Use of Adaptive Comfort Degree-Days to Compare Energy Savings

CIBSE Technical Symposium, DeMontfort University, Leicester UK
6th and 7th September 2011

The emerging realisation of the dual challenges posed by climate change and energy security has renewed interest in adaptive comfort as a means of achieving thermal comfort at little or no cost in terms of energy expenditure, through the displacement of mechanical systems. Designers and energy managers in the UK have a choice of two adaptive standards, the European adaptive standard EN15251 and the ASHRAE adaptive standard 55, but there is little guidance available to help them make their selection. This paper uses a novel metric, the Adaptive Comfort Degree-Day, to help
inform the decision-making process by comparing the rate at which energy savings can be achieved by each of the two for high and low emissions scenarios for London, Manchester and Edinburgh over the course of the century. The energy savings deriving from implementation of counterpart European adaptive standard EN15251 (Category II) are compared with those from its ASHRAE adaptive standard 55 (80% acceptability), the upper limits of the thermal comfort zone of which latter standard are approximately 0.8-1.0ºC higher than those of the ASHRAE adaptive standard.
The results indicate that the potential energy savings returned by the European adaptive standard accrue at a significantly faster rate in consequence of its wider applicability: the additional buildings allowed to avail of the Adaptive Comfort Model
in view of the more easily achieved compliance may return levels of savings in the 2020s which an ASHRAE adaptive standard-compliant building could not achieve until the 2080s or later.