ENERGY EFFICIENCY | OVERCOOLING When spaces are cooled to uncomfortable temperatures, negative impacts are seen on peoples health and the environment. Tim Dwyer looks at a new paper that attempts to measure the extent of the issue SENSIBLE COOLING S pace cooling is a significant energy end-use within buildings, responsible for roughly 20% of the energy consumed in buildings globally, and contributing to 8% of total energy-demand carbon emissions. Population growth and an increasing number of buildings together with the availability and affordability of space-cooling systems make this the largest consumer of energy in warm climates, but also the fastest-growing. A recent paper The comfort and energy impact of overcooled buildings in warm climates, by Abdulla Alnuaimi, Sukumar Natarajan and Tristan Kershaw, of the University of Bath reports that the majority of built-environment growth will occur in warmer climates. Although the global trend in power-generation carbon intensity is decreasing, the significant future increase in cooling energy demand is estimated to triple. Current carbon emissions from cooling energy annual demand is expected to rise from about 2,000TWh currently to 6,000TWh by 2050, because of increased air conditioning use, urbanisation, population growth, and a warming climate. The authors of the paper note that it is remarkable that a proportion of this projected growth in cooling energy demand is being driven not by an increase in the overall installations of air conditioning, but through the unnecessary expenditure of energy, or overcooling, that produces uncomfortably cool thermal conditions. The extent to which overcooling is defined and quantified, in terms of thermal comfort, has not been systematically studied. Unmanaged, overcooling will not only lead to significant unnecessary energy consumption within a rapidly expanding building stock resulting in increased cooling energy demand and carbon emissions but also to persistent occupant discomfort, leading to negative health effects. Overcooling has also attracted media attention, with anecdotal reports from a range of buildings, including offices and shopping centres, commonly featuring terms such as summer freeze and freezing. Overcooled spaces in public buildings are reported as being too cold inside, while it is nice and warm outside. In East Asia, the term air conditioningitis is used to describe the negative health effects arising from the large differences in indoor and outdoor temperatures caused by low setpoints in air conditioned buildings. The sensation of being overcooled causes occupants to resort to unsustainable strategies: opening windows to dump the coolth, which can unwittingly admit more heat; increasing clothing during the hot season; and, in some instances, simply avoiding overcooled spaces. The analysis revealed that, within comparable air-temperature ranges, occurrences of warmer climate overcooling outweigh those of cold climates. Within both climates, differing perceptions of thermal discomfort are indicated, suggesting a cultural link to thermal comfort. Unmanaged, overcooling will not only lead to significant unnecessary energy consumption, but also to persistent occupant discomfort, leading to negative health effects 78 September 2022 www.cibsejournal.com CIBSE Sept 22 pp78-80 Over cooled buildings.indd 78 26/08/2022 18:38