Consider moisture and air leakage control
When installing a slab foundation and insulating it, it’s also important to consider moisture and air leakage control, as well as termite control.
Termites can tunnel undetected through exterior slab insulation to gain access to the wood framing in a home’s walls. As a result, some insurance companies won’t guarantee homes with slab insulation against termites. Building codes in several southern U.S. states prohibit installing foam insulation in contact with the ground.
“Floating” slab foundations with interior insulation provide more termite resistance. However, some builders in the southeastern United States have reported termite infestations through foam insulation on contained slabs.
To help offset termite problems, follow these guidelines:
* Provide effective moisture control systems.
* Remove all wood from around the foundation before backfilling.
* Install termite shields continuously under the sill plate of the building. The shield should project beyond the sill plate and all other portions of the exterior wall. While not 100% effective, the termite shield may deter or delay widespread infestation. It may also force termites into an exposed area where they can be detected. A continuous layer of a membrane—such as rubberized roofing material used in commercial buildings—may be used as an alternative to the termite shield.
* Use a foam insulation treated with a termiticide. Usually a derivative of boric acid, the termiticide should pose no more threat to homeowners than traditional termite treatments.
You’ll also want to regularly inspect for termites. If you use a pest control company, obtain a good warranty for its work.
Source: EERE, U.S. Department of Energy