National Fire Protection Code question

[jmarkwolf]

Exhaust vent question:

The structure is a detached 2-story garage.

The vent from my new Beacon-Morris furnace, hanging from the ceiling of the 1st floor, exits the back of the unit and will immediately turn upward to exit out the roof.

The vent stack will run vertically through the 2nd story behind the upstairs kneewall.

13.2.16 of the ANSI Z223.1-101 "Multistory B vents Required" states that "where used in multistory systems vertical common vents shall be Type B double-wall...

Is my 2-story garage considered a "multistory system"?

If so, is a "thimble" required for double wall, as it runs through the roof?

 

[LS6 Tommy]

If the vent runs indoors through that 2nd floor or where people can come into contact with it, yes.

Tommy

 

[jmarkwolf]

It'll be behind the knee wall, so no, people couldn't come into contact with it.

But now I'm thinking maybe I should just go with the double wall vent stack and appropriate fittings and thimble, etc. and call it good. The double wall system is probably more rubust and would need less attention over time correct?

Any reason the inspector wouldn't like a double wall vent stack, provided of course it's dimensioned, installed and supported correctly?

Would double wall vent stack require insulation as it runs through the un-heated space behind the upstairs knee wall?

 

[mygarageone]

no insulation required and no matter what you'll need to run double wall pipe all the way through the roof. With a 1" clearance around the pipe or you can use a thimble . The roof penetration you only need the clearance from pipe to combustibles and of course your roof flashing..

 

[frankush]

Clearance to combustibles is what the inspector is going to be looking for. The height of the stack, as determined by roof pitch is another.

 

[jmarkwolf]

Clearance to combustibles is what the inspector is going to be looking for. The height of the stack, as determined by roof pitch is another.

Do I understand the code correctly that there can be no "seams" in the vent stack within the building"?

I haven't measured the dimension within the building yet, but I'll need 3ft above the 12:12 pitch roof. If a 5ft section of vent pipe doesn't provide enough length, I can just add an appropriate length section at the top, as long as it's "outside" correct?

 

[Jackfre]

The rule is that once you go thru a floor or wall you must go to an approved vent material. That will be B-vent in your case. You need a 1" clearance to combustible and you should have a firestop going thru the ceiling. Thru the roof you can simply cut the sheathing enough to provide the 1" clearance placing the flashing to cover. If I was you I'd come off the back of the unit with a 6" piece and a tee with plug in the bottom and go B vent all the way.

 

[frankush]

Others would know better. but I see no reason why you can't join pieces together within the wall cavity. It's listed as a system and as long as you stick with the same manufacturer, you should be fine. I prefer to use the longest lengths I can whenever possible.

 

[Mustang51js]

Go to a plumbing supply store for the double wall pipe, I just di my furnace pipe after putting an addition on and I was thinking it's going to cost over $1000 for the pipe(20 feet). Supply house had it for $200 for galvanized. All the others I saw were stainless and ridiculous in price.