Jacob
What goes around comes around.
Good point. Maybe just insulate through the top room, if not both.
Last edited:
Wood stove idea
- Thread starter Jacob
- Start date
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I did not open our flu/chimney, but had a uninsulated SS liner for our wood stove on the ground floor all the way to the roof and beyond up a 4M high chimney, I broke into the chimney in the loft and had a VMC box distribute hot air to all the upstairs rooms, worked well.
https://www.leroymerlin.fr/produits/chauffage-et-ventilation/vmc-et-extracteur-air/
This may be of interest:
Single flow VMC is the most economical system to install.
The ventilation system consists of a box and a system of ducts connected to the humid rooms of the house (kitchen, bathroom and toilet).
The humid air is thus extracted by the ventilation system. Fresh air enters through ventilation grilles generally located in the joinery.
Simple Flow VMC
In double flow VMC, stale air is extracted from the house by the ventilation system, but fresh air is also blown in by the VMC.
A heat recovery unit captures calories from the extracted air in order to preheat the air coming from outside.
A significant bonus, this system also allows the incoming air to be filtered in order to retain dust, pollen and other pollutants that can pollute the air in the home.
This system therefore makes it possible to breathe healthier air but also to save on heating.
Single flow VMC is the most economical system to install.
The ventilation system consists of a box and a system of ducts connected to the humid rooms of the house (kitchen, bathroom and toilet).
The humid air is thus extracted by the ventilation system. Fresh air enters through ventilation grilles generally located in the joinery.
Simple Flow VMC
In double flow VMC, stale air is extracted from the house by the ventilation system, but fresh air is also blown in by the VMC.
A heat recovery unit captures calories from the extracted air in order to preheat the air coming from outside.
A significant bonus, this system also allows the incoming air to be filtered in order to retain dust, pollen and other pollutants that can pollute the air in the home.
This system therefore makes it possible to breathe healthier air but also to save on heating.
Discover the VMC installation packages
-
Installation of a single flow humidity-controlled VMC
Access the service -
Installation of a self-adjusting single flow VMC
Access the service -
I did the 1st year of my apprenticeship with the CEGB at Bankside power station. The classroom/workshops were located in sheds in front of the main building. The exhaust gas “scrubbing” involved spraying with a chalk laden mist. The contaminated chalk slurry was collected in tanks then transferred to barges and dumped at sea.
All getting rather off topic now but couldn't resist! I worked on an industrial plant in Norway where the flue gasses from a certain process were 'scrubbed' with 4000 m3/hr of sea water, fed by two 22" pipes, equivalent to 1.6 Olympic pools an hour, a lot of water! The process removed the sulphur dioxide from the gas. The sales literature described how there was so much sulphur in the oceans that the additional was inconsequential. The comparison was based on all the sulphur in all the ocean water on the whole planet, rather than just the local fjord, quite a poor comparison as it turned out and one that the local fish population didn't endure so well!
That is a breach of the HETAS regulations, you are only allowed single skin pipe to within 450 mm of the ceiling at which point it has to transition to twin wall pipe for the rest of the way. The other important requirement is that you need at least 5 times the diameter of the single wall pipe to any combustable material which includes plasterboard which is not A1 fire rated.
I discovered most of this when a heating guy came out to give me a quote and turned what I thought was a simple job into a lot more because of the HETAS certificate he would have to issue.
Jacob
What goes around comes around.
I knew that but wondered if it could revert to single skin in the room above. Probably not but there's a fair amount of heat coming off the twin wall pipe so it helps with heating the room above. Having it black would help.
What set me off on this quest was house move pending and going to a talk by an architect about his conversion of a very ordinary house into a "low energy" house, with insulation, heat pump, solar panels etc. He'd got a wood stove with all the flue outside the building - a great shiny twin skinned pipe right up the gable end which struck me as a great waste of heat. Hence how to lose the least heat possible by having it inside and exposed.
No because you are only allowed a single transition and the single wall pipe is a much higher fire risk, the twin wall running through a loft has to be caged as well even though it is much less of a risk. This can be a simple frame and mesh or something brought but they do charge OTT. There is no reason not to run the twin wall internally though as long as you keep the distances and I dare say some shielding so combustables cannot make contact. Yes I much prefer the black pipe, looks nicer and when buying twin wall pipe I was told you can tell the better quality stuff because you can see the insulation material from the ends and it uses clamps. The other stuff you cannot see the insulation and it connects with a course twisting action. The issue with this is the inner and outer are bridged at each connection. The worst idea is when people use twin wall from the burner all the way with no stove pipe because as you say this gives of heat which is the whole point in the first place.
