Browse Forums Windows & Doors Re: Double glazing windows: do they make a BIG difference? 61Jul 27, 2009 12:35 pm One last point in favour of DG windows. Thermal mass works really well for a 'non-conditioned' / free running house ie you will rarely need to turn the heaters / air con becuase of the thermal mass is a heat sink etc. A lightweight, low thermal mass house, with really good insulation, draught sealing, DG windows, shading etc ... when you turn the heater / a/c on you will only use a very little bit of power to cool or heat the house ... effectively an esky effect. Where you are cooling or heating your house mechanically I think DG will make a large % difference in your running cost. Re: Double glazing windows: do they make a BIG difference? 62Jul 27, 2009 12:56 pm lambchoppa Where you are cooling or heating your house mechanically I think DG will make a large % difference in your running cost. You are quite correct. Assuming no other energy inputs apart from your heating system, retarding heat loss is your primary concern. But why would you ignore the 1000W/m2 of free solar energy that can heat your house during the day. In other words, every m2 of window that lets sun in is equivalent to having 1 bar radiator operating inside. Re: Double glazing windows: do they make a BIG difference? 63Jul 27, 2009 1:09 pm dymonite69 lambchoppa Where you are cooling or heating your house mechanically I think DG will make a large % difference in your running cost. You are quite correct. Assuming no other energy inputs apart from your heating system, retarding heat loss is your primary concern. But why would you ignore the 1000W/m2 of free solar energy that can heat your house during the day. In other words, every m2 of window that lets sun in is equivalent to having 1 bar radiator operating inside. D69 I couldn't agree more ... but its hard to do something about that on a retrofit (ie for me and others here) ... I would love to reverse the orientation of my house ... but its not going to happen. Just making the point that if you have limited thermal mass you can still get a good result ie save money improve comfort. Re: Double glazing windows: do they make a BIG difference? 64Jul 27, 2009 1:43 pm lambchoppa I would love to reverse the orientation of my house ... but its not going to happen. Just making the point that if you have limited thermal mass you can still get a good result ie save money improve comfort. Sometimes people find it possible to reverse the function of the room. e.g. switch the bedroom with the rumpus room so the kids get to be on the sunny side during the day. Re: Double glazing windows: do they make a BIG difference? 65Jul 29, 2009 9:25 pm fox 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? The first thing to remember is that every part of your house's external structure leaks heat. If it didn't you wouldn't need a heating system. The ceiling, walls and floors all have U-values. Cold air can also move inside from gaps in the structure. So onto an example: Let's take a terribly inefficient 1 star house which needs 38000 kWhr to keep warm each year or $5000/year on your heating bill. But I will describe it as an analogy. This house is like a big leaky rusty bath with lots of holes in it. The holes represent sites of heat loss. Let's say there are 20 equal sized holes. 9 of the holes represent loss through the ceiling, 4 through the walls, 3 through gaps in the house, 3 through the bare windows, 1 through the floor * Water is running into it. The tap represents your heater and water is the heat. You want the bath to be at 3/4 full. The water level represents the interior temperature. Too high and you are too hot. Too low and you are too cold. Now my aim is to start plugging holes so that I can reduce the water flow (turn the heater down). Plugging the different kinds of holes will need different strategies e.g. weatherseals, insulation, double glazing, curtains Reminding ourselves that the current heating bill is $5000/yr 1) Plug 'ceiling holes'. Cost of retrofit $5K. Reduce heating bill by $2250/yr 2) Plug 'wall holes'. Cost of retrofit $5K. Reduce heating bill by $1000/yr 3) Plug 'air gaps'. Cost of retrofit $200. Reduce heating bill by $750/yr 4) Plug 'floor holes'. Cost of installation ?$2K. Reduce heating bill by $250/yr So after plugging most of the holes with an investment of $13000 I can reduce by heating bill down from $5000 to $750. The tap (heater) is now running at a moderate trickle. So the final 3 holes to plug..... 5) Plug 'window holes'. Cost of retrofit $11500. Reduce heating bill by $750/yr ** I would need to spend almost as much as what I did for insulation and weatherseals to squeeze my last $750 of savings. Of course 'window holes' can be plugged by another pane (double glazing) or by heavy curtains. DG is a plug 24/7. You tend to 'unplug' curtains during the day but that isn't so bad but because you tend to fill the bath only at night. The decision whether to spend $$$ to plug the window holes is dependent on how may of the other important hole have already been blocked off. This equation works only for an exisiting house. For a new house the cost for installation can be significantly cheaper if you decide to do these things from the outset. * These are estimated percentages based on the Your Home Technical Manual ** In reality you can't reduce the leakage to zero because the 'plugs' are not perfect and are a little 'leaky' themselves http://www.yourhome.gov.au/technical/fs45.html http://www.yourhome.gov.au/technical/fs47.html Re: Double glazing windows: do they make a BIG difference? 