Actimetry for Estimating Occupant Activity Levels in Buildings: A Step Toward Optimal and Energy-Efficient Indoor Conditioning

This article presents an improved approach for assessing occupant thermal comfort and, in turn, more efficient indoor conditioning. The occupant activity level is an important determinant of required comfort conditions and thus building energy use. For nine volunteers, the activity pattern during typical office days was monitored. Detailed profiles of the occupant activity levels were obtained and, using clustering analysis, divided into "Sedentary" and "Active" groups. Although occupants were in their respective Sedentary cluster for 80% or more of the time, the Sedentary cluster was not limited by the currently used metabolic level for estimating sitting at a desk and working. Overall, just 30.7% of the recorded activity levels were less than or equal to the desk-work activity levels. These findings point to the need for revising typical activity rates used in designing indoor conditioning systems and defining control set-points for thermal comfort in offices.