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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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    • CommentAuthorPenkestle
    • CommentTimeAug 9th 2019
    I need to call on the experience of you guys
    Our main heating/hot water source we are undecided on. I would prefer a wood burner with back boiler but the barn conversion being an upside down arrangement with vaulted ceilings would mean that the woodburner would be above the thermal store. My research to date suggests that this is very difficult to implement. There is a small attic area that would hold a header tank and a heat sink rad which is approximately 2m above the woodburners position. Space in this attic would be limited so it would be likely that the space wouldn't be sufficient for the size of rad required. Utilising the Towel rads as a heat sink would be the ideal but again with the upside down arrangement gravity feeds can't be implemented. A woodburner would be installed regardless so having that facility to heat water from it would make good sense that and the fact we have access to a plentiful wood supply. My wife prefers the option of an air source heat pump which regardless of which way we decide to go I have already run in pipework and electricity supplies to accommodate. I guess my reluctance to go down the air source route is having a gun held to my head by the electricity companies and the ridiculous price that they are. I would really like to hear your thoughts on this and any info you might be able to provide regarding the woodbuner back boiler situation and the air source arrangement. Thanks In Advance
    • CommentAuthorrevor
    • CommentTimeAug 9th 2019
    I procrastinated a long time over our heating hot water requirements and considered what you are also considering. Our situation was that the thermal store was at the same level as the wood burner boiler but the pipework situation meant that we needed a pressurised system with the inherent inclusion of the safety inclusion of water quenching and yearly testing. (This would be a solution for your arrangement I think.)We continued with wood burners and have 2 but no back boilers. We have MVHR so the heat from the wood burners will eventually circulate through the house. On the heat pump situation we considered both ground source and air source and discounted both because in terms of cost, maintenance and repairs in the future it would work out too costly. Due to the amount of insulation and solar gain from the design we would not qualify for much RHI (perverse really you get paid for what the size of the unit is not how little energy one would use.) Have solar thermal panels feeding the TS (350L) and u/f heating. Hot water comes from an external heat exchanger fed from the top of the store and returns into the bottom providing hot water at a controlled temperature without recourse to mixing valves. There is a gas LPG boiler installed but not connected to the supply yet will happen next week. Supply will be from bottles as at the moment we think that will be the cheaper option as we do not expect to use much. I know not very green but we reckon our demand will be low and our green credentials are otherwise pretty sound. The cost of the gas we are likely to use over the rest of our years dwarfs the cost of heat pump installation. Quite pleased with the performance so far with the solar thermal it has off course been a good time of the year, and have been using the source to commission the u/f heating. The next bit of development is to install solar PV and feed a storage battery and the immersion of the TS.
    • CommentAuthorowlman
    • CommentTimeAug 10th 2019
    FWIW, IMO don't go down the back boiler route, keep the WBS as a simple, no frills, room heater.
    I think your wife is right, go for an ASHP and complement it with some solar generating capacity.
    • CommentTimeAug 10th 2019
    Depends on how much heat the solar thermal panels provide. If they completely heat the thermal store for say eight or nine months a year, then it may well be a lot simpler and cheaper to use an immersion heater to supplement during the other few months. Perhaps extend the solar thermal or add some PV if either of those look sensible.
    • CommentAuthorGreenPaddy
    • CommentTimeAug 10th 2019
    Penkestle, here's my view on your dilema...

    there's no reason NOT to have the TS below the LBS. You just need a pumped flow/return. I almost always fit a pumped system, as siting a TS vertically above the LBS rarely fits with clients' layouts. The heat leak rad might be around 2kW (need to calc of course), but that doesn't have to be large, and could be mounted at an angle to fit in the roof space, and of course below the upper level of the F&E tank.

    I always go open vented, and keep away from relief streams...spent enough years designing and calcing relief streams to know that I wouldn't trust my family's safety to something that will prob never get maintained or tested.

    You've got a plentiful supply of timber, so use it to heat your hot water.

    Yes, a stove will give you space heating, but you HAVE to light it when you need the heat. A LBS with TS means you can have that heat when you want it (via UFH), and light the LBS when you want to. Also, that will push a greater %age of your ASHP load to making DHW, which has a lower COP.

    You've done the right thing future proofing for an alternative heat source (pipes/cabling already installed). With age, moving logs might get too demanding, so you can add something later.

    I personally struggle with the cost of ASHP, never mind GSHP, and point my clients in the direction of minimising heat energy requirements, making the potential savings of heat pumps probably less than the annual maintenance costs (of which the sales man tells you there is no annual maintenance, but the manufacturers' warranties seem to require it, from the ones I've come across).

    If you could get some solar input, that would sort out much of the summer DHW, which might otherwise be a bit expensive from 100% immersions, and not so nice to burn the LBS in summer, for an hour or so, to get the DHW.

    What the sort of space heating power required for your house for say -1 oC outside temp?
    Wot GreenPaddy said +1

    If you are running a wood burning stove to heat a TS (or provide CH then unless it is on gravity you should have a laddomat or similar to maintain the stove temp. to avoid over cooling the stove and chimney. The Laddomat has a pump (and will shut off when the stove runs out of fuel) so having the TS below the stove is no issue. Combining DHW and space heating with a back burner wood stove is always a compromise where IMO both DHW and CH suffer - along with the occupants. If you have the space then I would suggest a TS and back burner stove for space heating with a separate DHW tank heated by solar thermal or PV with an immersion to cover when the sun don't shine.
    • CommentAuthorphiledge
    • CommentTimeAug 12th 2019
    Have you the option to locate your HW cyl/TS to the side of the woodburner? If you can get the woodburners coil/connections a few inches above the top of the stove outlet then you can set up a gravity loop to heat the cylinder and provide a heat dump. The further to the side the store is, the higher the coil needs to be to get the gravity loop flowing. This will save you having a heat dump rad. If you run with the rad in the loft, your going to loose alot of heat into the roof.
    • CommentAuthorPenkestle
    • CommentTimeAug 12th 2019
    Thank you so much for the input it is very appreciated - going to fully get my head round the responses and then come back to this thread - - GreenPaddy and Peter in Hungary you have managed to get the grey matter working :bigsmile: like what you are saying. The Laddomat sounds like a great piece of kit, reading to do - Thanks all
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