Frame and insulate interior chimney chase or not? (pics)

[smokingtundra]

Hello all,

Thanks everyone for the great forum. I've done some searching, but haven't found anything that helps me with this question:

I just had a new 5" insulated chimney installed, as the old 7" one had several pieces that were rotting (old security chimney brand installed in mid 80's).

It is connected to a newer system 2000 oil fired boiler in our basement (hence changing it from 7" to 5"), which goes out the top of the basement wall, and up though a cold crawlspace, and though an 2nd floor addition to the house (which used to be the outside wall of the original house). The old 7" pipe went through large holes built into the floor and ceiling of the addition (no heat shield//ect...just large hole) with the chase being built with 2x4's and insulated with fiberglass (sheetrock on the inside and out). The old chase was much bigger than it needed to be, in part because of a plumbing vent tube that also went up to the right of the chimney. You can see in the picture how big the old chase was by looking at the floor tile & ceiling.

The new install has metal heat shield/box in the floor and ceiling now, and I've rerouted the ABS vent tube up behind the metal box to save space. I've framed in the hole in the floor, and am going to re-tile that area, as well as patching the ceiling drywall. My question is regarding the rebuild of the chase....the chimney installer said I should just screw the drywall directly it into the metal box that sticks out of the floor and ceiling--no need for insulation or framing, as it is just going to be decorative. Another person suggested framing around the metal box (which I'd rather not do to save on every inch of space in the small hallway I can), but I'm a little worried that if i don't, there won't be enough "meat" under the drywall to make it solid enough.

Now I am a little confused, and hoping I can get some idea's from the trusty old Hearth folks!

Thanks for ANY help here!
Mike.

 

[bholler]

I would frame it you could turn the 2x4s so they are only 1.5" thick to save space

 

[begreen]

No need to insulate. The simplest solution would have been to just run the protective chase duct from floor to ceiling and paint it. At this point I think I would just box it in with smooth-sided, paint-grade 1/2" or 3/8" plywood. Fasten a 1x1 cleat in the inside corners and use that to attach the face sheet. Cut the face sheet 1" less than the width so that there is a 1/2" edge and put in 1/2" quarter round molding to trim it out.

 

[smokingtundra]

Thank you for the suggestions! Using 1/2" paint-grade plywoood sounds like it would be a better idea than just the sheet rock. Today i'm going to tile in the space, and will start the chase tomorrow.