Building 6: Solar Umbrella House

The initial structure for this house in Venice, Calif., dates back to the 1920s with a renovation 10 years later. In 2005, owners decided to renovate sections of the house as well as add portions, increasing it to more than twice its original size. These changes, which focused on making the structure more sustainable, included adding a "solar umbrella" of PV panels which ended up providing 95 percent of the home's energy [source: AIA]. 

In addition to providing most of the energy for the house, the PV panels shade the house, reducing any energy needed for cooling the house. In addition, the structure allows cross ventilation to provide significant cooling. Also, three solar panels contribute to heating water for the hot water supply as well as for the swimming pool. A heating system that releases heat through the concrete floors of the house heats the house very efficiently. The structure allows for significant use of daylight -- so much so that artificial light is not necessary at all during a sunny day.

Construction materials used for the renovation included concrete that is 50 percent fly ash and recycled mild steel as well as other recycled materials [site: AIA]. Because they started with an existing structure, the builders were able to forego using a significant amount of new material. Not only that, but builders recycled about 85 percent of the waste that resulted from construction [site: AIA].

The amount of water runoff from the house is low as well, thanks to gravel that lets water seep into the ground. Eighty percent of the water that doesn't enter the ground doesn't turn into runoff either because of a water retention system that collects the water in a basin [site: AIA].

Owners chose particularly energy-efficient appliances and also implement lighting systems to reduce electricity use. After all is said and done, the home ends up consuming half of the gas that it did before, even though it is more than twice its original size.

If you really want to encourage earth-friendly behavior, don't just build a sustainable structure but make it difficult for the people who use the structure to park cars there. Learn more about this strategy on the next page.