You could try looking up the words "Sustainable Development".
Most traditional used explanation has three EQUAL components (basically the Earth’s biosphere, People’s communities and Money).
This is an idea that says you can meet the needs of these three in the present without compromising the ability of future generations to do the same.
A real sustainable built environment would have to consider the actual percentage being more towards the Earth’s biosphere and the people, with money and commerce being placed much smaller in the equation.
Buildings that are filled with habitats for more species than just humans and their pets.
Actually built in such a way as to actively improve the sites biodiversity possibility. Turf roofs, bird boxes and ponds are small moves in this direction.
References :
http://www.concrete2jungle.co.uk/services.php

The ‘S’ word hey, everyone likes to use it.

Most built environments could be argued to be sustainable, the question is what inputs would be needed to sustain them. Do you need a team of highly trained engineers replacing sections at regular intervals, do the buildings need regular and intensive maintenance?

Perhaps the idea in some peoples’ heads is that the the materials used are from sustainable sources. I don’t really know, It’s all a bunch of spin nowadays really.

The term sustainability in this context comes from Permaculture (google it) which is an ideal about living without the need for resources, cultural or physical, beyond what you can create or maintain yourself, or as a group.

As a permy I’d say a sustainable built environment would be one that was created by those living in it and maintainable by those living in it. All from local resources. The importance would be economic, cultural and environmental. Anything less would be BS, and those living there would know it, whether they’d acknowledge or admit it or not!
References :