Optimum Roof Overhang

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Optimum roof overhang.

You can use the free software sketchup to draw the house and it will draw sun shadows for any date time at your location. An important component of passive solar design is calculating building openings doors and windows and roof overhangs. They are essential for framing and shading windows reducing splashback and getting rain to fall far enough away from the foundation. The size of the window width and height and the window s relationship to the roof the space above the window influences the direct.

Optimum overhang dimensions for energy saving 295 sun fig. Doing so keeps basements and crawlspaces dry and it also helps to. 180tan 10 in order to estimate the radiation received by windows with overhangs the beam diffuse and reflected com ponents of irradiance must be estimated as functions of time and day of the year. Roof and overhang systems should be designed to resist wind uplift especially in hurricane prone regions.

Borst passive solar roof overhang design calculator. Those larger than 2 feet wide have to withstand very high uplift so they should be engineered. Geometry of overhang separated from top of window. Overhangs are most effective for south facing elements in the northern hemisphere and at midday.

Roof construction and materials considerations roof decking. For high wind resistance use 7 16 inch or 19 32 inch plywood or osb roof decking attached with nails not staples. Because the sun travels a higher path in the sky in the summer than in winter the overhang blocks. There isn t general rules to size an overhang.

Jonr senior member posts 5341. 24 dec 2012 02 45 pm. Figure 2 illustrates how this is possible. Roof overhangs at the eaves and rakes protect the walls below from rain and sun.

The optimum depth varies with the latitude and the type of climate. With composite siding such as boral s truexterior siding over a ventilated rain screen and with properly executed flashing at the windows and doors the walls on the fhb house will be able to handle rain just fine. Roof overhangs should be no more than 2 feet wide. If the building element bears more than about 30 off true south the effectiveness of an overhang as with any solar feature begins to decrease significantly.

But are they really necessary. Oversized overhangs can increase the risk of roof or truss uplift. For instance several features of a window will influence gain of solar heat and shade.