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Many energy codes require that ductwork installed outside of the conditioned space be sealed. Prescriptive codes have no performance standard for what constitutes an acceptable level of duct sealing. Testing and anecdotal evidence indicate that many new homes have extensive leaks on both the supply and return sides of the heating system. A field study of 29 recently built homes was conducted in the Spokane, Washington, area. Systems were visually inspected; all defects were documented and duct tightness quantified using duct testing equipment. Average duct leakage rates to the exterior were: - 406 CFM at 50Pa for normal code enforcement; - 395 CFM at 50Pa for aggressive enforcement of prescriptive requirements; - 687 CFM at 50 Pa where building cavities were used as returns; - 140 CFM at 50Pa when air handlers were located inside. The paper recommends improved sealing materials, avoiding locating systems outside, and using building cavities as returns, and it stresses the importance of performance-based testing standards.

Units: I-P