Duct Sealing:
All ducts must be sealed according to energy codes using UL 181-rated tape or mastic to reduce air leakage.
Supply and return ducts must be sealed from the equipment connection to the last register boot.
Sealing Methods:
Foil Tape (UL 181 Rated): Often used on rectangular ducts and high-pressure areas like plenums.
Mastic: Applied to duct joints and seams throughout the system, typically with a brush, and is ideal for sealing metal, fiberglass, and flex ducts.
Tape Application: Use a squeegee to press foil tape and remove air pockets for a secure seal.
Mastic can be applied indoors or outdoors and is water-based, fiber-reinforced, and UL 181 listed for code compliance.
Sealing Timing and Accessibility:
Ducts are sealed after installation unless specific fittings are inaccessible once installed.
Allow mastic to cure for 24-48 hours before performing pressure testing.
Duct Insulation:
Insulation is required when ducts pass through unconditioned spaces to prevent heat transfer or condensation.
A maximum of a 15°F temperature difference between the inside and outside of a duct is allowed before insulation becomes necessary.
Types of Insulation:
Pre-insulated ducts from manufacturers or foil-faced fiberglass insulation applied manually.
Insulation should be secured by lapping, stapling, and using foil tape to prevent moisture entry, and the backing serves as a vapor barrier.
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