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Energy Assessment: How are EPC ratings calculated?

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    • CommentAuthoratomicbisf
    • CommentTimeNov 6th 2014 edited
     
    I've just had a Green Deal Assessment and the resulting EPC rating of D 57. However I've looked at the online EPC register and an identical neighbouring house has a rating of C 76, despite every listed element either being the same or worse than my house. For example I have more loft insulation, better heating controls, better wall insulation etc, better lighting etc. They do not have a single listed thing that scores better than me, yet are nine points higher.

    Can this number be trusted at all?

    Ed
  2.  
    What do you expect if you call your house 'Widdershins'!
    • CommentAuthorDarylP
    • CommentTimeNov 6th 2014
     
    atomicbisf,

    It depends on many factors.... not least when the assessments were done. rdSAP has evolved, on the back of SAP, over the years.

    However, if yours is a BISF house, as your neighbour's, I would suggest that your neighbour's is wrong.
    Very few DEAs would recognise a BISF house, or know how to input it to the rdSAP s/w....:cry:

    At least you know the score...
    • CommentAuthorMikel
    • CommentTimeNov 6th 2014 edited
     
    Ed, do you know when the neighbouring house had their EPC done? Methodology has changed over tIme.
  5.  
    It was done in August 2013 so fairly recently. The house is also a BISF house so identical in size and in every way apart from any improvements that have been done.

    The assessor was actually much better than I expected and wanted me to show him photos of the wall insulation as evidence and did adapt the report based on what I told him I was going to DIY.

    On the EPCs itself it just says for walls "system built, as built, no insulation (assumed)" one out of 5 stars/"system built, as built, no insulation (assumed)" four out of 5 stars for me (as some walls have IWI and some don't. On the other EPC it says ""system built, as built, no insulation (assumed)" one out of 5 stars, so I'm not sure if it depends on any knowledge of the construction apart from it being system-built.

    Ed
    • CommentAuthorDarylP
    • CommentTimeNov 6th 2014
     
    atomicbisf,


    Any future DIY works cannot be included in the EPC. It is a reflection of the dwelling as assessed.
    It sounds like the DEA accepted what had been done, and included the extra insulation in at least some of your external walls?

    However there are still differences between the data for your EPC compared to your neighbour....

    Cheers :smile:
  7.  
    Sorry, I think I've overlooked the obvious! The house in question has solar PV, but this is not listed on the EPC.

    Ed
  8.  
    Posted By: DarylPatomicbisf,


    Any future DIY works cannot be included in the EPC. It is a reflection of the dwelling as assessed.
    It sounds like the DEA accepted what had been done, and included the extra insulation in at least some of your external walls?

    However there are still differences between the data for your EPC compared to your neighbour....

    Cheershttp:///forum114/extensions/Vanillacons/smilies/standard/smile.gif" alt=":smile:" title=":smile:" >


    Ah yes, I mean he has taken into account I will be doing the insulation myself and so has not listed it as a recommended measure. I'm not sure how he has scored the walls to reflect that about 30% has been IWIed and 70% is still original as it just lists that there are both.

    Ed
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 6th 2014
     
    Here are the numbers for 5 of the 6 houses near me

    House A: D 66 (end terrace)
    House B: D 67 (mid terrace)
    House C: C 76 (mid terrace)
    House D: D 59 (end terrace)
    House E: D 62 (end terrace)

    They are all the same size though the EPC does not reflect this

    House A: 56m^2
    House B: 95m^2
    House C: 54m^2
    House D: 57m^2
    House E: 79m^2

    The kWh/year is also different

    House A: 4995 (space), 1793 (DHW)
    House B: ND,ND, 27455 (estimated from EPC figures of 289kWh/m^2)
    House C: 2756 (space), 1860 (DHW)
    House D: ND,ND 27022 (estimated from EPC figures of 458kWh.m^2)
    House E: 6920 (space), 2222 (DHW)

    Just a lot of inaccurate nonsense.
    Rubbish in, rubbish out.
    • CommentAuthorskyewright
    • CommentTimeNov 6th 2014 edited
     
    Posted By: atomicbisfSorry, I think I've overlooked the obvious! The house in question has solar PV, but this is not listed on the EPC.

