Woodstoves

[Watch-keeper]

I witnessed a masonry stove being deconstructed in a very basic (2 room) eastern European house a few years ago. It was a very simple construction, it must have worked reasonably well as it had been there long enough for the hinges to be almost worn out.
It was just a large brick-wall container with the burner boxes and oven set in to the sides and then the rest of the space filled with rocks sand and dirt. The brick shell was around 2.5 x 3 x 4 feet in size. It had 2 burner boxes one below the oven and one below the hotplate and the flues ran through the rest of the construction. It was clearly a home made device and I would hazard a guess the burner boxes and oven may have been home made too. I only have a picture after most of it was removed but you can see the filling on the floor and in the wheelbarrow and the bricks used for the exterior.

 

[GreyCat]

I would also worry what the house insurance companies would think of one. I do find the mainstream companies don't like anything nonstandard.

It's that and the building Regs that made my mind up, as well as the cost.

Same money as one Masonry stoves gets me a refurbished Rayburn Royale plus 3 other modern high efficiency multifuel stoves.

The chimneys for 3 of then run through inside the house and the other is in a thick wall 1 metre or so), so getting a similar benefit but in more rooms.......

GC

 

[Falstaff]

It's that and the building Regs that made my mind up, as well as the cost.

Same money as one Masonry stoves gets me a refurbished Rayburn Royale plus 3 other modern high efficiency multifuel stoves.

The chimneys for 3 of then run through inside the house and the other is in a thick wall 1 metre or so), so getting a similar benefit but in more rooms.......

GC

I have certified, swept/serviced 3 masonry stoves that came from Bulgaria and were installed in the UK. They are very clever at routing the "exhaust" through various channels within the masonry. It takes time to heat up the masonry, which, in a sole heat source for the building in the depths of winter is what you want.
I was only able to certify it to HETAS because it was a tested and manufactured design. It would be very difficult to design and make your own to pass Regs, but not impossible. However, modern stoves to Clearskies Design are now so good that I wouldn't bother.

@British Red/others - I'm curious, as your sole heat source, how much wood do you burn per year, and where do you get it from?
There is some data around that suggests a Cord and a half (Cord=8'x4'x4' high) per year, and area of woodland required to self sustain that. ( think it was 17 acres but might be wrong)

 

[Broch]

@British Red/others - I'm curious, as your sole heat source, how much wood do you burn per year, and where do you get it from?
There is some data around that suggests a Cord and a half (Cord=8'x4'x4' high) per year, and area of woodland required to self sustain that. ( think it was 17 acres but might be wrong)

I don't think our burner uses that but our hot water is on oil and the burner is our only heating during the main part of the day and evening. I suspect a modern log burner would burn less than 2/3rds the cord and a half (so around a cord ) based on how much more efficient our new log burner is compared with the old Villager.

I have around 20 acres of woodland but only use windfall and thinning at the moment. We have plenty of ash coming down so I don't need to fell healthy trees for now.

 

[British Red]

@British Red/others - I'm curious, as your sole heat source, how much wood do you burn per year, and where do you get it from?
There is some data around that suggests a Cord and a half (Cord=8'x4'x4' high) per year, and area of woodland required to self sustain that. ( think it was 17 acres but might be wrong)

Hi,

Amount of wood varies tremendously by type - I have always thought that weight would be a better measure than volume. we generally season our wood in wooden veg crates that hold about 2 cubic metres of wood. we burn pretty much anything. Pine and spruce needs really good seasoning, elder is very light when dry, ash, oak and especially holly are super dense and burn for a long time. Assuming a mix of wood types, all seasoned to below 20% moisture, 5 bins is average so 2 to 3 cords. Our wood is waste wood from tree surgeon friends - prunings, dead and diseased trees etc. It's now illegal to sell firewood unseasoned under 2 cubic metres but we can easily take large loads and season ourselves which is fine. We have capacity for 60 cubic metres which gives at least 3 years cover ( we give some away to older neighbours & people who can't physically process their own)

 

[Glow_worm]

I was only able to certify it to HETAS because it was a tested and manufactured design. It would be very difficult to design and make your own to pass Regs, but not impossible.

