Solar Design

Understanding Passive Solar Design

If you ever wanted to save electricity and improve the comfort of your home without using any high-tech gadgets, then passive solar design is the answer.

Passive solar design is a technique of using the sun to naturally heat and light up your home or office. This is achieved by using various building features and materials to improve heating and cooling efficiency. The best part about passive solar design is that it is relatively simple to implement, little maintenance is needed, and your home's market value can increase considerably.

Your home's passive solar potential is determined by where and how it is situated and by the types of windows and materials used. Although most buildings can be optimized to receive the ideal amount of sunshine, it is easier if they are on flat land or a sun-facing slope. If your home is surrounded by many trees, make sure they are deciduous so that they shade your home in summer, but their bare branches let sunlight through in winter. Also, try avoid nearby buildings that create too much shade.

When constructing a new home, make sure it is built so that the length of the house faces the sun, allowing the maximum amount of sunlight. Also note how the size, shape and placement of windows will determine the amount of natural heat and light in your home.

So how does the sun heat your home? There are three ways:

• Direct gain - direct heat from the sun shining on a surface.
• Indirect gain - radiated heat from objects heated by the sun.
• Isolated gain - determined by the airflow in your home.

To ensure the most natural heat from the above three sources, a number of large windows should be placed on the sun-facing side of your home, allowing maximum sunlight in.

All that sunlight and heat in your home is useless, if it cannot be stored and used when the sun is set. The solution is to use heat-absorbent flooring and walls that carry on radiating heat long into the night. A simple way to reduce power cost in winter is to locate to rooms in your house that get the most sunshine at certain times of day. Also, shady rooms should be cut-off (their doors closed) from the rest of the house to retain heat better.

During summer, the right length roof overhangs or eaves can be used to control the amount sunlight and heat in your home. The eaves should be wide enough shade out the intense midday sun, but let the let low-angle sunlight through during dusk and dawn to light up and warm the home. Again, the right trees and shrubs can be planted to regulate the house's seasonal exposure to the sun.

For current buildings, the simplest passive solar design solution is to replace your windows with modern ones, that use various methods to store up 50% more heat. Although they are 10% to 15% more expensive, they pay for themselves in the long-term from all the power saved to heat your home.

Double-glazed or Low-emissivity (Low-E) windows let solar heat in, but keep in the indoor radiant heat. Another way to reduce heat loss is to ensure tight seals around all windows or by using multiple panes that have gaps between them filled with argon or krypton gas.

What your windows are made from can make a big difference too. While metal framed windows generally conduct heat out the house, wood, vinyl and fiberglass frames insulate the heat better. Always ensure any modern windows bought have labels issued by Energy Star or the National Fenestration Rating Council. These labels provide statistics on how effective and efficient the windows are at retaining heat, which helps you purchase the right windows for your conditions and budget.

So you can see, passive solar design is the effective use of nature and physics to maximize the use of the sun's natural lighting and heat. Always remember, the point of solar passive design is to reduce your electricity usage and bills. So it is recommended to always weigh up the costs against the potential power savings when installing any passive solar solution at home.