【正文】 e the same position of air at an elevated temperature and humidity is perceived as stale and stuffy. During inhalation it is the convective and evaporative cooling of the mucous membrane in the nose that is essential for the fresh and pleasant sensation. Warm and humid air is perceived as being stale and stuffy due to the lack of nasal cooling. This may be interpreted as a local warm disfort in the nasal cavity. The PMV model is the basis for existing thermal fort standards. It is quite flexible and allows for the determination of a wide range of air temperatures and humidities that result in thermal neutrality for the body as a whole. But the inhaled air would be perceived as being very different within this wide range of air temperatures and humidities. An example: light clothing and an elevated air velocity or cooled ceiling, an air temperature of 28186。C and a modest air humidity. Moderate air temperature and humidity decrease also SBS symptoms and the ventilation requirement, thus saving energy during the heating season. And even with airconditioning it may be beneficial and save energy during the cooling season.PMV model and the adaptive modelThe PMV model is based on extensive American and European experiments involving over a thousand subjects exposed to wellcontrolled environments. The studies showed that the thermal sensation is closely related to the thermal load on the effector mechanisms of the human thermoregulatory system. The PMV model predicts the thermal sensation as a function of activity, clothing and the four classical thermal environmental parameters. The advantage of this is that it is a flexible tool that includes all the major variables influencing thermal sensation. It quantifies the absolute and relative impact of these six factors and can therefore be used in indoor environments with widely differing HVAC systems as well as for different activities and different clothing habits. The PMV model has been validated in climate chamber studies in Asia as well as in the field, most recently in ASHRAE’s worldwide research in buildings with HVAC systems that were situated in cold, temperate and warm climates and were studied during both summer and winter. The PMV is developed for steadystate conditions but it has been shown to apply with good approximation at the relatively slow fluctuations of the environmental parameters typically occurring indoors. Immediately after an upward stepwise change of temperature, the PMV model predicts well the thermal sensation, while it takes around 20 min at temperature downsteps .Field studies in warm climates in buildings without airconditioning have shown, however, that the PMV model predicts a warmer thermal sensation than the occupants actually feel. For such nonairconditioned buildings an adaptive model has been proposed. This model is a regression equation that relates the neutral temperature indoors to the monthly average temperature outdoors. The only variable is thus the average outdoor temperature, which at its highest may have an indirect impact on the human heat balance. An obvious weakness of the adaptive model is that it does not include human clothing or activity or the four classical thermal parameters that have a wellknown impact on the human heat balance and therefore on the thermal sensation. Although the adaptive model predicts the thermal sensation quite well for nonairconditioned buildings of the 1900’s located in warm parts of the world, the question remains as to how well it would suit buildings of new types in the future where the occupants have a different clothing behaviour and a different activity pattern.Why then does the PMV model seem to overestimate the sensation of warmth in nonairconditioned buildings in warm climates? There is general agreement that physiological acclimatization does not play a role. One suggested explanation is that openable windows in naturally ventilated buildings should provide a higher level of personal control than in airconditioned buildings. We do not believe that this is true in warm climates. Although an openable window sometimes may provide some control of air temperature and air movement, this applies only to the persons who work close to a window. What happens to persons in the office who work far away from the window? We believe that in warm climates airconditioning with proper thermostatic control in each space provides a better perceived control than openable windows.Another factor suggested as an explanation to the difference is the expectations of the occupants. We think this is the right factor to explain why the PMV overestimates the thermal sensation of occupants in nonairconditioned buildings in warm climates. These occupants are typically people who have been