Browse Forums Windows & Doors 1 Jun 26, 2009 3:13 pm Hello all, Thinking of converting our windows from single glazed to double glazed. Winter chill is starting to make impact. I have read about double glazing and reading the facts about U value reductions - they read quite impressive - by more than half. But in reality, for those who have Double glazing, does this really make an impact? Do you feel there is a difference in heat retention, insulation in the room, warmth, less convection currents? We have one large open plan living, kitchen which is 11m long, 5m wide and 3m high. One 11m wall is made up of 2 bifolds, which are 2m high (these have cellular blinds). One of the other walls, has windows which is 4m long and 2m wide (with just venetian blinds). This room is connected to a hallway, which is 9m long and one side is again full of glass, 2m high. I'm just concerned by spending all this money to improve insulation, will I really see a difference? Thanks Fox Re: Double glazing windows: do they make a BIG difference? 2Jun 29, 2009 9:41 pm Well it alldepends.... Firstly - People have successfully designed low-energy homes with single glazing in temperate climates. - Adding an insulative window covering adds more R-value than two extra panes of glass - There are varying qualities/costs of double glazing. Shop around and check the WERS data for the product - There are plenty of other places that you could be losing heat from the house. Most of them can be addressed with far less expense. We have double glazing but we live in cold temperate region and our house has been specifically designed for high efficiency and includes a raft of other components that work in synergy. I would only consider double glazing if: a) the entire house has been weathersealed adequately including door and window frames, vent and ducts b) ceiling and roof insulation meet Australian regional recommendations c) window coverings are adequate to prevent internal air moving against the cool glass c) has maximised the amount of natural sunlight that can enter the house during winter If you find that these measures are inadequate then double glazing would be the next consideration. Re: Double glazing windows: do they make a BIG difference? 3Jun 30, 2009 5:47 pm fox Hello all, Thinking of converting our windows from single glazed to double glazed. Winter chill is starting to make impact. I have read about double glazing and reading the facts about U value reductions - they read quite impressive - by more than half. But in reality, for those who have Double glazing, does this really make an impact? Do you feel there is a difference in heat retention, insulation in the room, warmth, less convection currents? We have one large open plan living, kitchen which is 11m long, 5m wide and 3m high. One 11m wall is made up of 2 bifolds, which are 2m high (these have cellular blinds). One of the other walls, has windows which is 4m long and 2m wide (with just venetian blinds). This room is connected to a hallway, which is 9m long and one side is again full of glass, 2m high. I'm just concerned by spending all this money to improve insulation, will I really see a difference? Thanks Fox I am not unbiased... but I can give you facts. Your kitchen and hall windows amount to 48 square metres of windows. Given a 10 degree difference between inside and outside temperatures, these alone will require energy equivalent to 3,480 watts to maintain your inside temperature (assumed U Value . That's 92 kilowatt hours per 24 hours or around $14 per day (@ $0.15/kWh). Double glazing would half that cost - just check it's got a decent U value - not all double glazing is double glazing. Comfort? I hope someone else can answer that subjective question... Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Double glazing windows: do they make a BIG difference? 4Jun 30, 2009 8:42 pm Dear dynomite and Ed Thanks for the replies We are currently living in a cold climate- Victoria. Out house is draft proof, and I think ceiling, walls, subfloors have excellent insulation in our double storey house. Maybe if summer is a good example, that despite the heatwave in Victoria, our house remained quite cool, despite the large amount of north and west facing windows. So I think insulation wise we are good, except for the windows Ed, you are correct, with the architect design house, there is a lot of north facing windows ( the hallway is the main culprit ), and the informal living,kitchen with the 9m of bifold door forming one wall. Especially these windows/doors are all floor to ceiling, makes the amount of glass huge. Our windows were made by Rylock, and am told it would be relatively easy to remove the inner single frame glass and replace with double glazing. Cost will be the issue, and will try to pick a balance between things such as low-E for the west windows, and ? need for Argon for the others. The only disadvantage is I think the windows frame are non-thermal alumunium where you can lose a lot of heat. Thanks for your replies Fox Re: Double glazing windows: do they make a BIG difference? 5Jun 30, 2009 9:02 pm Thanks Ed, I knew a smart fella would pop in with the facts Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 6Jun 30, 2009 9:51 pm ed @ EcoClassic Your kitchen and hall windows amount to 48 square metres of windows. That's 92 kilowatt hours per 24 hours or around $14 per day (@ $0.15/kWh). This assumes that you leave the windows uncovered for 24 hours. A heavy window covering with pelmets or cellular blinds would increase R value (and also prevent radiative loss) significantly. Let's say you get 2kWh/m2/day of solar insolation during winter. Don't forget that 46m2 of north facing windows will let in 92 kWh of sunlight during the day as well. You probably won't need that much because you still want to have a natural cycle in temperature between day, evening and night (21 degrees would be far too warm to sleep in). Re: Double glazing windows: do they make a BIG difference? 