World Renewable Energy Congress VIII (WREC 2004). Copyright 2004. Published by Elsevier Ltd. Editor AAM Sayigh. 1 NEW DEVELOPMENTS IN THE SCIENCE AND ART OF BREATHING WALLS Mohammed Salah-Eldin Imbabi School of Engineering & Physical Sciences, The University of Aberdeen King’s College, Aberdeen AB24 3UE ABSTRACT Breathing walls provide a practical and viable technology that enables provision of high quality indoor environments, uses less energy, and combats urban air pollution. The paper presents a state-of-the-art review of how breathing walls work, the materials used in their construction, and how they can be integrated in environmentally responsive buildings. The latest research findings into life-long particulate and bio-filtration will also be outlined. Design and construction of maintenance-free, modular breathing wall cladding panels and their implementation in actual building projects is briefly described. INTRODUCTION The world's great cities are an important manifestation of growth and development in human civilisation. The buildings that make up these cities may be as varied and diverse as the people who populate them, but there is also commonality in the way they are designed, built and maintained. If the job is well done, buildings can have a profound beneficial effect on the health, happiness and productivity of those who live and work in them. The demand for high quality regulated indoor environments, however, has in the past led to wasteful energy use, with the consequence that many cities today are characterised by pollution hotspots. Breathing walls forming all or part of an air permeable building envelope or façade offer a potent and comprehensive solution to the increasing and serious problem of self-inflicted environmental damage that many cities now face. Correctly specified, they integrate functions normally associated with Heating, Ventilation and Air Conditioning (HVAC) plant such as ventilation, heat recovery and air filtration into the very fabric of the building itself. The resulting breathing buildings are simple to implement, elegant and sustainable. To the casual observer, a breathing wall cladding panel may be indistinguishable in appearance from any conventional building cladding. A generic breathing wall panel typically comprises ventilated outdoor external rainscreen and indoor wearing surface encapsulating air permeable dynamic insulation materials, buffered and supported internally by special air distribution screens. Ventilation air thus flows indoors through a breathing wall when a pressure difference is applied, picking up conduction heat loss as it flows through the wall, with filtration of airborne pollutants occurring simultaneously. The breathing wall concept reduces complexity over conventional building construction yet delivers significant gains in performance when part (or all) of the building facade is transformed into an active, integrated component of the building’s environmental control system, and the source of clean, efficient ventilation. Significantly less energy is used in keeping the building warm (or cool) since the wall is now a