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Indoor airPLUS

Technical Guidance to the Indoor airPLUS Construction Specifications

1. Moisture Control

Sections 1.11 - 1.13: Interior Water Management

Best Practices: Recessed Can Lights

Recessed lights (can lights, high-hats) installed in insulated ceilings should be of the type rated as “insulated-can, air-tight” (ICAT), instead of standard recessed fixtures, and the housing should be caulked to the finished ceiling if no gasket is provided for the trim ring.


In cold weather, warm room air that enters an attic can condense on cold surfaces, wetting insulation and even causing mold to form. An ordinary recessed lighting fixture, such as a can light or hi-hat, leaks air when the light is off. It acts like a heated chimney driving air through to the attic when the light is on. ICAT-rated recessed lights help prevent warm air from entering attics. Attic insulation can contact fixtures rated IC (insulation contact) without the risk of fire, but fixtures with this rating alone are not sufficient because the units will not stop the flow of air. Fixtures must also be designated AT (air tight) to ensure a tight seal between the light can and the ceiling to prevent the movement of air up through the can.

Note: Some brands of can lights designated ICAT may leak air; check the fixtures you intend to use to see whether they appear to be well designed to be air-tight.


Look for the ICAT rating when selecting recessed can lights. Recessed lights installed in insulated ceilings should be of a type that allows insulation to be in contact with the housing, and the housing should be sealed to block the escape of conditioned room air into the attic above.

During installation ensure there is a tight seal between the recessed light can and the ceiling. The manufacturer typically supplies a gasket to help make this seal tight, but if a gasket is not provided, caulking the fixture to the gypsum can help.

Detailed Illustrations: Best Practice Techniques

Air Tight Recessed Light Rated for Contact with Insulation

Air Tight Recessed Light Rated for Contact with Insulation

(Click on the image for a full-page version)

References/Additional Information

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