We picked the 15 practices to talk with – all with a track record of sustainable design – for their variety. They range from one-and-a-half architects to several hundred, spread around the country, urban and rural, with green clients and clients who are indifferent to sustainability, clients from public and private sectors, some practices more focused on energy while others major on community, taking formal and informal approaches to organising and sharing knowledge and learning within the practice, bemoaning contractors or getting very hands-on on with projects, and all in different ways green in their practice housekeeping.

It may appear illogical to include fuel cells among renewables. While they combine what are effectively-inexhaustible resource of hydrogen and oxygen in the generation of electricity, plus heat and water vapour, in practice hydrogen is usually extracted from a hydrocarbon fuel such natural gas, a process that generates CO2. Depending on your definition of a renewable, the nearest you get is extracting hydrogen from the methane from waste tips. Though a future possibility is to use regenerative fuel cells as batteries in electricity generation from wind, PC or CHP.

This page provides a link to the Labyrinths and Earth Tubes article (on the web only). These technologies are rare in the UK today and there is (as yet) no infrastructure of information sources and grants.