Center for the Built Environment

In this study, we present the results of a post-occupancy assessment on thermal comfort, indoor air quality, and acoustical quality from 568 occupant surveys in eight LEED-certified buildings with radiant heating and cooling systems, and trends in low-energy consuming buildings based on building characteristics, radiant design, and building operator interviews. This study follows-up on a quantitative assessment of 60 office buildings that found radiant and all-air buildings have equal satisfaction with indoor environmental quality, with a tendency for increased thermal satisfaction in radiant buildings. Our objective was to investigate reasons of comfort and discomfort in the radiant subset, and to relate these to building characteristics and operations strategies. Our analysis revealed that the primary sources of temperature dissatisfaction are lack of control over the thermal environment (both temperature and air movement) and slow system response, both of which were seen to be alleviated with fast-response adaptive opportunities such as operable windows and personal fans. There was no optimal radiant design or operation that maximized thermal comfort, and building operators were pleased with reduced repair and maintenance associated with radiant systems compared to all-air systems. Occupants reported low satisfaction with acoustics. This was primarily due to sound privacy issues in open offices which may be exacerbated by highly reflective surfaces common in radiant spaces. Indoor air quality satisfaction appears to be aligned with thermal comfort more than ventilation strategy, and buildings with low annual energy consumption take advantage of free cooling and avoid heating and cooling in the same day or same season.