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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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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.
  1.  
    Posted By: aclarky

    - 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!


    Yes, you can, see photo here http://www.damtp.cam.ac.uk/people/j.e.sutton/concretetes.jpg . This is 5m3 of concrete. It cost me £5k to build and with current electricity costs saves me about £250 a year by utilising E7, so that's a 20yr payback! Still, the 16mm PEX pipe is rated at 75yrs at 10bar and 90C (AFAIR) which running at 2bar and 45C should be good for hundreds of years, I would think. Ditto the concrete. I have two concerns long term: that the 10inch of polyurethane on which it sits will collapse at some point in the future, and (if I run it too hot) that the bonding between pipes and concrete will fail and the transient response will become too poor.

    The latter will be tested when and if I get a wind turbine installed as I will then be able to drive it up to 60C or more (my GSHP goes up to 75C). That was my original plan but some pesky bats have put paid to that for the time being...

    If I could have persuaded my wife to give me the space to build a 2m3 water tank instead I think that would have been preferable on balance. But if you are short on space and fancy digging out the living room down 1m, go for it!

    Except in the _very_ long term I don't think it likely, but, should the polyurethane collapse, and take the living room floor with it, I do pity the poor sod who tries to remove a concrete slab 6.2m x 2.1m x .375m with 5 layers of 8mm steel mesh reinforcement. Ouch!
    • CommentAuthordereke
    • CommentTimeFeb 9th 2019
     
    I came across this project recently - https://icax.co.uk/CHOICES.html

    They use an ASHP during the summer to charge up a GSHP borehole for use in the winter - it takes the ground temp up from 12C to 25C.

    If you are looking at installing GSHP then this might be worth a go. However I am guessing you wouldn't get RHI payments on both systems. Total COP is something like 8 so if you want a toasty house and scalding hot showers it might be a good option!
    •  
      CommentAuthordjh
    • CommentTimeFeb 9th 2019
     
    Posted By: derekeThey use an ASHP during the summer to charge up a GSHP borehole for use in the winter - it takes the ground temp up from 12C to 25C.

    I don't understand. Why the extra ASHP? Why not use the GSHP?
  2.  
    The heat energy to heat up the ground would have to come from somewhere. Options are either to get it from the air (ashps do that cheaply in summer) or from a second shallow ground loop into the GSHP (=extra capital cost). Their website proposed laying this under asphalt carparks. They are aiming at district-scale heating.

    Wasn't clear how they'll avoid the heat that they pump down the borehole being carried away by the ground water and lost before next winter.
    •  
      CommentAuthordjh
    • CommentTimeFeb 10th 2019
     
    Where I used to work had a GSHP doing seasonal storage and it used the same GSHP to absorb heat from the air (thus cooling the building in summer, but it could have been fresh air) and pump it into the ground store.

    I still don't understand why a second heat pump is needed.
  3.  
    Have a click around their website, there's plenty of discussion on which option suits which application.

    If the GSHP absorbs heat from the air, then it's an Ashp.

    But likely not as efficient as a purpose-built ashp, which exchanges heat directly between the refrigerant and air, rather than going via an intermediate medium and through a building. So adding a separate Ashp means more capital cost but less operating costs, and becomes eligible for RHI. Pays your money, takes your pick. This is all commercial scale so the answer is different than for houses.

    The project linked to by Derek is district heating (IE no summer cooling is available - hence they proposed using an air source). They have other projects which used summer building cooling, or loops on rooftops, or loops under road surfaces.
    •  
      CommentAuthordjh
    • CommentTimeFeb 10th 2019
     
    Posted By: WillInAberdeenHave a click around their website,

    Sorry, I've never been impressed by ICAX, I'm not going to wade through their pages of fluff.

    If the GSHP absorbs heat from the air, then it's an Ashp.

    Ha ha very funny. According to the manufacturer its a 'hydronic system'; actually 5 off ERACS-WQ/B S 1902

    But likely not as efficient as a purpose-built ashp

    I'm not quite sure why you're sniping at the engineers who designed the largest ground source heat pump in the UK. I expect they know their jobs. And it does get RHI, by the way. Yes, it's commercial scale; the enthalpy wheels are simply ginormous, for example. IIRC it has 55 off 50 m deep boreholes.
  4.  
    Interesting. Link?
    •  
      CommentAuthordjh
    • CommentTimeFeb 11th 2019
     
    Haven't found a good summary. There's a variety of pages with some details if you search for MRC LMB GSHP or similar.
  5.  
    Posted By: WillInAberdeenHave a click around their website, there's plenty of discussion on which option suits which application.

    If the GSHP absorbs heat from the air, then it's an Ashp.

    But likely not as efficient as a purpose-built ashp, which exchanges heat directly between the refrigerant and air, rather than going via an intermediate medium and through a building. So adding a separate Ashp means more capital cost but less operating costs, and becomes eligible for RHI. Pays your money, takes your pick. This is all commercial scale so the answer is different than for houses.

    The project linked to by Derek is district heating (IE no summer cooling is available - hence they proposed using an air source). They have other projects which used summer building cooling, or loops on rooftops, or loops under road surfaces.


    A GSHP that runs air conditioning in the summer is still a GSHP - and it still stores the rejected heat in the ground ... but you hope that ground water movement doesn't remove it all!

    Paul in Montreal.
    • CommentAuthoraclarky
    • CommentTimeFeb 14th 2019
     
    Just came back to this, interesting stuff..

    The compromise so far - some of which is on a different thread is to:

    Internally insulate with PIR backed plasterboard - 27.5mm total depth, get the U to 0.8ish
    Concrete slab bottom floor underfloor heating
    GSHP with boreholes

    Main Qus now if anyone has any advice:

    1) what is the best way to use E7 - massive buffer tank or do I need to programme my own actuator valves etc to control a separate massive thermal store tank to build up its temp to 50-60C over night?

    2) there are a lot of GSHP firms out there, hard to know who to pick - any advice for Glasgow area?

    Thanks again for all of the above!

    Andy
    • CommentAuthorgoodevans
    • CommentTimeFeb 18th 2019
     
    First make sure E7 will pay for itself - yes the electricity is cheaper at night, but the daytime rate is more expensive. At the moment the Eon variable tariff rates mean that you must use at least 30% of your total electricity usage at night on average over the whole year to break even - more so If you have energy losses because of thermal store requirements (if the store is inside the insulation envelope not a problem). But that store will have a capital cost, and will take up space that has a value also.

    Unless it is a no brainer cost wise - go with a regular tarrif and give yourself the flexability to heat and use power at your convenience.
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