Recycled lumber can be used for studs. Insulation made of recycled jean material may be used for walls. Many of the plastic wood products are made from recycled material. Materials that last a lifetime reduce the amount of waste that goes into landfills — and save resources that would otherwise be used to replace them. These products include cement board siding, stone and brick, and stand and seam metal roofing. It is also important to use materials that don’t release toxins (labeled LOW-VOC for paints and formaldehyde-free for particleboard).

One of the most important features of eco-friendly houses is that they are designed for energy efficiency. Of course, it is essential to use high-efficiency appliances, heating and cooling equipment and water heaters. But green design can also include windows placed to allow ventilation throughout the house, south-facing windows that take advantage of the sun’s warmth, and shade trees and awnings for summer (see References 1 and 2). Skylights in interior rooms reduce electricity use during the day.

Alternative energy sources are becoming more common in private homes. Some systems generate electricity directly, like photovoltaic (PV or solar electric) and wind power systems. Other systems, such as geothermal and solar hot water, use the sun to heat or pre-heat water for domestic use or for space heating and cooling. Usually, the PV and solar hot water systems can be mounted on a roof, while wind systems have land requirements.