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General: Passive House EPC figures

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    Hi folks

    I'm just wondering, if a standard EPC report is made on a house built to Passive House standards, what sort of figure would you expect to see in terms of kW/hr/M^2 per year?

    Thanks,
    Martin.
    • CommentAuthorEd Davies
    • CommentTimeJun 28th 2012
     
    Yes, that'd be interesting to know. I'd not be very surprised if it depended a lot on how you achieved PH standards - e.g., balance of solar gain against insulation.

    I read somewhere that the Hockerton houses only get to band D. I think it's because the EPC doesn't take enough (any?) notice of thermal mass so, in the absence of better heating, assumes they're heated with electric resistance heating.

    Pedantically: “kWh/m^2 per year”. I.e., multiplication of kilowatts by hours, not division (ideally with a middle dot if you can manage it, “kW·h”, but presumably you don't know how to do that on your system otherwise you'd likely have used “²” instead of “^2” as well); 'h' rather than 'hr' as the standard symbol for hours and lower case 'm' for metres. Avoiding writing “kW/h” (except for the very very rare occasions it's what's really meant) is the main thing, though.
    • CommentAuthorskyewright
    • CommentTimeJun 28th 2012
     
    I don't think it was specifically designed to a Passive House standard, but here's someone who managed >100% on both energy efficiency and environmental impact for a new build SAP (N.B. they are off-grid).

    http://www.navitron.org.uk/forum/index.php/topic,15679.0.html
  4.  
    The passive house standard is 15 kWh/m2/y for heating, or 120 kWh/m2/y including heating/hotwater/appliances/lighting.

    I'm understanding that a lot of EPC reports are done using the rdSAP method, which is based on the age of the house and the price of its primary fuel source, not how well it is construced, so could give confusingly low score for a passive house?

    Pedantically (we all enjoy pedantry), the SI units for [kWh/m^2 per year] are [W / m^2]. Or if we prefer [J / m^2 / s]. Or even [grammes / second^3]. Or something involving a lot of electronvolts. But I guess so long as we all understand what is being meant, thats the main thing.

    How did you do that thing with the scalar product dot, I can only get full stops ?Interestingly (or not) the SI symbol for hour is "h" not "hr", but it is not defined whether year should be "y" or "yr".:bigsmile:
    • CommentAuthortony
    • CommentTimeJun 28th 2012
     
    In the latest GBM there is a survey of Passive Hauses with heating energy usages ranging from zero to 48 with a mean of 16kWh/m2/y
    • CommentAuthorEd Davies
    • CommentTimeJun 28th 2012
     
    “How did you do that thing with the scalar product dot”

    http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=5434&page=3
    •  
      CommentAuthorJSHarris
    • CommentTimeJun 28th 2012
     
    I ran my proposed design (which just about meets passivhaus standards but isn't going to be certified) through FSAP and it only got a B. The main problem was heating and hot water, had it been on mains gas then it would have got an A....................
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 28th 2012
     
    What this • as opposed to that . ♥☻
    Alt + 7
    • CommentAuthorDarylP
    • CommentTimeJun 28th 2012
     
    SAP (and by default RdSAP) is a CO2 reduction assessment/tool. It does not model hot water energy demand at all well.
    I would be surprised if a PassivHaus-certified dwelling scored well in SAP?

    To get 'A' in SAP just plug in LZC/renewables that reduce grid electricity usage, and you're there.

    I use SAP on a daily basis, but I am not saying it's the 'bees knees' in any way....

    Cheers...:confused:
  10.  
    Thanks WillinAberdeen. That gives me some context for the figures I'm seeing in EPCs.

    Incidentally - I lifted the 'kW/hr/M^2 per year' straight from the EPC I was just looking at. Whether it's strictly correct or not, that's what they're using, it seems.

    Martin.
    • CommentAuthorTimSmall
    • CommentTimeJun 29th 2012 edited
     
    Posted By: palebluedotI lifted the 'kW/hr/M^2 per year' straight from the EPC I was just looking at.


