Solar Site Design Is No Shady Deal

It sounds like a pitch for one of those shady real estate seminars: “No investment needed, fantastic returns.” But this is no shady deal.

By properly placing a house on a site, you can slash heating and cooling costs, without investing an additional dime on the house. No fancy windows. No elaborate heat storage. No fans, ducts, or dampers.

Energy savings, comfort & natural light
By orienting a house to the south, you can capture solar heat in the winter and block solar heat in the summer. A study by the Bonneville Power Administration identified space heating savings between 10 and 20 percent. Another study conducted for the City of San Jose, California estimated savings in cooling costs ranging from 10 to 40 percent. These savings are based on house orientation alone and assume no special solar features to the building.

Saving energy is only one of the advantages. People are more comfortable–cozy in winter and cooler in the summer.

Plus, market research reveals that home buyers like spaces with lots of natural light. Proper solar orientation allows excellent use of natural daylight.

Sun Paths
Every day of the year, the sun takes a slightly different path. During winter the sun travels low in the sky. This allows sunlight to shine on south facing walls and enter south facing windows.

In summer, the sun rides much higher, shining mostly on the roof. Overhangs shade south facing walls and windows from the sun. Most of the sunlight striking windows at a high angle reflects off. But east and west surfaces are totally unprotected. The most severe problems occur on the west side, where the afternoon sun often causes severe overheating that drives up cooling costs. Just think how many times you’ve seen west facing windows covered with awnings, trellises, drapes and other sun blocking devices.

Building Orientation
Ideally, the long side of the house faces directly south and shorter sides face east and west. This arrangement captures heat and natural light in winter, but minimizes unwanted summer heat gain.

However, pointing the house up to 30 degrees to the east or west typically sacrifices only about 5 percent of the solar gain. Beyond about 45 degrees from south, the benefits drop dramatically.

Be especially careful if you shift house orientation to the west, because you could increase cooling requirements.

Solar site design is easiest to apply to large lots, but it’s also possible in high density developments. The best bet is to find a lot where the front or back of the house faces within 30 degrees of south. These are most commonly on streets that run east/west.

Landscaping
Selection and placement of plants can help control sunlight. Trees require the most careful selection. A “solar friendly” tree is a deciduous tree that has a low density branch structure, drops its leaves early in the fall, and regains them late in the spring. Size can also be an important factor. A tree that never grows tall may cause less of a shading problem.

The south yard needs the most careful planning. Try to leave it as open as possible, or select solar friendly trees. However, even the “friendliest” tree blocks 30 percent of the sunlight that passes through its crown. In this case, the best tree us one that doesn’t cast its shadow on the house.

Trees that aren’t “solar friendly” don’t need to be banished from the landscape. Evergreens work well on the north side to block arctic winds. Evergreens and the dense shade trees on the west block the intense heat of the setting summer sun. If planted within 15 ft. of the house, a tree can grow up to shade the roof in summer. Pruning the lower branches will allow the winter sun to reach the house.

Ground cover also affects heat gain. Minimize the use of masonry materials, such as concrete patios, on the south side of the house. They can reflect heat into the house. Lawn, shrubs, and other low-growing vegetation help prevent overheating in summer, while allowing sunlight to strike the south elevation.

Solar access
Proper orientation doesn’t mean much if vegetation or buildings block the winter sun. While home owners have control of construction and tree planting on their own lots, they cannot control what happens on other property.

When picking a lot, look to the south for buildings or trees that might shade the proposed house. Also try to anticipate future developments that might rise high enough to block the sun. Evaluating solar access will be much easier if you make a “sun chart.” A sun chart allows you to identify objects that currently block your sun, and trees that may soon become problems.

Many communities help you protect your investment with solar access protection ordinances. In Oregon alone, over 30 cities and counties have solar access laws. Even if your city or county hasn’t adopted an ordinance, you can still make individual agreements, called solar easements or covenants, with neighbors.
– Les Tumidaj

This article appeared in Energy Source Builder Vol. III No. 2, April 1991,
©Copyright 2008 Iris Communications, Inc.