Wood burning stove and flue install

[ProDave]

The last few days has seen me installing the flue for the wood burning stove.

 

First put up some scaffold and remove a few roof tiles

 

 

Cut a hole and put the flue through the roof, shown here after the first row of tiles was put back.

 

 

It is worth noting some detail.  I wanted to retain as much air tightness as possible, but flamable materials (the wood fibe sarking board) must remain 6cm from the flue pipe.

 

Solution:  An insulated sleeve. Obviously this is made of non flamable material, and is >6cm thick so this can be made a snug fit through the wood fibre, and any gap sealed with foam.

 

 

Here is the flashing on and tiles put back

 

 

The flue then runs down through the bedroom, down through the kitchen into the stove.  The cover plates cover up the holes that are at least 6cm larger than the flue in all directions.

 

 

 

 

And the test firing

 

 

And now a few questions:

 

I am going to need a heat shield plate up behind that flue downstairs.  Does anyone know where I can buy one that does not cost an arm and a leg? (seen prices of about £250 so far)?

 

And I expect the bedroom with the flue pipe is going to need a CO alarm. Are there any regs saying how close to the flue it needs to be? In particular with the flue going so high up the room does the CO alarm need to be that high? (Is CO lighter or heavier than air?)

[Declan52]

I used some of my stone cladding to put behind my stove.  Something like that or a  tile wouldn't be expensive. 

[ProDave]

The heat plate does not need to go behind the stove, that is rated to be only 100mm from combustibles.  It is the plain single wall flue.

 

This tells me I must have a non combustible shield but crucially with a 12mm air gap so can't use tiles.

 

[Declan52]

A piece of cement board attached to the wall but with a 12mm spacer(bolt maybe) to keep it out from the wall.  Then tile or whatever over it. 

[Russell griffiths]

Are you happy with that so close to those kitchen units, my wood burner would have that decor panel screaming out for help after a couple of nights, also the underside of the worktop

i don’t know if yours is more insulated than mine, but anything within 600mm soon becomes to hot to touch. 

[ProDave]

The stove is a convection stove with baffle plates on the side and the back, it is rated for 100mm to combustibles at the back (I have 150mm) and 150nn to combustibles at the side (I have 200mm)  The decor panel is just warm to the touch.

 

The overhanging worktop is temporary, that worktop and sink will end up in the utility room (hence why it is left over length) and will be replaced with a stone worktop.  I have fitted a metal plate under that worktop to protect it and it needs keeping en eye on, it would not pass building control like that.

[ProDave]

30 minutes ago, Declan52 said:

A piece of cement board attached to the wall but with a 12mm spacer(bolt maybe) to keep it out from the wall.  Then tile or whatever over it. 

That might be a good solution.

[MikeSharp01]

Tidy work, I wondered what the roof work was in one of your posts over the weekend ranting about the weather forecasts!

 

 

[Alexphd1]

Very tidy. We have a wood gasification boiler in the garage and underestimated the flue cost greatly?

[ProDave]

Just now, Alexphd1 said:

Very tidy. We have a wood gasification boiler in the garage and underestimated the flue cost greatly?

 

Yes, the flue cost more than the stove.

[dpmiller]

Looks neat, but is there not now a requirement for a longer length of twinwall to be through the ceiling, 450mm or something?

[Crofter]

I used cement board instead of plasterboard behind the stove, and the service void acts as the required air gap.

Being a little paranoid, I was worried that the airtightness/vapour membrane might at some point in the future sag and risk touching the back of the cement board, so I installed a second layer of cement board inside the service void as well- this ensures that the 12mm air gap will not be compromised.

[gravelld]

Doesn't the pipe in the bedroom get a bit hot - don't you need to guard around it?

[ProDave]

2 hours ago, dpmiller said:

Looks neat, but is there not now a requirement for a longer length of twinwall to be through the ceiling, 450mm or something?

I fear you might be right.  It's the 3 times diameter to combustibles rule for single flue pipe.

 

Easy to fix if I have to, insert an extra short section of twin wall above to push that twin to single wall adaptor down.  I might leave that as the "fault" for BC to find and fix it then.

[ProDave]

30 minutes ago, gravelld said:

Doesn't the pipe in the bedroom get a bit hot - don't you need to guard around it?

No it's barely warm to the touch, quite safe.  The rules say it has to remain 6cm from combustible materials but there is no way it is hot enough to do any harm.  You have to box it in if pt passes through a loft, but not where it passes through a room.

[dpmiller]

yup. from the BFCMA Install manual:

 

"Under BS EN 15827-1 the
twin wall system chimney
should extend 425mm
from the ceiling"

[PeterW]

There is no way that worksurface is 3 x D from that flue ..??? It’s a combustible so it counts in the regs - I’d be cutting it back in line with the cabinets. 

