In ecology, sustainability is how biological systems endure and remain diverse and productive. Long-lived and healthy wetlands and forests are examples of sustainable biological systems. More recent accounts have broadened the idea of sustainability to include social wellbeing, resilience and adaptation across four domains: ecology, economics, politics and culture. In economics-centred accounts, sustainability requires the reconciliation across the “three pillars” of sustainability: economic demands, environmental resilience, and social equity.


Green building (also known as green construction or sustainable building) refers to a structure and using process that is environmentally responsible and resource-efficient throughout a building’s life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition. This requires close cooperation of the design team, the architects, the engineers, and the client at all project stages. The Green Building practice expands and complements the classical building design concerns of economy, utility, durability, and comfort.

Although new technologies are constantly being developed to complement current practices in creating greener structures, the common objective is that green buildings are designed to reduce the overall impact of the built environment on human health and the natural environment by:

Efficiently using energy, water, and other resources
Protecting occupant health and improving employee productivity
Reducing waste, pollution and environmental degradation

The concept of sustainable development can be traced to the energy (especially fossil oil) crisis and the environment pollution concern in the 1970s. The green building movement in the U.S. originated from the need and desire for more energy efficient and environmentally friendly construction practices. There are a number of motives for building green, including environmental, economic, and social benefits. However, modern sustainability initiatives call for an integrated and synergistic design to both new construction and in the retrofitting of existing structures. Also known as sustainable design, this approach integrates the building life-cycle with each green practice employed with a design-purpose to create a synergy among the practices used.

Affordable Housing

Affordable housing is housing deemed affordable to those with a median household income as rated by country, province (state), region or municipality by a recognized Housing Affordability Index. Most of the literature on affordable housing refers to a number of forms that exist along a continuum – from emergency shelters, to transitional housing, to non-market rental (also known as social or subsidized housing), to formal and informal rental, indigenous housing and ending with affordable home ownership