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What is the normal u value for double glazing

Discussion in 'Building Regulations and Planning Permission' started by ey143, 12 Oct 2015.

  1. ey143

    ey143

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    Having spoken to a few double glazing firms, what is usually the average u value for most window companies, is it 1.1 or 0.6 (dont confused with triple glazing).

    Is 1.1 ok for a LUK profile compared to other profiles?
     
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  3. Gazman16

    Gazman16

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    Every make is different. Most are 1 - 1.4 I would say
     
  4. Gazman16

    Gazman16

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    I would be very wary of anyone claiming 0.6 with a double glazed unit.
    Even Residence 9 windows that have a 100mm frame with 9 chambers only claim 0.8 with a triple glazed unit
     
  5. ey143

    ey143

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    Would I notice much difference between 0.6 and 1.1?

    What is residence 9?
     
    Last edited: 12 Oct 2015
  6. noseall

    noseall

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    No.
    Any lofty claims by these companies are to be taken with a pinch of salt. Any gains from argon filled this or super profile that, can be mitigated by a poor fit in an instant.
    Insist you get the latest reg's compliant windows but, more importantly, ensure you have a quality fit.
    The company we use employ all their fitters directly (no subbies) and they take their time and always do a quality job fitting wise.
     
  7. Gazman16

    Gazman16

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    These are Residence 9, Their about 3 times the cost of normal PVC windows.
    http://www.residence9.co.uk/?gclid=CJmJ_sLxvsgCFUPnwgodz_0Egg

    As a homeowner you would never notice the difference in u values and as noseall says the fitting is the most important thing, A cheap window fitted well would be better than a great window fitted poorly.
    Go for a locally recommended company and avoid the national company's as a general rule.
     
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  8. SmileyDan

    SmileyDan

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    I agree with the second part of your sentence, but not your first. There's a massive difference (look at the numbers!) between a high spec 3G window and your common-or-garden 2G. Two layers of low E coatings on 3G makes a massive difference to perceived radiant heat loss.

    OP, make sure you are comparing the same numbers - Ug (U value of the glazing) and Uw (U value of the installed window). Generally the former is lower than the latter, because frames are often the weak spot. One of the clear differences between high spec windows and 'normal' windows is the detailing around the frame - thermal bridges, number of seals, composite insulation and so on.
     
  9. noseall

    noseall

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    Yes, if you are in a thousand window office block maybe.
     
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  11. SmileyDan

    SmileyDan

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    It depends what your goals are I suppose. Comfort, financial, environmental etc etc.

    As a back of the envelope calculation, we have 62m² of glazing in our house. Compare a Uw of 0.7 against what I'd consider a common Uw for a "normal" window of 1.4 at about 2200 degree days and that's £150 saved a year and a big comfort improvement - you can actually stand in front of the window on the coldest day and still not get any down draught or any perceived radiated loss. You will still get that against Uw=1.4 and also a bit of condensation on the colder days too.

    But as you say, installation is most important. Also design - thinking about where and how much glazing we have (because even the best glazing is not going to be as good as a properly insulated wall).
     
  12. ey143

    ey143

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    2G / 3G window, what's that? I visited a few local firms and saw their workshops and how they order the profiles from LUK, Linear etc etc and then weld them etc, but even as someone who has done their research, how will one even detect whether the product is good or installation is done correctly, it's very difficult.
     
  13. SmileyDan

    SmileyDan

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    2G is double glazing, 3G is triple glazing. You should be able to ask for the Window Energy Rating which gives a Uw and also a solar gain figure which might be important if you have a lot of glazing and a properly insulated house.

    Installation, ask others and try to see work. Ask exactly how they will fit the window, what products they will use.
     
  14. ey143

    ey143

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    It's fine asking how they will fit the window, but how I am going to qualify that other than saying "aha"?
     
  15. noseall

    noseall

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    Dont forget to rub your chin and nod meaningfully.
     
  16. ey143

    ey143

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    Exactly. Unless you're clued up about the trade, it's mainly luck. You might equally get a friend or family member who thinks they've got a good product or install only because they themselves don't know but pass it off as "they seemed good and nothing's fallen down yet". Blind leading the blind really.
     
  17. SmileyDan

    SmileyDan

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    Ask them what they use to seal between the frame and the wall and how they deal with open cavities. How is it fixed? What products are used?

    Whatever they say just note it down, you don't have to come up with a spectacular piece of insight on the spot. Then research it. Make it clear that's what you're going to do, if you like, because if they are enthusiastic and proud of their work then maybe they'll go into more detail.

    If the window supplier is any good they should provide technical drawings of how the windows should be installed.

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12420&Focus=207078
     
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