new supervent install question

[grokcam]

Hi, new to the forum, thanks for such a great resource. I'm installing a supervent chimney and I'm a little confused. The installation instructions call out for heat shielding @ joists / rafters which makes sense. However they don't elaborate on the immediate location of the decorator ceiling support (in my case a flat ceiling). It doesn't seem to offer much joist protection. The instructions do indicate the attic heat sheild can be used w/ the ceiling support in the case of an attic immediately above but doesn't elaborate on my situation of a living area directly above. I called Selkirk and they said the ceiling support provides enough protection but I find it hard to believe as it is just 4 fastening straps from the looks of it. The joist shield is never called out in conjunction with the ceiling support. I'm sure one of you guys is a wiz with this system. Any help is much appreciate.

 

[Z33]

I just installed this same system last month.

Before I hung the sheet rock back up around it I checked the joist for a week with an Fluke infared thermometer. The joist never got more then 10 degrees above ambient.

If you think about it it make sense. The ceiling support has Class A sitting in it and an air gap between the chimney and the support box which I am sure acts as shielding.

 

[webby3650]

It this situation we use the cathedral ceiling support. The box is 18" tall, it can be trimmed down to fit the space between the floors. You can even bend 1"ears on the top side and hang it from floor above. We cover the hole with a firestop and a SS cover plate for looks.

 

[grokcam]

So Z33 you just used the round ceiling support with no shield, joists exposed? I would like to stick with the round ceiling support as I like the look better but I could see the cathedral box providing all the necessary shielding. Looking back over the instructions it looks like the firestop joist shield mounts from below so it's 14 square flange would extend past the 17-7/8" of the ceiling support's trim flange so that wouldn't work. I might just install the attic shield for piece of mind as it mounts from above and is telescopic for the joist widths. BTW does does anyone know if there is a difference between the "decorator ceiling support" and the "decorator ceiling support-spun" besides cosmetics?

 

[Z33]

So Z33 you just used the round ceiling support with no shield, joists exposed? I would like to stick with the round ceiling support as I like the look better but I could see the cathedral box providing all the necessary shielding. Looking back over the instructions it looks like the firestop joist shield mounts from below so it's 14 square flange would extend past the 17-7/8" of the ceiling support's trim flange so that wouldn't work. I might just install the attic shield for piece of mind as it mounts from above and is telescopic for the joist widths. BTW does does anyone know if there is a difference between the "decorator ceiling support" and the "decorator ceiling support-spun" besides cosmetics?

Yes sir, I didnt see the issue with it since its all class A that's anywhere close to the joist and I still have my 2 inches of clearance on either side of the pipe. In addition the ceiling support acted as a type of radient barrier between the actual pipe and the joist.