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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    How should they respond to the questions you posted, if they are a quality firm?

    What is used between the frame and the wall, assuming either upvc or aluminium windows?

    What is the correct way to deal with cavities? Filler foam?

    Can I assume that UPVC windows don't have insulation foam attached to it at the aides and rear?
     
  2. noseall

    noseall

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    Grilling the fitters or asking the surveyor or interviewing the company boss isn't the way to go.

    One will tell you what you want to hear the other will tell you to sod off.

    Get recommended local small firms to price your job, preferably firms that have the means to make their own frames and units etc. Look at firms that have been trading a while and under the same name.
     
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  4. SmileyDan

    SmileyDan

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    One example is to preferably use compriband between frame and wall. Surface must be clean and dry. Foam can be used if it contracts (Soudal Flexifoam et al). This is especially important with uPVC. Best of all an understanding of air tightness. They should really ask you where the air barrier is in the house and how to tie it in. If you say the word "air tightness" and their faces go blank, that's normally a good proxy that they don't know anything about building performance. Unfortunately there aren't a lot of tradesman that do.

    What is very important is that there are no voids left which are tacked over with a piece of uPVC trim.

    Cavities - important not to return the blockwork, this becomes a thermal bridge and you will end up with condensation on the reveals internally. Assuming the windows are mounted in the outer leaf (assuming, again, you are just replacing windows). Instead use insulated cavity closers. Like with air tightness, knowledge of the existing insulation positions is required before you can really answer this. E.g. if IWI in the room, insulated reveals need to be added, or built into (with all gaps sealed with foam internally).

    Say you'll use a thermal imaging camera afterwards to inspect the seals. There will still be some thermal bridging in the reveals because the window is in the outer leaf, but there shouldn't be long blue lines emanating from the frame that would indicate air ingress.

    Don't really agree with noseall. I know that's the traditional way, but I don't understand why a good tradesman wouldn't want to explain what he/she does.

    It's not necessarily *what* they say, it's how they say it.
     
  5. ey143

    ey143

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    Interesting, thank you. I didn't know you get insulated cavity closers. Please look at the photo below. I don't suppose you can tell from the photos alone whether these cavity closers are insulated right? If not, is it worth me asking them to replace it, is it too late at this stage and are insulated cavity closers considerably more expensive? I guess all it offers is thermal bridging right, and not so much thermal efficiency?
    Also is it still possible to have cavity closer if we have 50mm Quinnboard insulation tapped to the inner grey leaf block?

    [​IMG]
     
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  7. SmileyDan

    SmileyDan

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    The CWI should be cut originally to allow the closers to be added. See http://www.quinn-therm.com/wallinsulation/cavity-walls.cfm . I suppose it might be possible to retrofit.

    TBH all this should be designed in from the start, including window details...

    Thermal bridging is a form of thermal efficiency. A thermal bridge is a path where energy can conduct with no insulation reducing its flow. When I said it "will" create condensation I don't actually mean that, I mean there's a higher chance. It probably will inside a bathroom, but in another room with lower humidity you will probably be ok.
     
  8. DIYnot Local

    DIYnot Local

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    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

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