Browse Forums Windows & Doors 1 Sep 29, 2019 4:40 pm We are planning to build and where considering double glazing until we got discouraged by builders saying it'll cost around $26K upgrade. One builder recommended considering other options, such as Low E glass. I started researching all these options, and I'm beginning to wonder if double glazing is worth the cost in Perth climate. Here is the reasoning. We are going to go with laminated (possibly security) glass anyway. Suppose we want to keep the house around 22℃ throughout the year. In summer we only have few weeks with temperatures above 36℃, and even than, during the night the temperatures drop in the twenties. In winter the lowest we get is 1℃ and for only a few hours in the mornings and few days in the year. A good chunk of the year the outside temperature is perfect. So, the temperature difference between inside and outside averages somewhere around 5-10℃ (correct me if wrong). Now, based on the R/U/<whatever else> value, how much money a double glazed window is going to save in reality? While researching windows/glass, one question I cannot find an answer to is, what do R/U values mean in regards to saving $$ based on temperature difference? I think these values are a good measure to compare products agains each other, but mean nothing to the average person when trying to decide if a product is worth the price. It would be great if we had something like 1square meter of glass/brick/whatever with R/U 1.0/2.0/3.0 saves $$/Kw per day/year based on 5/10℃ Re: Double glazing worth the $$ in Perth? 2Sep 29, 2019 7:55 pm Hi and welcome to the forum. Nice to have another WA contributor. I've built 3 times, the last 2 was OB. I looked at DG but like you struggled to justify the price. If you are owner building you can import from China much cheaper than getting local, but if you are building with a builder you won't have that option. My feeling is that good design that takes into account solar principles will be of far greater value than DG. Low E glass is a good alternative where required. I can't answer specifically what costs upgrading to DG would save per metre but I can't help that think that the pay back on $26k would take a long time. I'd prefer to use that money to install a 6kw PV solar system, RC air con and upgrade the roof insulation. It probably still won't cost $26k and will give you a better use of the money and will get you a tangible return on resale. That's my opinion anyway. Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Double glazing worth the $$ in Perth? 3Sep 29, 2019 10:59 pm The most important aspect of a house design is orientation. If you don’t have that right, then everything else is just fighting to get your house back where is should have been in the first place. Second aspect is windows, because they are the most thermally leaky element of your house (presuming you have basic insulation in the roof and your builder hasn’t left you with a sieve because they didn’t attend to gaps properly). Windows are not just glass, although that is the largest component, so you'd want to address the frames too. If you have aluminium, you'd want to make sure they are thermally broken. Read this before you even start deciding on designs - it will be the best couple of hours you have spent. Best of all, your taxes paid for it. http://www.yourhome.gov.au/passive-design/design-climate http://www.yourhome.gov.au/passive-design/orientation http://www.yourhome.gov.au/passive-design/insulation http://www.yourhome.gov.au/passive-design/sealing-your-home http://www.yourhome.gov.au/passive-design/glazing Re: Double glazing worth the $$ in Perth? 4Sep 30, 2019 8:53 am perth97 We are planning to build and where considering double glazing until we got discouraged by builders saying it'll cost around $26K upgrade. One builder recommended considering other options, such as Low E glass. I started researching all these options, and I'm beginning to wonder if double glazing is worth the cost in Perth climate. E Glass meets the energy code requirements in Perth which has a moderate climate ( goldilocks zone) while most spend more time outdoors than indoors. If you have a spare $30k spend it bringing the outdoors indoors It will add $100k in extra value upon resale...my2c OT Real energy Simulations involves FEA ) LOL, Open the windows and watched the energy and costs flow out the door for real data and proofs research Multiphysics CFD Simulations there are numerous (excuse the pun) Examples. hth Designer,Engineer (Civil,Const & Envir),Builder,Concrete & Masonry Contract.Struct Repairs Re: Double glazing worth the $$ in Perth? 