NATURAL EVENTS AND CYCLES

Principle: The residential site should be in concert with natural events and

cycles.

All residential environments are exposed to and dependent on a series of natural events, including sun exposure, wind exposure, and precipitation. The potential for fire and earthquakes impacts the landscapes in certain regions as well. Most of these phenomena occur in cyclical patterns that are seasonal and somewhat predictable. These events are ever-present and must be incorporated into residential design to make it sustainable, as discussed in the following sections.

Study Sun and Shadow Patterns

Before being able to effectively design with sun, it is necessary to understand the movement of the sun throughout the day and at different seasons of the year. The sun’s relative position in the sky is constantly changing in its plan orientation as well as its angle above the horizon (Figure 3—11). In the summer season (June), the sun rises in the northeast and moves in a clockwise direction around a site until it sets in the northwest. In the temperate zone, the sun’s total arc of transit is about 240 de­grees between sunrise and sunset. At the same time, the angle of the sun above the horizon is constantly increasing to a zenith of about 72 degrees from the south at noon (Figure 3-12).

In the winter season (December), the sun rises in the southeast and sets in the southwest while moving through a total arc of transit of about 120 degrees in the tem­perate zone. At noon, the sun rises to an angle of 27 degrees above the horizon. The sun is essentially a southerly sun at a very low angle above the horizon during the win­ter season. Thus, the sun is less intense, restricted in its time of shining, and limited in its direction of exposure in comparison to other seasons of the year. In the equinox months of March and September, the sun’s path and angle above the horizon are halfway between the extremes of June and December.

This information can be used to construct shadow patterns around a house on a residential site and to determine where the sunniest and shadiest zones are as well as the associated microclimates. Figure 3-13 through 3-15 illustrate the shadow patterns of a two-story house located on a level site in the temperate zone at four seasons of the year. Shadow patterns can be plotted by using information from sun charts available in many public libraries, some CAD programs, the National

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Weather Service, and various Internet sites such as the U. S. Naval Observatory (http://aa. usno. navy. mil/data/docs/AltAz. html). General deductions from these patterns are that:

• all sides of the house receive sun exposure during the summer; similarly, all sides of the house experience shadow as well.

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Figure 3-13

Shadow patterns from a two-story house at different times of the day in June.

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Figure 3-14

Shadow patterns from a two-story house at different times of the day in March and September.

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north

Figure 3-15

Shadow patterns from a two-story house at different times of the day in December

 

• the largest areas of shadow during the summer occur on the east and west sides of the house; the north and south sides of the house experience less shadow.

• the largest areas of shadow during March and September occur on the east, north, and west sides of the house.

• only the south side of the house receives direct sun exposure in the winter; the northern side receives no sun exposure at this time of year.

• throughout the year, the south side of the house receives the most sun expo­sure; the north side of the house receives the least.

Similar observations can also be made about different slope orientations on a residential site. A south-facing slope, like the south side of a house, receives the most sun throughout the year and is the warmest of all during the winter season. A north­facing slope is the coolest of all, especially during the winter. The frost is apt to stay in the ground one to two weeks longer on a north-facing slope than on a south-facing slope. An east-facing slope experiences moderate temperatures, whereas a west-facing slope is the hottest and driest of all slopes during the summer months.

An understanding of the sun exposure and shadow patterns on a residential site sug­gests two requirements: (1) sun protection is needed from late spring through the early au­tumn and (2) sun exposure is desirable for late autumn through early spring months of the year. These objectives are true for outdoor spaces as well as for the house itself.