Beyond that, the key, most experts in the field agree, is a flexible and holistic approach, trying to make environmentally friendly decisions at every point in the residential planning, design and construction process — while keeping in mind that there are always going to be tough, even seemingly impossible, choices to be made. An architect or homeowner deciding between a kind of roofing material that is wasteful to produce but available locally and an eco-friendly variety that has to be trucked in from 2,500 miles away will not be helped by a one-size-fits-all checklist.
None of those basics need add any cost to the construction of a new home (save for the potential higher prices of a piece of land near or in a city). Indeed, following the first size rule will necessarily lead to lower building costs.
Beyond that, greenness is generally a question of two issues — energy efficiency and the eco-friendliness of its materials — along with a broader sense of how a new house or apartment building ties into its local, regional and global context. Often, these concerns are intertwined, but in general architects committed to sustainability will rely on the following:
Recycled materials and even existing foundations or building shells.
Wood from stocks that are sustainably managed.
Materials low in embodied energy — that is, the energy required to extract and produce them and bring them to a building site.
Natural materials, such as bamboo, that are easily regrown or replenished.
Efficient lighting systems that take advantage of or redirect daylight to reduce the need for electricity, or include sensors and timers to shut off lights when not in use.
Water systems that collect rainwater or treat so-called gray water (from sinks and showers) so that it can be reused for gardens or toilets.
Strategies to ensure that a house will have a long life, because it is architecturally significant, comfortable, or adaptable to future uses.
Insulation, glass and facades that are energy-efficient or that promote air circulation by natural ventilation instead of air conditioning.
Strategies to take advantage of the sun's rays, either passively, by storing sunlight as heat, or actively, using solar panels to convert light into electricity.
Interior materials and finishes, from carpets to paints, that minimize unhealthy chemical emissions and promote a high level of air quality.
The point is not to meet some standard of perfection but to make careful, informed choices, from selecting a building site to picking out the appliances, cabinetry and plants for the backyard.