This paper aims to identify major characteristics of hybrid ventilation systems, whereby a clear distinction is made between ventilation for Indoor Air Quality control and ventilation as part of a strategy for control of thermal comfort in summer. The aim is to identify the major differences between the various approaches and to develop some kind of rationale. Various building projects are used as illustration for the classification.
In natural ventilation systems, fresh air is often provided through opening of windows, andthere is a wide range of possibilities with regard to selection of window type and position inthe facade. Different window types have quite different characteristics and thereby differentimpact on the thermal comfort conditions in the occupied zone. The thermal comfort is alsovery dependent on the selected natural ventilation strategy, the outdoor conditions and theavailable pressure difference across the window opening.
Conventional models of building occupants' environmental preferences such as thermal comfort are used to give guidelines for the average environmental conditions that will satisfy large groups of people. The research described in this paper investigates how the preferences of an individual occupant can be modeled to predict their preferred thermal and environmental conditions. A novel, Internet based questionnaire was developed to gather thermal sensation votes.
The paper presents a ventilation comfort chart that has been developed under Thailand climate and using Thai volunteers. 183 male and 105 female college-age subjects were exposed to different thermal conditions in order to investigate the effect of air velocity on thermal comfort in ventilated "non-conditioned" spaces. To this end commercial electric fans were used to control the air velocity near the subjects. The air velocity varied between 0.2 and 3 m/s. Room conditions varied between 26°C and 36°C (D.B.T.) and 50-80% relative humidity.
The vote of acceptance of the thermal conditions of a built space varies with the individual. The design of the space should consider the occupant's thermal comfort therefore the future users' opinion on thermal conditions. People's opinion regarding the acceptance of thermal circumstances of a room can be expressed by several indices the PMV the scale being the most used for this purpose.
In the mid 1990's the 'need' to mechanically air condition school buildings became a political issue in North Queensland. Research suggests that school children are susceptible to heat stress, acclimatisation or cultural factors aside. Cooling strategies are also desirable to protect capital investment in building fabric, resources and electronic equipment. Community expectations suggest that air conditioning in the tropics is a 'necessity' to maintain an acceptable 'standard of living'.
Login