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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.

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    • CommentAuthorSimonD
    • CommentTimeApr 3rd 2021
     
  1.  
    Interested that they are so critical of triple glazing.

    Their argument seems to be that the high embodied carbon of manufacturing the extra pane of glass and the thicker aluminium frame, together with the likelihood of replacing the glazing several times during the building's life, means that the extra carbon spent on manufacturing the triple glazing is not any improvement on double glazing.

    I'd have thought the answer might be to have smaller windows!
    • CommentAuthorSimonD
    • CommentTimeApr 4th 2021 edited
     
    Posted By: WillInAberdeenInterested that they are so critical of triple glazing..

    Their argument seems to be that the high embodied carbon of manufacturing..


    I'd have thought the answer might be to have smaller windows!


    Yes, that would be a sensible starting point wouldn't it.

    I spoke to an architect recently who works mostly on large commercial projects and he was saying the same in the context of the 3g windows for our new house.

    Interestingly, when I was doing my research I found that many window manufacturers in Scandinavia don't recommend 3g windows below certain latitudes (the border being further north than most of the UK) with one Danish manufacturer whose technical department recommended only 2g on the south face, 3g on the north face (as our house sits almost perfectly north-south. Obviously this didn't revolve around the embodied carbon but does consider overall energy consumption and life cycle.

    There certainly does need to be some further open public debate about embodied carbon of many products, often assumed to the the 'green' option.
    •  
      CommentAuthordjh
    • CommentTimeApr 4th 2021
     
    FWIW, the PH argument about 2G vs 3G tends to focus on solar gain vs insulation, and on minimum internal temperatures (to do with minimising convection) rather than embodied energy.
    • CommentAuthortony
    • CommentTimeApr 4th 2021
     
    3g is now standard in central and Northern Europe, for good reason, it is far superior, more robust, longer lasting, economic.
    • CommentAuthorSimonD
    • CommentTimeApr 4th 2021
     
    Posted By: djhFWIW, the PH argument about 2G vs 3G tends to focus on solar gain vs insulation, and on minimum internal temperatures (to do with minimising convection) rather than embodied energy.


    Posted By: tony3g is now standard in central and Northern Europe, for good reason, it is far superior, more robust, longer lasting, economic.


    This to me highlights a big glaring hole in the Passivehaus concept, and probably including 'highly energy efficient houses.' Rarely does embodied energy, and perhaps more importantly, life-cycle embodied energy including demolition, recycling and waste, come into the calculations. Given some of the materials used in some Passivehaus developments, this will account for a very significant amount. Until this is better understood, it's actually difficult, if not impossible to state whether 3g is superior to 2g over the lifetime of the house - especially in most of the UK.

    Disclaimer and conflicting interest here - I do have 3g windows (at least they're timber framed) which I installed in January, so I take my own right to question the nature of my own decisions based on new information and thinking around this whole property development thing :bigsmile::wink:
    •  
      CommentAuthordjh
    • CommentTimeApr 4th 2021
     
    Posted By: SimonDThis to me highlights a big glaring hole in the Passivehaus concept, and probably including 'highly energy efficient houses.' Rarely does embodied energy, and perhaps more importantly, life-cycle embodied energy including demolition, recycling and waste, come into the calculations.

    Agreed, passivhaus predates life cycle assessment so it doesn't pay it as much attention as maybe would be best. It does however deal with 'ecological construction' and suggests alternative materials for various constructions, so they are attempting to catch up. The standard was revised fairly recently to deal with renewable energy, for example.

    There are as many different philosophies about building as there are self-builders and building designers combined. Many straw bale builders want everything to be natural and care less about the 'efficiency' of the building. I'm somewhat on a limb since I was more concerned about meeting a specific energy goal (PH) than about being natural or organic everywhere. And more concerned also about low maintenance.

    So we too have 3g windows that are timber-framed; with plastic foam inserts to meet my performance criterion and aluminium external facings to meet my low maintenance criterion. Who knows what will turn out to have been the 'correct' path in the fullness of time and with the benefit of hindsight?
    • CommentAuthorjms452
    • CommentTimeApr 4th 2021
     
    Posted By: djhMany straw bale builders want everything to be natural and care less about the 'efficiency' of the building. I'm somewhat on a limb since I was more concerned about meeting a specific energy goal (PH) than about being natural or organic everywhere. And more concerned also about low maintenance.

