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energy-efficient, integrated design process
Success design depends on systems integration & a building's ecological functioning
Comfort, economy & ecology are the aims of designing energy-efficient buildings. Because regardless of how 'green' a construction is, few people would want it if is not as comfortable as a traditionally designed building. Likewise, if energy-efficient construction costs are higher than traditional construction costs, people are not likely to accept change.
Fortunately, passive solar and other energy-efficient technologies have made major advances in the last decades and people who want to lower energy costs and greenhouse gases no longer need to pay a premium to live in houses which require a lot of day-to-day maintenance. Now it is only necessary to integrate certain design principles into the master plan before construction begins. The most important of these are 1) siting and orientation to the sun; 2) window design and placement; 3) interior thermal mass for heat absorption and 4) other building envelope factors.
siting & solar orientation - bearing angle & altitude angle
Careful planning and a good understanding of the local climate is imperative for correct siting. For maximum solar gain in cold climates a rectangular building should be sited with the long side on an east-west axis within 10 degrees east or west of true south. In warmer climates the short side of the rectangle would limit summer solar gain and over heating.
But true south orientation may be undesirable or impossible for practical or aesthetic reasons. Although a true southern exposure maximizes gain, a deviation up to 22.5 degrees from south still yields 92%. Even orienting at 45 degrees off true south yields a 70% gain, which may be enough in certain temperate climates. But too much morning and afternoon sun caused by greater deviations causes over heating in warmer climates.
Bearing angle is measured from true north and refers to the sun's angle on the south face at different times of the day. The distance between the point of sunrise and the point of sunset is forms the insolation area. The angle depends on latitude and longitude, and these are available on line at such sites as www.squ1.org, www.gats-inc.com or www.susdesign.com. The angles are important to know because they allow calculation of the number of hours of sun exposure on the house's glazed facade. For example, exposure from 9 am till 3 pm is good (about 60 degrees of insolation) while exposure from 10 am till 2 pm is just adequate (about 45 degrees insolation).
The sun's altitude angle, also dependent on longitude and latitude, is important because it measures how high the sun is during different months of the year and allows caculation of window placement, overhangs, shades and deciduous trees. Since the sun's angle is higher during summer months, it is possible to have shades extend out enough to block summer sun, yet, when the angle is lower, let winter sunlight pass through glazing to warm interior mass. Window design and thermal mass are discussed in the glazing & thermo-mass section. See any reference on siting a passive solar house for more information.