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How to Use Insulated Can Lights in Ceilings

How an airtight recessed fixture saves energy and protects your roof for optimum cathedral ceiling lighting.

FH05SEP_CANLIG_01-2Family Handyman
Use airtight recessed lights in a cathedral ceiling to prevent heat loss, moisture problems and roof rot. The fixtures are inexpensive.

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Avoid heat loss with cathedral ceiling lighting

Recessed light in a cathedral ceiling

Recessed lights often leak warm, moist air against cold roof sheathing, which eventually causes roof rot. You also lose a lot of heat.

If youre concerned about heat loss through your recessed lights in a cathedral ceiling, turn off the light, unscrew the bulb and remove the trim to check the label inside. Your fixtures arent airtight unless they have an airtight rating. But dont simply plug the holes to make it tighter (see photo). Manufacturers submit fixtures to Underwriters Laboratories (UL) to receive a safety rating for their designated use. (Youll see a UL rating somewhere on the fixture.) Altering the fixture in any way may compromise its margins for safety.

This is a real issue. Recessed lights in cathedral ceiling lighting waste the heat from the light bulb and the warm air that leaks through the fixture. Even worse, moist, warm air will flow up against the cold roof sheathing (see photo). Chances are that itll condense there, wet the wood and eventually cause rot. Unfortunately, there isnt any easy way to know if you have moisture problems and rot until you find water dripping from the vaulted ceiling recessed lighting, stains or soft spots in the drywall. The fix is expensive.

Builders often try to prevent the problem by leaving a 1- to 2-in. airspace for roof ventilation. Roof venting can help dry the wood again in warmer weather, and itll flush out some of the moisture in cold weather. But it often doesnt work well.

The best solution is to avoid putting any recessed lights in cathedral ceilings. However, if you want them, use type IC airtight fixtures (available at lighting stores and home centers). These fixtures are sealed to stop airflow. In addition, they have gasketed edges to seal them to the drywall.

Replacement can be challenging. If youre lucky, you can pull the old mounting bracket out through the existing hole. Otherwise you have to tear open the ceiling. We recommend that you hire a licensed electrician for this tricky job.

Vaulted Ceiling Can Lights: Airtight Recessed Fixture

Airtight fixtures will be labeled. You can use a remodeling type to replace non-airtight fixtures. Usually they will be IC rated (insulation contact) as well.