66Jul 30, 2009 10:10 am D69 this is the best analogy yet. Thanks. Will use it. Having done all the first steps, you will then 'halve' your heating bill by plugging those windows holes with DG ... it is not economic as you point out ... but still will make a difference (ie by the time you do the first 4, 50% of your heat loss is through the windows) Re: Double glazing windows: do they make a BIG difference? 67Jul 30, 2009 10:18 am lambchoppa Having done all the first steps, you will then 'halve' your heating bill by plugging those windows holes with DG ... it is not economic as you point out ... but still will make a difference (ie by the time you do the first 4, 50% of your heat loss is through the windows) Actually more than halve. You would have already reduced it by more than 2/3rds! ($5000 -> $750). To get the last third (with DG) will cost you as much money again. ($750 -> $0) Re: Double glazing windows: do they make a BIG difference? 68Jul 30, 2009 10:20 am I have another question - I read on the government site Quote: Keep the area of glazing on east and west elevations to a minimum where possible, or use appropriate shading devices. Can someone clarify for me - does this mean limit the amount if windows on the East and West, or not to glaze windows on the East or West? A very large proportion of our windows are on our East side of the house (and no, we cant get rid of them! ) and Im wondering whether this means that double glazing on the east and west is ineffective? How would you know what windows are the most beneficial to glaze in comparison to others if this is the case? Custom European Cabinets - Melbourne Kitchen Specialist PM for business details as website currently being updated! Our Crazy Owner Builder Journey! Re: Double glazing windows: do they make a BIG difference? 69Jul 30, 2009 10:25 am Bam I have another question - I read on the government site Quote: Keep the area of glazing on east and west elevations to a minimum where possible, or use appropriate shading devices. Can someone clarify for me - does this mean limit the amount if windows on the East and West, or not to glaze windows on the East or West? A very large proportion of our windows are on our East side of the house (and no, we cant get rid of them! ) and Im wondering whether this means that double glazing on the east and west is ineffective? How would you know what windows are the most beneficial to glaze in comparison to others if this is the case? Bam, that isn't talking about double glazing. By "area of glazing", they just mean the area of glass/windows. When they say glazing they just mean windows, so yes they are saying to limit your windows. West is worse, I wouldn't worry so much about having lots of windows in the east side. It's lovely morning sun, only on the very hottest of hot days would it be a worry. The west on the other hand are more problematic and definitely need to be minimised and shaded. I leave you to fend for yourself, figure things out yourself. Terrence Malick Re: Double glazing windows: do they make a BIG difference? 70Jul 30, 2009 10:27 am Bam I have another question - I read on the government site Quote: Keep the area of glazing on east and west elevations to a minimum where possible, or use appropriate shading devices. Can someone clarify for me - does this mean limit the amount if windows on the East and West, or not to glaze windows on the East or West? A very large proportion of our windows are on our East side of the house (and no, we cant get rid of them! ) and Im wondering whether this means that double glazing on the east and west is ineffective? How would you know what windows are the most beneficial to glaze in comparison to others if this is the case? Bam the issue with east and west windows/glazing (glazing is the glass inside the window) is direct solar heat gain ie the suns rays hitting those windows and heating up the house. It means limit the amount of windows on east and west sides. DG will only be effective where you have external shading ie awnings etc so you stop the suns rays hitting the glass. Alternatively you can put reflective glass (eg comfort plus), reflective tint or renshade or similar on the windows. Blinds are also good, but better to directly stop the rays hitting the glass. Re: Double glazing windows: do they make a BIG difference? 71Jul 30, 2009 10:44 am Bam I have another question - I read on the government site Quote: Keep the area of glazing on east and west elevations to a minimum where possible, or use appropriate shading devices. Can someone clarify for me - does this mean limit the amount if windows on the East and West, or not to glaze windows on the East or West? A very large proportion of our windows are on our East side of the house (and no, we cant get rid of them! ) and Im wondering whether this means that double glazing on the east and west is ineffective? How would you know what windows are the most beneficial to glaze in comparison to others if this is the case? The best to understand this is to picture the sun's path throughout the seasons. Face north and raise your arms to the horizontal then pointing left and right at about 45 degrees either side of north. Your arms point to about where the sun rises and sets during winter. The sun rises and traces a low arc in the sky reaching its peak due north. Now pull back your arms so they are pointing immediately left and right of you at 90 degrees either side of north. Your arms now point to roughly where the summer sun sets and rises. The sun performs a much steeper arc and peaks at much higher angle facing north.