Electrical – C-rated recessed lights come in contact with sheet plastic

IC or Insulated Ceiling or Insulation Contact are required for can lights that touch the insulation. You cannot use a non-IC can by moving or cutting the insulation back the 3 inches required to use a non-IC can. Inspectors see insulation and they expect to see the silver cans, which is what an IC can would look like. The airtight cans are designed to use a cone that you would snap the socket into and peel of supplied foam gaskets to make the can airtight. On any other can you look up and see the inside of the can, and on airtights you look up and see only the trim and bulb.

Airtight cans can be IC and non-IC. The design of the cans and the gasketed trims help keep air conditioning or heating from leaking out of the home through holes in the can.

I guess overkill is appropriate and what ever the code calls for in your area is what is necessary. The prices should not be much different and even in areas like where I live, the ATIC cans are a little cheaper than the IC cans, and the same should hold true on the non-IC cans. I suggest using the airtight because it will make your house tighter.

Airtights come in new construction and remodel cans both 4 inch and 6 inch. Low-voltage 4 inch cans do no have an ATIC remodel can though, just non-IC and airtight.

Remember that the lamps and trims used in the Non-IC cans might not be rated for the ATIC cans. You have to give up some heat and that will come from lamp wattage. The inside of the can should tell you what you can use.

Good Luck

Edit 8/27/2016: Now with the new LED cans you can get 4 inch retrofit ICAT rated can. Actually on most LED cans, they are mostly ICAT cans, because of reduced wattage. With the exception of some dimming quirks, which has nothing to do with the cans, unless you are matching existing, I would go with LED.

Again, good luck.

I'm looking at doing the same thing in my house later this year. But, I want to emphasis that drilling through your windows/window frame can void your warranty. If these are new windows, you'll want to have that warranty in place just as an "what if" happens in the near future. You'll have to refer to your warranty documentation to see if drilling will void your warranty.

The Ademco 3/8" Diameter Miniature Press Fit Magnetic Contact looks pretty standard. Just to be on the cautious side, you can always measure your frame to see if you have enough space. Otherwise, I see no issues with installing these on your door and the frame. Also, I've seen them installed on the top of the door or the side of the door. That's your call.

You may want to re-consider and utilize non-recessed/surface mounted contact switches for your windows and its frame. First of all, research more about your windows. If they contain spring mechanisms in the inside of the window or the window frame, then you will not be able to drill a hole. Otherwise, if there are no physical obstructions, then you can normally drill the required diameter near the bottom of the window. You want to make sure that the hole is covered and not exposed to the outside environment. If exposed, you could use some sealant to protect the contacts. Also, if your windows are double-hung, you'll need contacts installed at the top and the bottom of the window. You can connect the two contacts in a series so that you don't have to run two sets of wire to the control panel.

All the recessed options you provided are for different scenarios of windows/doors. Normally, regular sized contacts are used except where these sensors may be too large to fit the door or window frame. Stubby contacts would be used in such occassion. The stubby/earth magnet contacts are great for window applications because of the size of the magnet (depending on your window type, you may not need to drill into your window to fit the magnet).