I have a recessed light installed in a sloped ceiling - no attic space over it. On a cold morning when there is frost or snow on the roof and I stand outside the house, I can see a warm spot directly over where the light fixture is. The light has been off all night so I believe this isn't heat from a bulb - just warm air escaping. What are some good options for preventing this heat loss?

I don't know the model of can (I might be able to poke around to find it) so I don't know yet if it's IC-rated. It's 120V (no transformer).

EDIT: I haven't tried to pull the can down but with the bulb out I can see it's a Juno ICT926 which is IC-rated. I see Juno offers two products: the ALG6 (Airloc Gasket) which is a plastic ring and a VB6 (vapor barrier) which seems like it wraps the box. Is one more desirable than the other or more appropriate for this problem?

Recessed can light

4 Answers 4


if its ic rated i recommend roxaul mineral insulation over the fixture. if it is not ic rated or the rating cant be determined i advise replacing it with one that is ic rated and placing insulation over it.

  • "... no attic space... "
    – isherwood
    Dec 16, 2015 at 18:02
  • Many can lights can be replaced from the living area. Depending on how the box is attached to the structure, you should be able to get an LED replacement, look for "air-sealed", and use that. This will reduce some loss, and you can fill whatever cavity exists with insulation. You may not have much, but even an inch of insulation can do wonders. Closed Cell insulating foam will give you the best results, and a single can is pretty cheap.
    – ench
    Dec 16, 2015 at 18:41
  • @ench You should post all that in an answer, not in a comment.
    – isherwood
    Dec 16, 2015 at 20:52

Since you noticed this overnight, the most important vector for heat loss is going to be air circulating above the fixture.

There are retrofit kits available that can be installed from the living space. I would recommend getting one of these that is Air Sealed, and IC-rated. When replacing the fixture, you can insulate the space above it. There may not be more than an inch of space, but any amount of insulation will help, after the air leaks are fixed. Insulating spray foam (Great Stuff is one brand) should perform best, providing the highest R-value per inch and acting as a moisture barrier.

While you have access to the underside of the roof, make sure to check for mold or water damage. If warm air has been making it's way to the roofing, there may have been water build up. When insulating, make sure the bay isn't connected to a soffit or other vent, since that should not be blocked off.

If the bay where this light is situated is vented, then do not insulate it, and concentrate on air-sealing the recessed light fixture as much as possible.

UPDATE: It's also worth noting that LED fixtures can be shallower than older styles, and would provide more space for insulation.


This is going to be hard to do if you can't access the can from the top/outside and do what Arion recommends (or build an insulated box around it). What you can do in its current state is at the very least seal it. That will minimize convection losses, although it won't really help conduction losses.

To seal it from the inside, remove the bezel, if possible, and caulk the gap between it and the ceiling. Use high temperature foil tape to close any holes or gaps on the inside of the can.


The limiting factor will probably be the amount of space available between the can and the roof. If the can is just set up between rafters, there's not much you can do there - there's just no space for insulation. Even if the can light is rated to allow contact with insulation, there may be very little or no space for insulation.

A patch of radiant barrier insulation above the light would do some good, if you can install it safely above the light. If the light isn't IC rated, and the instructions / labeling tell you not to trap heat above the light, it may be that you just have to allow that heat to escape.

  • If the OP is losing heat overnight, a radiant barrier isn't going to do a lot. It seems much more likely to be due to air circulation past the can.
    – ench
    Dec 16, 2015 at 18:43

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