    I think you are probably right. I was just about to ask if there was any PV involved.

    We had a GDA today. The assessor definitely considered our PV as relevant - among other things he took a pic of MCS certificate, the GTI and the panels themselves.

    It's a 1970 built house that was un-improved when we arrived & all the insulation has been DIY'd using a variety of materials so given some of what I'd read on forums I was a bit unsure what he'd be able to count. Fortunately he was able to get his digi camera into enough voids to get pics that he seemed to feel were sufficient evidence.

    It will be very interesting to see how the figures come out.

    I presume that being "all electric" will drag our rating down, but doing something about that is part of the idea in getting the GDA in the first place (GSHP being the idea we are most interested in)...
  11.  
    The other nearby EPCs seem reasonable. For example the houses owned by Curo (housing association) that have EWI have higher scores, and the floor areas are only out by up to two square metres.

    The report does illustrate one of the big problems with the Green Deal though in that if you are a relatively low user of energy the savings to be made are not much.

    For example they have worked on 6040 kWh of space heating and 2131 kWh of hot water per year, giving an annual saving of £55 for installing a condensing boiler...

    Ed
  12.  
    By throwing the bones of a crow in the air, the way they land gives you all the info required
    • CommentAuthorJeff B
    • CommentTimeNov 6th 2014
     
    atomicbisf - you don't have a wood pellet boiler do you by chance? I only ask because we have one and we have a farcical situation here because all wood pellet boilers are given a "generic" efficiency value which I understand is way below the actual, about 60% I believe (ours is 93%). Hence our house has a lowly D rating despite being insulated to the hilt and an A-rated CO2 emission figure (99%). I could get a better EPC rating if I went back to oil! It's all to do with SAP apparently and I have written to the B.R.E. to ask why the respective boiler databases are not coordinated.
    • CommentAuthorDarylP
    • CommentTimeNov 6th 2014
     
    They are... but your wood pellet boiler has (probably) not been tested to BS ?
    SAP uses tested values, not what manufacturers want you to think!

    Look at http://www.ncm-pcdb.org.uk/sap/ for the tested values used in SAP calcs and EPCs.

    Cheers:smile:
  15.  
    Posted By: Jeff Batomicbisf - you don't have a wood pellet boiler do you by chance? I only ask because we have one and we have a farcical situation here because all wood pellet boilers are given a "generic" efficiency value which I understand is way below the actual, about 60% I believe (ours is 93%). Hence our house has a lowly D rating despite being insulated to the hilt and an A-rated CO2 emission figure (99%). I could get a better EPC rating if I went back to oil! It's all to do with SAP apparently and I have written to the B.R.E. to ask why the respective boiler databases are not coordinated.


    No, no wood pellet boiler or anything like that, just an antiquated gas back boiler. The house was originally heated with some sort of coal stove and early convection central heating system with a coal store in the out house.

    I should add that along with the EPC the assessor did an occupancy assessment that used my actual electricity and gas usage and it is the savings on the latter that the Green Deal savings are worked out on. The EPC assumes an average heating temperature and length of heating etc so you can compare homes, which might be quite different from the actual usage.

    It's all rather academic as it seems the only practical impact is on solar PV FITs, and I think the solar itself would have raised the rating from the original band E to band D anyway!

    Ed
  16.  
    Posted By: GotanewlifeWhat do you expect if you call your house 'Widdershins'!


    Whose house is called Widdershins? I was trying to think of a name, maybe that will stick ;)
  17.  
    I thought we'd got our posts crossed. You only need Widdershins if you want to replace an electro-osmotic d.p.c.
    • CommentAuthorGotanewlife
    • CommentTimeNov 6th 2014 edited
     
    No, I was just musing (perhaps too obliquely) on a possible cause of the contrary outcome of the EPC - ie like the bones of the crow. I must try harder...
    • CommentAuthorJeff B
    • CommentTimeNov 7th 2014
     
    Posted By: DarylPThey are... but your wood pellet boiler has (probably) not been tested to BS ?
    SAP uses tested values, not what manufacturers want you to think!