5Sep 30, 2019 4:32 pm chippy I'd prefer to use that money to install a 6kw PV solar system, RC air con and upgrade the roof insulation. Thanks chippy, exactly my thoughts. arcadelt Read this before you even start deciding on designs - it will be the best couple of hours you have spent. Best of all, your taxes paid for it. Thanks arcadelt, I have already read some, but not all. The glazing one got me interested and create spreadsheet to calculate the possible ROI. For my calculations I used the U values provided in this post https://forum.homeone.com.au/viewtopic.php?p=1082150#p1082150 Base on the formula from http://www.yourhome.gov.au/passive-design/glazing I got the below outcome. In the top part I used 70m2 of total glass in an house, 15℃ temperature difference for the whole year. I know, extreme! The bottom part I dropped to 40m2 of total glass area because I thought it is more reasonable and 7.5℃ temperature difference for the whole year. Averaging for Perth climate. But the numbers still didn't make sense in relation to reality. I would say my current house has more than 40m2 of glass and my total electricity bill for the whole year is below $2400. So I took the % savings from worse (ordinary glass) to best (Softcoat Low-E in double glazed unit + argon +hardcoat), which is 81% of saving and I assumed that the heat gain/loss from the windows contribution to my total bill is 20%, which give me $480 per year. If I had the best double glazing installed, I would save 81% of $480, which is $388.8 per year. $26,000 / $388.8 = 66.8 years for ROI!!! Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Re: Double glazing worth the $$ in Perth? 6Sep 30, 2019 4:42 pm Hi, I have no idea what actual $$ savings are associated with double glazing, but I guess you can model energy losses for your total glazing areas and go from there? There is info around the internet on this stuff. My thoughts on deciding whether or not to double glaze are:
A few negatives:
Anyhow I think on balance in our own climate zone (#7) I would always go at least double glazed now, even if just for the acoustic performance alone. Double glazed with something like: 6.38mm lam - 12 to 14mm Argon gap - 4mm safety glass......this will give you great acoustics and thermal performance I think. ** Like others have said here though, the frame is important. For us we couldn't justify the cost of thermally broken frames unfortunately as it was adding another 50% on top of our overall glazing quotes. Stupidly expensive still in Australia are thermally broken aluminium frames IMO. --------------------------------------------------------------------- Check our Homeone build blog here Re: Double glazing worth the $$ in Perth? 7Sep 30, 2019 5:04 pm That's pretty much my thoughts. In the real world with the use of curtains at night, I think it would stretch the advantages even further. If the price difference was closer then maybe it would be a consideration. Get the design and orientation right, use hardscape and landscaping to provide further solar shading/advantage if required and use the money saved to offset any slight power usage you may incur from not using DG. Perth climate is pretty good if you can keep the afternoon sun out in summer and get some winter sun in. Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Re: Double glazing worth the $$ in Perth? 8Sep 30, 2019 5:13 pm perth97 If I had the best double glazing installed, I would save 81% of $480, which is $388.8 per year. $26,000 / $388.8 = 66.8 years for ROI!!! Personally, as someone who spent $150K on windows in a custom build, and has lived in that house for over a year now, I wouldn’t rely on the numbers alone...or even at all. Re: Double glazing worth the $$ in Perth? 9Sep 30, 2019 5:55 pm arcadelt perth97 If I had the best double glazing installed, I would save 81% of $480, which is $388.8 per year. $26,000 / $388.8 = 66.8 years for ROI!!! Personally, as someone who spent $150K on windows in a custom build, and has lived in that house for over a year now, I wouldn’t rely on the numbers alone...or even at all. Arcadelt. You are obviously living in one million plus $ build. I've never lived in a house that expensive however our last 2 homes we have designed and built ourselves and I can tell you that in Perth you can get better bang for your buck and a better ROI in other ways. As I said, if you've got the money and it's not an issue go for DG but if it's a toss up spend some money on great design (using passive solar principles) and spend the money elsewhere. Figures don't lie. Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Re: Double glazing worth the $$ in Perth? 10Sep 30, 2019 6:18 pm chippy Figures don't lie. You might be misinterpreting me - I'm not necessarily disagreeing, but it’s hard to determine comfort from numbers...and yes, I don’t live in Perth, but a more challenging alpine environment. Re: Double glazing worth the $$ in Perth? 