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Renewable Energy: Wood burner instead of gas at all?

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    As our 20-yr-old multipoint and 18-year-old boiler survive on borrowed time we cast our thoughts towards the future and a move to an Aarrow Stratford stove/big back boiler unit supplemented by SWH in summer. The house is around 200m2 over 3 floors and occupied by up to 6 people. I'd value any comments from users of these stoves or any stove/BB (with rads) system as to the practicality of the idea. I am assuming that, apart from getting used to chopping lots of logs, we will have to get used to either heating the house at night (which we don't currently do) if we can get the fire to stay in, or getting up cold to stoke up/light the fire. I have in mind a 300 lt cyl.

    The house is solid-walled but I internally insulated it to the best std I could afford (mainly 35mm extruded poly) 20 years ago.

    I'd welcome any thoughts and advice.

    Thanks.

    Nick
    • CommentAuthorTerry
    • CommentTimeJun 4th 2007
     
    Hi Nick
    We are going down the same line at the moment.
    We have mains gas even though we are off the beaten track, but also lots of free wood so it makes sense to use the wood stove. Have been considering a gas boiler as back-up, but wondering if we can save on the purchase, instalation and maintenance costs by just including an immersion as an emergency back-up in the thermal store. Bearing in mind that gas will be getting more and more expensive as well.
    There are the lifestyle changes that have to be made of course, but you are also immunising yourself to a certain degree from future energy supply problems. That said you will probably get a usefull life out of a new boiler before the dung does hit the fan.
    Just wondering if a 300ltr store will be sufficient to cope with the energy input of a good long burn from the stove as well as catering for 6 people?
    Not quaulified to go into technical detail, but hope this is of some use.
  3.  
    Thanks Terry.

    You seem to have answered one of the q's I had not yet asked, in that you mention a thermal store rather than a HWC. I had wondered about that - it presumably is at least a partial solution to my "getting up cold to stoke up/light the fire. " I think you are right though - if I go for a thermal store it probably doesn't want to be any less than ?? 500 lt?? Any views, anyone? I have never used a thermal store. Are they so much more expensive than HWCs, and are there issues I haven't thought of that I should look for?

    Nick
  4.  
    Is a thermal store the only way to guarantee hot (warm-ish??) rads in the morning, stove/backboiler users?
    • CommentAuthorJohn11668
    • CommentTimeJun 19th 2007
     
    Just issue the kids string vests and wheelbarrows and apply the rule that if the stove goes out there is no pocket money for any of them.

    Seriously I fear you may be underestimating the work invoved in maintaining a small stove , let alone one which will heat 200M2
  6.  
    John,

    On the one hand I agree I probably am. On the other hand it is a decision which we *think* we are prepared to make (?and repent at leisure?). In not too many years when I (can't afford to) retire to commune with my arthritis, I may curse my decision, but right now we have a genuine desire to leave gas behind. Any advice and/or experience will be gratefully jumped upon, though.

    We may fall at the first hurdle anyway. Thermocrete want about £1600 + scaffolding to line one flue (we are thinking of having 2 stoves - one room-heater and one room-heater + BIG BBU). Threfore we probably will have said goodbye to £5000+ before we even begin to plumb in the back boiler, let alone add the SWH.

    Do you know where I can get designer-label string vests?
    • CommentAuthorwoffle
    • CommentTimeJun 20th 2007
     
    Hi

    That price for lining is extortionate - I'd look around if I were you. We've been quoted circa £1200 for pumice lining (including fitting), and circa £950 for double wall steel liner with insulation around it. Interestingly there seem to be two distinct camps on the ceramic (longer life) vs. steel (cheaper) liners debate - we were put off pumice by horror stories about pumice starting to break up with very costly removals (apparently national trust will not install pumice liners for this reason). The downsides with steel are a reduced life compared to pumice but this isn't a problem if you can get a decent warranty.

    Not sure why they'd need scaffolding - they should be able to do it from the roof - but then I don't know the particulars of your house!

    Also, not knowing where abouts in the country you are I can't recommend anyone but I'd get onto the HETAS website - there's a list of installers and suppliers of wood/solid fuel systems. We just picked out those in East Sussex / Kent borders and worked our way through to find someone. We're just in the process of organizing the installation of a new Aarrow Stratford woodburner with backboiler - our's is rated at 60,000BTU's I think - not sure of the model number though. Our total cost is £2800 inc. VAT - this is for the stove + chimney lining in steel with insulation + knocking out and construction of the hearth (our's was backfilled and replaced with a marble monstrosity some time in the 1980's) + slate for the hearth (£300 alone) + installation and connection to the plumbing.

    I think this is very reasonable £2800 - in comparison my brother's gas boiler has just packed in and he's being stung for £2000!

    Let me know if you want any more details of supplier / installer and I'll happily oblige.


