Using spray foam in a crawlspace another simple way to improve the energy efficiency of homes. It is particularly useful for energy efficiency upgrades to existing homes. Spray foam can be applied to the underside of the floor or to the foundation walls and on the framing foundation interface. Applying spray foam to the foundation wall and the framing foundation interface can create a sealed crawlspace. The interface between wood frame walls (above grade) and concrete or block foundations below grade can be major air leakage point. Spray foam helps bridge the gaps, providing both insulation and air sealing to limit problems.
Insulating the Sub Floor
Traditionally, homes have used vented crawlspaces, which allow for air to move through the crawlspace to control moisture. To meet Building Codes, builders will insulate the subfloor of the home. Spray foam is an ideal choice for insulating the subfloor of a home because it is air impermeable and a strong insulator. Any floor that projects over unconditioned space can benefit from the use of spray foam. Foam adheres to the underside of the floor and doesn’t sag or compress with time.
Unvented crawlspaces move insulation from the underside of the floor to the perimeter foundation wall, also insulating and sealing the framing/foundation interface. Again, spray foam is an ideal choice for unvented crawlspaces because it acts as an insulation and air barrier. Spray foam expands on application, filling gaps and sealing air leaks in the crawlspace walls and hard-to-seal areas in the framing foundation interface.
Energy Efficiency of Unvented Crawlspaces
Unvented crawlspaces also help keep duct work contained within conditioned space. This means that conditioned air that leaks from the ducts will not be wasted. It will remain in conditioned space and can passively condition the air in the occupied space. Duct air leakage commonly exceeds 20 percent of conditioned air flow, which results in a significant energy loss when ducts are in unconditioned space.
Unvented crawlspaces also reduce the loss of conditioned air through the attic (stack effect). Stack effect is the natural movement of cool air in through the bottom of a structure, which is pulled by warm air exiting the top of the structure in winter. In the summer, the process reverses and air conditioned air tends to leak out of the bottom of the building and it is replaced by hot and humid air coming in through the upper parts of the building.