24 dec 2012 02 45 pm.
Roof overhang for solar gain.
Borst passive solar roof overhang design calculator.
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.
Jonr senior member posts 5341.
At noon on january 21 the glass is completely exposed.
I used sketchup to help determine how the solar path would fall on the house i am designing.
How do i determine the correct amount of shading sun.
They reduce solar heat gain in the summer by up to 65 percent on south facing windows and 77 percent on west facing windows.
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.
The goal is to balance the amount of solar heat gain and amount of shading.
The overhang or solar control is used to keep the building s thermal mass in the shade.
The size of the window width and height and the window s relationship to the roof the space above the window influences the direct and indirect gain of solar heat.
In hot climates the general rule of thumb is to lengthen and extend the overhang.
Homeowners can take advantage of this natural phenomena by placing skylights on a south facing section of the roof near an overhang.
Think of how cool shaded tile or marble can feel on bare feet on a hot summer day.
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.
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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.
Solar awnings are a two in one win for energy efficiency.
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.
In order to better illustrate this principle in action.
The eaves overhang may also shelter openings to ventilate the roof space.
You can use the free software sketchup to draw the house and it will draw sun shadows for any date time at your location.
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.
These guidelines are useful in the construction of any gable or any cantilevered or flat roof.