    Joe
    • CommentAuthorwoffle
    • CommentTimeJun 20th 2007
     
    Oh - we've been told thermal stores are approximately 2x the price of your normal tanks. Whilst we can't afford to go with solar for the hot water as well at the moment hopefully we are going to install a thermal store in the loft so that we can plug it in at a later date without any problems.

    There's a good site called solarwind.org (I've no affiliation with them) who are very helpful regarding thermal stores - try dropping them a mail...
  9.  
    Thanks Joe. That's more like it. I am in Sheffield, S. Yorks. Our house is v. tall with a steep-pitched roof, and the stack stands directly up from the ridge by about 8 feet. I can fully understand the contractor wanting scaffolding. More later. Cheers. Nick
    • CommentAuthorpatrick
    • CommentTimeJun 20th 2007
     
    Access to stack - If the scafolding is expensive go through the roof. If you install a velux window as you close down the roof it can all be done from the inside of the roof space entirly safly and without scafolding. Cheaper and you get a free window!
    • CommentAuthorJohan
    • CommentTimeJun 20th 2007
     
    A little calculation on thermal store size, it's all a bit approximate but just to give a rough idea.

    You can roughly store 30kWh ((kJoule) per 500l water you have in the store. To be exact 1kWh increases the temperature 1.724C in 0.5m3. So if you allow for a Delta_t of 50C (going from 40C to 90C in the store) it gives you ~30kWh.

    I don't know how much gas you use to heat the house per year, but lets assume you've got a well insulated house consuming half of the UK average i.e. 12.500kWh annually, and that worst case is a factor of 2 in the winter. The required energy on an hourly basis is then (winter time): 12.500/365/24*2 = 2.85kWh per h (68.5kWh/day)

    Nick, I don't know which model of the Arrow Stratford stove you're thinking about using but I'll just assume the TF90 for the calculations. The TF90 gives you 24kW to heating.

    To cover your daily heating requirements you would need to run the stove for 68.5/24 = 2.9h, say 3h every day

    During the three hours the stove is running the house consumes: 3*2.85 = 8.55kW

    Hence, you need to store: 68.5-8.55 = 60kWh

    You should therefore have a store of around: 1m3

    This is just an estimate, I haven't considered the 4.5kW the stoves gives off to the room for example. But basically if you want to heat your house completely with wood you do require a large store. An Akvaterm store of 1m3 costs around £1100-£1200 I think.

    Hope it helps. :smile:
    • CommentAuthorJane Smith
    • CommentTimeJun 21st 2007
     
    Nick, we found it impossible to keep our stoves alight overnight using wood: had to use coal instead, which complicated matters and then wasn't very dependable. That was using a Franco Belge cooker and a Coalbrookdale stove. Horrible. Add to that the joy of chopping and barrowing in wood when it was five feet deep in snow outside, and the fact that we used up several barrowsful each day, and you'll see why I'm not keen on depending on woodburning stoves any more.

    When we switched over to oil, we freed up at least an hour and a half each day, of time spent buggering about with the stoves. I'm left with permanent damage to my back and hands, from carrying over-heavy coal scuttles and barrowing in firewood.

    I know our house is a big old draughty thing, but we were only heating three rooms, which we had pretty well insulated. It still was dreadful.

    As for the cost of the chimney--that cost seems very high to me. We got our own scaffolding in, I think, and it worked out much cheaper. Have you got a friendly roofer who could do the work? If not, let me know.
  13.  
    Haven't had time to reply fully, but in the meantime, for courtesy's sake, thanks v. much to you all. Jane, I see what you mean, and can see myself living to regret it, but hey....

    Johan, thanks for the calcs. V. useful. Joists may need some strutting to take 1000kg!

    Joe/woffle. Thanks again. I shall continue searching for sensible prices. I am trying not to be tempted to do it myself!

    Patrick. Going from inside, even if I perched on the ridge-board, the top of the stack would be 2 foot above my head. It rises from hte ridge, not the slope.

    Keep the views coming. I'm quite tempted by the 'stove in one room and lots of pullovers' option, but my sons believe in 365-day shorts and vests!
    • CommentAuthorMrT
    • CommentTimeJun 22nd 2007
     
    Hi Nick,
    I am a devotee of wood burning stoves and I'm planning on installing an additional wood burner for DHW this summer. I personally love managing my logs, look forward to loading the wheel barrow in the spring for the following winter. I get my logs from a forrester who provides FSC hardwood. There is no shortage of hardwood in my part of the world and talking with the supplier he says that there is currenly no market for UK hardwood. The wood has to be managed in the large woodlands, exmoor etc and it is better to clear trees which are about to fall than leaving the to rot. We currently have beech, in its second summer of seasoning which should generate alot of heat, the beech needed to be felled as it roots were undermined by recent dry summers and would have become unstable. Make sure the wood is well seasoned, I recommend 2 years, more for oak. A mix of dry softwood/hardwood is a good bet. However I don't think it sustainable to burn logs in urban areas where the percent of woodland is not sufficient for the population.

