Insulation under a raised floor home project

A thorough understanding of insulation options is critical to the health, energy performance, sustainability and overall livability of a raised wood floor home.

Carefully consider the choice of insulation. This decision should not be based solely on the minimum R-value required, but with consideration to construction cost, home occupant energy use and related cost, and off-gassing of volatile organic compounds. Also consider the insulation’s compatibility with all other construction methods and materials used, as well as with both the site-specific and the surrounding environment.

The selection of insulation can significantly impact moisture management. Particular attention is recommended in coastal and other moisture-rich environments, especially hot, humid climate zones.

Common thermal barrier-type insulations include a variety of options such as fiberglass or cellulose batt, open-cell sprayed cellulose, and closed-cell sprayed foam.

Thermal break insulation, including rigid foam board, is typically installed at the exterior face of the thermal envelope. Often placed behind exterior finish materials, or between footings/foundation walls and bearing soils in frost-protected or thermally enhanced foundations, this type provides continuous insulation, excluding thermal bridging materials.

Radiant barrier-type products, such as foil-faced structural panels, have been proven to enhance home energy performance where sufficient, continuous “air space” is provided immediately adjacent to the foil surface, but are redundant if insulation eliminates the required void.

Whether required or optional, important consideration of the type of vapor barrier is necessary for best performance of the insulation, as well as the sustainability of the structure. Wood, and wood fiber-based products, must be allowed to “breathe”; otherwise, their service life can be reduced. The improper use of vapor retarders, including insulation products such as closed-cell spray foam which forms a vapor barrier by its composition, may cause considerable damage to structural elements where wood products are unintentionally encapsulated.