    Look athttp://www.ncm-pcdb.org.uk/sap/" >http://www.ncm-pcdb.org.uk/sap/for the tested values used in SAP calcs and EPCs.

    Cheers:smile:" alt=":smile:" src="http:///forum114/extensions/Vanillacons/smilies/standard/smile.gif" >




    Our boiler is on the MCS approved list though (wouldn't have qualified for RHI if it wasn't). Presumably MCS required some actual data from the manufacturer?
    • CommentAuthorDarylP
    • CommentTimeNov 7th 2014
     
    JeffB,

    MCS approval is not testing. RHI is based on your EPC, which uses the tested data, or 65% if not tested.
    However, for RHI you benefit from a 'poor' EPC.....:confused: as the RHI is based on deemed energy consumption! :cry:
    • CommentAuthorJeff B
    • CommentTimeNov 7th 2014
     
    Posted By: DarylPJeffB,

    MCS approval is not testing. RHI is based on your EPC, which uses the tested data, or 65% if not tested.
    However, for RHI you benefit from a 'poor' EPC.....:confused:" alt=":confused:" src="http:///forum114/extensions/Vanillacons/smilies/standard/confused.gif" >as the RHI is based on deemed energy consumption!:cry:" alt=":cry:" src="http:///forum114/extensions/Vanillacons/smilies/standard/cry.gif" >


    Daryl - that's the irony of the situation though. By insulating the house well (in addition to cavity wall insulation and 270 mm in the loft which was already in place), we have reduced our heating demand by about one-third, down from 21,000 kWh to 14,000 kWh per annum. OK I know that's not exactly Passihaus standard but considering we have a detached 4 bed dormer bungalow in an exposed hilltop, windy situation, not too bad I think. Had we not done this work then we would have been paid quite a lot more under the RHI scheme!

    But to me that is not the point. I am rather proud of the fact that not only have we reduced our heating requirement we have also slashed our carbon footprint and yet we are "rewarded" with a D rating on our EPC. If I was house hunting I would not even bother to look at a property with a D rating. There is something inherently wrong here. I will await a response from the B.R.E.

    I understand what you say about the MCS approval and yet MCS will declare certain products as ineligible if they don't meet the relevant standards, so surely my boiler must have satisfied some standard to be on the approved list?
    • CommentAuthorSigaldry
    • CommentTimeNov 7th 2014
     
    If you know the ratings, presumably you know the RRN (reference number). In which case, go to: https://www.epcregister.com/epcadviser.html and you can find out what your calculations are based on / how they could be improved.

    Doesn't seem to work for new build ones though.

    A lot of the DEA / RDSAP stuff will be based on generic look-up tables based on observable things and the age of the property - but assessors can overide if they have sufficient proof of actual performance.

    Heating systems and controls can make quite a difference as well between two otherwise very similar dwelling...

    Equally with the knock down, cheap rate that assessors get for RDSAP /DEA work, I wouldn't particularly be surprised if the quality of their work might be a bit lacking.

    I've had 'panel' companies trying to get me to do EPC's for existing dwellings 60 miles away from where I live for the princely sum of £30.00, to cover my time, travel expenses, insurances etc and everything else - now that's at least an hours drive each way, plus survey time / getting it produced - really not worth it.

    (Glad I'm not a DEA - no idea how they make a living - I suspect by cutting all the corners they can)


    Sigaldry
    • CommentAuthorGreenfish
    • CommentTimeNov 7th 2014
     
    The assessor of our new build also gave me copy of his calculations which was interesting, I had assumed this was normal. Ask for yours perhaps?

    Because we had a wood burner rather than a gas combi, and the pathetic and inaccurate generic efficiency the procedure imposes, we just missed an "A". Lots of insulation, air tight, PV etc. the only thing that we could "improve" was to add a gas boiler, which is impossible given the lack of gas supply for mile. Whole thing is a crock, can we use crow method in future?
  24.  
    Posted By: SigaldryIf you know the ratings, presumably you know the RRN (reference number). In which case, go to:https://www.epcregister.com/epcadviser.html" rel="nofollow" >https://www.epcregister.com/epcadviser.htmland you can find out what your calculations are based on / how they could be improved.