    No need for coal Jane, perhaps your wood was not well seasoned. It's better to go for fast burn than slow over night as the emissions will be lower. Get the fire really going first with smaller wood, maybe softwood. Once this achieved any good stove will burn efficiently with refils of good seasoned hardwood.

    Nick some people push the liners up from ground level. I spoke with one of leading stoves maker and he was usprised when I mentioned getting scaffloding to put in flexible liners. Chimney sweeps push brushes upwards. I guess the experts no best.
  15.  
    I think some friends of ours pushed the flexible liner up from the bottom as well, something to do with there being an awkward bend just above the fireplace? Lots of twisting and cursing apparently.
    I don't know how you would finish off the top though, without being able to get up there (they were only dormer bungalow, so I think they used ladders)
    • CommentAuthorJohnh
    • CommentTimeJun 22nd 2007
     
    As Dominic says, you'd still have to get to the chimney top somehow to finish off the termination of the lining. Current H&S rulings may mean that to do this legally requires the use of scaffolding.

    In my own experience most installers prefer to lower the liner down the chimney with a nose cone attached. The liner is helped down the chimney via a rope tied to the cone. This way is favoured as it uses gravity to help the liner down and so puts less strain on the quite fragile Stainless Steel liner. On one lining job I was involved in, we had to feed the liner up from the hearth as the liner was lagged with rockwool for a section of its length to help to form a 'plug' in a huge inglenook so that it would hold loose vermiculite insulation.

    The recommended BEST way to sweep a chimney (if the chimney termination allows) is to sweep from the top down.
  17.  
    Mt T, Dominic and Johnh, thanks for your comments. Mr T, you said: "I spoke with one of leading stoves maker and he was usprised when I mentioned getting scaffloding to put in flexible liners. Chimney sweeps push brushes upwards". My only experience is with gas flue liners (corrugated S/S) of 4, 5 and 7" dia. It would have been totally impossible to insert any of those I did from the bottom. Yes, sweeps sweep from the bottom, but they screw on a semi-rigid straight rod as they go up. They don't try to wrestle something which has hitherto been coiled up. Is the liner used for wood-burners significantly different? Given the height of the stack and the steepness of my roof I wouldn't NOT use scaff, but I would be happy with a tower and a chimney scaff with roof ladders between. I get the impression that the contractors would not.
    • CommentAuthorNikoli
    • CommentTimeAug 1st 2007
     
    Why not consider a wood gasification boiler, coupled with a thermal store? Much more efficient and boilers with large enough hoppers to burn for 24hrs are now available. MOre expensive short term but in the long run economical and perhaps more practical:neutral:
    • CommentAuthorrae
    • CommentTimeAug 3rd 2007 edited
     
    Hello Nick,

    I found your post while researching something on the internet.

    I thought sharing my experience as a non-scientific person might help a little.

    We have a three storey, pretty poorly insulated at the moment home and run it completely on wood from September to April.

    Our woodburner is 12kw (not sure what that is in btus) and it is in 24/7 between those months. We run 7 radiators from that and it tops up (but doesn't solely heat) the hot water.

    Posted By: Nick Parsons I am assuming that, apart from getting used to chopping lots of logs,


    I have to say, that is pretty much an understament. It really is a lifestyle choice; especially if you really do plan to chop all the logs yourself.
    Throughout the summer months you need to collect and you need to have storage for a few months worth AT LEAST!

    We get through around 6 tonnes a year of wood (and that's a lot of trips out to collect, chop and store).
    Having it delivered is an option, but more expensive (in our experience and area where we live) than using electric heaters (which saddens me deeply; but is for another post, perhaps :))

    we will have to get used to either heating the house at night (which we don't currently do) if we can get the fire to stay in, or getting up cold to stoke up/light the fire.


    With the right materials (seasoned hard wood) then there is no problem to getting a fire stay in all night. It took us about 3 weeks of playing around until we finally really *got it* with regards to keeping it in. And yes, when reserves of the good stuff gets low, sometimes you have to get up and put your coat on, but we're all used to that now!

    Our home is usually around 15-16 degrees in the morning when i get up, but opening up the fire and putting decent wood on with lift the temp by a couple of degrees in around an hour or so. (but as I said, the insulation in our home is pretty par-standard at the moment).

    I hope this helps from someone who is out there, 'living the life' with a woodburner.

    Oh, and it probably won't bother you in the least, but it really does create a lot of mess - the walls ideally need painting each year in the room the fire is in, and then 6 trips to the woodshed and back a day in the rain can take its toll on the floors.

    Would I swop it - not in a million years, but it isn't the easy, cheap, romantic idea I had about living off the grid either ;)

    I would change things if I were to do it again, but we are working within a very tight financial situation and I'm sure there are options where the outlay would be more, but the use of fuel would be much more economical - I think that has been touched on, here.

    Best wishes
    Rae x

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