Sustainability is the capacity to endure through time. It can be defined in biological terms as the ability of an ecosystem to maintain ecological processes, functions, biodiversity and productivity into the future. 
 

Simple Rules to Follow

Create a flexible framework to optimize the potentials for infrastructure, urbanism, architecture, open space, recreation, and real estate values. This flexible framework serves to knit a social whole of the myriad uses and users. Comprehensive, whole system infrastructure planning is integral to planning, design and delivery. This focus on multiple scales:

Approach to the Land - maximizing ecological connections, responsible integration with regional growth patterns, a positive tipping of the jobs/housing balance for the region, and significant deterrent to suburban sprawl. 

Appropriate Development - pattern for the land that reconnects fractured patterns, maximizes walkability and positive social interaction among residents, including a mixed-use structure reinforced by a transect model for development at a variety of densities that make transit solutions feasible, and a meaningful integration of human and natural ecologies.

Buildings come in a wide variety of shapes, sizes, and purposes, and they have been built at different times according to different standards. Consequently, addressing energy use in any given building requires a holistic approach to ensure the best results.