BASC Search | Building America Solution Center

Wrong - Flex duct is improperly attached and sealed to duct boot.

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RIght - Seams in duct boot elbow are fully sealed with mastic.

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Right – The round metal ducts are sealed with mastic at all joints.

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Right – These duct take-offs are well sealed to the branch duct

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Wrong - Duct seams were sealed with regular duct tape which has failed to hold; seams should have been sealed with mastic or approved metal tape.

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Technology Solutions Case Study: Duct Sealing Using Injected Spray Sealant

Case Study

Case study describing the most cost-effective ways to reduce duct leakage in low-rise housing units.

Wrong – Duct is pulling away from floor because it is not sealed to floor

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Wrong – Duct is pulling away from ceiling because it is not sealed to the ceiling

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Wrong - Duct juncture seam should be sealed with metal tape or mastic.

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Right - Duct runs are straight with gradual bends; joints are well sealed.

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Right - The duct shows redundant sealing including the caulk, tape, and flashing

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Right – Metal or fiberboard duct is mastic sealed at junction with duct register box

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Right – Penetrations have been neatly cut and properly sealed with foam

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Wrong – This ductwork is not sealed where the round duct is attached to the square duct riser

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Right: A well-constructed air handler closet

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Air Distribution Retrofit Strategies for Affordable Housing

Reference

Report describing two retrofit duct sealing techniques - manually-applied sealants and injecting a spray sealant, that were implemented in several low-rise multi-unit buildings in North Carolina.

A technician assembles the spray sealant injection system to seal HVAC ducts from the inside

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The duct sealing spray injection system application tunnel inflates as the injection system operates

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Right – This register is sealed for a final test and the duct test pressure is being monitored at the register

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Building Science Introduction - Air Flow

Information Guide

Information guide describing the concept of air flow in residential buildings and its effects on occupants, building durability, and efficiency.

Wrong: The door and filter were removed, allowing unfiltered air to enter the air handler leading to premature failure of the system due to dirt accumulation.

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Right – Flex duct is properly connected to metal duct with a duct tie and connection is mastic sealed

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Compact Air Distribution

Guide

Guide describing design and installation of compact duct systems for central heating and cooling systems.

Wrong - Metal tape is poorly adhered and metal duct and duct-to-subfloor seam is not sealed.

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Duct boots sealed to floor, wall, or ceiling using caulk, foam, mastic tape, or mastic paste

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The duct sealing spray injection system includes a blower/heater (background) and the sealant injection unit (foreground)

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All of the ductwork for the efficient (8.5 HSPF, 15 SEER) heat pump is mastic sealed and installed in conditioned space.

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Seal seams in fiber board ducts with out-clinching staples, UL-181A-approved tape, and mastic

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Novel, Simplified Air Delivery System Design Gets Commercialized

Reference

Fact sheet describing a novel, simplified air delivery system using a plug-and-play model that features 3-inch diameter flexible ducts, efficient fittings, and a simplified installation process that resulted in successful market engagement through commercialization.

SMACNA HVAC Air Duct Leakage Test Manual (first edition)

Reference

Manual that identifies certain leakage limits for ducts and outlines procedures for testing ducts for conformity with air leakage limits that are set forth in a designer’s project specification.