For a properly energy efficient home, your home should be properly insulated from the roof down to its foundation including the basement walls and any crawlspaces.

How you insulate a crawlspace depends on whether it's ventilated or unventilated. Most building codes require vents for removing moisture from the crawlspace. However, many building professionals now recognize that building an unventilated crawlspace (or closing vents after the crawlspace dries out following construction) is the best option in homes using proper moisture control and exterior water drainage techniques.

If you have an unventilated crawlspace, the best approach is to seal and insulate the foundation walls rather than the floor between the crawlspace and the house. This has the advantage of keeping piping and ductwork in the crawlspace from requiring insulation for energy efficiency or protection against freezing. It’s best to locate the access door to the crawlspace inside the home through the subfloor or basement wall.

Concrete slab on grade insulation:

Cold concrete slabs can be a challenge to properly insulate. However, an insulated slab is much easier to heat and helps moderate indoor temperatures of the entire home.

Insulating a slab in an existing home can be expensive and disruptive, but if the slab in your home is cold it is possible to dig around the perimeter of the house and install insulation on the outside using foam boards. Insulating the exterior edge of a slab can reduce heating bills by as much as 10% to 20%.

Installing slab insulation during the construction is the best method and is quite easy to do. Foam boards or thermo blankets are installed either directly against the exterior of the slab and footing before backfilling or under the slab and along the inside of the stem wall of the foundation.

One of the drawbacks is that termites can tunnel undetected through exterior slab insulation boards to gain access to the wood framing in the house walls. This often raises issues with insurance companies for insuring against termites. Slab foundations with interior insulation are more termite resistance.

Insulating a crawlspace or concrete slab on grade is just as important as insulating the walls, ceiling, and foundation of your home.

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