Passive Solar Energy: Mantra of Energy Efficiency

Proper orientation of a new home allows the homeowner to take advantage of a powerful source of lower utility costs: passive solar energy. Certain realities that influence orientation of buildings never change. The sun rises in the east and sets in the west and midday sunlight is at a low angle in winter and a high angle in summer. Given those basic facts, much can be done to position a home so the daily and seasonal movements of the sun work to your advantage to increase indoor comfort while reducing heating and cooling expenses.

Homes with large front windows facing too far southwest, for example, may overheat in summer, while homes directed too far southeast will miss some of the benefits of available solar heating through windows during winter.

Walls facing south should have a total window area at least 50 percent more than the combined window area of walls facing east and west. Ninety percent of south-facing windows should be shaded by trees or architectural features like overhangs to deflect high-angle exposure to midday summer sun. Because west-facing windows face bombardment by heat energy from the sun as it declines and sets during summer, yet provide little solar heating during winter, walls on the short, west face of the home may benefit from minimal window area.

The exact amounts and proportions of glazing you choose will vary depending on other considerations such as:

• climate
• the level of insulation in your home
• the thermal performance of windows and window frames, particularly in existing houses.

Achieving the ideal orientation is about striking a balance between sun, breeze and these other factors. If you compromise on orientation in order to take advantage of views, you may still be able to make your home energy-efficient by using features such as good insulation and well-placed, well-sized windows.

One of the most important (and often overlooked) energy efficiency factors in any home is its orientation. Believe it or not, how a house is oriented in relation to the sun can have a dramatic impact on heating and cooling – the largest energy contributor in most homes. Not to mention – lots of natural light creates a desirable natural ambiance, contributing to the home’s overall comfort. While some passive solar features are relatively recent innovations, the practice of orienting a home to the path of the sun is as old as civilization itself.

Orient the floor plan. In addition to strategically positioning the building as a whole, design the home so that frequently used rooms (such as the kitchen and living room) receive an ideal amount of sunlight. This is also important when incorporating patios and decks – and likewise, situating the garage, laundry room and other areas used less frequently.

• South-facing rooms allow most winter sunlight, but little direct sun during the summer
• North-facing rooms admit relatively even, natural light, and almost no unwanted summer heat
• East-facing rooms receive the most morning sun. Locating the dining room or breakfast nook on an east wall makes the most of light potential in the morning. It’s also a good place for a dense floor that can soak up some solar heat. Bedrooms with east-facing windows will be great for early risers, but terrible for people who like to sleep in.
• West-facing rooms collect early evening light. Because the sun is so low in the sky, west-facing windows get direct sunlight blazing through them. This makes them a bad choice for TV rooms, since strong light makes screens harder to see.

References:

1. http://homeguides.sfgate.com/orientation-building-home-70471.html

2. http://www.clarum.com/energy-efficiency/sitting-with-the-sun-home-orientation-techniques-for-optimal-sun-exposure/

3. https://www.smarterhomes.org.nz/smart-guides/siting-and-location/house-orientation/