Project Title:

Adaptive Comfort Model

Studying the differences between thermal comfort in naturally ventilated and sealed air-conditioned buildings, with the aim of developing a new comfort zone for ASHRAE Standard 55.

Status (updated 08/01/2013): Complete

Funding sources: ASHRAE 884-RP


Project Objective

Examine the applicability of Fangerís Predicted Mean Vote (PMV) model in naturally ventilated buildings, and develop an adaptive comfort model based on world-wide field data.

Significance to Industry

It is very difficult for a naturally ventilated building to stay within the narrow comfort range prescribed by ASHRAE 55, which is based on controlled settings in laboratory conditions that are not representative of many environments in real buildings, especially those with operable windows. If a different comfort model is more applicable to these buildings, designers would have greater flexibility to design buildings with operable windows that could both enhance comfort and reduce energy use.

Research Approach

This research was based on analysis of 21,000 sets of data compiled from thermal comfort field studies conducted in 160 buildings located on four continents in varied climate zones. Detailed physical measurements, along with responses to questions about thermal sensation, acceptability, and preference were analyzed to determine the relationship between optimum indoor temperature and outdoor temperature.

In sealed, mechanically cooled buildings, optimum indoor temperature tracks outdoor temperature very slightly, but this can be explained purely by the clothing level variable in the lab-based PMV model. In naturally ventilated buildings, optimum indoor temperature is more strongly dependent on outdoor temperature. People accept and even prefer a wider range of temperatures than can be explained by the PMV model. This difference is explained by psychological and behavioral adaptation.

The results of this research form the basis of the Adaptive Comfort model that was adopted in the 2004 version of the ASHRAE thermal comfort standards.

Publications and Reports

Brager, G., and R.J. de Dear, 2000. A Standard for Natural Ventilation. ASHRAE Journal, October.

Brager, G.S., and R.J. de Dear, 2001. Climate, Comfort & Natural Ventilation: A new adaptive comfort standard for ASHRAE Standard 55. Proceedings, Moving Thermal Comfort Standards into the 21st Century, Windsor, UK, April 2001.

de Dear, R. and G. Brager, 1998. Developing an adaptive model of thermal comfort and preference. ASHRAE Transactions, 104 (1): 145-167.

de Dear, R. and G. Brager, 2001. The adaptive model of thermal and energy conservation in the built environment. International Journal of Biometeorology, 45 (2): 100-108.

de Dear, R. and G. Brager, 2002. Thermal comfort in naturally ventilated buildings. Energy and Buildings, 34: 549-561.

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Chart of comfort temperature for PMV and adpative models

Comparison of comfort temperature in naturally ventilated and sealed buildings.

Chart of adaptive comfort model

Comfortable temperature ranges in naturally ventilated buildings.