Browse Forums Windows & Doors 1 Mar 23, 2011 7:19 am We're looking at uPVC DG for our build and definitely want low-e for the westerly facing windows. We have an option to do it on the North and East facing windows - should we do this/will this make the place cold in winter/is this an overkill ? We're in Sydney and the rear of our home is due north and we have 4 windows/1 slider facing north and 4 windows facing east with 450 mm eaves, currently no shade structures over windows but we plan to put a pergola which will shade 1 (possibly 2) north facing windows and 2 east facing windows. Re: Low-e on W/N/E facing windows excessive ? 3Mar 24, 2011 9:13 am North & West is generally the way to go... IMO better to control the heat gain than to suffer... 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: Low-e on W/N/E facing windows excessive ? 5Mar 24, 2011 1:43 pm jklow888 Thanks Ed - just wondering if doing east is worth it, eg. morning winter sun ? I think not... morning sun would be what you want to take the chill off your home. 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: Low-e on W/N/E facing windows excessive ? 6Mar 24, 2011 1:59 pm I agree - love morning sun in the Winter - it's gorgeous! For info on our build: viewtopic.php?f=31&t=43093 Built the McLaren by Dechellis - slab down 22 Feb - handover 30 Aug 2011 - and gardens finished 9 Dec 2012!! Re: Low-e on W/N/E facing windows excessive ? 7Mar 26, 2011 10:36 am jklow888 Anyone ??? Don't want to have a new build turn into an ice box in winter Hi Jklow888, A few architects that specialize in sustainable design, had recommended their clients against using low-e on the northern side and only used low-e on the western side. Their reasoning was that to keep the house warm in winter, you will benefit by windows with glass that has a higher heat gain coefficient, to take advantage of the low winter sun, which is in the north. However, this also depends on the relative glazing area, and position of windows in the house. For instance, if the glazing area is large and is located in the living room, than low-e glass can be a good option. Most of the benefits of low-e glass in the north facing living areas will be felt in summer. If however, you have a bedroom with a single north facing window, consider using clear glass to improve comfort in winter. Also consider your plans for external shading - external shading is much more effective than any glass at reducing glare and lowering the heat gain in summer. In addition, a good and less expensive alternative to low-e glass is grey or bronze tinted glass. It actually has a lower heat gain co-efficient, and depending on the degree of tint, will be 40% more effective at cutting down glare. Grey tinted glass is particularly attractive, especially in a modern home. Sydney Double (and now Triple) Glazed Windows and Doors mob 0412 717 066 Sydney, Canberra, Newcastle, Wollongong www.doubleglazedwindows.net.au Re: Low-e on W/N/E facing windows excessive ? 8Mar 26, 2011 10:17 pm Low E glass is not good at lowering direct solar heat gain - that is lessening the sun light shining direct through the window into the house - which is desireable in summer. If you want to protect say a western window from hot late afternoon summer sun better to consider removable external shading (canvas awning blinds or similar) or failing that a toned glass or reflective film can limit SHG. However Low e glass can be effective at increasing the thermal insulation of the glass so therefore can be used in combination with an external shading strategy. Re: Low-e on W/N/E facing windows excessive ? 9Mar 26, 2011 10:34 pm Eccles Low E glass is not good at lowering direct solar heat gain - that is lessening the sun light shining direct through the window into the house - which is desireable in summer. If you want to protect say a western window from hot late afternoon summer sun better to consider removable external shading (canvas awning blinds or similar) or failing that a toned glass or reflective film can limit SHG. However Low e glass can be effective at increasing the thermal insulation of the glass so therefore can be used in combination with an external shading strategy. Sorry, that is incorrect. Low-E reduces solar heat gain by around 80%, while at the same time it hardly effects the transmittance. 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: Low-e on W/N/E facing windows excessive ? 10Mar 27, 2011 8:52 am All I will say is that the buyer should check the Solar Heat Gain Co-efficient (SHGC) provided by the manufacturer or from wers.net. Is the chosen low-e window sufficient to block western sun on a summer afternoon? Re: Low-e on W/N/E facing windows excessive ? 11Mar 27, 2011 2:07 pm You can check this out.. http://www.awa.org.au/documents/HowComf ... sWorks.pdf Clear glass transmits 84% of radiant heat absorbed and Low-E (ComfortPlus in this case) only 15%. 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: Low-e on W/N/E facing windows excessive ? 