* It has been described that windows are just leaky holes that allow heat to escape. The situation is a bit more complex than that. They allow the heat in the air to escape (not good in winter) but they also admit warming sunlight (very good good in winter, not good in summer). Passive solar design is all about positioning windows and shades to control this sunlight - to allow it to enter or block it. The east and west summer sun are low in the sky throughout the year. Good to let sun in the winter, but difficult to shade in summer. In passive solar design it is recommended that you try to get direct sunlight via the north side because a correctly sized eave will allow low winter sun to get in but exclude high summer sun. The north side also allows sun in most of the day whereas east and west sides only get half sun. If you have east/west windows then you will need to have a manually adjustable shade to block out summer sun. They can be left up during winter. But regardless of sunshine the west side will be colder in the morning and east side will be colder in the afternoon. Double glazing (like curtains) can stop heat loss particularly when there is no sun or when sun isn't entering your window. The question yo need to ask is are you going to use that room frequently at time of the day when there is a high likelihood of having no sun come in and you need the room as warm as possible e.g. living area. If so you it may be ideal to double glaze. If it is a bedroom or utility room then the heat loss doesn't matter as much and DG is not so critical. * The precise angles are approximate and related to how far south (or north) you live from the equator. Re: Double glazing windows: do they make a BIG difference? 72Jul 30, 2009 11:01 am dymonite69 Actually more than halve. You would have already reduced it by more than 2/3rds! ($5000 -> $750). To get the last third (with DG) will cost you as much money again. ($750 -> $0) Here are some reference figures from my AccuRate Report (I have rounded them to nearest 50 in case of copyright issues). House energy star rating (for Adelaide Hills) 1 star - 900 MJ/m2 2 star - 700 3 star - 500 4 star - 400 5 star - 300 6 star - 250 7 star - 160 8 star - 100 9 star - 50 10 star - 1 For a 150m2 home this translates to the following heating energy bill where electrical heating is used at 0.13c/kWhr = 46.8c/MJ * 1 star - $4900/yr (a non-insulated leaky shack) 2 star - $3800/yr 3 star - $2700/yr (an average Oz home with some old ceiling insulation) 4 star - $2100/yr 5 star - $1600/yr (New house building standard with good insulation) 6 star - $1400/yr 7 star - $800/yr (Passive solar house with double glazing) 8 star - $550/yr 9 star - $300/yr 10 star -$5/yr (German Passivhaus standard with three times recommended insulation and triple glazing) * The cost of natural gas heating is half price of electricity *** The cost of wood heating is about a fifth the cost of electricity Re: Double glazing windows: do they make a BIG difference? 73Jul 30, 2009 2:30 pm joles Bam, that isn't talking about double glazing. By "area of glazing", they just mean the area of glass/windows. When they say glazing they just mean windows, so yes they are saying to limit your windows. West is worse, I wouldn't worry so much about having lots of windows in the east side. It's lovely morning sun, only on the very hottest of hot days would it be a worry. The west on the other hand are more problematic and definitely need to be minimised and shaded. Aaah, thanks for clearing that up Joles! When we purchased the block, we had an option of two blocks with the driveways on opposite sides. We specifically selected this one as we wanted our living areas to have morning sun (east) and not afternoon sun (west) - so at least we have done something right so far Our west windows are the laundry, bathroom and two bedrooms - not fussed about the laundry and bathroom but will look in to ways of shading the west bedroom windows lambchoppa Bam the issue with east and west windows/glazing (glazing is the glass inside the window) is direct solar heat gain ie the suns rays hitting those windows and heating up the house. It means limit the amount of windows on east and west sides. DG will only be effective where you have external shading ie awnings etc so you stop the suns rays hitting the glass. Alternatively you can put reflective glass (eg comfort plus), reflective tint or renshade or similar on the windows. Blinds are also good, but better to directly stop the rays hitting the glass. We will be having 600mm awnings around the entire house, and on the East side we will have our alfresco under the roof line which will shade a lot of our larger windows and bifolds. We might need to look in to ways of shading our west windowed bedrooms if the eaves arent sufficient - there is only 1m to the fence line so plants wont work. I dont mind having external awnings on the west side of the house, as they wont be seen. They will be empty for a few years, so that can be added later down the track. dymonite69 The best to understand this is to picture the sun's path throughout the seasons. Face north and raise your arms to the horizontal then pointing left and right at about 45 degrees either side of north. Your arms point to about where the sun rises and sets during winter. The sun rises and traces a low arc in the sky reaching its peak due north. Now pull back your arms so they are pointing immediately left and right of you at 90 degrees either side of north. Your arms now point to roughly where the summer sun sets and rises. The sun performs a much steeper arc and peaks at much higher angle facing north.