problems caused by mold, mildew and rot. An alternative to this is to treat the crawlspace as a heated, insulated space with a drainage system of some sort like a sump pump. This is particularly sensible in cold climates where a heated crawlspace would contribute to energy savings. Insulation requirements are very different in a vented crawlspace as opposed to a non-vented, heated space.

There are two important problems associated with vented crawlspaces. The first is heat loss. By design, the vents allow fresh outdoor air to circulate through the space. If the weather is nice, this feature is beneficial. If the home is located in a cold winter climate, the crawlspace could get as cold as the outdoors making heat loss an important consideration. It should also be noted the during humid summer months, the vents would allow humid air to enter the crawlspace as well, contributing to mold and mildew problems.

If you choose to insulate a non-vented crawl space, it is usually best to insulate the exterior foundation walls rather than the floor structure for the floor above the crawl space. When the floor structure is insulated, fiberglass batts are typically fitted between the floor joists and stapled in place, and then wire mesh or thin plywood can be used to secure the insulation in place. If the walls are insulated instead, a blanket insulation product is usually used instead, which is draped down the wall sides and then secured with screws or other metal fasteners. There are many advantages to insulating the walls instead of the floor structure above the crawlspace:

• The amount of insulation required will be less
• Pipes, ducts and electrical wiring all remain accessible
• There are fewer concerns about sealing the living space out from the crawlspace
• There are fewer seams between insulation components with blanket insulation than with batt insulation

Insulating a crawlspace with vents requires careful consideration to how carefully the floor structure is insulated to avoid heat loss through the floor. When the walls are insulated, special care must be taken to heat the air and remove humidity. No matter what type of crawlspace you have, you will benefit greatly by making it dry and insulating it properly.