HOW TO DESIGN ENERGY EFFICIENT HOMES
In Australia we have our buildings nominated with energy ratings. These mean that the buildings can compared to each other regards the cost of heating and cooling.
In Australia most of our cities are in climates where 40 C (104 F) is not unusual. The capital of Australia gets to minus -50 C, while up in the northwest of Australia it gets to 55 C (131 F). So it behooves us to know how our home is going to perform under these conditions, before we make the purchase.
In Australia there is the system of stars representing energy efficiency ratings. Each home is assessed in an algorithm determined by a computer program as to its worthiness or not. A high staring house of six stars is way better than a house of two stars, and so on.
These programs can differ depending on circumstances. There is one program for existing buildings and another program for designed buildings.
How the Algorithm Works
There are many factors that determine if your building is energy efficient or not. Here are the determining factors:
1. Materials play a big role. Will they keep the heat out, and is that good? For example, a building that has a big wall mass, such as double skinned brickwork, might allow the wall to heat up during the day, before the heat finally penetrates into the building. This might keep a building cool during the summer, during the day, but what happens at night is that the heat continues to penetrate its way in and heat up the house during the night. In some Australian homes it has been found that the houses are way hotter inside that out during the evening exactly for this reason.
2. Orientation affects the building. Does the house face the sun, and does the sun shine directly into the building in winter, and does the sun then not enter the building in the summer?
3. Insulation is an important factor. Does the insulation work? How thick is it? How much does it reflect? This is called an R rating. Is there insulation in the walls? What type? During a monastery the author was the project manager, and the demands of the client were that they wanted a mass of double brick in the wall the winter, to heat the building, but wanted it to be cool in the summer. So this meant different insulation was catered for within the brick wall cavities.
4. Do the eaves allow the sun in during the winter, but not the summer? Eaves are an important part of buildings as they keep the rain away from where it might penetrate the building envelope, but more importantly, they offer significant energy efficiency.
5. Outside cover is important. Are there trees outside, and do they shade the building? Is the afternoon sun shaded from? Is there a pergola nearby? All this is in the algorithms.
6. Internal treatment of windows is important. One looses heat and gains heat when air travels past a glass window pane. The movement of the air molecules against the pane transfers energy. So if you put in double glazing, this is very efficient. But blinds and curtains can also prevent a lot of energy exchange as well. And if you use curtains with heavy drapes, and have big pelmets over the top, they are the best of all.
7. Floor coverings play a significant role. If a house has bare concrete or tiles, it will absorb the heat of the direct sunshine through windows during the day, and radiate it back into the home during the night. This can be a boon for homes plagued by cold winters. Carpet on the other hand, while it seems warmer, will act as an insulator to the concrete mass and the concrete is then unable to absorb the heat. That is good for summer only.
With the above information in mind when designing a home, a house could be made solar efficient. We hope this information helps you.
Nick Broadhurst is the author of science fiction books, children’s picture books, and comics. He also writes articles on contemporary philosophy. For a living he is an architect, building contractor, building inspector, and worked in many countries.