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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorJulio
    • CommentTimeMar 10th 2020
     
    Slightly random question, but where in the building regulations is it laid out the actual requirement for space heating? I cant seem to see it covered explicitly in Part L. And how does a passive house then meet any requirements for this?

    Cheers
    •  
      CommentAuthordjh
    • CommentTimeMar 10th 2020 edited
     
    There is no requirement for space heating. If you provide it then the space is a heated space and subject to all the regs about insulation etc. If you don't then its an unheated space and the insulation etc regs (i.e. conservation of energy) don't apply.

    edit: I don't understand your question about passive houses?
  1.  
    It's stated in Scottish building standards:
    " Standard 3.13 Every building must be designed and constructed in such a way that it can be heated and maintain heat at temperature levels that will not be a threat to the health of the occupants....

    "Passive design, such as use of the orientation of glazing for solar gain and of the building mass to store heat with controlled heat release may only need minor supplementation from a lower output fixed heating system."


    I don't know if there is a clear statement in English regs, but I expect the regs would require an EPC based on SAP, which would assume electric space heaters if there's no fixed system. If there were enough solar gains or PV etcetc then the deemed electric heating requirements would be low and could still give a good SAP rating.

    Edit after checking: the English building regs do work like that: your house must perform better than the TER, as assessed using SAP. If you built a house without heating, SAP assumes the occupants will bring in electric heaters to make up any shortfall in heat from solar gains. So you are free to build without heating, so long as your passive features result in a low enough residual electric heating demand, so you can still meet the TER.

    The insulation regs apply to new dwellings, irrespective whether heated or not.

    SAP uses 21degC in the main living room and less elsewhere in the house. Scottish regs require that the heating in one room can be upgraded to 21degC in case it is occupied by elderly or infirm folks in future.
  2.  
    Purely conjecture, but I'd venture a guess that this might spring from the misconception that Passivhauses don't need heating. Spoiler alert: they do, just markedly less than a conventional building.

    As djh says, the Building Regulations set minimum fabric (insulation) standards as an absolute performance figure. The passivhaus standard doesn't, since the form of the building influences the u-value required, but a safe assumption is around 0.1W/m²K for most of the opaque fabric.

    I think I'm right in saying that both systems effectively assume an indoor temperature of 20°C should be maintained for heated habitable spaces, but I might be wrong about that in the way SAP/BRUKL is calculated. If you were to propose permanently heating a building to something dramatically higher or lower, it might be difficult to justify to the BCO unless a particular use class required it.
    • CommentAuthortony
    • CommentTimeMar 10th 2020
     
    If it is habitable accommodation then insulation regulations apply -

    for all homes I think we should talk about better than the Passive Haus 15kWh/m2/y it is after all over 30 years old now
    •  
      CommentAuthordjh
    • CommentTimeMar 10th 2020
     
    Posted By: tonyfor all homes I think we should talk about better than the Passive Haus 15kWh/m2/y it is after all over 30 years old now

    On what basis, Tony? Think about the reasoning behind setting PH at the level it is and justify different conclusions.
    • CommentAuthortony
    • CommentTimeMar 10th 2020
     
    We need to radically reduce the amount of energy that we are using going forward
    •  
      CommentAuthordjh
    • CommentTimeMar 10th 2020 edited
     
    I don't think PH heating is a major concern, to be frank. Looking at https://www.withouthotair.com/c18/page_103.shtml and translating to the same units:

    PH 15 kWh/m²a * 35 m² (per person standard figure) = 1.44 kWh/d
    or even with the gross space we have in our house 15 * 72 = 2.96 kWh/d

    So I'd say effort was better focussed on reducing flights, car and stuff.
    • CommentAuthorJulio
    • CommentTimeMar 10th 2020
     
    Brilliant, ok was worried that I was missing something in the English building regs. I am kind of surprised that it isn't specified that the internal temperature has to have the ability to be kept at a comfortable temperature.

    Yes I agree that we should be using passive house levels of insulation, although sometimes it is hard to specify it in. Although I do get dh's point (I think), that when a building reaches the level of insulation when it requires little or no heating, surely this is the point that extra insulation becomes a waste of embodied energy and time?
    • CommentAuthortony
    • CommentTimeMar 10th 2020
     
    No, that depends on things like design life, cost of upgrading in the future (homes being built now could be insulated to a proper standard for a grand or two and will need upgrading before 2050 costing tens if not twenties of grands.
  3.  
    Posted By: Juliohat when a building reaches the level of insulation when it requires little or no heating, surely this is the point that extra insulation becomes a waste of embodied energy and time?


    And space for insulation. We're not at passive levels but our water heating is already 3-4x the energy we need to heat the house.

    Neighbours are even closer (probably passive but uncertified. Heat their home with a single plug in electric radiator.

    I can't see that it makes sense to go beyond that, especially if you can solar generate and store power. It's possible PH already goes beyond sensible point if your climate is SE UK?
    • CommentAuthorgoodevans
    • CommentTimeMar 11th 2020 edited
     
    I have to say I would recommend not to go any further than I have for my house wrt insulation.

    150m2 gross floor space 100m2 ground, 50m2 floor in roof, 375m2 envelope, 175mm graphite eps on single skin wall, 300mm rockwool at roof level, 225mm white eps on suspended floor, 3g doors and windows, ASHP. No solar, no gas, all electric. other than the 3g nothing to write home about.

    Early results for the two of us in the house: - 580kWh pa for hot water (1.6kWh/day), around 600kWh pa for space heating (just over 1.6kWh/day average - approx 6kWh/day when 0 deg C average outside). And around 5000kWh pa for everything else.

