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Energy Assessment: How to compare heating energy of homes

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    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    We seem to be entering a very confusing and often meaningless era of comparing percentage energy savings.

    Why arent we using absolute numbers like kWh/m2/y?

    These can then be tabulated for different types of homes, all homes different years etc

    but at least we would be able to what was going on.
    •  
      CommentAuthorSteamyTea
    • CommentTimeMar 20th 2011
     
    Posted By: tonyWhy arent we using absolute numbers like kWh/m2/y?


    Good start but a house is a 3D object so there has to be some sort of adjustment for this.
    Volume/Footprint and Surface Area/Footprint would be more meaningful. Think I have read somewhere that this is done in SAP.
    The other unknown is the temperature of houses, these are usually one room means or perception of hot or cold, very misleading. Geographic location/solar orientation is also a problem. All these things have to be standardised before a correlation between energy use and age can be established.
    My mate who did this research is sunning himself in Bali at the moment, but shall see if I can grab the data off him when he is back in a couple of weeks.
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    As average ceiling heights 2.4m , i'd have though m2 of floor area would be fine rather than m3.
    kwh/m2/year is what passivhaus, AECB and others use to judge energy efficency of buildings
    internal temperature, would depend on the user, so out of the designers control, the kwh/m2/year set at say presumed int. temp. of 20 deg. C would give a possible average expected energy use?

    How about a more green lefty view, should we be looking a kWh/m2/year/person(building user/occupant)
    •  
      CommentAuthorSteamyTea
    • CommentTimeMar 20th 2011 edited
     
    Posted By: jamesingramHow about a more green lefty view, should we be looking a kWh/m2/year/person(building user/occupant)

    kWh/m2/year/person/building user/occupant/income/education/newspaper

    I read 4 different ones so would have to vary it by weekday, Saturday and Sunday, Thursday I get my comic so that may skew it even more :wink:
  5.  
    "Thursday I get my comic so that may skew it even more "

    What's that Viz ?
    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    the problem with the per person idea is that it is measuring something very useful and very green

    But I was trying to get a handle on building or house energy use.


    I like the idea that PH and AECB etc are using real numbers rather than percentages and for me this is the way to go with it.
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    http://retrofitforthefuture.org/projectbrowser.php
    all the project on the low energy building database are expressed in kWh/m2/y and kgCO2/m2/y
    Fancy sticking your place on it Tony ?

    i put up a project i finished a while back , Longwall house, still need to up date some info though
    http://retrofitforthefuture.org/projectbrowser.php?fbt=0&fbs=Private%20Residential
    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    I tried and got rejected!
    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    :cry:
    • CommentAuthorskyewright
    • CommentTimeMar 20th 2011
     
    Posted By: jamesingram...the kwh/m2/year set at say presumed int. temp. of 20 deg. C would give a possible average expected energy use?

    How about a more green lefty view, should we be looking a kWh/m2/year/person(building user/occupant)

    Should degree days perhaps be in there somewhere too?
    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    degree days would be implicit in the internal temperature

    Passivehouse allows less good insulation the further south you are

    so are you asking if there should be more insulation in homes in colder regions? -- I recon yes there should be

    Low energy use is the aim.
    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    anyone know what current building regs are requiring in terms of kWh/m2/y?
  13.  
    Posted By: tonydegree days would be implicit in the internal temperature
    How so? The internal temperature is determined by the incidental gains (occupants, appliances, solar etc.) and the heat supplied by the heating system. The HDD (and CDD) make a significant difference to the amount of energy the heating system has to supply to maintain that internal temperature. Of course, a fluctuating internal temperature, as is the norm in the UK, makes the calculation all the more difficulty compared to, say, where I live and a more static temperature is used in winter etc.

    Also beware with kWh/m2/year as units as some places use this as a measure of primary energy (eg the amount of energy in the coal used to fire the powerstation) and other places use it to measure energy delivered in the house. Programs like hot2000 calculate the total amount of heat energy that has to be supplied to the building to maintain a specific internal temperature for a full year, taking average insolation and weather data into account. This is measured in mega or giga joules. The user can turn this into primary energy if desired, assuming the conversion factors are known.

    Paul in Montreal.
    •  
      CommentAuthorSteamyTea
    • CommentTimeMar 20th 2011
     
    Posted By: jamesingramWhat's that Viz ?

    Nothing as abstract as that :bigsmile:
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    "Also beware with kWh/m2/year as units as some places use this as a measure of primary energy (eg the amount of energy in the coal used to fire the powerstation) and other places use it to measure energy delivered in the house. "
    Yes needs to be primary energy to make any sense as a energy efficiency measure
    Ph , AECB, retrofit for a future , use primary energy

    Posted By: tonyI tried and got rejected!

    strange , i wonder why ? is it worth following up , i'd have thought your build/energy usage info would be a useful addition
    • CommentAuthortony
    • CommentTimeMar 20th 2011
     
    I didnt understand it either
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    <blockquote><cite>Posted By: tony</cite>anyone know what current building regs are requiring in terms of kWh/m2/y?</blockquote>

    EST house comparison data sheets for various house types showing potential effect of energy efficiency improvement, forgot about these , as they seem a very useful tool and need publicising.

    http://www.energysavingtrust.org.uk/Publication-Download/?oid=1532044&cg=bestpracticedocs&ci=energyst
    "these ‘House Type’ scenarios show the base case and improvements for refurbishing an existing dwelling to a high level of energy performance"
    http://www.energysavingtrust.org.uk/business/Business/Housing-professionals/Existing-housing/House-types

    from the above
    2002- mid terraced home
    gas. 103 kwh/m2/y
    elect. 48 kWh/m2/y

    so total primary energy
    103 + ( 48 x 2.78) = 236 kWh/m2/y
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    <blockquote><cite>Posted By: tony</cite>I didnt understand it either</blockquote>

    http://www.carbonlite.org.uk/carbonlite/lowenergybuildings.php
    I think it may only be AECB and retrofit for a future members that can post projects , not sure

    I'll ask .

    just received an email
    "The low energy building database is open to all.The only information which is required to create a user account is a name and contact address.Telephone and email contact are requested but not mandatory."

