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is it worth double glazing

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  • is it worth double glazing

    It costs a lot of money, Does it add as much value to the house

    Is it a wise investment?

    note. we are considering it for our own home which we do not plan on selling for quite some time. Just in case that affects your opinion on the value of double glazing

    we have wooden windows, have had quotes for retrofit and full sash replacement
    Is it worth replacing with aluminium or upvc?

  • #2
    Where in the country are you - warm or cold?

    Are you in a loud city or the quiet country?


    • #3
      It will make your home more comfortable (through better temperature control), much cheaper to just put up good curtains if it's cold or see through blinds if it is hot.

      How old is your house? If it's really old you'll ruin the look by replacing the wooden windows. Also, the cheaper aluminium windows have terrible insulation properties (aluminium is a REALLY good heat/cold conductor).

      It will help if you can say where in NZ you are and what problem are you trying to fix.


      • #4
        I think that's quite an open question as it depends on the house. If you're asking if the $ investment will relate to a $ increase in the value of the property... probably not. But it would depend a lot on what you spent, what existing insulation there was and what kind of house it was. A purist might be horrified at the thought of aluminium or upvc in an old villa.
        You can find me at: Energise Web Design


        • #5
          I am in wellington. out in the suburbs.. so reasonably quiet
          the house is 60's. I prefer wooden, unless there are huge benifits from other materials
          The condition of our sashes are not the best. painting may save them though. unsure on that

          goal is warmer drier house. We have just completed insulation for walls. South end bedrooms have been cold and damp
          We do not like damp

          hope that answers questions. Our quotes are about 23k for whole house with low E + argon windows


          • #6
            I'd be looking at installing more heating, perhaps heat pumps or some sort of central heating.

            $23k pays for a whole lot of heat pumps and electricity.

            Assuming of course that you've already got ceiling and under floor insulation and someone has checked to see the dampness isn't coming from a leak or under the house.


            • #7
              I live in the deep south and am a firm believer in double glazing because the benefits are immediate. Warmth and quiet.

              However I'm doubtful that the extra cost of low E and argon is worth it. It would be interesting to see research on this - presumably North America and Europe are sources.


              • #8
                I've got a brochure from an outfit that retrofit doubleglazing (www.warmmyhome.co.nz). That has comparative insulation values:

                single-glazing: 0%
                single + low-E: 38%
                double: 54%
                double + argon: 57%
                dbl + argon + low-E: 73%

                And a brochure from one of the PVC frame suppliers (www.homerit.co.nz) has this table:

                Single glazing clear (any frame): R value 0.15
                Double glazing with thermally unbroken aluminum frame: R 0.26
                Double glazing with thermally broken aluminum frame: R 0.31
                Double glazing with PVC or wooden frame: R 0.36
                Double glazing with PVC or wooden frame and Low E glass: R 0.48

                Based on those, I'd say PVC/wood frames make a decent difference, and so does low-E glass. Not so sure about argon.

                I've seen an old house with NK window's wood-look PVC windows and they looked very like wood. Impressively convincing.

                www.warmmyhome.co.nz also retrofits into existing wooden frames. That might be cheaper, or at least look better.


                • #9
                  I love our double glazing in Central Otago, a great selling point and lovely and warm, no condensation either


                  • #10
                    Originally posted by One View Post
                    I've got a brochure from an outfit that retrofit doubleglazing (www.warmmyhome.co.nz). That has comparative insulation values:

                    single-glazing: 0%
                    single + low-E: 38%
                    double: 54%......
                    Interesting info, thanks for that.


                    • #11
                      From this month's copy of the Consumer

                      Insulated frames for double glazing

                      29 Oct 2010
                      If you're putting in double glazing, it's preferable to specify insulated frames.
                      Aluminium is a popular material for making window frames. It's also a really good conductor of heat. This means the inside temperature of an aluminium window frame is going to be almost the same as the outside. And that means cold when it's cold outside.
                      Those cold window frames cause moisture in the nearby air to cool enough to condense into water. That's how condensation forms on the cold window frames – even if the windows themselves are double glazed.
                      Reducing condensation

                      What's the answer? If the frames are already installed, you're stuck with them. All you can do is to keep down the household moisture levels as much as you can during cold weather.

                      But if you are renovating or building from scratch you have some choices. You could choose wooden or PVC window frames, which don’t have the same condensation problems as aluminium.

