Browse Forums Eco Living 1 Jul 09, 2009 6:33 pm We are currently designing a new house and I'm trying to make sure we maximise airflow through the house. (We are in Mackay and so we are planning for a cooling design rather than being concerned about passive heating for winter.) The house design has a skillion roof with the "flat panel" offsetting the two roofs on the northern side. My thoughts are to have a raked ceiling and louvre clerestory windows to allow warm air to flow up and out of the house drawing cooler air in. Q1. Because Mackay is north of the Tropic of Cancer, am I on the tright track in thinking the sun in summer should not shine directly through those clerestory windows? Q2. For a large part of the year the sun will still shine through those windows. Should we be thinking about changing the windows out for some sort of venting arrangement that would still allow the warm air to flow out but not have to worry about the sun's rays beating in and counter-acting any cooling effects? TIA Kylie Re: Clerestory windows and sun angle 2Jul 09, 2009 10:18 pm kb46 (We are in Mackay and so we are planning for a cooling design rather than being concerned about passive heating for winter.) Because Mackay is north of the Tropic of Cancer, am I on the tright track in thinking the sun in summer should not shine directly through those clerestory windows? Why don't you this Sun position calculator to see what angle the sun is throughout the year - on any given day or time: http://sunposition.info/sunposition/spc/locations.php#1 Choose Bundaberg as the nearest latitude to Mackay. It shows that the sun doesn't get any lower than 40 degrees in the sky at midday in the middle of winter (and gets to about 25 degrees by 9am) You design the depth of your eve depending on what time of the year you wish to completely cut out the sun and by about what time of the day you want this to occur. Climate data for Mackay: http://www.bom.gov.au/climate/averages/ ... 3046.shtml If you don't want any sun, you could reverse the skillion so that the clerestory windows face south. Re: Clerestory windows and sun angle 3Jul 09, 2009 11:30 pm Thanks, I had a look at the link you gave me for sun position and another site as well. After some mild brain hurt I managed to decipher the results. It seems the sun is only south of us for Dec-Jan so we would rely on the eaves to block the sun in the other months. Once we have some plans drawn up I can do the measurements to check the eaves for the other months. It probably wouldn't be all that difficult to retrofit some exterior awnings to shade the windows if we find it too hot after the house has been built. I'll also do a bit more research to see if I can find any vent alternatives that will allow the airflow but block the sun. dymonite69 If you don't want any sun, you could reverse the skillion so that the clerestory windows face south. Reversing the skillion isn't an option because it would place the bedrooms on the wrong side of the block. Because of the house construction method it's not practical to change the skillion position without mirroring the floor plan as well. Kylie Re: Clerestory windows and sun angle 4Jul 10, 2009 12:52 am During winter the sun path is the shortest. It rises in the NE and sets in the NW and makes a low arc across the sky. As you move through spring, the days lengthen. The sun rises closer to due east and sets due west and traces a higher arc in the sky. By summer time, the sun rise and sets in the southern half of the sky and will reach its highest point in the year. Roughly if your eave length is equal to its height above the bottom of the window then you will have partial to full shade of your window outside the winter months. You can make it up to double its length if you wish to also block most of the winter sun as well. Re: Clerestory windows and sun angle 5Jul 10, 2009 11:27 am dymonite69 Roughly if your eave length is equal to its height above the bottom of the window then you will have partial to full shade of your window outside the winter months. You can make it up to double its length if you wish to also block most of the winter sun as well. Handy rule of thumb! Thanks, that will be very useful - very easy to draw on the plans.\ Kylie Re: Clerestory windows and sun angle 6Jul 10, 2009 5:54 pm kb46 dymonite69 Roughly if your eave length is equal to its height above the bottom of the window then you will have partial to full shade of your window outside the winter months. You can make it up to double its length if you wish to also block most of the winter sun as well. Handy rule of thumb! Thanks, that will be very useful - very easy to draw on the plans.\ Kylie Can I qualify this rule as applicable only for the subtropical latitudes. For temperate latitudes, north facing eaves will need to be much shorter because you will benefit from being exposed to the sun for a greater part of the year. Here is some info on the Your Home technical manual (there is a lengthy discussion on temperate areas but also has a section warm humid areas) http://www.yourhome.gov.au/technical/fs442.html And some info on natural cooling: http://www.yourhome.gov.au/technical/fs46.html Importantly, the best to minimise overheating is to have as few windows facing east or west (or at least combine them with vertical shades) Re: Clerestory windows and sun angle 7Jul 10, 2009 7:51 pm I'd be inclined to extend the eaves out over the windows and that will give you the shade you require and the airflow that you want to encourage. Another option is louvres - metal or glass, tinted if you like. Without seeing your design it's hard to advise other options. Do you need the light that these windows will introduce? Yes? - well that then limits what you can use up there. Windows high up can be very effective at assisting the airflow, but also make sure where you introduce it downstairs to make sure that it can move through all the right areas. ie the downstairs inlets need to be in the right places, as well as ensuring they catch your prevailing breezes at each time of the year. Your prevalinig breeees seem to be SE in Jan to March, and anywhere from North to SE in Oct, Nov an Dec, so you need to be encouraging these breezes to come in and out of the house from the prevailing directions - when it matters most - ie those UGGG months of Oct, Nov and Dec till the rains set in. So think about windows on all these sides of the hosue to let the air, round and out up through the clerestory windows. This doc should be of interest to you in the design phase. http://www.environmentdesignguide.net.au/media/TEC02.pdf Might make you add a few more doors or windows somewhere. and the data at 3pm from here is your best guide of where the breeze you want typically comes from each month. http://www.bom.gov.au/climate/averages/wind/selection_map.shtml Flashings over doorways and windows our carpenter has installed flashings that is buckled and short of the window frames and door frames is this right Is there a… 0 10923 There is evidence of water on the head reveals. That could have happened during the build, or may be happening currently. There are water stains above a couple of windows… 2 3830 Personally, considering your layout (study/work desks in bedrooms), I don't think you have any other option but to leave NW windows and make them as big as possible e.g.… 7 10470 |