Save Electricity With Passive Solar Design

Passive solar design is one of the most cost-effective ways to save electricity and improve the comfort of your home – without using a bunch of high-tech gadgets.

Passive solar design makes use of various building features to improve heating and cooling efficiency.  In essence, it is a method of harnessing the sun to provide natural light and warmth to your home or office.

The biggest advantage of passive solar deign is that the features are simple to implement (especially with new constructions), they need little maintenance, and they can boost your building’s market value.

Your home’s solar potential is determined by its site, how the sun shines on the building, and the type of windows used. Most building sites can be optimized to get the ideal amount of sunlight possible, but it is easier if you are on a sun-facing slope or on flat land. If you plan on planting trees, make sure they are deciduous so that their bare branches in winter can let sunlight through.  Also, try avoid shady areas (such as from other buildings).

When building a new home, it should be oriented in such a way that the length of the house faces the sun to get as much sunshine as possible. Also consider how the shape, size and placement of windows affects the amount of natural lighting and heat in the house.

So how exactly does the sun warm your house?

Basically there are three ways the sun regulates the temperature in your home:

  • Direct gain – this is the direct heat from the sun shining on your skin.
  • Indirect gain – this is heat radiated from objects that have been heated by the sun’s rays.
  • Isolated gain – this is controlled by airflow in the house from opening and closing certain doors or windows.

Allowing the most sunlight in on the sun-facing side of your home will ensure the maximum use of all three sources of heat – this can easily achieved with a number of large windows.

Although you want to get as much direct sunlight as possible, you can store the sun’s heat by using heat-absorbent walls and flooring.  Long after the sun has set, these materials carry on radiating heat throughout your home. To cut down on heating costs in winter, move to rooms in the house that receive the most sunlight at particular times of day.  Also, close off any rooms that recieve little sunlight from the rest of the house.

In summer you can make strategic use of roof overhangs or eves to regulate your home’s temperature reduce glare.   These eves are wide enough to block out the hot midday sun and keep your house cool during the day, but allow the low-angle sunshine during the morning and evening in to light up and warm your home.  As mentioned earlier, trees and shrubs can also be used to control your home’s seasonal exposure to the sun.

For buildings that have already been constructed, the easiest passive solar solution is to replace your windows with technologically advanced ones.  Although they are generally 10% to 15% more expensive, modern windows use multiple methods to retain up to 50% more heat.

Low-emissivity (Low-E) and double-glazed windows allow solar heat in, but prevent indoor radiant heat from escaping.  Loss of heat can also be prevented by ensuring tight seals around the windows and using multiple panes with a gap in between that is filled with krypton or argon gas.

The materials that your windows are made of can also make a big difference.  Metal framed windows tend to conduct more heat out of the house, as opposed to wood, fibreglass and vinyl window frames.  When buying any modern windows, look for labels issued by a National Fenestration Rating Council or by Energy Star.  These labels tell you the how effective the window is at retaining heat, which helps you to objectively weigh up the cost against the potential electricity savings of each window.

As you can see, passive solar design is making practical use of physics and nature to maximize the benefits of free heat and light from the sun.  Just remember, the whole idea behind passive solar design is to save electricity. So before implementing any passive solar solution at home, always compare the cost with the energy you could save, and take it from there.

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Originally posted 2008-11-19 22:11:14.

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