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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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    • CommentAuthoraclarky
    • CommentTimeSep 17th 2018
     
    ...this is reposted on a new thread.

    Buying a house - detached 5 bed, which is 100 + yrs old, mains gas, EPC report says in needs 60000 kwh heating a year.. 2000 for hot water. Existing old gas boiler.

    We are looking to go greener and cut costs and steer away from climbing gas prices so the plan is:

    Get a GSHP as it is basically free with the subsidies and use boreholes as the garden isn't big enough. I think we will get solar PV but not thermal as the pay back is too loooong.

    To keep it cheap I really want to use economy 7 and store the energy for the following day which makes it equal or lass than current mains gas. We may also add in a wood/pellet burner at some point. What is the bast way?

    - A separate thermal store just for heating which could cycle between 25 and 50 deg (if 1000L tank = 29KWH) so may need 2000L. Keep hot water separate?

    - could I pour 2m3 (5 tonnes) of concrete (equal to 1000L water), insulate it well and run a coil through it and warm it at night. Used to be a site engineer so v happy with concrete or grey gold as its known!

    - DIY water storage looks like it could cause more problems than it solves.

    - or is there another way.

    And

    I am going to insulate under the suspended floor (and walls and roof as well as possible). Would under floor heating at GSHP temperatures work - the idea was to attach pipes to underside of floor boards and insulate and close off the joists.

    And..

    And is anyone familiar with Spacetherm plus wall liner - There is a lot of cornicing etc that would not be feasible to remove so it seems like a good option (apart from cold bridging perhaps) - is there a cheaper alternative?

    Thanks!

    Andy
    •  
      CommentAuthorDamonHD
    • CommentTimeSep 17th 2018
     
    I used Spacetherm on plasterboard and with Fermacell.

    Eg see here and links leading from it:

    http://www.earth.org.uk/note-on-Spacetherm-aerogel-thermal-insulation.html

    We used a different magnesium board product to try to save space:

    http://www.earth.org.uk/note-on-superinsulating-bedroom.html

    but the builders found it fragile and it ended up not saving space in the end.

    Also 10mm just isn't a huge amount of insulation. 30mm+ starts to get you to something like modern building regs and sensible heat loss. Maybe with more than that and good attention to thermal bridges and unplanned ventilation you could get your space heat demand down to something that won't need a YUGE heat pump. (For comparison, our small family house annual space heat demand is about 3000kWh or 3MWh, an order of magnitude less than yours, and a heat-pump might struggle a bit here.)

    http://www.earth.org.uk/saving-electricity-2017.html

    Rgds

    Damon
    • CommentAuthorCWatters
    • CommentTimeSep 17th 2018
     
    We have 80mm insulation, wet UFH and 21mm Engineered Oak. Have to run the UFH hotter than I expected to push enough heat through the floor. Plenty of pipe used. House built to slightly better than Building Regs 12 years ago.

    I'm thinking that you may need to run the UFH at >40-50C if the house isn't well insulated making storage needs bigger.

    Can you see actual winter bills or meter reads rather than the EPC?
    • CommentAuthorjfb
    • CommentTimeSep 17th 2018
     
    I think there is a debate to be had as to whether it is greener to install a big gshp setup or just use what is there and have a gas boiler. You might find.looking at similar/older threads on here that if a property has a gas supply it is better to use that. More so if a property is not optimal for heat pump ufh (well insulated, airtight, low temp). Electric prices can go up as well and has to be generated from something (though clearly good cop from a heat pump gets more out than you put in).
    •  
      CommentAuthordjh
    • CommentTimeSep 17th 2018
     
    Comments reposted from old thread....

    Posted By: aclarkyEPC report says in needs 60000 kwh heating a year.

    EPCs are notoriously unreliable, so get a better model if you're dependent on the answer. How big is the property?

    could I pour 2m3 (5 tonnes) of concrete (equal to 1000L water), insulate it well and run a coil through it and warm it at night.

    Yep, that would work. You need to account for the relative slowness of heat transmission and allow for future maintenance needs somehow. Plus the screams from eco-concious people about cement and latterly sand.

    or is there another way.

    The traditional answer at this point is insulate, insulate, insulate. i.e. first reduce the heat demand, then optimise the means of heating.

    I am going to insulate under the suspended floor (and walls and roof as well as possible). Would under floor heating at GSHP temperatures work - the idea was to attach pipes to underside of floor boards and insulate and close off the joists.

    Good, you mention insulation. :bigsmile: I'm sure there are details that would need working out, but in principle, yes.

    There is a lot of cornicing etc that would not be feasible to remove

    Is the lack of feasibility due to legal constraints, or economic ones?
    • CommentAuthoraclarky
    • CommentTimeSep 17th 2018
     
    Wow thanks, that is really useful.
    in reverse order:
    djh - Cornicing would be prohibitively expensive to remove, but yes we would do as much insulation as possible. Point taken about concrete, CO2 and maintenance, I think I will focus on a massive water thermal store and calculate the size when I know more about the heat demands of the building. The building is a big old detached house in Glasgow, 3 stories and 11 rooms.

    jfb - that would be a whole lot simpler.. but as the grid goes greener and assuming I can keep output temp of gshp at near optimum value I think it seems like a pretty good option - and its more than paid for by someone else over 7 years..? But I hear your point and unless I could loan the initial cost it may be tricky!

    CWatters - I think if you have to work it hard then we may need to supplement it with a radiator or fan assisted radiator. And we don't want to go above 50 deg really. Even with our internal insulation proposal I think we would be considerably worse than yours. Shame there isn't a rectangular pipe section to fix against the boards to increase the conduction through the floorboards

    DamonHD - that was a very interesting post, and concerning that it was so fragile.. The one that got my attention was the Spacetherm Wall Liner - https://www.proctorgroup.com/products/spacetherm - which looked like you could just bond it to the wall.. We would be doing it to to significantly improve a situation but know its not perfect. Still the chat on the brochure says a 600mm stone wall goes from U 2.18 to 0.83..

    Thanks again very much for all of the above.
    •  
      CommentAuthorDamonHD
    • CommentTimeSep 17th 2018
     
    Note that the *unimproved* walls for my 60s council flat (timber frame) were 0.8W/K/m^2. English part L requires more like .3 now, I think. I can't imagine Scottish regs are more lenient as there is real weather up in your neck of the woods.

    Rgds

    Damon

    PS. I had many chats with (Sam) Proctor about what I think has become that product, and I would have no problem with it, though sticking stuff on potentially comes with its own 'windwashing'/mould issues I suspect, without taking some care.
    •  
      CommentAuthordjh
    • CommentTimeSep 17th 2018
     
    Posted By: aclarkyShame there isn't a rectangular pipe section to fix against the boards to increase the conduction through the floorboards

    That's what things like aluminium spreader plates are for.
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