Twin Wall Flue Price - Ouch!

[Wendelspanswick]

I'm installing a new wood burner with back boiler into the barn and I've just been pricing up some 6" stainless twin wall flue.

Why is it so expensive!
I need an inspection door, 2 x 30° bends and about 3m of straight pipe and I'm looking at about £500.
I've got my eye on some used stuff on eBay but if that falls through I may have to rethink my plans and use stainless single wall to get up to ceiling height and then change to twin wall which should save me about £200, the only problem with that is I'm worried that the building is so well insulated the single wall will put out too much heat.

 

[slim_boy_fat]

the only problem with that is I'm worried that the building is so well insulated the single wall will put out too much heat.

To save £200, just open a door.

 

[gaz1]

if i had my way id use single wall and just buy 3m galvanised tube then put shims to space the stainless flue away from the galvanised pipe

dont forget twin wall is there just to insulate the building from the heat of the flue nothing more

 

[Wendelspanswick]

if i had my way id use single wall and just buy 3m galvanised tube then put shims to space the stainless flue away from the galvanised pipe

dont forget twin wall is there just to insulate the building from the heat of the flue nothing more

Your last statement is completely wrong.

Twin wall is also to help the chimney draw by keeping the flue gases hot and more importantly to protect the fabric of the building.
Twin wall can go as close as 50mm to flammable surfaces whereas single wall has to be 3 times the flue diameter away, so 150mm single wall needs to be at least 450mm away from flammable surfaces, that's a big difference!
It's all in the building regs.

 

[gaz1]

twin wall is to stop the build up of creosote build ( wood fires ) up by using a twin wall system you are keeping the flue hotter by also aiding in the draw of the flue gasses as it rises

the statement was half right

 

[Burdekin]

Try Greymetal.co.uk

 

[addjunkie]

Ive had the same heart attack for my shed.

I looked here, cheaper than some

https://www.flue-supplies-uk.co.uk/Convesa-KC

 

[fixerupper]

Yes it's not cheap ...when I was installing wood stoves for a living my rule of thumb guide for twin wall stainless was £1 an inch... I don't know what its now .... ... and yes twin wall is used to keep the flue gasses hot to reduce condensation ....

 

[Burdekin]

Just read it's for your barn. Just use carbon steel for inside and double wall once it goes through the ceiling. This is what I did at the workshop with no issue. It won't radiate too much heat compared to the stove and being inside it will draw fine.

View attachment 119310

 

[Wendelspanswick]

Just read it's for your barn. Just use carbon steel for inside and double wall once it goes through the ceiling. This is what I did at the workshop with no issue. It won't radiate too much heat compared to the stove and being inside it will draw fine.

View attachment 119310 View attachment 119311 View attachment 119312

Looks good, is that the grey european type flue from grey metal?

 

[Burdekin]

Yep, all from Greymetal. Also a very helpful guy so if you have questions it's worth giving him a call.

 

[julianf]

Wendelspanswick -

Ive done a few installs, and would always buy selkirk 2nd hand. If you plan ahead, it comes up on ebay for a fraction of what it costs new.

The reason i specifically say "selkirk" is that you can buy a bundle of used flue, and, if your missing one specific part, you can always (re-mortgage your house) and buy it new.

Also any spare parts are saleable. Try selling a single part of some other brand, and it wont happen.


Ive been selling grant flue for a while now. The one (single) part i wanted was something like £400 (rrp) - i purchased a load of liquidation stock (£75) that included what i wanted, and have been flogging the rest on ebay. I broke even on the 2nd sale...

 

[W.olly]

Yes keep an eye on Ebay, i got enough sections and cap of there for the full house height ( twp floors plus the extra meter or what ever needed above the gutter ) for £100, had single skin to the twin when it went through the roof though.

 

[postie jon]

ours is twin skin from the stove up through the vaulted ceiling to the chinese hat outside, 5 lengths in total ,u cant even touch the second section for heat, was burning earlier tonight at 500 so had to open the stove door to let it cool a bit.

 

[Wendelspanswick]

The stove I've bought puts out 5KW to hot water and 3Kw to space heating but the barn is so well insulated I'm using it at the moment with no heating and I haven't even put any double glazing in yet, it's just got corrugated plastic over the appetures.

 

[Wendelspanswick]

Thanks for the tip from @Burdekin I managed to get all the bits I need from greymetal.co.uk without having to drop my pants too far!
It was worth it though.

 

[julianf]

Here's a question for you -

I was just checking the distances in doc j for a log burner install. It will be easier to do the flue if i put it against a studwork wall (plasterboard over timber) than a stone wall, but i suspected the clearence would need to be large.

But doc j says "at least 150mm or to a suitable heat resistant wall"

the or makes me think that you can put a burner right up against a stone wall (fair enough) and that you only need 150mm to any other wall.


....which, to me, seems a bit on the slim side, considering the (ive not looked it up today) (X) multiples of the flue diameter to combustibles thing.


Im asking you as, in your photo, it looks like youve got plasterboard over timber studding, but it looks like somthing else is set to go directly behind?


Anyhow, what's your understanding of the regs with regard to this?

 

[Burdekin]

I can't remember the measurements but I use cement board from B&Q. Doesn't get hot.

 

[addjunkie]

With twin wall its only 50 mm air gap from memory

 

[Wendelspanswick]

The stove manufacturer states 200mm from a flammable surface and doc J states 3 times the single wall flue diameter.
The twin wall states 60mm from a flammable surface.
I've got a sheet of cement board to go behind the stove and even though I've got 200m between the stove and the wall I was concerned about the polythene vapour membrane being in close contact with the boiler pipes so I shoved a sheet of cheap radiator foil/foam over the polythene.