Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

Buy individually or both books together. Delivery is free!


widget @ surfing-waves.com




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthortony
    • CommentTimeJun 18th 2016 edited
     
    I saw someone recently quote the passive house figure of 15 kWh/m²/y and say that it could be viewed as a waste of money to go lower than this.

    The standard was set up over thirty years ago and a lot has changed since that time. Within the next thirty years energy prices will have risen hugely.

    What is the optimum energy demand for a building, is there such a thing and is it time or energy price dependant?
    • CommentAuthorEd Davies
    • CommentTimeJun 18th 2016 edited
     
    15 kWh/m²/y.

    Of course, the North American argument is that in very cold climates even going down to this level is a waste of money.

    If you're looking at carbon emissions then, considering the embodied carbon in PUR and the like, when U values get below about 0.1 W/m²K you start to lose out over reasonable periods of time (30 to 50 years). With mineral wool (which has lower embodied carbon per unit of thermal resistance) it makes sense to go lower but then you get a very thick wall with associated structural costs and, in some cases, planning footprint considerations.

    Something to consider is that buildings tend to need heating at just the times of year when in future we might expect energy to be expensive (unlike, for example, cooling which tends to be needed when PV is producing so energy is likely to be cheap). Suppose everybody lived in a Passivhaus but all consumed their 1500 kWh, or whatever, as electricity in the same six weeks of the year. Roughly 1.5 kW per house (6 weeks is 1008 hours). With something like 25 million dwellings in the UK that's an extra 37 GW or so. Smart meters are likely to really rack up the prices during that period.

    (Obviously it'd really be spread over a longer period with a ramp up and down but this serves to illustrate the sort of peak that'd be involved).
    • CommentAuthorbarney
    • CommentTimeJun 18th 2016
     
    Well I guess money and energy are entirely interchangeable

    What's the value of money now compared to the point when we see these large energy cost increases (if we actually do see them)

    I think the other point might be "what's the building type" and "what is the intended life"

    It's not difficult to show diminishing returns being magnified by projections on energy costs

    Regards

    Barney
    • CommentAuthoratomicbisf
    • CommentTimeJun 18th 2016
     
    But will energy prices have risen a lot in thirty years? The price of renewable energy is falling dramatically and is having a downward pressure on electricity costs in many parts of the world already, even with today's low fossil fuel prices. Nimbyism, excessive constraints and poor government policy are keeping them up here, compared with many other countries (Eg the USA where wind power is being built for under 2p/kWh) but even so I wouldn't bet on large increases.

    Ed
    •  
      CommentAuthorfostertom
    • CommentTimeJun 18th 2016 edited
     
    Energy costs, as well as the cost of 'stuff', will continue to plummet from now on, as humans needing to be paid are squeezed out of the system - but massive energy demand reduction is part of that picture.
    And incomes will continue to fall much faster than prices, until some way other than work is invented, to distribute value as spending power instead of as paper stock-market valuation.
    • CommentAuthorringi
    • CommentTimeJun 18th 2016
     
    I believe that the key to the passive house figure of 15 kWh/m²/y is that is removes the costs of having a heating systems. But it assumes lights etc give out enough heat, yet we are now getting lights that give out less heat.

    But I don’t like XX kWh/m²/y at all, as having a smaller home with a higher XX kWh/m²/y can use fewer resources to both heat and build. I expect by better design we could reduce the size of homes “self builders” believe they need for a given quality of life.
    • CommentAuthorgravelld
    • CommentTimeJun 18th 2016
     
    On the flip side to that, plenty of houses are built now which just aren't big enough, mainly in terms of room proportions but also green space.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 19th 2016
     
    Whenever I take a close look at energy prices across Europe and the US, I find they amount to 5% (or there about) of household income. This has been pretty steady for the last two decades.
    So it is really just a matter of working out the marginal costs of reducing energy usage via increased insulation, better airtightness/MVHR, better appliances and lighting.

    What is hard to do is work out an average figure as houses are different sizes, different shapes, have different occupancy levels.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 19th 2016 edited
     
    Posted By: ringihaving a smaller home
    PH deliberately steers clear of the hot-potato suggestion that we 'should' make do with less floorspace per person. It's an area where eco-responsibility is all tangled up with egalitarian politico-righteousness.
    • CommentAuthortony
    • CommentTimeJun 19th 2016
     
    One of the problems is that for those in or close to energy poverty their proportion of household income is higher or step changes to zero when they have to choose to heat rather than eat.

