Insulation, Radiant and Vapor Barriers - Recessed lights and air leakage.
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rkoudelka
10-18-05, 01:42 PM
Let me start by saying that I am putting this same post in the electrical section also. 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.
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.
resercon
10-18-05, 08:47 PM
http://www.neo.state.ne.us/home_const/details/rcld.htm
You have to use IC rated canisters and even then that is not enough. The above webpage illustrates the correct way to install an IC rated recess light.
Forget about heat loss and energy savings. Failure to do what that webpage recommends promotes Ice Dams, roof leaks which usually causes delamination of roof sheathing. Worse case senario is rafters becoming saturated, freezing and then cracking. Coupled with delaminated roof sheathing, results in structural failure. Mold and mildew is considered a minor problem but is almost assured if the recess light is not properly sealed air tight.
You have to use IC rated canisters and even then that is not enough. The above webpage illustrates the correct way to install an IC rated recess light.
Forget about heat loss and energy savings. Failure to do what that webpage recommends promotes Ice Dams, roof leaks which usually causes delamination of roof sheathing. Worse case senario is rafters becoming saturated, freezing and then cracking. Coupled with delaminated roof sheathing, results in structural failure. Mold and mildew is considered a minor problem but is almost assured if the recess light is not properly sealed air tight.
rkoudelka
10-18-05, 10:36 PM
If you are using an airtight can, then the work is done for you.
Also, Ive done so many searches on this that I cant remember where I read certain things. Anyway, I did come across one web page (this MAY have been it but I am getting "server not found" now) where some electricians ran tests to test that method. It was very interesting, and very impressive - these clearly werent just a couple of DIYers playing around. They simulated environments and temperatures of attics and ran tests with different bulbs, enclosed gypsum board cases (like the one you linked to), and a few other things. They took temperature readings in all situations and did there analysis.
The conclusion they came to was that if a case like that is built it should NOT be covered with insulation. Without the insulation the temp was safe, with it, it was too hot. Im not sure what cans they used specifically, or if it matters - but it was very interesting.
In any case, Ill be using IC either way. My question is whethere I should use airtight (which is new construction) or just plan IC (which can be remodel and easier to install)
Also, Ive done so many searches on this that I cant remember where I read certain things. Anyway, I did come across one web page (this MAY have been it but I am getting "server not found" now) where some electricians ran tests to test that method. It was very interesting, and very impressive - these clearly werent just a couple of DIYers playing around. They simulated environments and temperatures of attics and ran tests with different bulbs, enclosed gypsum board cases (like the one you linked to), and a few other things. They took temperature readings in all situations and did there analysis.
The conclusion they came to was that if a case like that is built it should NOT be covered with insulation. Without the insulation the temp was safe, with it, it was too hot. Im not sure what cans they used specifically, or if it matters - but it was very interesting.
In any case, Ill be using IC either way. My question is whethere I should use airtight (which is new construction) or just plan IC (which can be remodel and easier to install)