Chimney flue/woodburner question . . .

[dangerousB]

Just moving into a new house and looking to install a woodburner.
I've had conflicting advice about fitting the flue . . . bottom line is, the new gaff is 350ish years old and has cob walls.
I've had one mate telling me it's essential to insulate the flue with vermiculite (he's got a cob property) and another (who hasn't, but is a mind of useful information) saying it's not necessary as an air gap is nature's best insulator and vermiculite insulation could impede the efficiency of the woodburner (cooling down the exhaust gases affecting the "draw").
Has anyone who's had any experience tell me which one of my mates is right??!! Cheers!

[Elskeggso]

Depends on the fitter - some insulate it, some don't. So long as it's HETAS approved/signed off according to building regs then there's nothing to worry about really.

[dangerousB]

Ahh, OK. It's not a particularly long run from the register plate to the closing plate, so I'm not sure it'll make much difference either way . . . just wondered whether cob needed any TLC with regards to the heat of the exhaust gases.
Cheers anyway!

[rovermorris999]

It's not the normal heat of the exhaust gasses you have to worry about, it's the potential heat generated if you get a chimney fire. I was chatting to the HEATAS chap who installed a twin-wall flue for me recently. He said the regs cater for 1000 degree C in the flue if it caught fire, hence the minimum 50mm gap between the flue and anything combustible.

[casbar]

Most fitters recomend vermiculite or similiar. Only dissadvantage, is if you ever need to replace the register plate, you'll have to get the vermiculite out and then replace it when fixed. I've cracked a couple of register plates