    I cannot see renewables being implemented quickly enough to prevent very rapid energy price rises as oil and gas run out.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 19th 2016 edited
     
    Posted By: tonyas oil and gas run out
    They're not going to run out - 'peak oil' (which hasn't happened even yet) means that the rate of production has never been higher - not remotely that oil is running out.

    However Saudi in particular has understood that fossil's days are numbered for technological/environmental/political reasons and, while transitioning to post-oil itself, is flogging off its own end-game oil (which has lower production cost than anyone else's) so cheap as to clear its own stocks while everyone else's become uncompetitive, mothballed.
    This is the surprising twist that has reversed the expectation of oil's end by pricing itself out.
    It's one more of the rare examples that should have been in
    https://www.amazon.co.uk/Collapse-Societies-Choose-Fail-Survive/dp/0241958687/ref=sr_1_1?ie=UTF8&qid=1466331234&sr=8-1&keywords=jared+collapse
    of nations that see the light just in time to avoid the usual lemming-rush over the cliff.

    So much for the trillions USA has spent on the contradictory policies
    a) of rendering the middle east helpless to resist US oil-grab, and
    b) of 'oil independence' via high cost, low-EROEI fracking and tar-sands production.
    Both turn out to have been a waste of time and money.
    • CommentAuthortony
    • CommentTimeJun 19th 2016
     
    They are a finite resource and we are still using them at an increasing rate. The only reason that they won't run out is that they will become too slow and too expensive to extract from the ground.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 19th 2016
     
    That's what I used to think; now I think Saudi is effectively shutting oil down, for other reasons.

    One such reason could be how England embarassed and disadvantaged its imperial competitors by leading the abolition of slavery. England had discovered a more profitable way (to create and quasi-enslave a homegrown working class) so could well afford to outlaw overseas farm-based slavery, which the rest of the imperial powers were still hooked on.

    Saudi is rich and nimble enough to build a post-oil economy, at a pace it can modulate to its advantage through oil sales, thoroughly embarassing the US behemoth which can do no such radical thing.
    • CommentAuthorEd Davies
    • CommentTimeJun 19th 2016
     
    Posted By: fostertomSaudi is rich and nimble enough
    …and tends to get a bit of sunlight.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 19th 2016
     
    Exactly, has a lot going for it now there's new blood at the top.
    •  
      CommentAuthordjh
    • CommentTimeJun 19th 2016
     
    Posted By: Ed DaviesSomething to consider is that buildings tend to need heating at just the times of year when in future we might expect energy to be expensive (unlike, for example, cooling which tends to be needed when PV is producing so energy is likely to be cheap). Suppose everybody lived in a Passivhaus but all consumed their 1500 kWh, or whatever, as electricity in the same six weeks of the year. Roughly 1.5 kW per house (6 weeks is 1008 hours). With something like 25 million dwellings in the UK that's an extra 37 GW or so. Smart meters are likely to really rack up the prices during that period.

    That's why I think it makes some sense to design dwellings to 'overheat', so that more of their energy demand is for cooling in the summer rather than heating in the winter. It would tend to balance demand somewhat and be beneficial to the extent that energy was derived from sunlight.

    Note that I said 'dwellings' because larger commercial building typically behave in this way already.
    • CommentAuthorEd Davies
    • CommentTimeJun 20th 2016
     
    Yes, the worry about overheating in the UK is well overblown. With a split air pump, cooling for the odd week or two it's needed is easy, particularly if you have your own PV. It's unfortunate that Passivhaus regards running an air conditioner off PV as energy consumption but allows heat through a window as “free” - seems rather arbitrary to me.
    •  
      CommentAuthordjh
    • CommentTimeJun 20th 2016
     
    I can see the PHI view that an air conditioner plus PV system versus no air conditioner and no PV system is added complication. I can also see their view that you have to have windows to admit light and so you may as well optimise them for heat transfer too. But I think their overall treatment of PV is fundamentally flawed.
    • CommentAuthorEd Davies
    • CommentTimeJun 20th 2016
     
    Short Twitter thread about where Wolfgang Feist points this out, too:

    https://twitter.com/passivistas/status/744800758231506944 Passivhaus in Greece

    Only 2 hours before my post.
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press