Sun protection is most needed for the midday and afternoon hours during the summer season when air temperatures are the hottest. Exposure to the sun during these
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Figure 3-16
Desirable locations for outdoor spaces during the summer season.
times increases heat generated from exposed surfaces and reduces the ability of people and animals to shed heat from their bodies. As a general guideline, people feel most comfortable in the following conditions: (1) shade, (2) no air movement, (3) air temperatures between 70 and 80°F, and (4) relative humidity between 30 and 65 percent.[3] This so-called comfort zone is exceeded when air temperatures rise above this level and/or there is direct exposure to the sun. The broad intent should be to shield the sun from the house and outdoor spaces used during the summer season, especially during the afternoon hours.
One way to accomplish this is to plan where outdoor uses are located with respect to sun. The best position for outdoor spaces used during a summer day is on the east or northeast side of the house or tree mass (Figure 3—16). An area immediately to the north of the house or a tree mass is also good, though the size of this shaded area is small because of the relatively high vertical sun angle shining from the south at midday in the summer. These locations are noticeably cooler and more comfortable than other potential locations on the residential site for the summer season.
Introducing elements that cast shade on a residential site can also create sun protection. The most common means is to strategically locate large shade trees to
shield the midday and afternoon sun from the residence and outdoor spaces used during this time of day. Shade trees provide sun protection by several means. First, they block the sun’s rays from striking roofs of one – and two-story buildings, exterior building walls, and ground surfaces throughout the landscape. When directly exposed to the sun, these surfaces convert sun rays into heat, which is radiated away from the surfaces (Figure 3—17). The heat generated by exposed building roofs, walls, and ground surfaces radiates out into the nearby air, thereby elevating the temperature. Heat is likewise transferred inward to interior spaces from exposed building surfaces. By comparison, shaded surfaces do not heat up beyond the ambient air temperature and thus do not add to the temperature of the adjoining air mass or building interior.
Figure 3-17
Shade trees can shield roofs, exterior house walls, and the ground from the suns rays.
