Question about windows – is it better to use aluminium, or uPVC windows

Hi Jay! We lived in the UK and UPVC is really common over there and it has been for ages, it’s cheaper, quicker to manufacture and install and it has great heat retention too and we loved ours so when we moved back to NZ eight years ago we made it our top priority to get it installed in our new house. Well, that was one of the biggest mistakes we have ever made! The stuff was exactly the same as the stuff we had in the UK but what people who import it or manufacture it here don’t realise (or they do realise but they hope you might not) is that the direct sunlight down here is ten times as strong as in the UK and it turns the plastic yellow or spotty (if your choice is a light color) or fades it dramatically and then spotty (if your choice is a bright/dark color) and then the plastic gets brittle and breaks. Our UPVC joinery started yellowing after 4 years and then breaking off in pieces the year after that, we took our supplier to court and won only half our money back (I would love to tell you their name but we are not allowed). At the time the cost of the UPVC was only 5K cheaper than a quote of aluminium Altherm Joinery, but we got the Altherm Joinery to replace the UPVC anyway and by then the cost of the Aluminium Joinery had gone up so when we did the sums, we actually lost $45K in the end. That was a eight years ago though so they may have adapted the plastic for the harsh NZ sun by now? What I would do is ask them if they have any houses that have their product in them that are over ten years old, and then ask if you can go and have a look and talk to the owners. I would also double check too that the plastic composition and manufacturing process is exactly the same as the joinery that’s in the house they are referring you to. We were trying to argue that our UPVC was not fit for purpose, but the suppliers blamed the manufacturer and accused them of “changing the UPVC production recipe without their knowledge” which can happen, so we were only awarded half our money back because we got 5 years worth out of the product before it failed and the supplier could prove that it wasn’t really their fault. I do know of one other person who got UPVC and it started to spot and discolour after two years but it never became brittle, so when they took their supplier to court they lost because they couldn’t prove that the windows were not doing what they were designed for and the Judge deemed them fit for purpose, even though they looked terrible. They did try to touch up the joinery with various paints & resins in the end but it looked tacky and cheap and I felt really sorry for them I will forward them this chat link and see if they’ll talk to you too. UPVC is not a favourite in Australia either, and that’s also because the sun is too strong, but like I said before, they may have adapted the plastic to our conditions and some independent testing may even be available but time is the true test of UPVC I think. We love our Aluminium Joinery, and like our builder loves to remind us, there is a reason we have used Aluminium for so long and that’s because it works. Good Luck and I hope our experience helps, it makes what we went through worth it if it can 🙂

Hi Jay – agree with MB. UPVC is awesome but the stuff here isn’t made for NZ conditions unfortunately. We also have a friend who has run into this issue and his joinery is starting to discolour after just a year. Go with aluminium – make sure you go with one of the better companies eg Altherm as there are different qualities of window build here in NZ. If it were me I would go with thermally broken windows and also the argon gas fill. Helps with heat loss. Also if you can afford it, get tinted windows – the sun is a killer. My husband built our house just before we met and it has standard glass and the carpet and bedspreads have terrible sun fade – drives me mad! Also look into the Low-E glass which I have heard very good things about. 🙂

Hi MB and Sarah WOW – this is valuable information. Thank you very much!!! We are contemplating whether to use aluminium or uPVC mainly because I’ve read from somewhere that the aluminium framing would still form some condensation in cold temperature even if you’ve got double glazing. I’ve read that uPVC does an excellent job with condensation. However, if durability will be an issue then that’s no good. We are definitely going for Low-E. I guess if we see any small amounts of condensation, then we’ll just use a dehumidifier. Again thank you both – this is really helpful. We have been thinking about this for a very long time and we will go with our initial preference, which is to go with Altherm Aluminium.

Hi Jay – yes you are correct about the condensation on aluminium. If you go for the thermally broken ones they have a rubber seal thingy (that’s the technical term 😉 ) between the layers which helps to stop that. It’s not perfect by any means but it helps – I will definitely be getting them on next house (didn’t have them here when we built current place). IF there’s any one piece of kit I could advise anyone building a house to have its a ducted heat pump system. We have one and its the best thing we ever did. It also really helps to circulate air round and we don’t have much condensation on our windows during the winter – we only get it at the bottoms where the air doesn’t get to because of the curtains. Anyway just a suggestion but worth looking into it if you can afford (if you are planning in staying in house long term then a great investment). Good luck with your build 🙂

I meant to add that a large number of our members have had issues with the quality of the low-e glass produced in NZ. Scuffing from the ceramic rollers when the glass panes roll out of the machine have caused the glass to present white stripes in certain light conditions and because it also leaves a minute indentation in the glass it also cause distortion when looking through the glass. What they will also not tell you is that when the Low-e glass is doing its job it shifts the dew point to the outer face of the exterior glass pane and therefore on certain days, particularly in Autum and Winter, you will find that you can’t see out the windows until the ambient outside temperature increases and the condensation evaporates. This came as a surprise and a real disappointment to many members who had magnificent views out of the windows that they could not enjoy in the morning unless they went outside and squeeged the condensation off!! Regards, John Gray President of HOBANZ http://www.hobanz.org.nz

Thanks Sarah! Our budget is a bit limited. We’ve considered ducted heatpump but we can’t afford it at this stage. Will ask our builder about those rubber seals. Thanks heaps 🙂

Hi John. Thanks for your reply. That’s a really useful insight – we will take that on board. Were the complaints mostly in regions where there is snow and extremely low temperatures? We’re based in Wellington and I wonder if the dew point/exterior condensation issue is mainly due to extremely low temperatures? Thanks.

