If you decide to put a basement under your home, then it should be insulated to provide comfortable living space. If you are not going to use your basement for living space, you should consider building on a slab. The two most common construction techniques used for basements are cast-in-place concrete and ICF. ICF basements are more expensive, but will generally save in energy consumption compared to a framed and insulated cast-in-place basement. Insulating a cast in place foundation from the outside is more desirable than insulating it from the inside; however, insulating from the inside is the most common and practical approach.

An alternative approach to enhance the R-value of your cast-in-place basement, and to help with moisture issues as your green concrete dries, is to put a water resistant rigid insulation against the concrete, behind the insulated framing layer. This also lessens thermal bridging, which is always a good thing. ICF construction does not have much thermal bridging because of its design.

Whether or not you have a heated basement floor, insulating under the basement floor is important, both from an energy efficiency perspective and to prevent condensation during periods of high humidity. This condensation is responsible for those musty smells and leads to the growth of undesirable organisms. It is also important to provide a thermal break around the edge of the slab to prevent it from making direct contact with the concrete walls. This will prevent heat from the slab being transferred from the inside of your house to the outside.