Browse Forums Building A New House 1 Jan 14, 2009 1:57 pm Hi,
I am planning to use my eaves as a shading device for controlling the summer/winter sun penetration in my house. I am living in Perth, WA and this is 33degress South... I am planing to have large sliding doors and windows on the northerly facing aspect of the house. How do I work out what the width of the eave is that I need to incorporate into the design. I saw one website (SEDO) that it needs to be the height of the window multiplied by 0.7 to shade the windows in summer, but that make it 1.47m eave if the height of my window is around 2.1m from ground. Does this make sense? Has anyone else used their eaves in this way? Thank Alot Regards pdaemon Re: Eaves as shading device for controlling Sun - Please Help. 2Jan 14, 2009 2:01 pm Alfrescos are perfect for this and they just do that.
An eve can be a portico, alfresco or similar. I have seen houses that have roof lines extend past house. and have a nice bbq area all the way around. Re: Eaves as shading device for controlling Sun - Please Help. 3Jan 14, 2009 2:07 pm Doesn't need to be eaves, maybe louvres - and in double storey eaves can't help the ground floor.
This may help... http://www.yourhome.gov.au/technical/fs44.html Re: Eaves as shading device for controlling Sun - Please Help. 4Jan 14, 2009 2:17 pm Thanks EcoClassic,
I was looking at extending the eaves during the build as it might be a cheaper option, but the louvers would do the same thing and are adjustable. If a standard eave in WA is 480mm, then a 1m solar louvre would be adequate on North facing aspects. Can someone verify this?? Re: Eaves as shading device for controlling Sun - Please Help. 5Jan 14, 2009 2:23 pm I guess you have been here > http://www1.sedo.energy.wa.gov.au/pages/windows.asp
And it talks about this... Quote: North facing windows It is recommended that around a third to a half of the north face of your home be glass, as it is very effective at trapping winter warmth and can be easily shaded from summer sun with correctly designed eaves. To calculate the overhang needed, multiply the distance from the eaves-line down to the bottom of the window by 0.7. This will ensure the glass is adequately shaded from September until March. For cooler regions, multiplying by 0.4 will provide suitable shade from October until February. I think the 0.4 factor would be adequate - so your 1m width would be the go. Ed Re: Eaves as shading device for controlling Sun - Please Help. 6Jan 14, 2009 5:02 pm Hi Ed,
Yes, I've been at this website... So really, I could have an eave that is: 2.1x0.4 = 0.85m... I will have to ask my builder if you can build an eave that is that width without needing support.. Regards pdaemon Re: Eaves as shading device for controlling Sun - Please Help. 7Jan 14, 2009 6:17 pm The distance you use when multiplying by 0.4 (or whatever) is from the bottom of the eaves to the bottom of the window/door. If you want to use a 0.84 m overhang, it will need to be placed directly above the north facing sliding doors. Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Eaves as shading device for controlling Sun - Please Help. 9Jan 14, 2009 7:48 pm Casa2 The distance you use when multiplying by 0.4 (or whatever) is from the bottom of the eaves to the bottom of the window/door. If you want to use a 0.84 m overhang, it will need to be placed directly above the north facing sliding doors. Casa is correct. The formula requires you to multiply the factor by the distance from eave to bottom of window and not actual height of window. The Your Home link makes this clearer. The whole of point of this exercise is to admit as much sun during the cooler months and completely block out the sun during the hotter months. The calculations are an approximation. The perfect system would have fully adjustable shading depending on the daily weather. The formula that you are using deals with when the sun should be blocked completely in summer. But if the top of the window ends too close to the eaves than it may be in permanent shade even in winter (and a source of heat loss). See the Your Home weblink above. There are two limiting factors about how you set windows sizes and heights (and hence eave length). Generally the top of windows tend to be set level with external door height to create a pleasing line. The second issue is that the bottom of the window may be set differently on each elevation. Generally you would use the window which extends closest to the ground for calculation purposes. The best solution over all of this are uptilt eaves which prevent any winter shading of the top portion of the window. But this is not everybody's cup of tea. If you don't use this with a skillion roof then you will need a box gutter. Whilst the 0.4 recommendation is a useful guide, the actual degree of shading required will be dependent on your local climate. You may need longer eaves if it gets hotter earlier on average in the year or shorter ones if the winter is prolonged. Remember as well that it is easier to err on the shorter end and add another shading structure if it gets too hot than find that you aren't getting enough winter sun from excessively long eaves. My feeling is that 1m would be too long for your area. If you want to optimally tweak this then I suggest an Energy Rating assessment. This will show what effect of different eave lengths based on your house plan, window schedule and climate will have on your net heating and cooling requirements. Re: Eaves as shading device for controlling Sun - Please Help. 10Jan 15, 2009 8:50 am It might be worth getting a costing anaylisis from the builder on these options, and any other that are suggested;
Option 1) 1 meter wide eaves overhang. Option 2) Double glazing or Low E glazing. Option 3) Additional pagola or alfresco structure. Re: Eaves as shading device for controlling Sun - Please Help. 11Jan 15, 2009 9:21 am Pat the draftie It might be worth getting a costing anaylisis from the builder on these options, and any other that are suggested; Option 1) 1 meter wide eaves overhang. Option 2) Double glazing or Low E glazing. Option 3) Additional pagola or alfresco structure. Except each of these elements achieve different kinds of things. Eaves are designed to reduce cooling requirements sufficiently in summer but not so deep as to prevent winter sun entering the building. Double glazing and low e glazing are to reduce heating requirements. Special low SGHC heat reflective windows can be used to reduce heat gain but aren't usually needed on the north face that has appropriate shading. You more commonly see this type of window on the Adelaide beachfront where the hot afternoon low sun comes from the direction of the sea. Pergola (and definitely an alfresco) might leave the north face in permanent shade even in winter. Re: Eaves as shading device for controlling Sun - Please Help. 12Jan 15, 2009 11:27 am Pat the draftie It might be worth getting a costing anaylisis from the builder on these options, and any other that are suggested; Option 1) 1 meter wide eaves overhang. Option 2) Double glazing or Low E glazing. Option 3) Additional pagola or alfresco structure. Option 2) double glazing or Low E glazing will do nothing towards preventing heating caused by sunlight entering the inside of the house. You have to stop the sunlight from getting inside the house, so eaves, external blinds etc are OK. Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Eaves as shading device for controlling Sun - Please Help. 13Jan 15, 2009 12:55 pm Thank you very much for the info everyone!
