![]() ![]() For example, if a home had a 2.5-ton (30,000 BTU/H) cooling system moving 1,000 CFM (cubic feet per minute) of air and the ducts had 10% leakage (which is typical in code-built homes), the leakage rate would be 100 CFM. If ducts are located in an unconditioned space, such as a vented attic or vented crawlspace, they should be sealed and insulated to prevent heat loss due to air leaks and conduction and to provide some protection against harsh conditions.ĭuct leakage is a double hit on the utility bill: 1) duct leaks are an uncontrolled loss of conditioned air to the outdoors and 2) duct leakage drives building infiltration. Ideally ducts should be located in conditioned space, such as within a dropped ceiling, between floors, in an insulated basement or crawlspace, or in an unvented attic that is insulated along the roof line. ![]() See the Compliance Tab for related codes and standards, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Single-Family New Homes, and Indoor airPLUS. Consider insulating all metal ductwork located in conditioned space, including supply and return ducts, duct boots, and exhaust ducts, to minimize condensation.Ensure that insulation completely covers ducts and connections without gaps, voids, or compressions.pressure balancing (connections for jump ducts, dedicated returns).ventilation ducting (connections to exhaust fans, for ERV/HRV dedicated ducts).return ducts (connections to return box).supply ducts (connections to boots, trunk ducts, other ducts, i.e., duct splicing).Ensure that all duct connections and seams are air sealed for the following, regardless of whether they are located in conditioned or unconditioned space:.See the Compliance tab for R-value minimum requirements specified in the IRC, IECC, DOE Zero Energy Ready Home program, and ENERGY STAR criteria. Meet code or program minimum R-value requirements. Insulate all supply and return ducts located in unconditioned space.Seal insulation blanket seams with mastic or UL-181 metal tape and mastic. Install duct blanket insulation that is covered with a foil or plastic vapor barrier over the ducts.Cover all seams that are wider than 1/8 inch with fiberglass mesh tape then apply mastic. Seal all seams and joints in the ducts with mastic.Wipe ducts to ensure they are clean and dry especially at seams and joints. (The DOE Zero Energy Ready Home program requires that heating/cooling system supply ducts be installed within the conditioned space of the home.) Design the home to include ducts within conditioned space if possible. Design a compact duct layout with short straight runs and minimal bends. ![]()
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