All fuel vent

Bob Harper_2

If you must vent up the outside of the building, you want an insulated solid packed chimney and not an air cooled triple walled one. Thermosyphon air cooled chimneys run very cool. Too cool. Yes, enclose the chimney inside a chase but be sure to maintain your clearances to combustibles. Most require a 2" clearance to combustibles. If this chase is insulated, be sure to sheath over the insulation so to cannot fall against the outer wall of the chimney. The listed instructions will spell out how to ventilate the chase top so it doesn't overheat.
You should be able to get Metalbestos 316stainless factory chimney from most supply houses or an equivalent. If not, check with your local chimney sweep.

If you can get it in the diameter you need, type L vent is designed for oil. Pellet stoves use 3" and 4" L -vent.

HTH

Stan_5

All fuel vent

I'm installing a metal flue up the outside of my house. I have an oil-fired furnace and was wondering if triple wall All Fuel vent pipe would be the best choice. The framing contractor is going to box in the flue. Should I be concerned with the heat build-up inside the chimney chase.

Brad White_171

I would use the triple wall all-fuel

chimney system especially in that it will be outside the heated envelope. All of those cold starts, you want to maintain your stack temperature. EDIT: To be clear, the type I am referring to has an inner wall, 2" insulation, an outer wall and an annular 1" air space.

Heat build-up is secondary and the triple wall will minimize that. Check the ratings. I believe (from memory) that the surface temperature should be no more than 95 degrees with 400 degrees (or some other specific) flue gas temperature.