The new parliamentary building, Westminster.

Providing people with a quality indoor environment means full air conditioning with an energy use tag that we would rather not mention in the debate about environmental impact and sustainability. But is this really the case? Is it not possible to design mechanical systems so they use less energy than their naturally ventilated counterparts? The law of conservation of energy means we can use the same energy repeatedly. As long as we are aware of how energy is degraded in quality and temperature terms, we can design systems that repeatedly recover and reuse energy. The catch often comes in the form of the high grade parasitic energy these systems themselves consume to achieve this process. This is where the use of passive building fabric environmental control has a major advantage because generally it uses natural energy flow mechanisms which need no parasitic energy for them to operate. Thus there emerges a strategy that seeks to maximise the use of passive environmental control and only supplement it where necessary with simple mechanical support. This creates two major issues for the designer. Firstly, he must have complete faith in the physics of passive environmental control. This is difficult for someone who is used to the reassurance that a mechanical system can provide in the form of a last minute pulley belt change to enhance performance. Secondly, it requires considerable time to design mechanical and control systems from scratch without the standard systems rules-of-thumb upon which he normally relies.This paper describes a project where the design time and full design team commitment allowed the conventional approach to indoor environmental control for a polluted central urban site to be re-examined. The end result is a design that takes the principles of passive design, simple mechanical systems and integrated design, to achieve an energy use target of 75% Jess than typical, and Jess than best practice naturally ventilated alternatives.