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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthormarsaday
    • CommentTimeNov 7th 2021
     
    I am doing a refurb on a flat which i hope will be a holiday let.

    I am going down the route of all electric. So electric shower, small electric heater for the HW under the kitchen and bath sink. Its only a 2 bed flat.

    I have gas currently, but I don't want to go with gas. The system is 30 yrs old so i have ripped it out. I am at the stage where i am rebuilding all the walls and ceilings. I have ripped everything out and i am making it a full height space right into the roof apex. New windows going in. So everything being done.

    My epc guy has run through the data on his system and i come out with a D 57 rating. I am not too happy with this and it is the heating and HW which is letting the rating down. Longer term I may need to achieve a C rating if i rent it as a home (not sure if the rating will apply to a holiday let).

    It recommends High retention storage heaters (econ 7)

    Any recommendations for E7 heaters ? Or even better could i use these modern oil filled panel heaters and run this off standard electricity rates ? The reason being is that i am wary of Econ 7 as it doesnt give you that much control over the heat. Too hot you open windows etc.

    I will need 3 rads plus a towel rad in the bathroom.

    I cannot improve any other aspect of the EPC. I am doing new A rated D/G at the moment and spending £2k on new insulation. The roof will get 125mm insulation and the walls will get 50mm, The floor has a flat below and now has 200mm soft insulation between the joists as nothing there previously.. I cant fit solar as in a conservation area.

    Longer term it seems electric heating will be more highly regarded on EPC's compared to gas, but not currently. So i am forward thinking a little. Got the EPC today, so I need to really think carefully how i go forward. Got plenty of time to decide, but now is the time to get this sorted.
    • CommentAuthorMike1
    • CommentTimeNov 7th 2021
     
    Yes, longer term electric heating should be more highly regarded. EPCs are based on SAP 2012 which, as the name suggests, is nearly 12 years old - and which fails to reflect the huge drop in carbon intensity of the electricity grid. You're doing the right thing by going with electricity (see http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16654).

    I'm installing wet underfloor heating in a refurb that I'm doing, to be powered by Willis heaters. Your timber floor could make that tricky, though there are low-height options available. It frees up the wall space, gives are more even room temperature (potentially saving a couple of degrees on the thermostat) and could theoretically be connected up to a future district heat network, though you loose on responsiveness.

    For hot water, if you can afford it consider a Sunamp unit.

    Your roof insulation thickness is rather skinny - I guess because you're going with a full-height ceiling - but it may be possible to improve a bit on that. Not sure if you've got airtightness & MVHR covered, or if regular EPCs take any notice of either, but worth doing if you can.
    • CommentAuthormarsaday
    • CommentTimeNov 8th 2021
     
    Is the Sap system due to change soon ?

    EPC doesnt take into account loft insulation above 150mm i think. The EPC guy said the last category on the software for loft insulation is 150mm and above. So if you have 200mm of soft insulation it makes no difference compared to 150mm. For kingspan, he just doubles what you have. So 125mm KS is = 250mm soft insulation and so you get no more points as it is all classed as over 150mm soft.
    • CommentAuthorMike1
    • CommentTimeNov 8th 2021 edited
     
    Posted By: marsadayIs the Sap system due to change soon ?
    Theoretically, Yes. SAP 10.2 is supposedly coming in next summer, though not sure if Covid or other factors may cause a delay.

    The draft version (10.1) cuts electrical emissions from 0.519 to 0.233 kgCO2/kWh. That's still much too high (just found a figure* for 2020 of 0.181 kgCO2/kWh), and maybe it will be changed again in the final version (does anybody here know?) but it does redress the balance significantly in favour of electricity.

    It may be worth getting someone to rate your plans against the full draft of SAP 10.2 - which must surely take into account the actual insulation thickness too - rather than the cut-down version of SAP2012 (rdSAP 2012) that your current assessor seems to be using.

    * https://www.nationalgrideso.com/news/record-breaking-2020-becomes-greenest-year-britains-electricity
  1.  
    All true, but just to add that the EPC rating is presently based on the £ costs of energy, not the carbon. (See recent heat pumps thread for ranting about this, not only by me!).