[ProDave]

11 minutes ago, PeterW said:

There is no way that worksurface is 3 x D from that flue ..??? It’s a combustible so it counts in the regs - I’d be cutting it back in line with the cabinets. 

I have already said that is temporary. That worktop and sink will be going to the utility room, that's why it is over length, as that's what is needed there.  It will be replaced with a stone worktop in the kitchen with no overhang and complaint with clearance distances.

[Crofter]

Those little Burley stoves are extremely efficient and have a flue temperature of less than 150degC, so the twin-wall section of flue is never going to feel dangerously warm. Of course the regs are all written with the worst case scenario in mind, where creosote build-up leads to a 1200degC chimney fire and a glowing red flue.

[ProDave]

Except mine is not a Burley, It's a Mendip stoves Churchill 5 convection model.  SWMBO thought the Burley looked too small.

 

The Churchill is only rated at 4.5KW so a small power stove for it's physically much larger size. Ducted primary and secondary air intake.

[ProDave]

The final bit arrived today, the 80mm aluminium duct to connect the stove air in to the duct going down under the floor (the first firing a dew day back was done with the stove drawing air from the room)

 

I was keen to see how it performed, and whether the warnings people have given that it will overheat the room and I won't be able to get in for several days were true or not.

 

So this morning I light the stove and kept it burning for somethng like 5 hours.  I was running it at a fairly low load, but enough to keep the flue gas temperature high enough, so a reasonable burn, though no doubt at less than it's 4.5Kw rating.

 

When I light the stove, the room it is in was at 20 degrees having been kept there by the UFH.  It's in a reasonably large room, 5 by 7 metres, but this room opens by double doors onto the stairwell, and double doors the other side of the hall to the snug living room.  All bedrooms open from the landing above.

 

When I stopped loading the stove the room it was in was up to 24 degrees, and the snug living room the other side of the hall up to 23 degrees.  The bedrooms had all risen about 2.5 degrees in the process as well.

 

So no we didn't overheat or make the room unusable, though if you shut the door to that room and stoked the fire up, it would be easy to do so.

 

So the conclusion is managed properly (treat it as whole house heating with all the doors open and don't burn it too high or too long) then it is a perfectly usable source of heat. Particularly so as generally we get all our wood for free.  24 degrees is not "over heated" but warmer than we would pay to heat a room.

 

The ability to quickly get more heat upstairs is useful as we had been finding the heat transfer to the unheated bedrooms is not quite as good as I had hoped and I was starting to get complaints that our bedroom was down to 16.7 degrees.  It is now back to over 19.

 

The temperature today was 3 degrees outside so I would only expect the stove to get use when it is this cold or colder.

 

If we wanted to with careful management, I am sure this one stove would heat the whole house with no other heating input.

 

The original plan of having a second stove in the snug living room has been shelved, the one stove heats the whole house so no need for more complication end expense (plus installing a flue for that one would be a bit harder)

[Declan52]

I find the same with mine.  Keep it at a nice glow and open the doors to my kitchen Sunroom and to the hallway.  I had mine lit on monday and haven't needed any heat since.  

But if I'm not at home and the wife closes the doors the room can quickly get to 30+.

[joe90]

Yup, me too, took a while to get used to it and I do find mine does not draw as well as I expected but it warms the lounge (door to hallway open) nicely, not overheated yet. I also have bifolds out to a sunroom so could disperse heat that way if necessary.

[JamesP]

On 19/11/2018 at 13:52, ProDave said:

It is worth noting some detail.  I wanted to retain as much air tightness as possible, but flamable materials (the wood fibe sarking board) must remain 6cm from the flue pipe.

 

Solution:  An insulated sleeve. Obviously this is made of non flamable material, and is >6cm thick so this can be made a snug fit through the wood fibre, and any gap sealed with foam.

 

Great work Dave. I need to fit a flue through 40mm Pavatherm and then Tata steel roof soon. Have you just used some taped Rockwool as a sleeve?

Do you know what distance the stove / flue needs to be away from flammable material, thanks for your help.

 

 

[ProDave]

In my case the flue came from flue-pipes.com  It has to be 60mm from flamables.  That sleeve was sold by the flue manufacturer as an insulated wall / ceiling sleeve so made for the job, you cut it to the angle of your roof, 45 degrees in my case.  It is a hard sort of rockwool batt type material.

 

Obviously as it is sold for this purpose by the flue manufacturer, it is a non flamable material, and as it's >60mm thick, it is okay for flamable material to touch the outside of the sleeve as that flamable material will be >60mm from the flue.