Insulation, Radiant and Vapor Barriers - Roof Insulation

I need to insulate a 9 square foot area over a small pop-out in my kitchen. Currently, there is insulation installed against the interior walls, but I need to remove this insulation and install insulation on the exterior/roof because I will be installing recessed lighting in this space. The recessed cans are non-IC, so I can't have a temperature difference in the space above, which is why I need to install the insulation against the outside wall/roof. My question is if it is ok to install insulation against the exterior of the roof? My second question is, if it is ok, why don't builders put insulation against the roof in the attic, but rather against the interior/ceiling wall?

They spray closed cell foam on the roof deck all the time. Why don't builders do it! Because they are cheap and do stuff half @ss. If you have two homes side by side one with spray foam one with fiberglass the one with the spray foam will cost thousands more but will pay for the upfront cost in a few short years. If I was you I would put the IC lights up and leave what you have in place.

Not going to leave it as-is because this small space wasn't insulated properly, so I will be reinsulating it properly (I hope). Please take a look at my drawing and let me know if I should place the insulation in the red area or the blue area (or both?). Since the recessed lights are non-IC and warm air will likely seep into this space, it seems like I should insulate the blue area. Any help/advice would be greatly appreciated. I'd like to take care of this today http://img24.imageshack.us/img24/189/popout.jpg

I've also heard that when insulating a roof deck, a minimum of 1" should be maintained between the insulation and the roof sheathing. Is this accurate? If so, I may need to use a styrofoam board insulation, which may work out better anyhow. If I do end up using styrofoam, how do I attach it (glue?). If anyone can answer my previous question, that would be great (insulate red area or blue area?). Thanks

As an alternative to cutting out the drywall and installing insulation, I think I may try to find a 4" remodel IC-rated can and hire someone to blow insulation through the holes. I'm planning on getting additional insulation blown in my attic, so I could have this done at the same time. Any suggestions?

Does it have to be recessed lighting? It would be easier to just install a regular light fixture and fill the space with fiberglass. That space you illustrated is tiny and would make working inside it difficult.

Yes, I am definitely putting recessed lighthing in that space. It will be used for over-counter lighting. I figured I would install one recessed can then blow insulation through the second hole until the space is filled. Does this sound reasonable? Also, since that space isn't ventilated, do I need to have a vapor barrier? If so, blown insulation may not work in this application.

If you do the blown in insulation you will need to have an IC rated fixture. It is difficult to find 4" remodel fixtures that are IC and air-tight (which is something else you want to look for).

Your other option is to get a new-work IC Air tight fixture, cut a work hole, then plug it back up.

Caulking under the fixture where it meets the back of the sheetrock is also a good idea.

You can use chopped fiberglass insulation and use insul-shield to protect the perimeter of your can lights. But your thermal boundary will have to either be the wall ( the 1.5 ft section) and the ceiling, or the roof deck. I would suggest the wall and ceiling combo....what kind of access do you have to this area???

A little too late to change plans. I already installed IC-rated recessed cans and cut a 6" square hole in the center of the ceiling to have insulation blown in tomorrow morning.

AWWWW.....well if you can't beat em'...

only thing is...if you are blowing in insulation...you need to insulate that 1.5 foot portion of wall above the lights....that area separates hot and cold...so in order for your space to be properly insulated...you have to insulate all the areas in red.

The 1.5ft wall was already insulated, so everything is good now. Thanks!