Green Architecture: Passive designs and heating

Of course, sunlight is not the only factor in designing an energy-efficient building. Heating and cooling takes up huge amounts of power. The first step is to make sure that all walls, windows and roofs are well insulated. Natural insulators such as wool are really almost as good as manmade fibreglasses, but it is important to spray them with flame retardants as fire can spread quickly through roofs lined with wool. Engineers and scientists are always coming up with new insulating materials that are also fireproof and long-lasting. In cold areas where heat from inside can be transferred to the freezing ground, it is a good idea to insulate under foundations and floors as well.

Brick walls and double-paned glass with special ultra-violet coatings are important because of their insulating abilities. However, in hot places it is not desirable for brick walls to retain the heat of the day, so walls are built with a double row of bricks with an air space filled with insulator. This means that any heat that is trapped in the outside "layer" of brick is not transferred to the inside wall.

Curtains can block sunlight to cool an interior but it is better to have shades installed outside the window. This is to prevent the sunlight from entering the glass window at all during hot weather. Once a light wave enters glass, it slows down and becomes heat, and while a curtain may block its entry into the rest of the room, there will be a buildup of heat between the curtain and the window. It is best to block light from the outside, if you want cooler interiors.

Architects can design overhangs to best suit the seasonal positions of the sun. A well-researched overhand will protrude far enough over a window to block much of the summer sun, while allowing most of the winter sunlight in. That means houses will be warmer and lighter in winter when the sun's path is low in the sky but won't overheat in summer, when the sun is high. The exact size of the overhand will depend on the height of the window above the ground and the geographical location, which dictates the sun's apparent path overhead.

In general, it is important to avoid unnecessary spaces in window panes and under doors to which might allow heat transfer between inside and outside, or between rooms if they are heated separately. However, there is a balance to be found between energy-efficient designs to stop heat transfer and the need for good ventilation. Energy-efficient office buildings from the 1970s were so efficient that very little of anything could enter and exit the buildings, including air. Air-conditioners could hardly be seen as the energy-efficient alternative to simple ventilation gratings, often seen in older houses.

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