Predicting the frequency and cost of hot and cold complaints in buildings

When building occupants become sufficiently hot or cold and have exhausted all coping behaviors available to alleviate their discomfort they often com plain to the facility manager. These complaint events trigger maintenance s ervice calls. This paper focuses on predicting the frequency of hot and col d complaint events so that control policies and decisions that affect both energy utilization and comfort-related service calls can be formulated. A m athematical model of the mean frequency of hot and cold complaint events in buildings is developed that is based on the level-crossing theory of stoch astic processes. The model quantitatively relates the statistical behavior and performance of the temperature control system to the mean complaint fre quency. When combined with the labor rate and with estimates of the mean ti me to respond to complaints, the model becomes an estimate of the mean cost of service calls resulting from hot and cold complaints. Data from a comme rcial facility are used to determine parameters of the model. The relations hip between this model and the Predicted Percent Dissatisfied (PPD) model i s discussed. The economic consequences of operating buildings at the limits of the ASHRAE comfort range are illustrated Examples illustrate how the mo del may be used to optimize the operational performance of buildings by bal ancing the energy-saving benefits of uncomfortable conditions with the cost of service calls caused by complaints arising from uncomfortable condition s, and for the cost-benefit analysis of retrofits.