    That speaks volumes…


    Do I get extra points for using the ellipsis character in my reply?
    • CommentAuthordjh
    • CommentTimeJun 29th 2012
     
    Posted By: WillInAberdeenThe passive house standard is 15 kWh/m2/y for heating, or 120 kWh/m2/y including heating/hotwater/appliances/lighting.

    ...

    Pedantically (we all enjoy pedantry), the SI units for [kWh/m^2 per year] are [W / m^2].

    Some more pedantry for the sake of future readers:

    The passive house standard is 15 kWh/m2/y for heating, AND 120 kWh/m2/y including heating/hotwater/appliances/lighting.

    But instead of 15 kWh/m²/y you can choose instead 10 W/m². 15 kWh/m²/y is a limit for the annual heat demand (i.e. the yearly heating bill). 10 W/m² is a limit for the instantaneous heat load (i.e. the size of the heating system).
  13.  
    Ed Davies - I stand multiply corrected. As I said, I lifted what I wrote from an EPC I was looking at yesterday, but I did write ^2 instead of superscript 2, as I don't know how to do that here (as opposed to a word doc). Also - I wrote M instead of m for metres - entirely my gaff.

    Really I was just trying to get a feel for whether a house that was advertised in an EPC at 220kWh per m^2 per year was leaking like a sieve or very respectable, or somewhere in between.
  14.  
    Tim Small...

    Extra points are always available for elipses...
    • CommentAuthordjh
    • CommentTimeJun 30th 2012
     
    Posted By: palebluedotIncidentally - I lifted the 'kW/hr/M^2 per year' straight from the EPC I was just looking at. Whether it's strictly correct or not, that's what they're using, it seems.

    Interesting; it doesn't appear on my EPC. Whereabouts on the EPC is it? Can you post an image?
    •  
      CommentAuthorDamonHD
    • CommentTimeJun 30th 2012
     
    I see this in my EPC:

    165 kWh/m^2 per year

    [Note: I've converted superscripted 2 to ^2]

    on page 1, posted here:

    http://www.earth.org.uk/data/20090330_WW_pressure_test/EPC_985041_.pdf

    Rgds

    Damon
    • CommentAuthorchriskemp
    • CommentTimeJul 3rd 2012
     
    • CommentAuthornprior
    • CommentTimeJul 3rd 2012
     
    Just to add another data point...

    We've had an EPC carried out for a house we are in the process of selling (before we start building our new one). This house is a 1980's vintage brick built with minimal cavity and wooden flooring. We have mains gas, 20cm loft insulation and have filled the cavity with something fluffy.

    Our EPC cert says: "166kWh/m2" with "156kWh/m2" possible if we put some energy efficient light bulbs in, from C71 to C73. (Then C74 if we went for solar thermal, and B83 if we spent a small fortune on PV)

    This based on a highly scientific in depth survey (RdSAP) of the property that took all of 15 minutes.

    It all feels fairly approximate - the expected cost of fuel per annum in the report is about 25% adrift in the optimistic direction.
    • CommentAuthordjh
    • CommentTimeJul 6th 2012
     
    Posted By: chriskempI asked this myself on LinkedIN.

    http://www.linkedin.com/groupItem?view=&gid=2892789&type=member&item=112882813&qid=ed2adeda-cda1-40e1-b40b-5d1f77fa11e3&trk=group_most_popular-0-b-ttl&goback=%2Egmp_2892789" >http://www.linkedin.com/groupItem?view=&gid=2892789&type=member&item=112882813&qid=ed2adeda-cda1-40e1-b40b-5d1f77fa11e3&trk=group_most_popular-0-b-ttl&goback=%2Egmp_2892789

    which maybe of interest?


    "Sign in to LinkedIn
    Make sure you have cookies and Javascript enabled in your browser before signing in."

    Sorry, you asked what?
    • CommentAuthorchriskemp
    • CommentTimeJul 15th 2012
     
    Sorry.
    I asked the same question on linked in with regards what EPC passive houses achieved...

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