Reducing Thermal Losses and Gains With Buried and Encapsulated Ducts in Hot-Humid Climates

Compact Buried Ducts in a Hot-Humid Climate House

“…ccSPF were also shown to prevent condensation in a hothumid climate. Additionally, effective duct and attic insulation values were calculated with respect to nominal insulation values (Shapiro, Magee, & Zoeller 2013). The U.S. Department of Energy Zero Energy Ready Home program allows buried ducts as an exception to the requirement that ducts are "located within the home's thermal and air barrier boundary" such that ducts must be insulated with minimum R-8 duct insulation, encapsulated with minimum 1.5-in.…”

“…The effective R-value takes into account round duct geometry, inner and outer duct surface materials, and heat transfer between the duct and conditioned space. Previous BA research established effective R-values for round buried ducts (Shapiro, Magee, and Zoeller 2013;Shapiro, Zoeller, and Mantha 2013). For this project, a value of R-30 was selected in the software to best represent the average for all buried ducts.…”

“…Heating, ventilating, and air-conditioning service technicians measured and verified that the supply air temperature was consistently 54°F-55°F after the cooling system was operating for a few minutes. [Shapiro, Magee, and Zoeller 2013]). The dew points at the tree sensors within the attic insulation (3.5 in., 6 in., and 8.5 in.…”

“…Current best practices for buried ducts developed through the U.S. Department of Energy Building America Program (BA) rely on encapsulating the insulated ducts with closedcell spray polyurethane foam (ccSPF) insulation to control the condensation and improve the air sealing. The concept of an encapsulated buried duct has been analyzed and shown to be effective in hot-humid climates based on research performed by the Consortium for Advanced Residential Buildings (Shapiro, Magee, and Zoeller 2013;Shapiro, Zoeller, and Mantha 2013). Additional research on systems with buried attic ducts by Home Innovation Research Labs (Home Innovation) resulted in two alternative buried duct designs with reduced duct encapsulations that have been successfully installed, tested, and monitored in mixed-humid climates (Energy and Environmental Building Alliance 2013).…”

High-Performance Ducts in Hot-Dry Climates

“…Building America teams have been researching methods for improving distribution system performance by burying ducts in ceiling insulation, moving them into conditioned space, or eliminating vented attics (Burdick 2013b;Shapiro et al 2013). Ongoing research has identified various strategies to place ducts within the thermal envelope (Lubliner et al 2008;Hales and Baylon 2010;Beal et al 2011) 3 and approaches to improve duct performance in unconditioned attic spaces (Shapiro et al 2013).…”