According to the EPA's Green Building site, the operation of buildings accounts for 39% of our total national energy consumption and 68% of our total electricity use. More than half of the energy used by buildings goes to heating, cooling and powering our homes. Providing energy from renewable sources like photovoltaics and wind helps cut building environmental impact, but at a price many times higher than simply not using the energy in the first place.

Increasing the energy efficiency of homes is paramount to improving their environmental performance: Green building starts with energy-efficient or "high performance" building. High-performance building uses a variety of techniques to make a structure easier to heat, cool and light. Techniques include using superior insulation and air-seal techniques, advanced double or triple-glazed windows, tight-sealing doors, and building design that avoids heat loss due to thermal bridging. The direction the building faces, window placement for best natural lighting and/or passive solar heating, and many other design factors also greatly impact building energy consumption.

Energy ratings are an important green building practice. There are two kinds:

1. Computer modeling of building plans and

2. Energy performance testing of finished buildings.

Performance testing measures building efficiency and removes uncertainty about the building's energy use. No matter how good the design is, performance is largely determined by execution, and everything must be correct to get the best results.

Performance testing (and subsequent good reports) allows developers to take advantages of recently-implemented tax incentives and allows buyers to take advantage of Energy Efficient mortgages (where applicable).

Additional Resources
Elements of an Energy Efficient House
Explains in more detail the differences between energy efficient and conventional construction.
Energy Efficiency and Renewable Energy Resources from the EPA