Since when has having a chimney been compatible with having a high performance home.....

Can you model it in PHPP? Are you modelling it?

effciency at what? Drawing away combustion gases? minimising heat loss when the stove is not in use?

All the above. No I am not modelling in PHPP. Mine is a more laid back approach, I know some of you will disagree but my attitude is a practical approach rather than a clinical one.

Perhaps I will look at the PHPP. The flue is to be insulated with Leica and the stove a room sealed one with outside air source and very good efficiency.

Are you building a new chimney or lining an existing?

What about stainless steel liner or chimney. The higher expansion/contraction and smother surface of SS means that deposits are less likely to collect on the liner. If it is a new chimney the prefab. SS chimneys hang off the joists and other timbers so don't need foundations etc. and are quicker to install so can work out cheaper. (I've one one DIY in a weekend easily)

Joe, if the outer structural chimney is masonry of some description I'd be inclined to build the inner flue with clay liners;--I don't remember them being expensive;-- and then fill between with vermiculite. At construction stage?? you can decide on the gap and hence insulation thickness.

Joe, my understanding is that a better insulated flue will help slow the inevitable cooling of the 'smoke' going up the chimney, which then helps limit the build up of oily 'gunge' in the chimney.

We have two squirrels heating our house (sole source of heat, apart from 'occupancy'). Both (new-build brick) chimneys were built using Isokern pumice liners with very well-packed 'vermiculite concrete' (1-1 cement mix - not too wet, mix a bit like screed) backfilled around the liners. The flues are regular stove pipe to a 2.5m ceiling, then 6x 600mm liners. We burn well seasoned wood and Homefire when we want heat overnight (i.e. Homefire will keep the stove temp at around 100 c all night).

Swept one of the chimneys this morning, for the first time – it’s been in use since autumn 2014. There was very little soot - about half a supermarket carrier bag of dry dusty black stuff. Presumably, this indicates that the flue is working well?

Hope that helps.

Joe,
I too went for Isokern pumice, but in the form of double blocks like Muddy I think (DM36 and have a few spare now). The only thing I wish I had done is spoken to a HETAS engineer prior to deciding the location of the stove. Simply moving the flue 4 inches into the room away from the external wall would have made things a lot easier and cheaper to connect to.

I ended up with a stove that has an external air supply, though we have not connected this yet as HETAS engineer and BC were insistent on an external vent to the room, which cannot be closed and don't see the point in having another hole - may change my mind after a year or two of use, will see how things perform.

Also if you have not got the stove yet, consider the following:
- What size flue does it need
- do you want a choice of wood or solid fuel - if not maybe stick with just a woodburner
- do you want an external supply to the stove - talk to HETAS Engineer and/or BC to establish if alters need for external vent to room (most likely it won't)
- think about sweeping the chimney/flue - unless you have lots of room, it will be cheaper to sweep through the stove - ensure you can do this.
- if you can check a source of wood to burn and establish what size logs they produce and buy a stove that takes that size ( or at least you know what you are in for :-)

- I eventually found a great HETAS engineer, though first few were either utterly useless (and very expensive) or never called me back. Eventually got it fitted, with vent and parts (about 2m double insulated and 2x30deg bends all for £825), which is about what it would have cost just to get the local BC officer to inspect it, had I done it myself.

All the best

It has sometimes been customary by some builders to put a couple of 45/135 degree bends in such flues. I'm not sure if it makes a difference, or indeed if your architect has drawn it as such already. It may be worth while investigating.

Our stove stands to the side of the chimney in a recess. The bottom end of the flue has a 45 degree bend so the 225mm diameter pumice liner comes out of the side of the chimney. Then it goes into a SS funnel down to 150mm stove pipe. Then another 45 degree bend to get it vertical again. Then into the top of the Clearview stove. All hidden in a wall that's as thick as the chimney. The space in the wall the other side of the stove is used as a cupboard in another room.

My builder did the chimney and liner and I fitted the SS funnel, stove pipes and stove. The BCO didn't ask me to get a Hetas engineer involved. Nor did he spot I didn't have the little wall plaque.