18. The principles of passive solar are nothing new. More than 2500 years ago in ancient Greece, entire cities were built to take advantage of the sun and the climate. Buildings were designed to take advantage of daylighting, ventilation and other good design practices.
19. In the U.S., drawings and photographs of the cliff dwellings of the American Indians and the sod homes of the early pioneers show the popularity – and the necessity – of building homes to respond to the environment.
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21. Passive solar designs include open areas with walls that absorb heat during the day and release it at night – into the home in winter and out of the home in summer.
22. Large windows take advantage of the winter sun, but blinds and drapes keep the home cooler in summer. Windows let daylight in, and operable windows let the occupants control the flow of natural ventilation.
26. Altitude Angle The altitude angle (sometimes referred to as the "solar elevation angle") describes how high the sun appears in the sky. The angle is measured between an imaginary line between the observer and the sun and the horizontal plane the observer is standing on. The altitude angle is negative when the sun drops below the horizon. (In this graphic, replace "N" with "S" for observers in the Southern Hemisphere. The altitude angle is calculated as follows: sin (Al) = [cos (L) * cos (D) * cos (H)] + [sin (L) * sin (D)] where: Al = Solar altitude angle L = Latitude (negative for Southern Hemisphere) D = Declination (negative for Southern Hemisphere) H = Hour angle
27. Azimuth Angle The azimuth angle is calculated as follows: cos (Az) = (sin (Al) * sin (L) - sin (D)) / (cos (Al) * cos (L)) where: Az = Solar azimuth angle Al = Solar altitude angle L = Latitude (negative for Southern Hemisphere) D = Declination (negative for Southern Hemisphere) The solar azimuth angle is the angular distance between due South (see note below) and the projection of the line of sight to the sun on the ground. A positive solar azimuth angle indicates a position East of South, and a negative azimuth angle indicates West of South.