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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    I have an 8kw Dovre woodburner that I did intend taking over to my new house, however I'd like to size it properly considering the house will be well insulated.

    I have my heatloss calcs for each room, do I just use those figures? Or do I just run a larger one and keep the doors open to allow the heat to circulate?

    The main reason for the wood burner is aesthetics, being cosy and to pull the chicks ;-)
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 1st 2014
     
    Depends how much and how often you put fuel in it. 8 kW is the max it will deliver.
    My car delivers 90 kW, but hardly ever use more than about 30 or 40 of them.
  2.  
    Yes but surely there is the efficiency aspect, it won't perform as well at 50% load compared to 100% load

    So what is the best method of sizing? Have one that covers the heatloss of the room it is in?
    • CommentAuthormike7
    • CommentTimeSep 2nd 2014 edited
     
    The main determinants of the stove efficiency will be having a vigorous fire at a high temperature with sufficient but not excessive air supply to ensure complete combustion. You could derate the stove by adding firebricks inside the firebox. To put it another way, to have a lower output stove at the same efficiency, you need a smaller fire, but burning just as vigorously. Whatever, if you're not having to add fuel every 45 mins or so, you'll be doing it wrong.
  3.  
    I'd rather not buy extra fire bricks but sell it and buy the correct size stove
  4.  
    anything over 5kw you'll need free air vent to pass BC, which are cold and draughty unless you put pillow in front of them :)
    As for accurately sizing I don't think they offer the range to make this a worthwhile detailed activity.
    make and model will probably make more difference eff. wise , though the eff. ones are the expensive one.

    my friend got a 8kw in a small room and it melts your face off !

    stick a 5kw in if you fancy it and you've got the cash
    • CommentAuthorowlman
    • CommentTimeSep 2nd 2014
     
    Posted By: jamesingram...........stick a 5kw in if you fancy it and you've got the cash


    Anecdotal, but that'd be my idea too, plenty around to suit all budgets.
  5.  
    Well my 8kw one I will get back what I paid for it so will see what's about
    • CommentAuthordb8000
    • CommentTimeSep 2nd 2014
     
    over 5kw you will need separate air supply but get one with a direct outside feed means you can dispense with the pillow.

    8kw might mean you can heat the whole house with the internal doors open one you've finished with your insulation!

    I spent ages agonising over stove size but after the fact, I don't think it matters so much - I just put more or less wood in. There is a sweet spot for the amount of wood per fill, so you just lengthen the times between re-filling if you have the more "powerful" stove.
    • CommentAuthorDantenz
    • CommentTimeSep 2nd 2014
     
    You can't/shouldn't size a wood burner for the "whole house" heat loss as the wood burner is not a "whole house" heating distribution system. If you do do this then the room the wood burner is in will be way overheated in order to deliver the required heat around the house.
  6.  
    Exactly Dantenz, so how do I size the woodburner properly?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 2nd 2014 edited
     
    Work out the heat loss for the room it is in. You do this in the same way as you would for your external house, just use different temperatures and u-values.
    • CommentAuthorYanntoe
    • CommentTimeSep 2nd 2014
     
    Victorianeco,
    How big is your room?
    Just work out the cubic meters and go onto stoves online where there is a calculator.
    From experience I'd just go for a stove to suit the room, otherwise you won't be able to use the room!
  7.  
    Well the heatloss for the room is 2kw, but a stove that size would look silly in the opening and I'm not sure they even do them that small?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 3rd 2014
     
    Posted By: VictorianecoWell the heatloss for the room is 2kw

    That is huge, about 5 times what my house uses. Thought you were making an 'eco' house?
    Is that the maximum heat load at an extreme, say -10°C?
    • CommentAuthordb8000
    • CommentTimeSep 3rd 2014
     
    I wasn't suggesting you only heat the whole house with one stove, but a happy side effect of a stove running a bit hot is that the excess heat can escape through the doors.
    If victorianeco has done everything he/she has suggested in recent months, then it might have quite an effect.
    If not sure between 5 and 8 kw, on that basis perhaps the larger doesn't seem so extravagent.
    •  
      CommentAuthorjoe90
    • CommentTimeSep 3rd 2014
     
    I plan to put a 5Kw stove in a near passive house but am going to duct from above the stove to other locations (with smoke control collars) to distribute some of the heat. Maybe only easy with a new build!.
    • CommentAuthorYanntoe
    • CommentTimeSep 3rd 2014
     
    So, how big the room?
    I have a poorly insulated room with a floor area around 13 sq metres. Average height is 3m. So, less than 40cubic meters.
    The 4.9kw stove is too big for this room.
    Yes the fire keeps the centre of the house warm, but the room itself is unbearably hot even with the door open, unless the fire is only kept in for short periods.
    • CommentAuthormike7
    • CommentTimeSep 4th 2014 edited
     
    The problems encountered trying for a WBS with a small output and high efficiency make me think that a small masonry stove might be a solution. Otherwise a small fire burning efficiently will need very frequent refueling to maintain a steady output.
    I've a feeling that this suggestion will not be up Victorianeco's alley, but the 8kW stove lined with some additional thermal mass in the form of engineering bricks - I've found Staffordshire Blue pavers quite effective and durable - would be a step in the masonry stove direction, and cheap to achieve.
  8.  
    If you are just looking for the "smooch factor" of a real flame without turning the room into a sauna then I would suggest you look at a bio ethanol stove.

    You may even be able to cheaply adapt your existing stove by removing the grate and installing a ethanol burner or you have options on something that is more like a traditional open fireplace or something completely modern.

    You can add fake logs over the burner if you wish.

    Huge range of options available on ebay.de just start to search for ethanolkamin and you can tailor your search from there.

    They don't require a flue so are much better in terms of air tightness, cold bridging or heat loss than a traditional stove. I was told that a small bio ethanol burner only produces the same fumes as 3 or 4 large candles but I would be happiest having a carbon monoxide alarm in any room with a burning device anyway.

    They claim to be odour free but up close I have found a smell similar to a gas fire. You can in any case add a range of scents to the fuel to enhance the mood!
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 4th 2014
     
    Bargain price on the fuel too. Shall start to run my car on it :wink:
    http://www.prestigiousfires.co.uk/bioethanolfuel.html?gclid=COm4yOCUx8ACFQoCwwodDz4Ayg
    • CommentAuthorRob_14
    • CommentTimeSep 4th 2014
     
    I'd expect 8kW to be more than adequate for the OP's house after all the EWI and other insulation done.

    My experience with an 8kW wood burner is that it provided enough heat for the whole house on cold days last winter. With all doors open the lounge was at 21º, the kitchen 19º and bedrooms were 16º. Which is what our gas CH thermostat/radiator stats are set to provide. The only 'problem areas' were the bathrooms and cloakroom.

    I'm not recommending it as the way to go, just that it worked for our house.
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