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Air Sealing the Air Handler Closet

Guide

Guide describing the repair and reconfiguration of the air handler closet and platform when replacing the air handler.

Wrong: This return air plenum is not lined and air sealed

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Air Seal HVAC Cabinet Seams

Guide

Guide describing air-sealing of the seams and holes in HVAC air handler and furnace cabinets.

Air seal and insulate flex ducts

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No insulation installed in cavity and not air sealed

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Air Sealing Colorado Homes – 10.634

Reference

Fact sheet describing air-sealing concerns and remedies, including HRV/ERV installation, caulking, spray foam, and weatherstrip installation.

Wrong - Penetrations in walls for ducts should be air sealed to reduce air leakage.

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Right: Use mastic to air seal the return air plenum and to seal around refrigerant lines coming from the slab in the floor of the return

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Right: Air seal all seams in the return air plenum before installing a new air handler

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Cavity used for return is not insulated and is not air sealed, which will pull in air from outside

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The air filter slot on this furnace is covered with a magnetic seal.

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Manually seal seams in the air handler box with foil tape

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Wrong - The holes around the HRV ducting should be air sealed.

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Technology Solutions Case Study: Sealed Air-Return Plenum Retrofit

Case Study

Case study describing the retrofit of a leaky air handler.

Spray foam insulates and air seals the underside of the attic roof and walls.

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A ducted central return brings air from central return registers back to the air handler through insulated, air-sealed ducts

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Right: The bottom of the air handler cabinet is well sealed to the return platform

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Right - All seams in the HVAC equipment and ductwork are sealed with mastic; because the HVAC equipment is in the garage, it is an air-sealed closet.

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Measure Guideline: Air Sealing Mechanical Closets in Slab-on-Grade Homes

Reference

Document covering two fundamental retrofit strategies for air sealing around air handling systems that are located within the living space in an enclosed closet.

The grille in the photo on the left brings air into a return air plenum under an air handler platform. As shown in the infrared image on the right, the plenum is not air sealed so hot attic air is being pulled into the air handler closet.

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Right - Ducts and heat pump cabinet are properly sealed with mastic, high MERV filter is installed, and duct and refrigerant lines are air sealed at ceiling.

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Right – All of the cabinet seams in this HVAC air furnace are sealed with an approved metal tape.

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Fiberglass mesh tape is installed around a duct boot in preparation for air sealing with mastic

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Duct boot is air sealed to ceiling by covering the seam with fiberglass mesh tape and mastic

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Duct System Flammability and Air Sealing Fire Separation Assemblies in the International Residential Code

Reference

Report identifying two barriers that limit the ability of builders to explore opportunities for higher levels of energy efficiency in housing: the use of duct system materials that inherently achieve airtightness and are right-sized for low-load houses, and, the ability to air seal fire separation...