Roof Overhang For Solar Gain

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Roof overhang for solar gain.

The eaves overhang may also shelter openings to ventilate the roof space. At noon on january 21 the glass is completely exposed. With the window heights and overhangs i used in the model at noon on june 21 the entire glazing of the south elevation windows are completely in shadow but just barely. The overhang or solar control is used to keep the building s thermal mass in the shade.

In hot climates the general rule of thumb is to lengthen and extend the overhang. They reduce solar heat gain in the summer by up to 65 percent on south facing windows and 77 percent on west facing windows. How do i determine the correct amount of shading sun. You can use the free software sketchup to draw the house and it will draw sun shadows for any date time at your location.

Think of how cool shaded tile or marble can feel on bare feet on a hot summer day. The skylight will allow the winter sun to enter and provide additional heat but the overhang will block the direct sun in the summertime so that solar gain does not work against cooling appliances. Borst passive solar roof overhang design calculator. Homeowners can take advantage of this natural phenomena by placing skylights on a south facing section of the roof near an overhang.

I used sketchup to help determine how the solar path would fall on the house i am designing. This will help keep the house cooler in the summertime. These guidelines are useful in the construction of any gable or any cantilevered or flat roof. The secondary function is to control solar penetration as a form of passive solar building design.

24 dec 2012 02 45 pm. The eaves overhang can be designed to adjust the building s solar gain to suit the local climate the latitude and orientation of the building. Jonr senior member posts 5341. For example if the roof s overhang does not shade the window during the hottest hours of the day direct and reflected sun light will heat the interior.

In order to better illustrate this principle in action. The goal is to balance the amount of solar heat gain and amount of shading. How roof overhangs or other window overhangs work to control heat and solar gain overhangs are most effective for south facing elements in the northern hemisphere and at midday. On the other hand some homeowners choose to embrace the look of solar panels by positioning them front and center in place of a patio awning or roof overhang.