Many crawl space repair contractors misinform homeowners about crawl space insulation in order to make their pricing look better. The facts are that insulation is required by building code and necessary to ensure your home is comfortable and energy efficient.
A minimum approach to any insulation whether in walls, basements, attics and the crawl space should be a thermal barrier and air sealing. Thermal and air barriers in crawl spaces are easily achieved and will increase comfort in your home for years to come.
Foam board Insulation in Crawl Space
Crawl space encapsulation projects require insulation. When installing crawl space insulation during the encapsulation process, foam board insulation is a great way to keep your crawl space comfortable.
Foam board is applied to the block wall or concrete wall in order to create a thermal barrier between the cold or warm wall and the crawl space. Just like attic insulation is designed to stop the thermal transfer of heat and cold from your living space to the attic.
Crawl space walls that are uneven like stone or old brick, may require a closed cell spray foam because the foam board cannot be properly attached to uneven surfaces. We recommend installing foam board mechanically due to adhesives failing over time.
Another benefit of foam board versus fiberglass is it can get wet without needing to be replaced or lose its R-value. Our foam board carries a 50-year R-value warranty and is termite resistant.
Batt Insulation in Crawl Space
Fiberglass batting insulation or rock wool insulation is typically the choice of insulating a vented crawl space or non-conditioned crawl space. When air is allowed to freely flow in and out of the crawl space, installing a batting insulation to the sub-floor helps create a thermal barrier between the crawl space and the living space.
Please note that it is appropriate to install batting in a closed or encapsulate crawl space but you never want to insulate the walls of a non-conditioned crawl space because air is able to freely move into the crawl space and wall insulation is ineffective when used in open crawl spaces.
It is also recommended to air seal the sub-floor no matter which type of insulation you decide to install. Air sealing will cut down on drafts in the home. It also will minimize the transfer of warm air to the attic in the winter and cool air to the crawl space in the summer.
Spray Foam Insulation in Crawl Space
Air sealing the crawl space with spray foam insulation or polyurethane caulk is probably the most overlooked way to insulate the crawl space.
The engineers at BuildingScience.com recommend air sealing the rim joist to ensure air movement is minimized up the outer walls of the crawl space and into the living space or attic. They refer to this as a "Critical Seal" and we recommend that every crawl space and basement have the rim joists air sealed properly.
Spray foam insulation is also great to air seal all of the plumbing, electrical and HVAC penetrations in the crawl space.
Many crawl space contractors over look air sealing large gaps in exterior cinder block walls as well. Make sure these are air sealed to keep the air transfer from the outside at a minimum. This may also help keep standing water from infiltrating the crawl space but normally that is better addressed in other ways.