Green buildings, including houses, are often referred to as "sustainable" and "high-performance". A sustainable design works to ". . . meet the needs of today without compromising the ability of future generations to meet theirs." Doing more with less is a good definition of high performance. In Green design, these elements are not just appended to the conventional consideration of size, style, budget and system of construction. Rather, they become the overarching principles from which all other considerations flow.

From a Green point of view, well-planned high density is to be encouraged. Development should be channeled to urban areas with existing infrastructure. Reusing prior developed land protects undeveloped land, wildlife habitat, and natural resources. Proximity to public transportation reduces the reliance on the automobile - a huge source of pollution. In site selection, preference is given to sites with pedestrian access to a variety of services. Green encourages the use of bicycles by providing convenient access and storage while discouraging automobile use by minimizing parking accommodations. Letting go of our love affair with the automobile is a reoccurring theme in our reach for sustainability.

A prime concern of Green design is water efficiency, for fresh water is a finite resource and water treatment is an expensive proposition. Vegetated roofs, permeable paving, rainwater harvesting, and eco swales are some of the proven techniques that work to reduce rainwater inflow into the sewer system - while at the same time replenishing the natural groundwater aquifer. As it often happens with Green design, these natural low-tech techniques produce co-benefits. They present opportunities to introduce nature and beauty, not as elements applied superficially after the fact, but as intrinsic features of the design. Green is not all low-tech, however. Technology such as low flush toilets, waterless urinals, and tankless water heaters are gaining acceptance as effective ways to reduce the wasting of precious fresh water.

The most technologically intensive aspect of Green design deals with matters of energy. Already there exist, in the market, systems and materials that make it possible to construct "Net-Zero" buildings: buildings that use only the energy they produce. Research and development of new products that will make this routine rather than the exception are based on new ideas like electrochromic windows offering the dynamic control of infrared energy, inexpensive highly efficient nanocomposite materials for solar energy conversion, thermoelectric materials that transform heat directly into electrical energy, solid state lighting that produces light at a fraction of the energy of current fluorescent lighting, selective water sorbent technologies that offer the performance of a geo-exchange system at the cost of traditional systems, distributed sensor systems that continuously optimize control devices, and integrated energy systems that provide on-site power as well as heating, cooling, and dehumidification. Products of this type are already transforming the marketplace and hold the promise of "Zero-Sum" buildings - buildings that produce more energy than they consume.

While environmental responsibility and resource efficiency are prime concerns of Green design, the most important is occupant well-being. In recent years, much has been learned about the poor quality of the average indoor environment. Indoor pollution sources that release gases or particles into the air are prevalent in conventional construction. Inadequate ventilation, high temperature and humidity often concentrate indoor pollutant levels to two to five times - and occasionally 100 times - higher than outdoor air. Rigorous studies inform us about the importance of natural light and its effects on productivity, health, and sense of well-being. Green design still holds concerns for style, fashion and aesthetics yet it subordinates them to concerns for a heathful habitat.

How much more does all this cost? This is the question often posed by skeptics. "Integrated Design" and "Life-Cycle Costs" are the Green answers. The integrated design process considers all the components as integral parts of the whole - more insulation in the walls equals a smaller mechanical system. This holistic approach is what makes Green buildings competitive in today's market. Because Green buildings invest in quality, durability, and energy efficiency, they may appear more costly. Life-Cycle Costs Analysis, however, reveals the true cost of buildings. During its life, the cost of operating and maintaining a poorly designed building dwarfs the initial building cost. Adding the cost of lost productivity, ill heath effects, and the contribution to the destruction of the biosphere raises the true cost of our conventional buildings to an astronomical level - a true cost that we can now no longer afford.