7Jun 30, 2009 10:17 pm I think you might need to re calc some numbers dymonite69 considering the sun will only be at it's lowest angle for a short time and the coldest time during winter. Solarpassive houses have good shading in summer. If I could keep my house at 21c at night I would be impressed I'd love to pack the duna away all year. Bearing in mind there will be heat activated roof vents, if it too hot. I kind of see where you are coming from, but, for my family and I live in the bush, and enjoy the view curtains take away. so I am having trouble understanding your distain for DB glazing. No offense intended and still willing to learn Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 8Jun 30, 2009 10:17 pm ed @ EcoClassic Comfort? I hope someone else can answer that subjective question... Both subjective and objective components. How much heat a human body gains or loses depends not only on air temperature but also on radiating heat, air movement and humidity. For the technically minded, start of with doing a search on Fanger and ASHRAE or follow the bibliography at the end of this review: http://www.k-state.edu/projects/ngml/re ... /rp657.pdf But here is an example. On a cold 10 degree clear day here in the Adelaide hills our north facing glass receives direct sunlight that extends several meters into the house. The temperature rises quickly to over 20 degrees in the interior. If I place a thermometer next to the window it can register up to 45 degrees! Sometimes we need to open the window to prevent the room overheating. Radiant heat gain during the day is several fold higher than conducted heat loss through the windows (single or double glazed) Re: Double glazing windows: do they make a BIG difference? 9Jun 30, 2009 10:22 pm Would a roof vent take care of this? d69 Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 10Jun 30, 2009 10:38 pm onc_artisan I think you might need to re calc some numbers dymonite69 considering the sun will only be at it's lowest angle for a short time and the coldest time during winter. Solarpassive houses have good shading in summer. enjoy the view curtains take away. so I am having trouble understanding your distain for DB glazing. Calcs are reliable. Log on to Bureau of Meteorology and check solar insolation figures for hundreds of weather stations around Australia. The low angled winter sun is the passive solar house's friend. It peaks in under the eaves to give you all of its radiant warmth. During the summer, the eaves will block the high angled sun and keep the rooms comfortably shaded. If you want your night time view without curtains then you need every assistance you can get. Double glazing would be the way to go and I would add a low-e coating to reduce radiation loss. We have lovely views here from our double glazed windows but leaving them exposed at night is still an energy liability albeit a lower one. Unless we have a great need to leave them uncovered, we lower our cellular blinds at night for heat conservation and privacy. But I will repeat my observation from above. There are plenty of comfortable owners of passive solar houses with low energy bills who only have single glazing. Clearly there are multiple factors that ensure the house stays warm. My disdain is not for double glazing but that fact that people think that there is silver bullet solution to energy efficient design. You need a combination of varying components to make the entire system effectively. A poor design or construction can sabotage all the benefits of double glazing or insulation with a very disappointed owner See an eco house that performed worse than expected after double glazing: http://www.yourhome.gov.au/technical/pubs/fs812.pdf Re: Double glazing windows: do they make a BIG difference? 11Jun 30, 2009 10:39 pm Personally I would not bother to double glaze windows with aluminum frames (this excludes thermal break frames) in Victoria, the cost to efficiency gain isn't that attractive (IMO). Maybe get the house modeled with double glazing by an energy rater to see if the benefits are worthy of the costs. Depending how much you believe in environmental sustainability, replacing perfectly good window frames with new ones may outweigh any environmental benefits gained from double glazing through reduced heating costs (of course this totally depends on what you do with the old panes). Re: Double glazing windows: do they make a BIG difference? 12Jun 30, 2009 10:41 pm dymonite69 onc_artisan I think you might need to re calc some numbers dymonite69 considering the sun will only be at it's lowest angle for a short time and the coldest time during winter. Solarpassive houses have good shading in summer. enjoy the view curtains take away. so I am having trouble understanding your distain for DB glazing. Calcs are reliable. Log on to Bureau of Meteorology and check solar insolation figures for hundreds of weather stations around Australia. The low angled winter sun is the passive solar house's friend. It peaks in under the eaves to give you all of its radiant warmth. During the summer, the eaves will block the high angled sun and keep the rooms comfortably shaded. If you want your night time view without curtains then you need every assistance you can get. Double glazing would be the way to go and I would add a low-e coating to reduce radiation loss. We have lovely views here from our double glazed windows but leaving them exposed at night is still an energy liability albeit a lower one. Unless we have a great need to leave them uncovered, we lower our cellular blinds at night for heat conservation and privacy. But I will repeat my observation from above. There are plenty of comfortable owners of passive solar houses with low energy bills who only have single glazing. Clearly there are multiple factors that ensure the house stays warm. My disdain is not for double glazing but that fact that people think that there is silver bullet solution to energy efficient design. You need a combination of varying components to make the entire system effectively. A poor design or construction can sabotage all the benefits of double glazing or insulation with a very disappointed owner See an eco house that performed worse than expected after double glazing: http://www.yourhome.gov.au/technical/pubs/fs812.pdf I agree with dymonite69, there are so many things you look at before considering double glazing. Good design is paramount!!! Re: Double glazing windows: do they make a BIG difference? 