As I understand it, and it's a very grey area, It is only manufactured designs which require testing and compliance to the current standard.

A home built masonry stove (following one of the many well proven designs for highly efficient, clean combustion) would need to follow the British Standards which apply, as well as the requirements of building regs, but would not actually need to be certified or tested as an official design.

However, finding somebody who understands this and is willing to sign it off is the issue! I'm in the process of trying to do this myself, and build a masonry stove for the house I'm restoring, using one of Peter van den Berg's recent designs of combustion core. Previous designs here https://batchrocket.eu/en/

 

[Falstaff]

You are absolutely correct. There are numerous US adobe examples of this. The problem is that it requires a professional to stake their livelihood and insurance, and potentially risk a prison term, to sign it off. Building Control will, quite rightly, require a third party professional report.
Although I take on many projects that others don't, I would not be very keen to take this one on.
Initially, you need a gas flow calculation to show that it will work. This does get you over a few of the British Standards and Building Control issues but not all.
There are gas modelling programmes around, typically just for the chimney element, but I don't know if they can do this. Stove manufacturers have more complex software, are unlikely to support you, but you could ask. Possibly requires UK/EU acceptable metrics not US.
Then you need a willing insurance company(s) both for yourself and the professional's insurance risk. Plus, a professional who can show it is within their professional competence and is willing to take the job on. If it involves manufacturers parts then either they must agree to it, or it has to go against your own/professionals insurance and risk.
Then at the end, it will need a live fire commissioning test and demonstrate that it meets the software calculated draught data etc., and Environmental Health's view of the emmissions. "View" is literally that, do they think it creates a "Nuisance" in their opinion. This is of course challengeable in the courts if your pockets run that deep.

 

[Glow_worm]

On discussing options with somebody with a lot of experience with masonry heaters, it was suggested I stump up for the HETAS course, and briefly set up in business for the purpose of certifying my own heater, given that I know I can design and construct something which will be safe and durable so in reality the risk is zero. Seems a somewhat desperate last resort though!

I really would love to work through the headaches and get this done, correctly and officially, as mass heaters have so much potential to make real changes in terms of reduced emissions and reduced fuel consumption as well as providing heat in a far more useful form. They also pair well with older buildings. Somebody needs to start stirring things up, increasing interest, campaigning for simplification of the hurdles currently in the way.

and Environmental Health's view of the emmissions. "View" is literally that, do they think it creates a "Nuisance" in their opinion. This is of course challengeable in the courts if your pockets run that deep.

CO and O2 are easy to measure with a flue gas analyser, I haven't come across portable particulate measuring equipment but assume it exists! I imagine if the results are below the current EU requirements EH would have difficulty making a fuss.

 

[Falstaff]

Somebody needs to start stirring things up, increasing interest, campaigning for simplification of the hurdles currently in the way.
The Regs/hurdles are there for a reason and are based on hard-won experience and fatalities, and have resulted in prison terms for not complying and resulting in fatalities. Grenfell Tower might not seem relevant but actually is, the material shortcomings were well known.
Without trying to slight you, the only hurdle is that you want to create one yourself. A variety of masonry stoves are already available on the market. You just need to buy one and get it installed. If a HETAS person near you is willing, you could assemble it yourself and leave them to do the chimney/flue.
They are more common in europe in areas with very cold winters, so you might buy over there and import one.

I registered 3 stoves from these folk. Very good stoves, together with an insulated twinwall chimney system for each.
https://tulikivi.com/en_gb/. All installed in a UK version of a Dacha in the woods.

CO and O2 are easy to measure with a flue gas analyser, I haven't come across portable particulate measuring equipment but assume it exists! I imagine if the results are below the current EU requirements EH would have difficulty making a fuss.

