Center for the Built Environment

This paper describes the logic of a microprocessor-controlled thermostat termed 'comfortstat' to address the needs of temporary room occupants such as hotel guests while reducing energy consumption. The 'comfortstat' design grew out of a study of thermal control in a luxury hotel in San Francisco, California, USA. Hotel guests frequently arrive from widely disparate climates and have high expectation so of the thermal environment. Their short-term occupancy (for periods ranging from one day to several weeks) provides a unique challenge for thermal comfort control. We examined the hotel complaint log, collected detailed physical measurements of the thermal environment in typical hotel rooms, assessed the HVAC (heating, venting and air-conditioning) system capacity and response time, and surveyed 315 hotel guests over a five-month period. The results of this study led to the design of a thermostat control system (the 'thermostat') what would solve the most serious problems. The 'comfortstat' integrates an infrared occupancy sensor, door switch, radiant temperature sensor, and control logical to optimize room conditions while 'learning' about the occupant's preferred comfort zone. This paper focuses on how the joint requirements of the guests and the hotel management guided the design of the 'comfortstat' for increased occupant satisfaction and lower energy use in the hotel. The concepts are completely generic and could be applied to the design of comfort systems for other types of short term occupancy. We present control logic flowcharts and typical examples of hotel 'comfortstat' in response to data received from the physical environment and/or human input.