Flexible future comfort

Cooling is the fastest growing user of energy in buildings, and predicted to triple globally by 2050, driven not least by demand from hot countries such as India. This single trend has already had, and increasingly will have significant consequences around the world, driving up carbon emissions, energy insecurity and triggering blackouts. Mechanically cooled buildings are typically designed using international comfort standards, like ASHRAE 55, that mandate a static indoor environment (typically 23 ± 2°C) leading to unnecessarily high energy use. The impacts of a more flexible approach to comfort are considered here, involving a more active role for occupants. This flexible approach is described, and tested, using a simulation-based case study of a typical residential apartment in India. Compared to a fixed setpoint of 24°C, the flexible comfort approach results in reduced peak load and total cooling demand by 20% and 41%, respectively, at the cost of slightly elevated discomfort (average 12% PPD). The study demonstrates how this flexible comfort approach can be both thermally comfortable and more energy-efficient in mechanically cooled buildings, under extreme summer conditions. Finally, ways in which comfort in buildings might evolve are discussed, regarding changes in climate, work practices, cities, energy and transport.