    So we too have 3g windows that are timber-framed; with plastic foam inserts to meet my performance criterion and aluminium external facings to meet my low maintenance criterion. Who knows what will turn out to have been the 'correct' path in the fullness of time and with the benefit of hindsight?


    The best is the enemy of the good etc.

    I think pretty much all of us can be envious of a strawbale PH
  2.  
    Well my 3g windows are the ultimate solution with no frames and the glass direct into the stone mullions sealed with burnt mastic pointing. I dont expect them to be replaced anytime soon.
  3.  
    Posted By: djhFWIW, the PH argument about 2G vs 3G tends to focus on solar gain vs insulation, and on minimum internal temperatures (to do with minimising convection) rather than embodied energy.


    And the lack of convection improves internal comfort and effectively increases the usable floor area. we have a couple of chairs that are very close to windows and still perfectly comfortable when sub-zero outside. I've worked in open plan, glass walled, offices where the desks against the window were noticeably cooler (to the point of some people having fan heaters under them). And this was in a, for the time, 'eco' building with semi natural ventialation (ie you could actually open vent panels in summer)

    From that Guardian piece
    "they have a huge amount of built-in obsolescence, given that their glazing systems are often only guaranteed to last for 30 years. You would expect these towers to last at least a century,” he says, “but they have a big embodied cost when these deep, triple-glazed units will have to be replaced so often.”

    That's rather missing the point - Guarantee has nothing to do with expected life - it's not a 'mean Time to failure' and any manufacturer would want a very low claim rate at that point. With a 30 year guarantee I'd expect most to last more like 50 years. The issue with commercial buildings seems to be that the *planned life* of the buildings is often only 20-30 years and stuff tends to get pulled down and replaced after that. You see quite a few buildings being stripped to steel frame and rebuilt - I was told that environmental regs mean once a refurb goes beyond a certain (cost?/level?) the building has to be upgraded to current insulation standards and it becomes more viable to completely rebuild.

    Residential is rather different - no matter how badly built the way we own resi buildings means theres very little demolition however poor the build.
    •  
      CommentAuthordjh
    • CommentTimeApr 6th 2021
     
    Posted By: Simon Stillthe building has to be upgraded to current insulation standards and it becomes more viable to completely rebuild.

    I wonder how much of that is due to the different tax treatment of new build (0% VAT) versus upgrade?

    Residential is rather different - no matter how badly built the way we own resi buildings means theres very little demolition however poor the build.

    It was noticeable on our build though that both the architect and engineers were using 60 years as the 'design lifetime' for various decisions. There was the odd time I had to remind them that I hope the building will last a lot longer than that and should be designed accordingly. I hope I last a lot longer than that too, but I'm not so optimistic about that. :tongue:
    • CommentAuthorShevek
    • CommentTimeApr 6th 2021
     
    Such a shame the new UK building regs almost outlaw timber. They could have at least designed the structure in CLT.
  4.  
    If it's a commercial building, the client will be VAT registered and will reclaim the VAT on a refurbishment? Or did I misunderstand?

    Last time I looked at housebuilding stats, the ratio of [new builds per year : existing housing stock] works out at 101years. But that is flattering because most new builds are additions not replacements. So the average replacement cycle of the existing stock is much more than 100years.

    How would the house be designed any differently if the intended lifetime were 100years instead of 60years? You'd still expect to replace windows, heating, roofing, wiring etc?
    • CommentAuthorEd Davies
    • CommentTimeApr 6th 2021
     
    Posted By: ShevekSuch a shame the new UK building regs almost outlaw timber.
    In what way?
    •  
      CommentAuthordjh
    • CommentTimeApr 6th 2021
     
    Posted By: WillInAberdeenIf it's a commercial building, the client will be VAT registered and will reclaim the VAT on a refurbishment? Or did I misunderstand?

    You're quite right that the situation is different for commercial property. I hadn't realized that new build is only zero-rated for dwellings. The VAT situation seems to be quite complicated for commercial property.
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