Using task ambient system to improve comfort and productivity in office buildings

Ventilation and thermal conditions inside a building are among the primary factors determining human health, comfort and well-being. They cause different effects on the human body through the physiological effect of air purity and motion, and indirect effect through their influence on the temperature and humidity. Uniform, stable and neutral indoor thermal environments are the purposes of heating, ventilating, and air-conditioning (HVAC) systems. The aim is to assure neutral sensation in order to achieve thermal comfort for the occupants. In the last six decades many researches have demonstrated how the thermal environment and the air quality in buildings affect occupants'health, comfort and productivity. As well known thermal dissatisfaction is the major complaint in office buildings, mainly caused by local discomfort. Building occupants are a rich source of information about indoor environmental quality, its effect on comfort and productivity as confirmed by the results of a survey developed by the Center for the Built Environment at the University of California, Berkeley. [Zagreus L. , 2004] The result of this survey confirmed how the almost homogenous environment does not take into account individual preferences in terms of air temperatures, movement and thermal sensation. Cool hands and feet, and warm head discomforts are common complaints in office environments. These localized discomforts of the extremities dictate the overall thermal comfort felt by the occupant, and removing discomfort in these body parts is essential in maintaining whole body thermal comfort. The extremities are vulnerable to discomfort in part because they are uninsulated or relatively uninsulated. However the low clothing levels make it possible to locally heat or cool the extremities in an energy-efficient manner, thereby restoring comfort. The air that reaches the occupant's breathing zone may be of poor quality because has already been mixed with the room air, gaining heat and humidity and being polluted due to emissions of building materials and the occupants themselves. Recent evidence from laboratory researches suggested that diversified environments could produce higher levels of thermal comfort than is possible for the best-controlled neutral and uniform environments. [Zhang, H., 2003] Personalized Ventilation System (PVS) is a development of the HVAC system that has the potential to improve occupants' comfort with the possibility of generating and controlling their own preferred microenvironment, decrease Sick Building Syndrome (SBS) symptoms and reduce the risk of transmission of contagious agents between occupants. PVS systems aim to avoid the undesirable effects of the traditional HVAC system by supplying treated outdoor air directly to the breathing zone of each occupant. In order to perform efficiently in room practice, the design of PVS should take into consideration the occupants' activity and the airflow interaction with the thermal plume around the human body. [Melikov A. K. , 2004] The use of PVS systems could allow a large range of environmental temperature by introducing local cooling/heating asymmetries. In this way the energy needed for ambient conditioning could be optimized while the individual is empowered to adjust the immediate environment to his or her personal preferences. The purpose of this study was to evaluate whether it is possible to provide comfort to the occupants by PVS in cool and warm environments, and whether the productivity of people is enhanced. We also compared the efficiency of PVS vs. traditional HVAC system by the use of different computational tools