Agent_zed
Established Member
I might be mis-understanding Jacobs but I thought he was talking about opening the front of an exisiting chimney, which I would think would get around this problem. Although finding someone to sign it off might be difficult. Basically if you ran your flue pipe surrounded by brick on 3 sides you could cover the front with a sheet of steel that would act as a radiator. The single skin flue would be completely within a fireproof box. You could even put a vent top and bottom to allow more or less heat into the room.
having said that if you were going for a new install you could run the single flue as high in the room as allowed and put fins on to take more heat out eg 6 heat Reclaim / Radiator Fins 6 inch dia wood stove pipe flue stack exchanger | eBay you could then experiment with the amount of fins to ensure a good flue temperature. which would be a lot simpler. Only downside is having one really hot room.
I think his idea was to only use twin wall through a floor and then as much as possible as single skin which in theory does make a lot of sense because it would radiate a lot of heat, maybe to much. The problem with this apart from the potential fire risk is that you would lower the flue gas temperature which would effect the draw.
dannyr
Established Member
way back I lived for a while in Newfoundland Canada in - while modern homes had oil furnace/boilers, the older homes and weekend cabins mostly had woodburning stoves and it was standard to have a length of the steel chimney pipe running through the room - some even with a purposefully designed bend to get extra length - all to get more radiated heat - yes it took more attention to get the fire drawing but once it was going worked fine
note also that most were burning softwood (with some birch and aspen) - doesn't burn as well as ash etc burnt in UK
it was said that a winter's heating took as much volume of wood as the volume of building heated (often poorly insulated back then)
so J's idea is not nonsense even if there are many issues - I guess that's why he posed the question
note also that most were burning softwood (with some birch and aspen) - doesn't burn as well as ash etc burnt in UK
it was said that a winter's heating took as much volume of wood as the volume of building heated (often poorly insulated back then)
so J's idea is not nonsense even if there are many issues - I guess that's why he posed the question
Jacob
What goes around comes around.
Just working out how to make woodburning efficient. Size and dryness of wood top issue, design of stove next, then heat distribution from the stove and flue pipe etc.
The draw is important but even a long single skin pipe will draw well once started.
I've seen draw started by brief application of a blow lamp up the pipe from back of stove. Similarly with a handful of loosely screwed up newspaper etc.
Single-skin flue pipe is MUCH cheaper than insulated, so it's often preferred to use as much of this as possible within the same room as the stove. In cabins it's therefore much cheaper to use this to the ceiling (and it will also give out more heat, but I would guess the stove itself is the source of 95% of the heat, not the flue).
Once near/above the ceiling, it should be insulated pipe. I don't think you want to change to single-skin pipe in rooms above (even if HETAS allowed it) because it would be dangerous (would need some protection from fingers), and you'll probably have funny smells from burning dust.
In my experience (several wood burners) once there is a reasonable length of flue, the pipe doesn't really make much difference to how well the fire burns. Most important is a good stove and good wood.
Once near/above the ceiling, it should be insulated pipe. I don't think you want to change to single-skin pipe in rooms above (even if HETAS allowed it) because it would be dangerous (would need some protection from fingers), and you'll probably have funny smells from burning dust.
In my experience (several wood burners) once there is a reasonable length of flue, the pipe doesn't really make much difference to how well the fire burns. Most important is a good stove and good wood.
BruceK
Established Member
I'm planning to build and fit a rocket stove in my workshop with a single-skinned flue pipe (with suitable fireproof protection of combustible materials of course) adapted to a twin wall flue where it goes through the roof and with capped twin wall flue thereon up. There'll also be a heatproof silicone flange on the outside for weather protection. Can't see any problem with single skin as long as it doesn't become a fire hazard and HETAS will see to that. Unfortunately you'll likely need a HETAS certificate (which will probably be the expensive bit) or your insurance company won't cover you.
Agent_zed
Established Member
now what would be really clever is a contra-flow system where the flue gas temp is monitored and allows or restricts air flow past the inner skin removing heat from the flue in a controlled manner.
When you have a solid chimney stack you find all the mass heats up and does give warmth out, including upstairs rooms the stack passes through so the idea of using a flue for radiated heat makes sense just not allowed. The idea of this twin wall is really a quick fix for those who do not have a proper chimney or like myself feel to old to be bothered to fit one. My original concept was to use the Isokern Pumice system which is modular and like lego,
bansobaby
Accustomly titled
To drain any condensation forming between the brick skin and the flue. This is the section most likely to produce any as its going to have the largest temperature differential. A bit OTT though..........
Standard practice on any chimney above where it emerges from the roof - any water that gets in above the tray from cracks in the flaunching or through any gaps in the brickwork finds its way out again before getting inside the roof.
Phil Pascoe
Established Member
The purpose of the tray.
