Airtight or just IC needed?

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  #1  
Old 10-18-05, 01:41 PM
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Airtight or just IC needed?

Let me start by saying that I am putting this same post in the insulation section. It applies to both sections and Id like input from both perspectives -so please dont think Im abusing the boards.

I am doing a cathedral ceiling and installing 4 recessed lights on a sloped ceiling. It is 2x10 rafters and I insulated with R30 and used baffles to keep an airspace.

Im not sure if I should use airtight cans. All the airtight ones seem to be new construction. These will be tougher to install the sheetrock after they are up. Its hard on to cut around recessed cans on flat ceilings , I can only imagine a lsoped ceiling.

Or do I use just plan IC so I can use the remodel. This way I can put the rock up and just cut ahole and fit the light in.

What do I lose by not useing an airtight can? Does it really allow that much hot air to leave the room? I have read that it does but I cant find anyplace to quantify it.
 
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Old 10-18-05, 02:50 PM
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It's a piece of cake to make a perfect cut around cans with a rotary cutting tool like a Rotozip.

I'd use air-tite cans. All the ones I've seen are also IC rated.

If you live in a climate where the inside temperature and outside temperature are significantly different for some of the year, air infiltration will increasing your heating and/or cooling costs. Air outflow also allows condensation to occur in the joist cavity, possibly causing mold and/or rot.
 
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Old 10-20-05, 01:02 PM
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I was on the phone with a woman from the place where I will get my lights and her opion was that if the light is covered in insulation then THAT is your air barrier in a cthedral ceiling since the insulation is tight against the baffle. Im not so sure - but maybe.

Here is my situation...

I have a cathedral ceiling. 2x10 rafters. R30 insulation with a baffle for airspace that is about 2 inches (so the R30 is compressed slightly).

If I put in an IC can (not air tight) will I lose much heat in this situation. I think that if I put a good thick layer of insulation above the can , so it is pretty tight against the bbaffle, I wouldnt lose any air - or very very little. I know isnulation shouldnt be compressed b, but I cant imagine a 6 inch section above a light where it is packed tight would make much of a difference.

The reason Imasking is because the airtigh ones are almost twice as expenseive!

If it makes a difference Ill open the wallet, but if I dont really gain anything by using airtight (compared to making sure my IC is covered well in insulation) no sense in getting the air tight.

Any thoughts?
 
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Old 10-20-05, 03:45 PM
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Most forms of insulation (except maybe closed foam insulation) is not a vapor barrier. Vapor barriers are always put on the warm side of fiberglass or celulose insulation. Otherwise, the insulation gets soaked by the condensation of the considerable moisture inside your home.

How much air flows through the holes in IC cans? Beats me.
 
  #5  
Old 10-20-05, 06:44 PM
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i got the airtight

I got the Ligtolier airtight anyway. The airtight vs non-airtight didnt even factor into it, the IC prodct with the wattage and angle i wanted only came in one type - air tight.

Plus, when I was talking to the guy in the store, he said code requires that I use airtight in a cathedral ceiling. he has heard of guys that had to replace lights whenthe inspector saw they put plain IC in a cathedral.

I didnt think it was code, but he probably knows better than me.
 
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Old 10-20-05, 06:51 PM
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Thanks for the report back.
 
 

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