    In SAP10 the cost of electricity (17.56p/unit) is treated as much greater than gas (3.93p), so electric heating is penalised on an EPC, despite it being lower carbon than gas. It's even more of a difference than in SAP2012.

    SAP 10 treats Economy 7 night time electricity as less than half price (8.13p) of daytime, so storage heaters should improve the EPC.

    Wildcard option is a heat pump but maybe not preferred in a flat, and see heatpumps thread for EPC problems with air/air heatpumps.
    • CommentAuthorEd Davies
    • CommentTimeNov 9th 2021
     
    Posted By: Mike1That's still much too high (just found a figure* for 2020 of 0.181 kgCO2/kWh),
    To be fair, the emissions for heating should be compared using a weighted average for the heating season, not the annual average.
    • CommentAuthorbxman
    • CommentTimeNov 9th 2021
     
    I think you can safely say the EPC is a broken system and no one has an interest in reforming it


    With my property there were clear and obvious discrepancies at the time of the survey




    EPC Discrepancy / Our ref 1844

    xxxxxxxxxxxstroma.com>
    22 Mar 2021, 11:45
    to me

    Good Morning Mr XXXXXXXXXXXX

    I hope you are well.



    I have been assigned to look into the complaint that you have raised regarding the EPC on your property XXXXXXXXXXXXXXXXXXX



    Firstly I apologise that the assessor has not responded however unfortunately she would not just be allowed to amend the certificate details , the survey was conducted in June 2014 so this is now aged.



    I’m unsure as to why you are questioning the EPC details at this stage , are you selling your property ?



    You have informed us in your correspondence that the property has been fitted with new windows within the last 3 years so a new survey would need to be conducted in order to evidence the changes.



    You can find an assessor on the gov website here is the link https://www.gov.uk/find-an-energy-assessor if you put in your postcode it will show Domestic Energy Assessors local to you , once the Energy Assessor lodges the new EPC on the register this then will supersede the previous one.



    If you need to chat about this then please do not hesitate to contact me , I will be happy to explain.



    Take care

    Kind Regards



    xxxxxxxxxxx
    Complaints Handler / Administrator

    Office Contact Number
    0330 124 9660



    stroma.com/certification


    They will or may discuss on the phone but will not commit to paper
    • CommentAuthorJohn Walsh
    • CommentTimeNov 9th 2021 edited
     
    Posted By: Ed DaviesTo be fair, the emissions for heating should be compared using a weighted average for the heating season, not the annual average.


    On 'carbon intensity' and kgCO2/kWh, the National Grid ESO carbon intensity phone app currently shows a UK average of 206g CO2/kWh. The app also shows regional breakdown of East Midlands (where I am) currently at 306g CO2/kWh and North East England is 33g CO2/kWh.

    https://carbonintensity.org.uk/ has downloadable data which shows, in the first week of Nov an average of East Mid: 253g, NE: 50g. Data available hour by hour. Some number crunching required here - be interested to to see the average E7 period data by month and region. Such data could be part of trying to force upgrades to EPC based on easily available data.

    To get back to EPCs - can't see how anyone can defend the current situation. Appalling and it would make a big difference if EPCs were part of driving standards not holding them back.
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    Posted By: bxmanI think you can safely say the EPC is a broken system and no one has an interest in reforming it

    I fully agree, but government keeps talking about using them to drive various carbon reduction measures, so it may eventually come back to bite us. At the moment I'm not concerned enough to bother trying to do anything. I'll happily join in with jumping up and down and screaming if it will help.
  2.  
    Posted By: John Walsh
    Posted By: Ed DaviesTo be fair, the emissions for heating should be compared using a weighted average for the heating season, not the annual average.
    be interested to to see the average E7 period data by month and region. Such data could be part of trying to force upgrades to EPC based on easily available data.
    Me too, the EPC should be based on a lower intensity for off-peak electric heating such as E7/E10. Dunno how they would deal with Agile, but they should.

    But more importantly, the EPC lasts for 10 years, so should be based on the likely intensity over the next decade, not on historical numbers, which is now the problem with SAP2012. The draft version of SAP10 is trying to look ahead, but even so it looks like being out of date soon.