That would be like you turning up at an MOT station and telling them your exhaust is fine. The standards are set for a specific defined laboratory set up, undertaken only by certified independent firms. I'm told it costs c.£10k per stove. The manufacturers are not allowed to self-certify.
Environmental Health don't do that, it is purely a visual/smell opinion on a number of visits, the same way as Sound complaints are done. If you are not in a Smokeless /Clean Air Zone it's not a concern unless the neighbours complain.

 

[Glow_worm]

The Regs/hurdles are there for a reason and are based on hard-won experience and fatalities, and have resulted in prison terms for not complying and resulting in fatalities...... .......Without trying to slight you, the only hurdle is that you want to create one yourself.

Sound points well made, and of course I understand the significance of the regulations when lives are at stake. What I take issue with, and would like to see change to, is the blanket application of a system which does not account for the characteristics of a type of heater with unique qualities which were likely not understood by those setting said regulations. A combustion core sealed inside a twin-walled masonry bell with an expansion joint between each skin, which only reaches a temperature at which a human can keep their hand applied to it, with an exhaust gas exit temperature of 80-90C is a very different beast to an older design of cast iron stove which may incandesce at times.

Regards not doing the sensible thing and buying one of the kit examples (thanks for the link, they look fantastic!) it is way beyond my budget, and there is nothing on the market which suits my situation and requirements. Having something custom built around a certified core would also be cost prohibitive, and as with so many things it is frustrating to have the skills and experience to make something safe and durable myself, but would have a huge amount of work and cost to get it signed off. At the same time there are no regulations preventing me knocking up a dodgy woodburner from a gas cylinder to heat a homemade sauna and bringing 20 mates round to use it, of course.

Got you regards Environmental Health. Out in the wilds here, neighbours all burn wood! I have built a number of heaters (non residential buildings) using the types of combustion core I am interested in over the years, and the exhaust is always clean and just cool enough to hold your face in for extended periods, so that part should be easy.

Could you point me the British Standard and part of Building Regs which relates to the gas flow calculations, that's something I've overlooked! I really appreciate this input by the way, all food for thought!

 

[slowworm]

I'm curious, as your sole heat source, how much wood do you burn per year, and where do you get it from?
There is some data around that suggests a Cord and a half (Cord=8'x4'x4' high) per year, and area of woodland required to self sustain that. ( think it was 17 acres but might be wrong)

We currently use about 5 cubic meters a year for most of our later autumn, winter and early spring heating, plus most cooking and small amounts of hot water. That's about a cord and a half.

We can provide all our wood from about 15 acres of woodland, mostly thinnings and windfall (which often includes huge mature trees).

To be more comfortable we could do with about 10 cubic meters, so about 3 cords and our 15 acres can produce that, I just don't have the time and room to store it at the moment.

Also worth noting we're trying out a few things to replace all the ash that has ADB. Loads to be cut out but not sure what will provide the firewood in say 20 years time.

 

[Falstaff]

@slowworm- Thanks, that's very interesting. The regrowth vs burn timescale is a challenge. There is a uk small consultancy that specialises in this but I've lost the link.
At the time I was looking at Elephant grass, which is highly regarded as a quick-growing fuel, circa 3 years from memory.
The most touted for fast turnaround is willow, but this largely requires moist/wet ground. The consultancy specialist grows and burns this himself and has had no problems. However, a warning, in my totally differing experience, Willow produces road-quality tar in flues. We replace one old guys chimney liner every 3-4 years and another had a chimney fire 3 months after I fitted a brand new twinwall chimney! In both cases the wood was "dry", well under 20% I measured it myself. (15-16% is best, 20% is too high , you lose too much heat boiling the water off).

I would suggest that pollarding/coppicing would be your best bet, Alder, Ash, Beech, Birch (3-4 year cycle), Hazel (7 year cycle), Hornbeam, Oak (50 year cycle), Sycamore Sweet Chestnut (15-20 year cycle), Willow but Sweet Chestnut, Hazel (7 year cycle), and Hornbeam are the most commonly coppiced tree species currently.
Those split Chestnut paling fences are made on a 17 year cycle.

