[wdlanger]

I am going to be insulating a sunroom in the Seattle area. The roof is 2x8 and the walls 2x4. I can get more than code insulation in them by using Thermasheath polyisocyanurate rigid foam panels, even though it is wicked expensive. I want the room to be warm -- it has, of course, lots of windows and glass -- and safe.
Code says that rigid foam must be separated from a potential fire source by 1/2" sheetrock, or similar non-flammable material, which is fine for the walls, but I want to put beaded fir 1/2 X 4 on the ceiling. That's not fireproof. Does anyone have any idea for a fire barrier which I can put up over the rafters after the insulation is in, to which I can nail the beaded fir?

 

[DeckPros]

You can use fireboard attached to the rafters. Then nail the T&G w. 2.5" nails.

But honestly, if you have that much glass in the room, is going overboard on the insulation going to be worth the added cost?

 

[wdlanger]

Well, that's a very valid question; let's just say that I'd like to compensate as much as possible for the low R-value of the glass with good energy-efficient walls. Also I really like to meet or beat code. It might be that I have to put fireboard up under the beaded fir, but if I do that then I may just forget the beaded fir and think about an appropriate ceiling color.