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Avoid heat loss in a cathedral ceiling
If you’re 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 aren’t airtight unless
they have an “airtight” rating. But
don’t simply plug the holes to make it tighter (see photo).
Manufacturers submit fixtures to Underwriter’s
Laboratories (UL) to receive a safety
rating for their designated use. (You’ll 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 ceilings 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 it’ll condense there, wet the wood
and eventually cause rot. Unfortunately,
there isn’t any easy way to
know if you have moisture problems
and rot until you find water
dripping from the ceiling, stains or
soft spots in the drywall. The fix is
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 it’ll flush out some of
the moisture in cold weather. But it
often doesn’t 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 you’re 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.
Airtight recessed fixture, remodeling type
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.