I got some basic ideas from Martin’s fine article here: http://www.finehomebuilding.com/design/departments/energy-smart-details/insulated-skylight-shaft.aspx

Armed with that information, I am contemplating some various methods to re-insulate and seal several skylight shafts in my attic. These shafts were originally insulated using faced fiberglass batts that were somewhat haphazardly installed. After 18 years the strapping has deteriorated, and some of the batts have turned away from the sheetrock. And as can be seen in the photos, there are areas where the exposed sheetrock is clearly visible.

One thing that makes it all a bit disturbing is that the framing for the shafts were done “on the flat” instead of on edge, resulting no real cavity to house the batts properly.

In my case the options I’m considering are as follows:

1. Keep the fiberglass, and fur out the framing to accept the full width of the batts without compression. I would then cover the batts with rigid foam board of some kind, and air seal the whole assembly.

2. Do away with the fiberglass, and install pieces of foam board in the 1 1/2″ spaces provided by the “flat framing”, then cover the entire framing with layers of rigid foam board of some kind, sufficient to give me a respectable R-value. And I would air seal the whole assembly.

3. Do away with the fiberglass, and have the shafts sprayed with closed cell foam. Sounds like the easiest and perhaps the best method. But surely the most costly I would think (?)

I am aware of the possible code requirements for a fire barrier for the foam board in these first two proposed methods of installation. I’m checking with a friend who is an inspector for a definitive answer on that for my locale.

Any opinions would be greatly appreciated! I’m sure there are things I haven’t considered.

I’m in Zone 2 BTW….