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Double vs Triple Glazing - am I missing a trick?

Discussion in 'Windows and Doors' started by dogfonos, 22 Mar 2016.

  1. dogfonos

    dogfonos

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    Would appreciate opinions on this subject...

    Having asked around in the recent past, both on this forum and local window fabricators & suppliers, there wasn't much enthusiasm for triple glazed windows/doors fitted to typical domestic properties. However, I have quotes from two local fabricators/suppliers for replacement aluminium windows, sliding doors and a standard outer door. I asked for two quotes - for double and triple glazing. Both companies' quotes (including fitting) for triple glazing came in about 8 to 10% higher than for double glazing. That price difference doesn't seem much to me so I'll probably go with triple - unless anyone knows of a downside?

    I understand that the gaps between panes will be less with triple glazing due to limits on overall glass width. I've also compared the visual difference between double and triple glazing and, understandably, there's less light getting through triple glazing but it's not a problem in my situation. Thanks for your consideration.
     
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  3. ronniecabers

    ronniecabers

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    Only 8-10% ... that is surprising, I wonder if both companies have inflated the double glazed price ...also what energy rating are yo being given for the triple glazed?
     
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  4. dogfonos

    dogfonos

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    Could be. I narrowed down the choice of window supplier to two particular local fabricator & suppliers from a 10 company shortlist. Soon learnt that many supply the same product. I've been pretty thorough in checking out these companies hence narrowed it down to two I'm comfortable dealing with. Still one or two things to check but I believe they're both sound, honest companies. And they fabricate and fit their own windows.

    Have lots of info on double glazing but little on the triple glazing option as I only enquired about triple glazing option after receiving the double glazing quotes (duh!) - it's something I need to check out before making a decision.

    All I know is that either double or triple glazing will have a 'U' value of 1.61 W/m2K or lower but that's for the whole window - frame and all. One company has supplied more info which gives a glazing only 'U' value of 1.2 W/m2K for their double glazing units.

    I'm a bit wary of the WER values as it includes a solar heat gain factor which I think confuses the issue of thermal insulation (does for me anyhow). Let's face it, solar heat gain is all very well but at -10C on a cold winters night, I'm far more concerned with thermal conductivity and trying to minimise the thermal draught effect, particularly on a proposed 3.8m high window and two, 2m+ high sliding doors. And solar gain on a 30C summers day isn't something I'd appreciate either.
     
  5. ronniecabers

    ronniecabers

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    a 1.6w/m2k is the minimum that can be supplied by a window company these days, and as you say it is for the whole frame. Triple glazed , i'd be asking the make up of the sealed unit , as some are only putting a 28mm sealed unit in , which effectively would give a 4mm pane of glass / 8mm spacer / 4mm pane of glass/8 mm spacer / 4mm pane of glass ( 4/8/4/8/4 ) , and I am pretty sure that most Low e doesnt work as effectively below a 12mm spacer bar....When I'm pricing Triple glazed I normally price for 4/12/4/12/4 , which means the frame rebate is bigger, so the frame isn't the normal profile for double glazing ( unlike the 4/8/4/8/4 scenario , which I'm guessing is what they are selling )

    As goes light loss .... you shouldn't lose ....
     
  6. dogfonos

    dogfonos

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    Thanks for the info.

    The triple glazing info I've received from one company says the glass can be up to 32mm double or triple glazed (4/10/4/10/4 - I imagine) with the frame we want, yet when I check the same frame online (on the manufacturer's website) it says a max of 28mm glass (4/8/4/8/4 - as you state). Conflicting info that I'll check out. The frame in question is Smart's Alitherm 800.

    I'll try to find out the typical 'U' values for all these options because 4/8/4/8/4 doesn't really impress me. Might even be better off with 4/20/4 double glazed panels?
     
  7. DHFrames

    DHFrames

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    You've done a lot of research on the companies, product, u values etc, hopefully you've done the same on the installation team you'll be getting. All your research goes to pot if the installation is done poorly.
     
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  8. dogfonos

    dogfonos

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    Totally agree. I only have to look at my own circa 1987 (ish) Everest windows to remind myself of that (i.e. a basically sound product, poorly fitted).

    The two companies I've researched use their own installers and, if I remember correctly (must double check), said they don't subcontract out the work. In fact, whilst both companies would sell me their products for my builder to fit, both companies said they provide guarantees only when their own fitters/installers are employed.

    Another question I need to find an answer to - and would appreciate your input: what is the most thermally effective method for attaching window and door frames to the wall? I want to minimise any cold bridging between the inner and outer edges of the aluminium frames due to their contact with standard facing bricks used in the construction of the outer wall. Such thermal bridging has recently been an issue for someone I know where slate was used around part of the frame, so I'm told. Occasionally causes a little condensation on the inside aluminium frame, evidently.

    Could the aluminium frames be bedded onto an insulation strip/pad - attached to the brickwork - all round the frame edges?
     
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