I have incorporated an alfresco, but not north facing as it would defeat the purpose of my solar-passive design... Do you know who could do an energy assesement rating and the cost involved in this?? Most likely I will get 0.75 -> 1m eaves on the Northerly facing sides and if needed add a solar pergola type of structure which can be adjusted in Summer/Winter... I have attached a copy of the current plan below: Note: Disregards the eaves...these are just working plans.. Re: Eaves as shading device for controlling Sun - Please Help. 14Jan 15, 2009 1:46 pm pdaemon Do you know who could do an energy assesement rating and the cost involved in this?? http://www.absa.net.au/findass/2nd%20Ge ... r_v.04.pdf AccuRate is a 2nd generation program. They charge per the hour. Time required depends on complexity of modelling required. I think an average assessment = $200 Re: Eaves as shading device for controlling Sun - Please Help. 16Jan 15, 2009 1:47 pm pdaemon Do you know who could do an energy assesement rating and the cost involved in this?? http://www.absa.net.au/findass/2nd%20Ge ... r_v.04.pdf AccuRate is a 2nd generation program. They charge per the hour. Time required depends on complexity of modelling required. I think an average assessment = $200 but I asked them to try other scenarios and that cost $1000[/quote][/quote] Re: Eaves as shading device for controlling Sun - Please Help. 17Jan 15, 2009 2:11 pm pdaemon I have attached a copy of the current plan below: Looks like a good passive solar layout. Is this your own design? I can see that you might need deeper eaves because the living room windows are off-angle to solar North. The bedrooms are well located on the cooler side of the house although your master might get cop the afternoon summer sun. You may wish to get additional shading control on that window, use low SGHC or change location/size. I was wondering if your kitchen will get enough natural light in. It is set a fair way into the house. The only comment about functional layout is the distance from bathroom to living area for the guests. Re: Eaves as shading device for controlling Sun - Please Help. 18Jan 15, 2009 3:44 pm Thanks for the comments Dymonite69...
Yes, this is my own custom design....I was planning to trees on the Master bedroom side for shade if possible...the bedroom will only have a highlight window... mmmm...hadn't considered this about the kitchen, but some sunlight should still get through the Alfresco area and from the North facing windows I hope.....This is the best design I could come up with...What would your suggestion be?? Have the Kitchen to the top of the Living area near the alfresco? There are no programs out there you can use yourself are there or you don't have to pay for?? Re: Eaves as shading device for controlling Sun - Please Help. 19Jan 15, 2009 4:48 pm pdaemon Thanks for the comments Dymonite69... Yes, this is my own custom design....I was planning to trees on the Master bedroom side for shade if possible...the bedroom will only have a highlight window... mmmm...hadn't considered this about the kitchen, but some sunlight should still get through the Alfresco area and from the North facing windows I hope.....This is the best design I could come up with...What would your suggestion be?? Have the Kitchen to the top of the Living area near the alfresco? There are no programs out there you can use yourself are there or you don't have to pay for?? You can try using a sunpath calculator: http://www.sunposition.info/sunposition ... ions.php#1 It tells you from what direction (azimuth) and how high (altitude) the sun is on any given time and date of the year. Looking at your plans it looks like the middle of the kitchen is set back about 9 metres from the NE living room window. Assuming a window height of 3200m then the sun has to be less than 15% in altitude for it to penetrate into the kitchen. Furthermore the sun won't be at the correct angle until it is 30% + of solar north. If you verify with the calculator you are can see that your kitchen is going to miss all the low angled morning sun and by mid-morning it will be to high to reach that far. The problem is that the kitchen is set dead centre in the house where it is difficult to get light in. One alternative is to use a skylight or solartubes. Re: Eaves as shading device for controlling Sun - Please Help. 20Jan 15, 2009 9:20 pm Do a couple of solar tube light or similar for the kitchen and re the family room.
Small change of design - maybe loose some minor floor space but gain winter warmth and a more useable area, put in a 45 degree window at full height across the front RH corber and make it face due north. Gets full sun all winter when you need it and with the right angled eaves - does everything you need re warmth. And keeps the council happy too. Steve Update from me! Couldn't find the trimmer - not sure if there isn't one simply because the eave is so narrow. Went ahead with the spring toggles and it all worked out… 7 5869 The two 15mm holes are obviously not compliant. The Dept of Fair Trading would love to see this one! Do the gutters pool water after it stops raining? Although it's… 4 7859 Thankyou so much 😀 I've decided on White on white for doors and trims, White on white 50% on ceiling and Mt buller for walls. Fingers crossed it will look OK 😀 2 7158 |