    To get back to EPCs - can't see how anyone can defend the current situation. Appalling and it would make a big difference if EPCs were part of driving standards not holding them back.
    Absolutely, they are having a real world impact on people who want or need to let out their home, sometimes for reasons beyond their control If they can't make the ludicrous EPC hurdle then they can't let their house while they relocate to a new job, or to move in with their partner for example. An elderly couple near us have been asked to move out of their rented home, the landlord needs to sell it , in part because he can't reach the necessary EPC to continue letting it in the long term.

    The Scottish government is thinking about plans to set EPC hurdles for all owner-occupied houses, possibly EPC C by 2030, possibly to be enforced when the house is sold.

    As a first step they are going to reform the EPC system, consultation here (non-Scots also welcome to comment!)
    https://www.gov.scot/publications/domestic-epc-reform-consultation/documents/
    • CommentAuthorMike1
    • CommentTimeNov 9th 2021 edited
     
    Posted By: Ed Davies
    Posted By: Mike1That's still much too high (just found a figure* for 2020 of 0.181 kgCO2/kWh),
    To be fair, the emissions for heating should be compared using a weighted average for the heating season, not the annual average.
    An interesting point! I just looked up the figures and looks like the result would still be well below 233 gCO2/kWh:

    Oct 2020 = 194
    Nov 2020 = 177
    Dec 2020 = 185
    Jan 2021 = 218
    Feb 2021 = 179
    Mar 2021 = 185

    https://electricityinfo.org/carbon-intensity-archive/
  3.  
    Hi Mike, SAP 10.2 is available on the BRE website. It uses a headline figure of 136 gCO2/kWh for all electricity, apparently an average number looking ahead only to 2024.

    However on closer examination it does indeed provide figures per month, that are used depending which months it thinks that the building needs heating and hot water and different per tariff:
      Screenshot_20211109-130336.png
  4.  
    And here's the UK government's shopping list for the next-but-one upgrade of SAP

    https://www.etude.co.uk/news/the-future-of-sap-calculations/
      Screenshot_20211109-131917.png
    • CommentAuthorMike1
    • CommentTimeNov 9th 2021
     
    Posted By: WillInAberdeenHi Mike, SAP 10.2 is available on the BRE website. It uses a headline figure of 136 gCO2/kWh for all electricity, apparently an average number looking ahead only to 2024.

    That's more like it. Looks like I have some homework to do :)
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    Hmm, "For background on tables 12d and 12e please see SAP technical paper S10TP-17 on the SAP website."

    But https://www.bregroup.com/sap/sap10/papers/ says:

    "Standard Assessment Procedure (SAP 10)

    "This page hosts papers and other supporting materials relating to SAP 10.

    "[SAP 10.2 is not yet complete. Papers will follow its publication.]"

    and all I've been able to find is "SAP 10 Technical Paper S10TP-15: CO2 and Primary Energy Factors for SAP Version 1.1 (25/11/2020)"
    https://files.bregroup.com/sap/S10TP-15_-_CO2_and_Primary_Energy_factors_for_SAP_v1_1_10_1.pdf

    Anybody know where the get the actual stated reference? Or to whom to apply to get it made available?

    (PS I want to see it because I'm puzzled by the 'electricity sold to grid, PV' row.)
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    Just noticed also in SAP 10.2 Table 13 that my DHW heating will get treated at E7 rate, which is one step closer to reality at least.
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    But Table 12A is depressing. It shows they really haven't thought about highly insulated houses at all. Why would I operate my heating outside the E7 period? The notion that there's a fixed percentage appropriate for all types of houses is just nonsense.
  5.  
    With a smart meter (which we hear elsewhere are replacing the old dual-rate meters for new E7 installations) you can change tariff/supplier easily. What stops someone being on E7 on the day the assessor visits, taking credit for the low prices on their EPC, and switching to a different tariff the next day?

    Marsaday would need to install a few storage heaters to pull that one off. DJH could get one for ornamental purposes. Perhaps they could be returned to the supplier the day after the assessor visits.

    (Don't try this at home folks!)
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    Posted By: WillInAberdeenWith a smart meter (which we hear elsewhere are replacing the old dual-rate meters for new E7 installations) you can change tariff/supplier easily. What stops someone being on E7 on the day the assessor visits, taking credit for the low prices on their EPC, and switching to a different tariff the next day?