Hi Sarah, separator in thermal break joinery is polyamide between internal and external Ali. Depending upon build location thermal break might be an overkill. Condensation bleeding is down to internal vs external environmental conditions and ventilation/causations of such should be looked into, not dehumidifiers as a solution. Double glazed with Low E is the best solution and maybe look at LowE film placement on glass face to target heat retention/loss. The supplier should be able to talk thru options for supply to meet any budget constraints.

Hi Jay, The thermally broken and double glazing wont eliminate the formation of condensation – it simply helps to limit the development. It is a big misnomer that ducted air conditioning (heatpumps) will solve the problem too unless it is a system like the Mitsubishi Losnay system (Click here: http://www.beattiegroup.co.nz/images/Brochures/Mitsubsihi_LossnayVL220.pdf) or the Daikin HRV system: (Click Here: http://www.beattiegroup.co.nz/images/Brochures/Daikin_PCH0601_-_VAM_Brochure.pdf) that introduce fresh air from the outside, recovers the heat energy from the stale inside air as it is vented to the outside. The important thing, and something that most people do not realise is that in order to have healthy air and to significantly reduce or eliminate condensation the air in every room needs to be “changed” regularly and this can only be achieved by installing a ventilation system with or without heat pumps. There are heat recovery ventilation systems available which would be a good interim measure but without the expense of the heatpump. But later you can use the previously installed ducting for the ducted heatpump when you can afford it. Remember to plan ahead for where you would have to install the condenser units outside your home and it is worthwhile pre-wiring and pre-plumbing during your build phase to avoid the expense of removing cladding and cutting holes everywhere in the future when you decide to install the ducted heatpump. There are a number of Heat Recovery Ventilation systems available and there are some amazing products new to the NZ market that have been in Europe for decades that are worth investigating. I’ll give you some links below to assist you in reviewing the options but I love the FANTECH system that recovers heat from the earth!! Another favourite of mine to help keep the cost down, especially if it is difficult to run large ducts to any particular room, is the de-centralised ventilation fans which incorporate a heat recovery mechanism. These are also very useful for renovation of older homes where running 300mm ducts might e impossible without incurring huge expense. Please note that I do not have any commercial affiliation to any of the products to which I have provided you links for – I have garnered this knowledge by helping thousands of HOBANZ members look at their alternatives and also in researching the options for my own renovation. https://www.eboss.co.nz/library/stiebel-eltron/lt-50-decentralised-ventilation-system http://www.fantechhhv.co.nz/pages/whyVentilate.asp?page=ZN https://www.stiebel.co.nz/ventilation-systems https://archipro.co.nz/blogs/view/the-future-of-ventilation-with-the-heating-compant-the-heating-company https://www.theheatingcompany.co.nz/lunos-decentralised-ventilation.html Good luck with your build!

Hi Jay, No it has happened all over the country, even Wellington and in warmer climbs in the North. The local climate will simply have an effect on the frequency with which the condensation forms on the outside of the windows to the extent that you can’t see outside or that it seriously limits visibility. Cheers, John

Thanks John. We will have a rethink. I wonder if Thermal Heart for aluminium would be a better option then? Has anyone had any experience using Thermal Heart?

Hi John Many thanks for taking the time to provide this useful information. Lots to think about. We will certainly re-evaluate our options. It is interesting to find out that thermally broken and double glazing will not completely eliminate the formation of condensation. Thanks very much for the links you provided. 🙂

Hi Jay, Thermal Heart is just a fancy marketing name for a thermal break between the exterior and interior aluminium components of the window or door joinery. There is no doubt that any joinery that has a thermal break around the entire perimeter of the window or door is more energy efficient in so far a limiting the heat transfer. Several manufacturers have included thermal breaks in the joinery so the options remain wide open in that regard. It is interesting that some experts say that they most efficient thermal break (barrier) is timber framed windows given the natural insulation properties of timber! Whilst on the subject of thermal breaks and insulation – please make sure that your foundation slab is properly insulated and especially around the outside to prevent heat transfer down and out through the sides of the slab. Cheers, John Gray President HOBANZ http://www.hobanz.org.nz

Hi Jay – I meant to say that whilst I have made comments about some of the draw-backs of low-e glass I should say that it is really beneficial in terms of thermal efficiency. It is just that we have seen some serious quality issues arising from production problems and of course the unexpected high degree of condensation forming on the outside of the windows. The condensation is, ironically, an indication of the low-e glass actually doing it’s job to keep heat in. So please don’t dismiss the idea of low-e glass, rather be aware in advance of the potential for quality issues in the glass panes which you would demand replacements for and of course that any lovely views out of your home in the morning over any vista you might have may be impaired by the presence of condensation of the outside. You just have to weigh up the pro’s and con’s by being fully informed. John Gray President HOBANZ http://www.hobanz.org.nz