12Mar 27, 2011 7:10 pm Ed - thanks for that link. It proves to me how complex low-e glass is. In the first dot point in the articles is says “During a summer day, the coating absorbs nearly half of the sun’s energy shining onto it.” - which begs the question what happens to the other half – is it reflect or does it pass straight through – I would think that it passes straight through. The dot point then goes on to tell what happens to the 50% of the solar that has been absorbed. So it only radiates into the building 15% of the absorbed radiation of 50% - or 7.5%. So if my assumption of the initial 50% transmission is correct there is a total transmission of solar of 57.5%? Not 15%? If the glass is toned then the initial absorption will be higher so total solar transmission will be less. There are different formulations of low-e glass and ways of applying the coating which effect its properties – the coating on surface 2 will behave differently to a coating on surface 3 - etc. the glass can have various tonings or laminates. So you can set up a double glazing unit with low–e glass to be effective at stopping solar coming in or stopping heat escaping. However some of its effectiveness may be due to its toning or laminate layer as well as the low-e coating and it location. For simple clear glass with a low e coating I stand by my statement that in certain configurations a simple low-e glass will have a relatively small effect on the solar heat gain through the window. The amount of solar heat gain that is allowed through the window is measured by what is called the solar heat gain co-efficient (SHGC). One example of a glass is the Viridian product: http://www.viridianglass.com/products/d ... Energy.pdf At top of page 5 - Clear glass unit 3/12/3 - SHGC = 76% At top of page 6 - Low-e glass unit 3/12/4 - SHGC = 71% So that is about a 6.5% decrease due to the low e coating - in my opinion this glass would not be sufficient if you want the glass to cut down on heat gain to the house through a western window in summer. The Comfortplus glass seems to come in a range of glass colours from clear to grey to blue. According to the pdf the clear single pane glass has a SHGC of 68% - a long way from a 20% SHGC. However “SuperGreen 49” has a SHGC of 37%. Perhaps Ed can clarify whether the windows he supplies are clear Comfortplus window glass or toned in order to get a low SHGC. Here is another supplier of insulated glass units. http://www.australianglassgroup.com.au/ ... 202010.pdf Again a quick inspection of this pdf also indicated that in order to get the low SHGC the glass needs to be toned as well a low-e. So as I said check the Solar Heat Gain Coefficient for the window unit with the manufacturer and on wers.net – that will tell you whether the unit is suitable for limiting solar heat gain. The other aspect to remember is that in most situations the Low-e coating will be specified for its ability to increase the thermal resistance ( R ) of the window, not to stop solar heat gain. The best way to stop solar heat gain is to stop the sun hitting the glass in the first place - with external window shading - external blinds or trees etc. Re: Low-e on W/N/E facing windows excessive ? 13Mar 27, 2011 8:35 pm Eccles Ed - thanks for that link. The other aspect to remember is that in most situations the Low-e coating will be specified for its ability to increase the thermal resistance ( R ) of the window, not to stop solar heat gain. The best way to stop solar heat gain is to stop the sun hitting the glass in the first place - with external window shading - external blinds or trees etc. You're welcome... but I disagree with your analysis and conclusion... 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: Low-e on W/N/E facing windows excessive ? 14Mar 28, 2011 10:11 am Thank you for all the responses. I've confirmed our DG supplier is Viridian and had a look at one of the Viridian links earlier in the thread and it looks like we're going to go with (all windows are 4/12/4): 2 of our westerly windows (2nd bedroom and ensuite): 1. VFloat Supergray = SHGC of 0.26 OR 2. VFloat Supergray + low E = SHGC of 0.20 The 3rd westerly window is for the ground powder/shower with adjoining laundry (both separated by a door leading from laundry to power/shower). We would like some airflow and also some heat to dry out the laundry so we're opting for SuperGreen (0.47 or 0.41 with low E). The 2 bedrooms facing north will be left as clear float to get some solar gain in winter. For summer we'll see how the 450 mm eaves cover the windows (8 ft ceilings) and consider additional shading if required. We are contemplating Green or SuperGreen for the north facing family room window (1.8 m x 1.8 m) on the ground floor with the remaining north facing windows and patio door to be clear float as we will eventually cover these via a patio. The easterly windows will remain clear float as these will also be under the patio cover eventually. Any comments/thoughts on our "final" selection ? Re: Low-e on W/N/E facing windows excessive ? 