    Maybe that's why EPCs are based on costs rather than carbon? You're unlikely to want to either be rated on a more expensive tariff or switch to one afterwards.
  6.  
    Maybe someone would rather be on an Agile tariff? Or an EV tariff?

    Both could be cheaper and/or lower carbon for some of us than E7/10, but both would score badly on an EPC.
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    Posted By: WillInAberdeenMaybe someone would rather be on an Agile tariff? Or an EV tariff?

    True. This is a separate point though, yes? SAP 10.2 doesn't deal with such tariffs. Maybe why not is explained in the missing technical paper, or maybe they're just too new. But anything that affects timing of consumption affects both costs and CO2. Short of dynamically varying EPCs based on some sort of moving average I don't see any way to allow for all possible tariffs.

    Adding a carbon price to the electricity is likely the only way to influence behaviour reliably.
    •  
      CommentAuthordjh
    • CommentTimeNov 9th 2021
     
    Posted By: WillInAberdeenAs a first step they are going to reform the EPC system, consultation here (non-Scots also welcome to comment!)
    https://www.gov.scot/publications/domestic-epc-reform-consultation/documents/

    Just beginning to read this.

    I'm a bit unsettled by them attaching the phrase 'energy use' to the unit 'kWh/m²/year'. The unit doesn't indicate energy use it indicates efficiency of energy use. But both are important. 'energy use' should be attached to 'kWh/year' (or equivalently 'W' :bigsmile:) and it's important to measure both and probably regulate both too (to limit the actions of both good and bad 1%ers maybe?)
    • CommentAuthorCliff Pope
    • CommentTimeNov 10th 2021
     
    <blockquote>

    Marsaday would need to install a few storage heaters to pull that one off. DJH could get one for ornamental purposes. Perhaps they could be returned to the supplier the day after the assessor visits.

    </blockquote>

    No need. Just fit an empty box, like a dummy burglar alarm.
  7.  
    Efficiency is fundamentally a ratio, so should be quoted with units of %, or unitless.

    But the current EPC quotes an 'Energy Efficiency Rating' with underlying units of m².a/£ ..... not exactly SI!

    TBF the Scottish gov propose to reframe that as a Cost Rating in £/a, retain a Carbon Rating in kgCO2/m2/a and add an Energy Use Rating in kWh/m²/a. (Or possibly the inverse of those units, high ratings for low usage).

    The last one is actually not Energy Used, it is based on Energy Delivered from the grid* divided by floor area, so a lossy house with PV or a heatpump will still score highly I think, better than the same house with gas or with storage heaters.

    *or by truck

    They refer to EPC "C" as the threshold required to let a property and to sell a property, from different dates, but is not clear if the "C" rating is required for Cost, Carbon or for Energy as the three metrics will have equal prominence in the EPC.

    The big unknown is how it is going to be applied retrospectively. If you currently have cheap gas heating, that gives you a good EPC. If the new system gives you a poorer EPC because of the carbon emissions, meaning that you can't let, sell or (so presumably) remortgage your house, that will cause disruption (perhaps necessary). Will that be fudged by letting people retain their old ratings?


    Posted by me:>>>>"However on closer examination [SAP] does indeed provide [carbon intensity] figures per month, that are used depending which months it thinks that the building needs heating and hot water and different per tariff:"

    On even closer examination, the different carbon figures per month and per tariff are not actually very much different from each other. Maybe this is too much detail.
    •  
      CommentAuthordjh
    • CommentTimeNov 10th 2021
     
    Posted By: WillInAberdeenBut the current EPC quotes an 'Energy Efficiency Rating' with underlying units of m².a/£ ..... not exactly SI!

    TBF the Scottish gov propose to reframe that as a Cost Rating in £/a, retain a Carbon Rating in kgCO2/m2/a and add an Energy Use Rating in kWh/m²/a. (Or possibly the inverse of those units, high ratings for low usage).

    Yeah, my point was about the presence of the m² factor, which gives no weight to the overall size of the building and the overall scale of the building. Something like Buck House could score well in theory, whilst standing no chance of being a sensible use of resources for the planet.

    On even closer examination, the different carbon figures per month and per tariff are not actually very much different from each other. Maybe this is too much detail.

