Buried and Encapsulated Ducts, Jacksonville, Florida (Fact Sheet)

Ductwork installed in unconditioned attics can significantly increase the overall heating and cooling costs of residential buildings. In fact, estimated duct thermal losses for single-family residential buildings with ductwork installed in unconditioned attics range from 10% to 45%. In a study of three single-story houses in Florida, the Building America research team Consortium for AdvancedResidential Buildings (CARB) investigated the strategy of using buried and/or encapsulated ducts (BED) to reduce duct thermal losses in existing homes. The BED strategy consists of burying ducts in loose-fill insulation and/or encapsulating them in closed cell polyurethane spray foam (ccSPF) insulation. There are three possible combinations of BED strategies: (1) buried ducts; (2) encapsulatedducts (with ccSPF); and (3) buried and encapsulated ducts. The best solution for each situation depends on the climate, age of the house, and the configuration of the HVAC system and attic. For new construction projects, the team recommends that ducts be both encapsulated and buried as the minimal planning and costs required for this will yield optimal energy savings. The encapsulated/buriedduct strategy, which utilizes ccSPF to address condensation concerns, is an approach that was developed specifically for humid climates.