    Doesn't seem to work for new build ones though.

    A lot of the DEA / RDSAP stuff will be based on generic look-up tables based on observable things and the age of the property - but assessors can overide if they have sufficient proof of actual performance.

    Heating systems and controls can make quite a difference as well between two otherwise very similar dwelling...

    Equally with the knock down, cheap rate that assessors get for RDSAP /DEA work, I wouldn't particularly be surprised if the quality of their work might be a bit lacking.

    I've had 'panel' companies trying to get me to do EPC's for existing dwellings 60 miles away from where I live for the princely sum of £30.00, to cover my time, travel expenses, insurances etc and everything else - now that's at least an hours drive each way, plus survey time / getting it produced - really not worth it.

    (Glad I'm not a DEA - no idea how they make a living - I suspect by cutting all the corners they can)


    Sigaldry


    Hi, I had a look but couldn't see anything about the calculations. My reference number is 8795-4939-7029-3026-0043 if you're interested. It did give the option though to add various measures and see what the resulting (cumulative) score will be:

    Topping up the loft insulation from 100 mm to 250 mm (in reality this is basically done, I just had some of the top layer up up while putting boards down when he happened to come round) - no change at D57

    Condensing gas boiler - D66

    Condensing gas boiler with flue heat recovery - D67

    Solar PV 3.8 kW - B82

    As a comparison a BISF house nearby with EWI and condensing boiler is C74, ref no. 8657-7721-1020-9312-2902

    Ed
    • CommentAuthorDarylP
    • CommentTimeNov 7th 2014
     
    8 Shaws Way has "external insulation".... hence the improved EE rating....:bigsmile:
    • CommentAuthorDarylP
    • CommentTimeNov 7th 2014
     
    JeffB,

    No, MCS registration/certification is no indication of quality/efficiency... just that the mfrs/importers/distributors have paid up!

    If you want tested efficiencies, look for the PCDF values.....:smile:
    • CommentAuthoratomicbisf
    • CommentTimeNov 7th 2014 edited
     
    Posted By: DarylP8 Shaws Way has "external insulation".... hence the improved EE rating....http:///forum114/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt=":bigsmile:" title=":bigsmile:" >


    Sorry, that was just an example of a similar home with various upgrade measures. The one originally in question is 8795-4939-7029-3026-0043 (35 Freeview Road). Turns out the solar PV is listed, I just missed it because it's listed separately! :shocked:

    But there's still a bit of a mystery, because if I take off the 15 points for 3.8 kW of solar PV it takes them to D61, which is still higher than me even though their walls are worse, their loft insulation is worse, floor is the same, windows are worse, main heating is the same, heating controls are worse, hot water is the same and lighting is worse!

    Ed
  28.  
    Freeview Road?

    How many channels can it get?

    and...

    ''Turns out the solar PV is listed''.....


    Well, it had to happen sometime. Will you have to apply for LB consent every time you want to re-paint your panels? :bigsmile:
  29.  
    I'm not sure if the steel frame and cladding would help reception by acting as a giant antenna or hinder it by acting as a Faraday cage ;)

    Rather ironically, Freeview reception at Freeview Road and in most of Bath is poor as the hill to the south blocks the main transitter on the Mendips. The local explanation is that it refers to the free view of Bath City FC that could be had before the newest houses were built, but that sounds like a folk etymology to me and I think the boring explanation of the panoramic view across the Avon Valley to the north is more likely.

    Ed
    • CommentAuthorJeff B
    • CommentTimeNov 7th 2014
     
    Posted By: DarylPJeffB,

    No, MCS registration/certification is no indication of quality/efficiency... just that the mfrs/importers/distributors have paid up!

    If you want tested efficiencies, look for the PCDF values.....:smile:" alt=":smile:" src="http:///forum114/extensions/Vanillacons/smilies/standard/smile.gif" >


    DarylP: What about those products that are deemed ineligible then - presumably these manufacturers have "paid up" too otherwise why would MCS be involved with their equipment in the first place. What criteria are MCS using to disqualify the equipment?

    Where can I find PCDF values please?

    Jeff

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