* It has been described that windows are just leaky holes that allow heat to escape. The situation is a bit more complex than that. They allow the heat in the air to escape (not good in winter) but they also admit warming sunlight (very good good in winter, not good in summer). Passive solar design is all about positioning windows and shades to control this sunlight - to allow it to enter or block it. The east and west summer sun are low in the sky throughout the year. Good to let sun in the winter, but difficult to shade in summer. In passive solar design it is recommended that you try to get direct sunlight via the north side because a correctly sized eave will allow low winter sun to get in but exclude high summer sun. The north side also allows sun in most of the day whereas east and west sides only get half sun. If you have east/west windows then you will need to have a manually adjustable shade to block out summer sun. They can be left up during winter. But regardless of sunshine the west side will be colder in the morning and east side will be colder in the afternoon. Double glazing (like curtains) can stop heat loss particularly when there is no sun or when sun isn't entering your window. The question yo need to ask is are you going to use that room frequently at time of the day when there is a high likelihood of having no sun come in and you need the room as warm as possible e.g. living area. If so you it may be ideal to double glaze. If it is a bedroom or utility room then the heat loss doesn't matter as much and DG is not so critical. * The precise angles are approximate and related to how far south (or north) you live from the equator. Thanks dymonite! Your explanation has been a great help. Our East windows are living areas so will receive morning sun and become cooler at night so I think DB would be most appropriate. Heat loss in the morning of our West windows doesnt bother me too much, the heat gain in the afternoon would eventually (or at least, bother the future kidlets) so I said above that I would consider an external awning or something similiar Thanks so much everyone! It seems the more I read, the more I confuse myself But I think this particular issue is sorted now Custom European Cabinets - Melbourne Kitchen Specialist PM for business details as website currently being updated! Our Crazy Owner Builder Journey! Re: Double glazing windows: do they make a BIG difference? 74Aug 02, 2009 1:18 pm Bam We might need to look in to ways of shading our west windowed bedrooms if the eaves arent sufficient Actually you need a massive eave or verandah to completely shade the afternoon sun. During summer the sun 35 degrees above the horizon when it reaches due west. Let's take a window where the bottom edge is 1500m below the eave. A horizontal eave will need to be over 2.5m long to completely block out the sun. A vertical shade or awning is more effective. A good design will block out > 99% of radiant heat. If you want to preserve the view then a heat reflective coating is the best option. Some of them can reject 80% of heat. It is not possible to have a coating completely reflect thermal radiation yet admit visible light. An intermediate solution is using a white coloured sun shade that acts as a radiant barrier but allows some visibility. Re: Double glazing windows: do they make a BIG difference? 75Aug 02, 2009 4:33 pm Thanks! I will have to look in to it further... Custom European Cabinets - Melbourne Kitchen Specialist PM for business details as website currently being updated! Our Crazy Owner Builder Journey! Re: Double glazing windows: do they make a BIG difference? 76Aug 02, 2009 6:16 pm Hey Bam I'd be thinking go passive by reducing the window size and positioning it higher if there is a similar height house next door (1mtr to the fence?), spend 250$ on soil and planting a passion fruit for each of the windows. at widowbox height, +30$ea get a growing frame and eat the fruits of your labours while admiring how cool it is in the shade with the middle of summer and warm with no shade in the winter. I hope you like pashies(passionfruit) onc FWIW Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 77Aug 02, 2009 6:25 pm Our floor height off the ground is approx 500mm. Our window height from the ground range from flush (or thereabouts) to about 300mm. I think the large windows are fairly close to the floor... (this is East facing Im talking about) We will be higher than the house next to us I think, and there is 5.5meters to the fence from one point and 9.5meters from one of the large windows (however 4meters of this will be under the roofline) We dont really want to make the windows smaller, as they will look out to our alfresco area, and we dont really want to plant a tree which will obstruct the view completely.... But maybe one of those sunshade sail things would work? Custom European Cabinets - Melbourne Kitchen Specialist PM for business details as website currently being updated! Our Crazy Owner Builder Journey! Re: Double glazing windows: do they make a BIG difference? 78Aug 02, 2009 6:38 pm I was talking west Where you are coming from is where you are going to... Re: Double glazing windows: do they make a BIG difference? 79Aug 02, 2009 6:39 pm Aaahh We have two bedroom windows which arent that large and 1 meter to the fence Custom European Cabinets - Melbourne Kitchen Specialist PM for business details as website currently being updated! Our Crazy Owner Builder Journey! Re: Double glazing windows: do they make a BIG difference? 80Aug 02, 2009 6:46 pm ...and the shade sail sounds good too They flap a little, but I like the movement sounds weird Rather than rigid Where you are coming from is where you are going to... 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 19239 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 16231 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 7713 |