15Mar 28, 2011 10:30 am Hi I know I can read the U values and SHGC in WERS for Low-E and tinted glass, and it's obvious that being tinted, glass will remove some visible light and a proportion of infra red (heat). And it's also obvious that the performance can be expressed in a U value and SHGC.... but, having used tinted glass and having seen the properties of Low-E properly demonstrated, it is also obvious to me that the factual data leaves out the fact that Low-E only works on radiant heat (from my actual experience) and that the U value is therefore meaningless with very little IR radiation. My experience says that tinted glass also has an annoying habit of heating up under radiant heat, and reradiating the heat. That's my take on it.. Not a lot of help, sorry. Personally I stick with clear glass (and Low-E where necessary), and use tints for aesthetic reasons. 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: Low-e on W/N/E facing windows excessive ? 17Mar 28, 2011 10:49 am jklow888 Ummm - I feel more confused ! Yes, I think so, Sorry... 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: Low-e on W/N/E facing windows excessive ? 18Mar 28, 2011 9:17 pm I am sorry to confuse as well. If I understand your requirement you want to stop sunlight from entering through the western windows - on summer days. Ed has suggested clear low-e glass will be sufficient for this. I have some doubts about this based on the documented figures - however Ed has the experience. I do agree with Ed that you should only go with toned glass if you are happy with the look - and the outlook. Also remember that it will also be toned in the middle of winter when a few afternoon rays might be nice. (Whereas an external blind can be pulled up and down as the season and day requires.) Installing clear Low-e glass will not have any down sides on the west and east side of the house (well hardly any). It will increase the thermal resistance of the window (by an amount) saving on heating and cooling costs, it will lower the solar gain through the window (the amount is what we have been discussing) so it will lower the amount of morning sun heats though the window in summer - and also in winter. On the south the lowering of the SHG won't have much as much impact (as there is little direct sunlight) however the thermal resistance is still increased - which is worthwhile. For the North side it depends on whether you have designed your house to operate on passive design principles. If you don't know much about passive solar design can I suggest you read this which will give a very good overview of the subject -http://yourhome.gov.au/technical/fs44.html - and this - http://yourhome.gov.au/technical/fs45.html - and the rest of the pages on passive design. Very briefly passive solar design suggests smaller (or no) windows to west, east and south (and those windows that are on the east and west have removable shading (blinds) etc to block summer sun). The North windows are larger however they are shaded (with eaves or other shade structures) in such a way that the summer sun is blocked and the winter sun is allowed to enter. (Also include good household insulation (including internal window blinds), thermal mass and weather sealing, etc.) If you are relying passive solar gains in winter solar gains through the northern window in winter for part of the heating then lowering the solar gains from low-e glass might not be desireable (though if you have larger windows and would get too much solar with clear glass even in winter then it may still be worthwhile). Counteracting this loss of solar gain is the increased insulation of the Low-e glass (which not only acts in winter but in summer). If the house is not passively designed then perhaps low-e – but shade your north windows in summer anyway. (One downside I should mention is additional cost – Ed would know more about that.) Summary: make your Western windows small as desirable. Use clear low-e glass in them (or toned if you decide you like the look of toned). If you are still getting too much heat into the house through these windows in summer be prepared to install external shading devices – external canvas blinds (or even reflective film). Or do it from the start. Same with East - unless you want the full strength morning sun in winter. South should benefit from low –e (– not toned). North is on a case by case basis. Good Luck Re: Low-e on W/N/E facing windows excessive ? 19Mar 28, 2011 10:35 pm I'm going with low-e neutral laminate for a large north facing door in the living room and large north facing window in the kitchen. Also going with the same glass for west facing windows in the dining room and a guest room. Re: Low-e on W/N/E facing windows excessive ? 20Mar 29, 2011 1:18 pm 1sthome I'm going with low-e neutral laminate for a large north facing door in the living room and large north facing window in the kitchen. Also going with the same glass for west facing windows in the dining room and a guest room. Low-E laminated in single glazing has risks of spontaneous cracking, and other issues... check my other posts on this subject. Thanks 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 How good is Simeon?! Always taking time to help others out! Wish we were building in NSW and could work together. Thanks for all that you do! 7 6515 The warning is on the sticker on the door too. Second the aluminium powdercoat 6 18098 It might be a bit darker in the mornings but the light is still light, so you should be getting it. Similar to what you see from your western windows 3 19909 |