Sun Angles / Using the Sun

When settlers constructed haciendas and missions in early California, they used a design technique that today's builders all-too-often overlook: placing a building into its natural surroundings to make it more comfortable for its inhabitants.

Spanish missions were usually long rectangular buildings, situated so that their longer walls faced toward the south to absorb heat from the low winter sun. In the summer, when the sun was higher in the sky, long porches helped to shade the buildings and keep them cooler. Windows were placed to allow for cross ventilation.

While those principles still hold true, many modern structures are oriented not to the sun but to the street or the lot on which they sit. By getting back to basics, homeowners can reap the savings of energy efficiency and increase the comfort of their homes.

The most efficient building design to make use of the sun's energy for heat is still a rectangle, with one of its longer sides facing south. That way, windows and walls on the south side benefit from the effects of the low winter sun.

As the diagrams illustrate, the sun climbs much higher in the sky in summer than in it does in winter. As a result, relatively small overhangs can easily shade a house oriented toward the south from the intense summer sun. At the same time, the shorter east and west sides of the home will receive minimal direct sun. This orientation minimizes exposure to the summer sun and maximizes the benefits of winter sun.

Placing Your Windows

Windows in California's early missions were little more than holes in the wall to allow ventilation and light, with shutters that could be closed to keep in heat. Although today's windows are much improved, even the most energy efficient models are not as energy efficient as a well-insulated opaque wall. That's why the use of good windows and proper window placement remains very important.

Generally, for harsh climates such as those in Sacramento and the Central Valley, the greatest percentage of glass should face south. Since the valley experiences hot summers, the least amount of glass should face west, where it would be exposed to afternoon and evening sun.

In areas like the Sierra Nevada, where the summers are milder, the least amount of glass should face north, where windows receive no direct sunlight but can lose substantial amounts of heat. The next smallest window exposure should be to the west, followed by an eastern exposure. The greatest percentage of glazing should be on the south.

It is important to shade windows from the hot summer sun. Exterior shading is the best method for keeping unwanted heat out of a building. In addition to awnings and covered porches, carefully placed trees and shrubs keep a home much cooler in summer. If the plants lose their leaves each year, they also allow winter warmth and sunlight into the house.

Multiple-pane glass; gas-filled, low conductive framing materials; shading tints and low emissivity (low-E) coatings all help to make today's windows substantially more energy efficient than windows manufactured as recently as 10 years ago.

The Importance of Insulation

The thick adobe walls built by early settlers held warmth inside during the winter and offered cool shelter from the heat of summer. Modern insulation is just as important in keeping today's frame home comfortable.

The most effective insulation for a framed building is a continuous layer of insulation at the outside of the studs, combined with insulation between the studs. Special consideration should be given to areas where walls, floors and ceilings meet, for they offer a direct conductive path for thermal energy to escape.

While not required, homes in the Sacramento area that are built on a concrete slab can benefit from the edges of the slab being insulated to at least R-7; higher R-values are appropriate for more extreme climates. Similarly, the underside of floors over areas such as crawl spaces, cantilevered rooms, carports or garages should be insulated to R-21 or higher. Walls should be insulated to R-21 or higher and ceilings to R-38 or higher.

California's early settlers situated their buildings to make the best use of the sun. By using the same techniques, today's homeowners can maximize their comfort even as they minimize their heating and cooling costs.

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