13Jun 30, 2009 10:43 pm onc_artisan Would a roof vent take care of this? d69 What I would have liked to do was make more use of the solar energy for night time release. Letting it out again is not first best option. In the design phase it may be that I have overglazed for some north facing rooms or needed to compensate for the loss of thermal mass which has been covered by sections of carpet. My alternative solution is currently to run the ducted heating on fan mode and use my heat transfer kits to redistribute the warm air to the colder southern side of the house. This gets some heat stored in the other parts of the building fabric which is retained at night. Re: Double glazing windows: do they make a BIG difference? 14Jun 30, 2009 10:46 pm Please excuse my ignorance... But it performed badly because for some stupid reason it wasn't situated NNE. ...and an infloor heating system why? Too much money Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 15Jun 30, 2009 10:52 pm dymonite69 ed @ EcoClassic Your kitchen and hall windows amount to 48 square metres of windows. That's 92 kilowatt hours per 24 hours or around $14 per day (@ $0.15/kWh). This assumes that you leave the windows uncovered for 24 hours. A heavy window covering with pelmets or cellular blinds would increase R value (and also prevent radiative loss) significantly. Let's say you get 2kWh/m2/day of solar insolation during winter. Don't forget that 46m2 of north facing windows will let in 92 kWh of sunlight during the day as well. You probably won't need that much because you still want to have a natural cycle in temperature between day, evening and night (21 degrees would be far too warm to sleep in). Balance is not achieved by having one leg encased in ice and the other in boiling water... solar heat gain does not heat the home at night as the heat flows out of the windows. Comfort is everything... averages are just that - being comfortable on average is the same as living in the open air... sometimes hot sometimes cold. You need to moderate the impact of cold and heat. You can use heavy drapes or blinds - but they won't be anywhere near as good as double glazing and Low-E. Having lived in a cold climate where everyone knows (it's not new) that heavy curtains make a difference, they don't help much when your teeth are chattering, the difference they make is just not enough... Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Double glazing windows: do they make a BIG difference? 16Jun 30, 2009 10:59 pm Building_Nerd Personally I would not bother to double glaze windows with aluminum frames (this excludes thermal break frames) in Victoria, the cost to efficiency gain isn't that attractive (IMO). Maybe get the house modeled with double glazing by an energy rater to see if the benefits are worthy of the costs. Depending how much you believe in environmental sustainability, replacing perfectly good window frames with new ones may outweigh any environmental benefits gained from double glazing through reduced heating costs (of course this totally depends on what you do with the old panes). As I showed in another thread, there are many thermally broken frames that don't perform as well as double glazed regular aluminium. And there are some excellent designs in aluminium double glazing that rival PVC and timber (EcoClassic is one). So yes Fox, have your house modelled, but the calcs are simple... send me your window & door dimensions, your chosen brand selection and what you have now and I will calculate the savings on windows alone... and publish them here... Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Double glazing windows: do they make a BIG difference? 17Jun 30, 2009 11:03 pm That is the crux of the matter getting heat in and balancing the act. Is that offer open to anyone Ed? Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 18Jun 30, 2009 11:07 pm fox Dear dynomite and Ed Thanks for the replies Ed, you are correct, with the architect design house, there is a lot of north facing windows ( the hallway is the main culprit ), and the informal living,kitchen with the 9m of bifold door forming one wall. Especially these windows/doors are all floor to ceiling, makes the amount of glass huge. Our windows were made by Rylock, and am told it would be relatively easy to remove the inner single frame glass and replace with double glazing. Cost will be the issue, and will try to pick a balance between things such as low-E for the west windows, and ? need for Argon for the others. The only disadvantage is I think the windows frame are non-thermal alumunium where you can lose a lot of heat. Thanks for your replies Fox You're welcome... I would be surprised if Rylock windows can't be retrofitted with double glazing as this is what the primarily sell. While they won't be the best U value frames, I think it would be economically worthwhile getting them double glazed, over having new windows fitted. You would get about 66% of the benefit I calculated. Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Double glazing windows: do they make a BIG difference? 19Jun 30, 2009 11:08 pm onc_artisan That is the crux of the matter getting heat in and balancing the act. Is that offer open to anyone Ed? Yes, happy to calculate that (minus curtains ). Ed "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: Double glazing windows: do they make a BIG difference? 20Jun 30, 2009 11:15 pm ed @ EcoClassic Balance is not achieved by having one leg encased in ice and the other in boiling water... solar heat gain does not heat the home at night as the heat flows out of the windows. Ed, I don't think you understand the concept of thermal mass. A significant portion of that solar energy can be stored in the building fabric e.g. floors, walls, furnishings. With the immence heat capacity of concrete or masonry the temperature of these surfaces don't get very hot. At night time the heat is released from these objects in the form of radiation and convection which continue to maintain stable interior temperatures. In effect the thermal mass is a heat battery. You analogy of temperature extremes between day and night is erroneous. 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 19232 I don't know them all, the first 2 top of your list are best known. Rylock is a good company, Stegbar is for sale. 4 16227 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 7712 |