    Most of the heating comes from what appears to be profligate use of ovens, hobs, dishwashers, freezer, fridges, tv's and computers with a small contribution from heat escaping from the DHW cylinder and of course our body heat (this all accounts to heating the house by about approx 10 deg C from waste heat).

    As it happens my U Values are not much better than Building regs - but my house is cheap to heat because I am using MVHR instead of trickle vents and most importantly my envelope area is small relative to my floor area and simple (I have a simple op and over roof, no dormers, and just 4 straight external walls).

    We perhaps don't talk enough on this site about the enormous benefits of reducing the envelope area and reducing the length of the junctions between building elements.
    • CommentAuthorGreenPaddy
    • CommentTimeMar 11th 2020
     
    I seem to remember seeing the originator of Passiv Haus (Wolfgang somebody) giving a presentation at a conference years ago, and to paraphrase the whole concept of PH in a few poorly chosen words...

    the empirical research allowed them to plot the insulation increases versus cost over the lifecycle of the buildings, which was a Damascene moment for me...put a nail in the coffin of "where do I stop with insulation" arguement.

    Actually, what really got me hot and sweaty was that the capital cost increased with increased insulation, to a point where the heating system suddenly became much simpler/cheaper,and so the capital cost dropped sharply, thus bringing the lifecycle costs down, at that level of insulation.

    So for me, and this is just in my little brain, if you want to go with a method that is worked out empirically, go PH route. But of course, there are other brands available if you don't like the proven route of minimised lifecycle.

    That said, I don't follow PH to the letter, but steal lots of their good ideas.:bigsmile:
    •  
      CommentAuthordjh
    • CommentTimeMar 12th 2020
     
    Posted By: goodevansI have to say I would recommend not to go any further than I have for my house wrt insulation.

    150m2 gross floor space 100m2 ground, 50m2 floor in roof, 375m2 envelope, 175mm graphite eps on single skin wall, 300mm rockwool at roof level, 225mm white eps on suspended floor, 3g doors and windows, ASHP. No solar, no gas, all electric. other than the 3g nothing to write home about.

    Early results for the two of us in the house: - 580kWh pa for hot water (1.6kWh/day), around 600kWh pa for space heating (just over 1.6kWh/day average - approx 6kWh/day when 0 deg C average outside). And around 5000kWh pa for everything else.

    Your figures look considerably different to ours.

    Space heating of 600 kWh pa for 150 m² floor area is 4 kWh/m²a which is approximately a quarter of the passivhaus allowance, so something very strange is going on there. 6 kWh/day with 0°C outside is also very low. I can think of three possibilities:
    - a very weird local microclimate
    - you're not heating the house to 20°C so can't really compare
    - you have very high internal gains

    Now your 'other' consumption of 5000 kWh pa or 13.7 kWh/day is pretty high and almost the same as our total mains electricity usage, including both space heating and DHW heating, although we do have PV panels that reduce our DHW consumption and incidentals. So it might be worth investigating your incidental usage a bit more.

    Your experience and mine are sufficiently different that I'm very cautious about your recommendation not to insulate better.
  4.  
    ? Goodevan's 600kWh/a are going through a heat pump so need to be multiplied by CoP before comparison of heat losses with djh's direct electrical heated house?

    And GE was clear that most heating comes from appliances, cooking and people.

    But in terms of environmental impacts, GE's figures for total electric imports are directly comparable against the PH standard and against other people's houses.

    In terms of diminishing environmental returns, I don't know if it's better to a) have lots more insulation than bldg regs/stds; or b) use a heat pump; or c) both
    • CommentAuthorgoodevans
    • CommentTimeMar 13th 2020
     
    I would say

    1) fabric first - reducing heat loss is key.

    2) reducing heat loss by all means which means good insulation on flat surfaces, minimising thermal bridges at junctions BUT ALSO - simplicity of design, reduction of envelope surface area to floor area ratio, reduction of the length of junctions. With attention paid to reduction of infiltration.

    3) ASHP is secondary - and it only works well if you can run it at v. low temperatures

    Tree root protection measures prevented me from getting gas so I ended up with ASHP and UFH which has been not the disaster on running costs that I initially feared.

    The ASHP has performed well - and works well only because the heat losses are so low that the UFH runs at around 23 to 24 deg c with a COP of around 5 recently (if it doesn't frost up which when modulated right down it tends not to). So far heating It costs about the same as gas. Low temperature also works because more than 1/4 of my envelope is 'radiator'.

    The issue I have with Building regs is that I I have a inefficient shape house with lots of wings and protrusions, lots of windows, long and numerous junctions I don't need to compensate at all with better insulation.

    I can confirm that the house can maintain a 20 deg c internal temperature when it is overcast outside at an average of zero deg C for an all in cost of no more than 20kWh electricity per day - of which a maximum of 7 kWh is space heating. At these temps I'm assuming a cop of around 4 - total heat input is therefore 7*4 + 13 = 41kWh or 1.7kW average - plus 2 people and the DHW loss bring it up to approx 2kW - or 100 watts per degree difference with outside (my pre build calcs were 107 watts / degree difference - building regs would allow 193 W /deg diff).

    Yesterday, with the sun out, the house just about maintained temperature over 24 hours with an average temp outside of 6 Deg C. The heating was last on during Monday (its been mild in Cambridgeshire) - but I think the heating will cut in today if the sun doesn't come to the rescue.

    We are in a rural location, no special microclimate, and heating to 20 deg C.
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