                      But if you go with aluminium there are a couple of options for dealing with unwanted moisture.
                      You could specify timber-faced aluminium, where the inside surfaces of the joinery have timber facings. This can look nice and the timber acts as an insulator that reduces the heat flow through the frames.

                      Thermal-break frames insulate even better. The frame is made with separate internal and external aluminium components. The inner and outer aluminium frames are separated internally (and invisibly) by high-strength plastic spacers. The spacers keep the inside and outside frames insulated from one another.
                      Both of these options are more expensive than standard aluminium frames. But they save those annoying puddles of water.
                      "There's one way to find out if a man is honest-ask him. If he says 'yes,' you know he is a crook." Groucho Marx


                      • #12
                        Member Comments To Above Article

                        Got a question or comment on this topic? Share your views and experiences with other Consumer members...

                        To add a comment you need to be a member of consumer.org.nz. Login or Join.
                        Link to Krissy 03 Nov 2010 2:57pm
                        It would be great to see Consumer review double glazing options in more detail, as there are so many different suppliers (yet many - most using the same basic "metro glass" product & simply providing their own frames....
                        One genuinely useful site is that of the Window Association of NZ - this lists accredited manufacturers http://www.wanz.org.nz/manufacturers.htm and also has a condensation star rating system for various types of windows; http://www.wanz.org.nz/condensation_stat_chart.htm ....THIS would have been invaluable in the original Consumer article....
                        Graeme Sawyer (Kristin Aitken)

                        Thermal break is highly recommended
                        John, Taranaki 01 Nov 2010 9:34pm
                        We have just built with thermal break double glazed windows and doors and are very pleased with the absence of any inside condensation on our frames this winter - so definitely consider this worth the extra - especially if you are anywhere other than perhaps Northland or the east coast. However, I do agree that the choice and quality of profiles and catches leaves a lot to be desired - why can't static panes have the same appearance as sliding panes for example? The industry needs to get more style / quality savie

                        Auckland Experience?
                        Claire Hotchin 31 Oct 2010 6:57pm
                        Can anyone comment on their experience of un insulated double glaze aluminum in Auckland? We are considering Thermal heart but wonder if it would be overkill and it is considerably more expensive if not necessary. Thanks.
                        View replies (2)

                        surprised by condensation
                        Kate Clapham-Dorjee 31 Oct 2010 2:52pm
                        We built an extension in 2009 with all new double glazed aluminium windows. I was surprised that we do get condensation on the odd occasion if the night is very cold.
                        But the windows do have drainage holes and gutters to collect the condensation and take it outside so not a big deal.
                        More importantly I got all windows with passive ventilation grills installed which helps with airflow and reducing all humidity build up. Note that I had to ask for this as it was not offered by any salespeople of any company I got quotes from. And it is very inexpensive to get added to your windows.

                        uPVC Double glazing Douglas Mein 31 Oct 2010 2:41pm
                        I have been looking into getting double glazing for a new build. The quoted insulation / "R" values for wood and uPVC double glazing seem to be twice as good as aluminium double glazing.

                        People seem to worry about uPVC being discloured or damaged by the high amount of UV that we get. I have only found one "independant" source which said this was no longer a problem.

                        Can anyone confirm this??

                        Also does anyone know a good company for wooden double glazing (not Eurovision)?

                        Thank you
                        View replies (1)

                        Double glazing Wendy Galloway 31 Oct 2010 8:19am
                        We built a new house nearly 3 years ago and opted for double glazing before it came law and in that time have only had condensation twice on the windows in master bedroom (frost outside). We have been so pleased with the windows, noise level down and a warmer house we had Epic windows and aluminium frame - were not told about insullation of aluminium. We live in Tauranga only problem we have had in fading of furniture - we though double glazing would have helped. We now have film on the windows. Perhaps another topic for Consumer.

                        German Double Glazing Systems Sam Young 30 Oct 2010 7:27am
                        My husband & I built a house using a German double-glazing system licenced by Eurovision windows in Mapua, Nelson.

                        These windows have aluminium outside, timber inside, are fully thermally broken, lock on three points around each frame, have heavy duty window and door catches that fit the hand really well, and are very, very sturdy. They have been bog-standard in Germany for at least 30 years.

                        You can tilt the windows so they open a small amount at the top, to let in some air, but no weather. The only thing you have to cope with is that the windows open inwards to the house, not outwards (to allow for shutters to come down - you can't open windows outwards with shutters!).

