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Housing - Renovation: Not going to reach Passivhaus/Enerphit levels, what now?

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  1.  
    • CommentAuthorShevek
    • CommentTimeJul 19th 2012 edited
     
    So having produced a design targeting Passivhaus levels of insulation and having discussed it with Green Building Store, it's looks like we'd need about 1500 + VAT to reach anywhere near 30 to 40 kwh/sqm/ annum. Which is triple our budget.

    Attached is a preliminary section I produced targeting Passivhaus/EnerPhit (apart from the unresolved eaves detail).

    So what now? EPS everywhere? Add heating system? Upgrade suspended timber floor instead of replacing with slab?

    We've delayed start until March now, so we can price everything before we start.

    https://dl.dropbox.com/s/6tcyo0nkjnhpk5x/section.pdf?dl=1
    • CommentAuthortony
    • CommentTimeJul 19th 2012
     
    minergie?

    or do as well as you can and save the costs and fees spending on insulation etc, that is what I did
    • CommentAuthorRobinB
    • CommentTimeJul 19th 2012
     
    1500 or 15k? Be interesting to see where the money was going and what the mighty GBF can suggest! Very sensible to delay and rethink rather than rethinking on the run as I did.
    RobinB
    •  
      CommentAuthorSteamyTea
    • CommentTimeJul 19th 2012
     
    If your house is around the 200 m^2 mark, that would be £300,000
    You could invest that and take the winter off in a warm place that does not require heating.
    Not very helpful I know but neither is an estimate of £1500/m^2. Would buy a lot of PV and a heat pump.
    May we ask what you were hoping to spend?
    • CommentAuthorjamesingram
    • CommentTimeJul 19th 2012 edited
     
    whats your estimated m2 cost to reach current reg. any idea?
    Most extension would be at least £1000+m2 anyway and to a good spec probably £1500m2++
    I'm guessing your total areas around 120m2
    • CommentAuthortony
    • CommentTimeJul 19th 2012
     
    my build costs were lower than that, generally the first PH you build costs a bit some say 10% more then the rest are the same as current regs.
  7.  
    I would do a cost benefit analysis on the top 10 items driving the cost. They are usually architectural, structural &/or materials, not insulation & airtightness as such.

    It may also be useful to look at two extremes:

    1. What would be the cost of keeping the same scope, but building to current building regulations?
    2. How far would the scope need to be scaled back if built to Enerphit levels?

    David
    • CommentAuthorjamesingram
    • CommentTimeJul 19th 2012 edited
     
    Posted By: tonymy build costs were lower than that, generally the first PH you build costs a bit some say 10% more then the rest are the same as current regs.

    You did a lot of the work yourself Tony , plus it was new build so scale comes in , smaller projects are more expensive m2, though the refurb element should be cheaper than the extensions section .
    Loft conversions are also more expensive m2 than most presume. to add to that i think the project in London so you can stick some £ on it for that relative to the rest of the UK
    Tony what did it work out for your new build m2 if you count your own time at say £200 a day ?

    I believe Shevek doing alot DIY ( or his father is ??)
    Shevek, was your £1500 labour+materials
    • CommentAuthortony
    • CommentTimeJul 19th 2012
     
    £900

    I always built loft conversions for a lot less than things that needed foundations, loved doing them no one else to worry about, big scaffold, peace, quiet fresh air all blue skies to look at.
  10.  
    Yep loft conversions can be fun , though most the time seems to be cutting and fitting nasty and expensive PUR nowadays. I doubt you'll get one for much less than £30K in the SE and once you divide that by the usable space
    created , it can be above, say a single or double extension per m2
  11.  
    I reconise the need for quality assured certification schemes in the wider building world to achieve the required
    large scale energy efficient refurbishment program this country will have undergo to achieve CO2 targets ,
    but when you've got someone clearly keen to achieve the best they can, with an eye to detail , isn't it a waste of funds to try to achieve these specific requirement.
    As tony said early , do the best you can for your budget and forget about the box ticking exactness.
    • CommentAuthorShevek
    • CommentTimeJul 20th 2012 edited
     
    Thanks for all the great advice guys.

    Our budget is 30-50K. We settled on the upper end of 50K when we decided to explore the implications of Passivhaus, or at least EWI, etc.

    Existing gross internal floor area = 67 m2. (you only count stair once right?)
    After renovation = 97.5 m2.
    Ground floor extension = 13.5 m2.
    Loft conversion = 17 m2 (excl. low-height storage)

    We'll be doing as much DIY as we can (even more so now that we're starting in March as this means my father won't be on a deadline to get back home in a hurry).

    I'm seeking clarification on that 1.5K figure from GBS, to see if they were taking into account DIY and free builder or whether that was just a standard rate. (Edit: yes, this was a standard rate, so not taking account of DIY)

    We don't need to go for any particular standard. Passivahaus was just particularly attractive because it seems like the most sensible approach in terms of building performance.
  13.  
    I'd imagine a good approach would be to get a QS to give you a bill of quantities against the spec. you have.

    You will then be able to accurately price the materials you require.

    Then it's a question of pricing all the work you can't do yourself and you should then arrive at a reasonable estimate for the complete works.

    Personally I think it is probably a big ask to do almost 100m2 renovation to anywhere near PH standard for £50K I'd have thought that even allowing for a large diy input £90-£100K would be nearer the mark.

    Best of luck.

    Chrispy.

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