Single or double wall for high flue

Double is better than single, but moving 8-10 ft. horizontally sounds difficult to achieve unless you have a lot of head room. One thing I would recommend is that you put a T at the base of your vertical with a removable cap to make clean out easier.

I suspect single is OK as long as you can meet clearance distances, but that might be sticky with that long run. I think I would maybe try to get a manufacturers recommendation - any issues later (insurance etc.) would likely come back to that.

What is the composition of your outside flue? Too much cooling of the flue gases before they reach the top will cause condensation and create creosote in the pipe.

Siefert said:

There will be a clean out at the wall mount support going outside. I guess is could have a clean out inside too.

The reason I was thinking
Single was to let so heat bleed off in the basement. If that is a bad idea I'll just go with the double

Click to expand...

If the Heatpro is anything like it's smaller brother the Tundra - there will be plenty heat coming from the front/door/glass.

I see way more build up in my double wall connector pipe vs insulated class A. I'd hate to see what single wall would look like. Especially at 45 or 90 elbows.

I'd go double wall - it also lasts much longer than single wall because the inner is stainless.

You're jumping on a simple solution but I think your problems are going to run deeper than that. I would get a certified chimney installer to take a look at your setup and give his professional advice, it doesn't cost much for the pre-inspection and it could save you a lot of grief down the line.