    I was thinking that myself. SAP is full of weird little complications like all these different factors for some selection of electricity tariffs or for an apparently arbitrary selection of cylinder sizes. Lots of details and make-work all to not much effect and big gaps elsewhere. Written by a committee one suspects.
    • CommentAuthorMike1
    • CommentTimeNov 10th 2021
     
    Posted By: WillInAberdeenthe Scottish gov propose to reframe that as a Cost Rating in £/a, retain a Carbon Rating in kgCO2/m2/a and add an Energy Use Rating in kWh/m²/a.

    FWIW, the new French EPC is based on thresholds for kWh/m2/year & CO2/m2/year - you have to pass both thresholds to reach a particular grade:

    A = <70 kWh/m²/year + < 6 kg CO2/m²/year
    B = 70 to 110 kWh/m²/year + 6 to 11 kg CO2/m²/year
    C = 110 to 180 kWh/m²/year + 11 to 30 kg CO2/m²/year
    D = 180 to 250 kWh/m²/year + 30 to 50 kg CO2/m²/year
    E = 250 to 330 kWh/m²/year + 50 to 70 kg CO2/m²/year
    F = 330 to 420 kWh/m²/year + 70 to 100 kg CO2/m²/year
    G = >240 kWh/m²/year + >100 kg CO2/m²/year

    Seems logical to me.
    •  
      CommentAuthordjh
    • CommentTimeNov 10th 2021
     
    Posted By: Mike1the new French EPC is based on thresholds for kWh/m2/year & CO2/m2/year

    Just to check I've understood correctly - nothing about cost at all, no € signs anywhere?

    Is the kWh/m²/year figure Renewable Primary Energy Demand (PER, according to PHI method) or something different?
  8.  
    Posted By: Mike1FWIW, the new French EPC is based on thresholds for kWh/m2/year & CO2/m2/year - you have to pass both thresholds to reach a particular grade:

    A = <70 kWh/m²/year + < 6 kg CO2/m²/year
    B = 70 to 110 kWh/m²/year + 6 to 11 kg CO2/m²/year
    C = 110 to 180 kWh/m²/year + 11 to 30 kg CO2/m²/year
    D = 180 to 250 kWh/m²/year + 30 to 50 kg CO2/m²/year
    E = 250 to 330 kWh/m²/year + 50 to 70 kg CO2/m²/year
    F = 330 to 420 kWh/m²/year + 70 to 100 kg CO2/m²/year
    G = >240 kWh/m²/year + >100 kg CO2/m²/year

    Seems logical to me.

    Makes sense - except if the government (or others) fail to get the grid co2/kWh down then your EPC rating gets screwed, assuming you are on some form of electric heating.
    •  
      CommentAuthordjh
    • CommentTimeNov 11th 2021
     
    Posted By: Peter_in_Hungaryexcept if the government (or others) fail to get the grid co2/kWh down then your EPC rating gets screwed

    Well the French figure last year was apparently 57.3 gCO2/KWh and is likely to go UP to 70 gCO2/KWh by 2050.
    All of which is well below the number to mean you won't lose your certificate.

    France has a lot of nuclear.
    • CommentAuthorMike1
    • CommentTimeNov 11th 2021 edited
     
    Posted By: djhJust to check I've understood correctly - nothing about cost at all, no € signs anywhere?
    Definitely no €s involved in calculating the rating!

    The certificate does, however, include the expected range of the associated energy bill - for information - based on a standard usage scenario and set rates in a reference year.

    It also comes with an 'good / average / poor' rating for summer comfort (based only on passive measures, not aircon), ratings for heat loss through the various elements of the fabric, improvement recommendations...
    ...and an official 'leaks heat like a sieve' warning if it's rated F or G (it will become illegal for landlords to rent these).

    Also worth knowing that if the householder / tenant doubts the accuracy of the assessment, they have the right commission their own assessment and sue for damages if the original was incorrect...

    Posted By: djhIs the kWh/m²/year figure Renewable Primary Energy Demand (PER, according to PHI method) or something different?
    It's the consumation of primary energy used by heating, cooling, hot water, lighting & associated equipment (but pretty sure it doesn't include household appliances).
   
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