11Sep 30, 2019 6:23 pm Alpine environment, I'd be DG'ing all the way. It absolutely makes sense. In Perth. Good design, PV panels and RC AC are going to give you best ROI which I think is what the OP was trying to decide. Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Re: Double glazing worth the $$ in Perth? 12Oct 03, 2019 11:55 pm arcadelt chippy Figures don't lie. You might be misinterpreting me - I'm not necessarily disagreeing, but it’s hard to determine comfort from numbers...and yes, I don’t live in Perth, but a more challenging alpine environment. I agree that generally, it is hard to determine comfort from numbers, but in this case, the numbers are a representation of how much is going to cost you to get your comfort, around 22℃ in my case. In your case, the temperature differences could be as high as 42 (-20℃ to +22℃) which when using my spreadsheet shows savings between $20-33K per year. Based on my numbers and some assumptions I think in the alpine environment, you will have around 10 years ROI, which makes a case for DG windows. I do understand that DG also better block unwanted noise, but in my case, that is not an issue and even if it was it'll be cheaper to use noise cancellation speakers than DG. Re: Double glazing worth the $$ in Perth? 13Oct 04, 2019 7:36 am perth97 In your case, the temperature differences could be as high as 42 (-20℃ to +22℃)... -20°C God I hope not, but yes -10°C to 38°C, so a 48 degree difference. Anyway, all the best with your decision. Re: Double glazing worth the $$ in Perth? 14Oct 04, 2019 2:29 pm It would be great if everybody could have double glazing, but everything comes at a cost, & the cost of double glazing is certainly significant. I'm not expert, but in Perth's climate I'd expect you'd get better value spending your money elsewhere. Upping the (bulk) insulation levels in the roof & walls, reflective insulation in the roof & western wall also. Investing in a good PV system, & look at your hot water options. Investing in energy efficient heating/cooling options (reverse cycle AC), but in Perth a well designed home won't need much. So, as had been mentioned, it's really about the design of the home, & the orientation. Getting that right is free, & will play a major role in comfort & energy efficiency. Glass is such a poor insulator (even double glazing), so the best thing you can do is not overglaze, & make sure all your glass faces the right direction. West facing glass is always going to be a problem, no matter if it's double glazed (which has no effect on radiant heat, sunshine) or low-E glass. If you were going to double glaze you could stick to the southern side of the home. But you shouldn't have overglazed that side, so there shouldn't be too much glazing. Same with low-E glass. You could use it on the west & eastern side, but again you shouldn't have to much glazing here. Especially to the west, hopefully you have no glazing there, or a very minimal amount. Re: Double glazing worth the $$ in Perth? 15Oct 08, 2019 6:48 am We are currently building in Perth as well, a 5x3 2 storey home with Plunkett and we are going double glazing. We have very large casement windows everywhere and our upgrade cost was $36k with Arco. To be honest one of the biggest misconceptions of Perth is that it doesn't get cold and it's a hot place (obviously it is) , but there are in fact more days in a year in which you need a heater on than the air con on and the costs can be huge much more than the aircon. Having lived overseas I was tired of spending my winters in front of the heater and taking a shower in a freezing cold bathroom. Double glazing makes sense to me as I have experienced it, and it's crazy that in almost 2020 they still build houses with single glazed so inefficient. We looked at the E glass option as well, but it wasn't what we were after as our biggest trouble were the cold winter nights and keeping heat in and the Eglass is really only effective for sun and keeping the heat out, whereas obviously double glazed does both. Re: Double glazing worth the $$ in Perth? 16Oct 08, 2019 9:33 pm It's not just the glass though, Australian houses leak like sieves, & are poorly insulated. Double brick seems about the most stupid way to build, & it's all over WA. Especially uninsulated double brick, which was common in the past. My sister has a place like that in Sydney. It's the coldest house I've ever been in, absolutely horrible. Although double glazing would be great, I think you get much better bang for your buck elsewhere first. Upping the insulation, taped wall wrap to cut down on air ingress. Re: Double glazing worth the $$ in Perth? 