                        The windows were 33% cheaper than Smartwood (the NZ 'equivalent' that are nowhere near as secure, sturdy and have horrible door & window catches).

                        We also had shutters installed in our bedroom which was great; better than black-out curtains, and keeps the sun off the glass, so it is cooler still in summer.

                        We have come through our first winter with absolutely no condensation inside at all. The inside of the windows are warm and organic with the chunky timber.

                        I thought long & hard about whether I could live with windows that opened inwards, and decided to rework the designs to have lots of French doors (which also tilt at the top), huge sliders and fewer opening windows.

                        My husband & I are very happy with the results and are very glad we went with the German-style windows and Eurovision.

                        Think about using them; it is a fantastic, well-tested system. Only the window mechanisms themselves and the IP is imported from Germany; everything else can be sourced, made and assembled in New Zealand.

                        PVC framed windows Lawrence Blount 29 Oct 2010 11:50pm
                        We built this year with double glazed PVC windows from EuroWindows. They are great.

                        My understanding is that the thermal insulation of PVC and timber frames are similar but thermally broken aluminium frames are not as well insulated as most of the heat path is still made of aluminium (a great heat conductor)

                        European designed windows also have much better latches and seals.

                        Would a DVS unit help? Mrs Chappie 29 Oct 2010 11:05pm
                        I was wondering if having a DVS installed in your house would help? I am very glad to read this article, as I have been considering double glazing for our 2 yr old house. I wished I had done it when we built, but now I am feeling glad, as we might have bought a lot of problems. Very interesting subject, I'm glad consumer brought it up.
                        View replies (1)

                        NZ Behind the Times R M Scaife 29 Oct 2010 10:46pm
                        The aluminum window industry in NZ is in a very sorry state, hundreds of window retailers selling absolute rubbish, and expensive rubbish at that. Coupled with latching systems that are years behind whats available in the rest of the world.

                        At last great double glazing for aluminium. Kenneth Grant 29 Oct 2010 10:15pm
                        The technical description of the problem is "cold bridge" and the worst of it is the black mould the condensation produces.

                        PVC Windows used for 25 years Thomas S 29 Oct 2010 10:04pm
                        I have had PVC windows for with double glazing and sound proofing 25 years ago in Germany and only good memories. I have recently built a house with nearly 50 uPVC double glazed windows in Auckland and I am very happy with my choices. We will see how this will work out over time, but uPVC gutters etc. seem to have been in this country around for a while and have been accepted.

                        wishing I had known this sooner! Kirsty Gendall 29 Oct 2010 9:59pm
                        We built a house at National Park Village 3 years ago, thought we had it all sorted with double glazing but extremely disappointed to find a worse condensation problem than we had ever had before! Insulated frames would have been the answer and I would definitely have gone to the extra expense if builder or architect had raised the issue!

                        Tough to find in Auckland russell1 29 Oct 2010 8:54pm
                        When we renovated a year ago, everyone was happy to quote and install thermally broken double glazed aluminium windows, but virtually none of them had ever actually installed them before!

                        In the end we went with Metro Thermal Heart from WindowMakers as they had installed them previously (and we didn't want to be the guinea pigs!) plus they actually had full windows/doors to see in their showroom which no one else did.

                        The choice of thermally broken double glazing was the best choice we made - even in Auckland where it is not that common to install double glazing. We have had a cosy winter, with NO condensation. We also had a different colour aluminium on the outside than we have on the inside.

                        Definitely worth the extra $$.
                        "There's one way to find out if a man is honest-ask him. If he says 'yes,' you know he is a crook." Groucho Marx


                        • #13
                          If you live somewhere quiet in Wellington, I would invest in a heat pump instead, unless you spend 24 hours a day at home. For most home situations, it doesn't get cold enough regularly enough to justify in Wellington.


                          • #14
                            Originally posted by Devious0 View Post
                            I love our double glazing in Central Otago, a great selling point and lovely and warm, no condensation either
                            Really surprised at this. We had double glazing fitted by the Council (here in the UK) and now have massive condensation (and mould) problems that we didn't have before. Just about to dry line the bedrooms with foam back insulating fibre board, which I'm not looking forward to. We are also fitting a positive pressure air pump to try and reduce the problems.



                            • #15
                              Assuming you're paying for all that work (not the council), I'd start with the air pump and only dry line the bedrooms if the pump doesn't work. Sounds like the only ventilation in your house was old leaky window frames and now the place is sealed up too tight.