    Tony, if you're still keen to post up your place , I'll forward the email to you ( as they offer to help with registration if required. )
  19.  
    Posted By: jamesingram"Also beware with kWh/m2/year as units as some places use this as a measure of primary energy (eg the amount of energy in the coal used to fire the powerstation) and other places use it to measure energy delivered in the house. "
    Yes needs to be primary energy to make any sense as a energy efficiency measure
    Ph , AECB, retrofit for a future , use primary energy


    Whoa, be careful. For heating loss PH doesn't use Primary Energy, just energy lost from the house with no regard to where it comes from. The target is 15kWh/m2.a.

    PH does also specify an energy target for the total background consumption of the property, including heating, lighting, washing, DHW, appliances etc. and this is measured in terms of Primary Energy. This is 120kWh/m2.a and is generally much easier to hit than the heating loss figure.

    It's unlikely that PH itself would be an incentive to reduce the PE consumption of a property since you've really got to be trying to break the PE target. Pure immersion space and DHW heating might make it challenging but otherwise it shouldn't be hard.
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    yes, i'm muddling PH design target with the AECB standards, usage targets.
    I presumed 15kWh/m2.a. was the maxium allow energy use for space heating in terms of primary energy though

    http://www.aecb.net/PDFs/carbonlite/AECB_VOL3_EnergyStandard_V6FINAL.pdf
    • CommentAuthorjamesingram
    • CommentTimeMar 20th 2011 edited
     
    Though i've never quite understood the 120kWh/m2/y PH total primary energy usage target.
    My home achieves that , and its nothing special , only modest insulation levels.
    Why is it so high?

    the project i posted on the low energy building database been averaging about
    93 kWh/m2/y of PE for all usage for the last 2-3 years and it only to some where near AECB silver standard (slightly better insulation levels than required by current regs)
    • CommentAuthorskyewright
    • CommentTimeMar 21st 2011
     
    Posted By: tonydegree days would be implicit in the internal temperature
    Passivehouse allows less good insulation the further south you are
    so are you asking if there should be more insulation in homes in colder regions? -- I recon yes there should be
    Low energy use is the aim.

    I see where you are coming from, but if they are disregarded doesn't it become hard to make comparative use of "real life" (as opposed to theoretical) data?

    i.e. a figure established from actual use in one house might have been based on data for a year (or years) that happened to be warmer than average, while a figure for another house might have been based on a colder year? Ideally of course both figures would be obtained over the same period, but...
    • CommentAuthorjamesingram
    • CommentTimeMar 21st 2011 edited
     
    just received an email
    "The low energy building database is open to all.The only information which is required to create a user account is a name and contact address.Telephone and email contact are requested but not mandatory."

    Tony, if you're still keen to post up your place , I'll forward the email to you ( as they offer to help with registration if required. )
    • CommentAuthorjamesingram
    • CommentTimeMar 21st 2011 edited
     
    just received an email
    "The low energy building database is open to all.The only information which is required to create a user account is a name and contact address.Telephone and email contact are requested but not mandatory."
    http://retrofitforthefuture.org/projectbrowser.php

    Tony, if you're still keen to post up your place , I'll forward the email to you ( as they offer to help with registration if required. )
    • CommentAuthortony
    • CommentTimeMar 21st 2011
     
    OK then please pass mine on
  26.  
    • CommentAuthorneelpeel
    • CommentTimeMar 24th 2011
     
    Posted By: Brianwilsonhttp://www.dailymail.co.uk/news/article-1368837/Traditional-buildings-damaged-flawed-energy-reports-race-green.html?ITO=1490" rel="nofollow" >http://www.dailymail.co.uk/news/article-1368837/Traditional-buildings-damaged-flawed-energy-reports-race-green.html?ITO=1490

    Interesting article on approach to older properties


    ...study by 'The Society for the Protection of Ancient Buildings'. So no bias there whatsoever then. :confused:

    Some of the reader comments at the bottom are quite humourous.
  28.  
    Posted By: neelpeelSome of the reader comments at the bottom are quite humourous.
    Gosh how I don't miss The Daily Mail at all! One of my Uncle's is an avid reader, sadly :(

    Paul in Montreal.
    •  
      CommentAuthorDamonHD
    • CommentTimeMar 24th 2011
     
    The reader comments make me want to cry: presumbably competant adults day-to-day but apparently ignorant, idiots, paid shills, sociopathic trolls, people so narrow-minded that they could see through a keyhole with both eyes at once, or some combination. Or is that the columnists, I can never remember?

    Rgds

    Damon
  30.  
    Posted By: DamonHDThe reader comments make me want to cry: presumbably competant adults day-to-day but apparently ignorant, idiots, paid shills, sociopathic trolls, people so narrow-minded that they could see through a keyhole with both eyes at once, or some combination. Or is that the columnists, I can never remember?
    In the case of The Daily Fail, both!

    Paul in Montreal.

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