17Nov 07, 2019 12:37 pm Sorry Dis but I have to disagree with most of your statements. Dis To be honest one of the biggest misconceptions of Perth is that it doesn't get cold and it's a hot place (obviously it is) , but there are in fact more days in a year in which you need a heater on than the air con on and the costs can be huge much more than the aircon. I don't see how you'll need more heating than cooling in Perth, unless you are very sensitive to cold and your comfort temperature is close to 30°C. Perth does get "cold", but it is nothing compared to Europe. I did grow up in Europe and at rare occasions experienced temperatures of -20°C... Let's not compare apples with oranges. Here is data to support my claim: https://www.australia.com/en/facts-and-planning/weather-in-australia/perth-weather.html http://www.farmonlineweather.com.au/climate/station.jsp?lt=site&lc=9225 Heating and cooling costs are more-less the same if you use RC Air Con. KW of energy is KW of energy! Dis Double glazing makes sense to me as I have experienced it, and it's crazy that in almost 2020 they still build houses with single glazed so inefficient. It's not crazy, but it is practical and smart IMO not to spend $$$ on something that doesn't do much anyway. If you look at the calculations I did above you'll see that plain glass it is not so inefficient in Perth climate as a significant part of the year the desired temperature is not much different than the outside temperature. IMO it is crazy to spend $26K++ when doesn't add much of value to your comfort. Extra insulation, solar panels, automated window coverings etc. would be a much smarter way to spend that kind of money, especially if the cost of the house is in a range of $300K. Double (or even triple) glazing in Perth makes sense in few cases.
Dis We looked at the E glass option as well, but it wasn't what we were after as our biggest trouble were the cold winter nights and keeping heat in and the Eglass is really only effective for sun and keeping the heat out, whereas obviously double glazed does both. This is plain wrong. Low E glass affect both thermal and solar efficiency. Happy to be corrected on this by experts! DG doesn't do much for solar heat transfer if you don't use window coverings. See U and SHGS values under the performance section in here https://www.viridianglass.com/products/energy-efficiency/comfortplus Note that plain DG window U value is about 2.7. U-VALUE & SHGC EXPLAINED Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Re: Double glazing worth the $$ in Perth? 18Nov 08, 2019 6:40 pm I'd agree that at the price we pay for double glazing (far higher than overseas I believe), it doesn't usually make financial sense. That money could be better utilised first by upgrading insulation, using wall wrap & draft sealing etc. I'm no expert either, but believe you're right that double glazing has little effect keeping solar radiation (direct sunlight out). However I do think double glazing is far more effective in cold climates than low-e glass. Not that this is Perth Re: Double glazing worth the $$ in Perth? 19Nov 09, 2019 12:18 am Thank you for taking the time to reply to my message. Again as mentioned before our biggest issue, and the reason why we have decided to invest in DG is the cold NOT the heat. Although I'm sure you have experienced temperatures of minus 20° outside, if you have lived in Europe you would know that thanks to central heating and with the help of DG temperatures inside the house rarely go under 19/20°. This is not the case in Perth during winter. Where night temperatures inside the home in winter can drop even lower that 15°. Which to me feels uncomfortably cold. I am from Europe and inside my house I'm used to be comfortable, especially going to the bathroom in the morning. Again if you have grown up in these conditions and are used to battling a cold house during winter months, that's fine, but if you know there is a better reality out there, it's quite hard to make the switch. Re: Double glazing worth the $$ in Perth? 20Nov 09, 2019 6:42 am ddarroch I'd agree that at the price we pay for double glazing (far higher than overseas I believe), it doesn't usually make financial sense. That money could be better utilised first by upgrading insulation, using wall wrap & draft sealing etc. Seems like a bit of a circular problem. Double-glazing would be cheaper if it was ubiquitous, but because it is perceived as too expensive, people aren’t willing to install it, so it will never be widespread. This is one of the reasons I decided to go overseas for my double glazed windows. As the builder indicated, he's worked on many upmarket builds, these were the most well… 13 19245 For your reference Performance Labels: Window assemblies in housing, except timber windows, must be labelled so the label can be seen when it is in situ. For timber… 6 7718 In fairness nobody gave a crap about the ACCC and the gag clauses continued in the pro forma templates of a few other builders after the ACCC took on Wisdom, and more… 19 73492 |