How to Make Biomass Energy Sustainable Again

From the Neolithic to the beginning of the twentieth century, coppiced woodlands, pollarded trees, and hedgerows provided people with a sustainable supply of energy, materials, and food.

solar.lowtechmagazine.com

Forest Research also have a lot of info.

 

[Falstaff]

@ Gloworm - I think you are misunderstanding the depth or currency of the Standards, they are kept under review and are frequently updated. As it does cover masonry stoves, I suspect there are some concerns about the sort of stove/construction quality risks involved. Despite this, as you say, in non-habitable building most anything goes, but there have been fatalities. I mind one such, 6 teenagers in europe having a party died of Co2 in such a set up in a garden building.

I suggest looking at https://www.hetas.co.uk/trade/standards/
Sorry, I should know the BS for this but I just ask the manufacturer or supplier to do the calc for me. Your best bet would be to look at the HETAS website or ask them, ( by email as they will need check it's the right Gen first).
In the case of a solid fuel masonry rocket stove I don't know if it falls within Appliances or Chimneys. BS EN 13384-3:2005 covers some of this but whether that's the only one I don't know. I don't have access to the BS's, it costs bucks!

 

[Glow_worm]

Thank you @Falstaff, much appreciated. Last time I looked into this there seemed to be two British Standards that applied to the heater, BS EN 15544:2009 and BS EN 15250:2007 which I did manage to view at the time. |The standard you've linked to is likely valid for the flue, but getting in touch with HETAS is a good plan. Poor wording on my part, yes the standards are very much appropriate, but even if I follow them to the letter (it would be nothing but bad practice not to) there will still be a lot of effort and cost to get a design of my own signed off.

The 'rocket' thing is a bit of confusion these days, in the early days they were all crazy hippy contraptions constantly fed small wood in a vertical feed tube, with a horizontal flue piped through adobe benches or beds. Designs have evolved very close to classic masonry heaters now, a batch combustion core inside a bell or feeding a contraflow. All core designs share key design features of highly insulated core, restriction in the form of a narrow port (ensures self regulation), at least one 90 degree change of gas path during combustion to create turbulance, and some use secondary air.

No surprise the more recent woodburners have a lot of these features too... high levels of insulation, baffle to create turbulance through direction and volume change, highly controllable secondary and often tertiary air....

 

[slowworm]

I would suggest that pollarding/coppicing would be your best bet, Alder, Ash, Beech, Birch (3-4 year cycle), Hazel (7 year cycle), Hornbeam, Oak (50 year cycle), Sycamore Sweet Chestnut (15-20 year cycle), Willow but Sweet Chestnut, Hazel (7 year cycle), and Hornbeam are the most commonly coppiced tree species currently.

I was going to start another thread on what to plant as I'm often on the look out for new ideas.

The problem for us is most of our ash will be gone in a few years due to ADB. Hornbeam is loved by squirrels so is out; beech, sycamore, field and other maples and oak also get badly damaged so are out; we have a fair bit of alder and several acres of hazel so I want to diversify. I've planted some birch, poplar and willow but don't want too much of them. I've grown a mixed load of eucalyptus from seed and they are doing ok and planted laylandii, both are not everyones favourite but I have the room and can use the evergreens as winter shelter.

 

[Falstaff]

Between the squirrels and the deer not much gets away with it. I think sheer tree volume and regular squirrel hunts for the pot is my best guess. I need to get some catapult practice in...

 

[Falstaff]

Actually, just had a thought - Elephant grass seems to be of no interest to animals, or birds. It grows in dense blocks like grain crops, so it's very space efficient. I saw a field of it being trialled locally to me.
There was a secret commune in Wales that grew it all around them as camouflage and fuel for 7 years, then popped up and applied for Planning permission occupied time rule.