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Canned light, ic rated air tight and vapor barrier?

16 years ago

I will have 35 canned lights going into the ceiling of my home. The attic is on the other side of these lights. I live in Minnesota and code requires a vapor barrier. I will be buying an IC rated air tight canned light and I'm wondering what I can do to each fixture to provide a good vapor barrier/seal for heat loss. 35 is a lot so I don't want to spend too much time on each. I will be going with blown in insulation at r-40. Any thoughts?

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Comments (5)

sierraeast
16 years ago
Your concerns with the miniscule loss that cans can present leads me to wonder if you have other concerns such as hvac ducting, dryer vent, electrical outlets,etc. Imo, it's good to let a house "breathe" unless you have an indoor air purifying system because of indoor pollution due to a house being too tight.
jimonthebeach
16 years ago
HALO H7ICAT 6 inch Line Voltage IC Air Tight Recessed Lighting Housing can be had for $10 online (trim extra) and by definition, air tight will not leak conditioned (heated or cooled) air to your attic and IC means Insultion Contact so the light is it's own vapor barrier right up to its housing where you use whatever you were going to use for the rest of the ceiling and then pile the blown-in insulation over the IC can.

I think. Talk to your code department or GC.
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Regarding the comment: "An air tight fixture has no open holes to the above ceiling space." That's not quite true. We bought Juno air-tite IC cans in 6", 5" and 4" sizes for our new home. I can give you the specific model #'s if you want. My point is, I wanted true air-tightness, so being the curious guy I am, I took a 6" fixture apart. It was definitely better than the non-airtight variety, but it had plenty of punched sheet metal holes with assembly tabs inserted that resulted in leakage points through the inner can. The outer box had many more holes, but its purpose was to keep the insulation away, so holes can be tolerated in it. I'm not bad-mouthing Juno, I'm sure most brands of fixtures are this way, otherwise costs would be much higher. It appears the industry aim is to lower air leakage through light fixtures, not necessarily stop it. But, that wasn't my aim, I wanted leakage stopped. My wife and I set up a dissaseembly area and caulked the internal guts of the 6" and 5" cans to make them truly air-tight and then reassembled them. The 4" can internals were made from a one-piece deep-drawn piece of aluminum and thus had no holes - truly airtight. After drywalling and painting, I went to the effort of caulking the rims of all the cans to the drywall ceiling before installing the trim rings (they had no gasketing) to achieve a true air seal.
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I would remove them, close the holes, and replace them with surface mount fixtures.
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I think the guy with the old house air leak philosophy is basically saying it is important that the old walls be allowed to dry to the inside and the outside like they always have but that only works for sure in mild climates or if there is no insulation in a cold climate. With insulation installed in a cold climate, the interior side of the exterior sheathing becomes cold enough for moisture to condense against it before it can pass through to the very dry (in winter) outside. If an interior vapor retarder is omitted, the exterior sheathing must be highly permeable (no, I'm not going to say breathes) and that may be the case with old style horizontal boards or beaver/buffalo wood fiber board. Omitting the vapor retarder can sometimes work if all the other elements are right but I would add a coat of vapor retarding paint on the interior to slow down the passage of water vapor in the winter in rooms that have a lot of moisture. Think of water vapor as trying to equalize itself just like air pressure only incredibly slower. For me, the irony of all this is that interior air in old houses in New England is so dry, chairs are constantly falling apart so the idea that moisture would condense in a wall cavity is pretty far fetched except near a shower, a sink, a dishwasher, etc., or if the HVAC system has a really good humidifier.
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Problem Solved. I used a regular round trim that came with a lens....the kind you see in a closet. In fact I took the trim out of our closet! I popped a 75 EF bulb in. Its not very bright but casts a nice amount of light in the fireplace area and seems to block the cold. I had another option too...in fact I used it in the closet. It was a IC / Non IC shower trim kit. It is an airtight kit that comes with a samll glass bulb...sort of a mini mushroom. I had to bend the metal rods that pop into to the can that 'push up'. It was not a perfect match I guess. Also the socket for the bulb in my can does not come apart so I simply lowered it to the opening in the new kit. I believe it should all be safe and now I have a lot of light in the closet; again I used a 75W EF bulb. BTW, the closet can said not to insulate around it so I assume the can downstairs is the same.
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sierraeast
16 years ago
Insulated cans like any other can are not exactly air tight despite claims. The best your going to do is foam gasket around the perimeter where the cutout of the drywall will make contact. And as mentione above, the insulation,blown in or otherwise, can run up and over the housingon an ic can , providing uninterrupted insulation, but not air tightness.
rollie
16 years ago
IC rated means Insulation contact. These housings are anything but air tight.

AT means air tight. The IC housings become air tight when you gasket between the drywall and the housing, prior to hanging the ceiling. That takes care of that area of leakage.

Now, you need to address the actual leakage in the housing which is accomplished by using the air tight trim assembly.
The air tight trim assembly is a gasketed solid aluminum housing that you fit the bulb receptacle into. They will leak slightly around the bulb receptacle, but not very much.
thull
16 years ago
rollie- I was under the impression that the AT cans didn't need the air tight trim. I put in a few of the Halo's mentioned above a couple months ago, and my local HD didn't even have an air tight trim to go in them. They did have an air tight trim from Commercial Electric, but I skipped those figuring they might not be compatible. That said, the cans put in by our electrician a while back are air tight and have air tight trims. Since the air tight trims are a full cone, rather than just the baffle, they look better w/ the mini-twist CFLs we've installed.

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