Fan-in-wall for hybrid ventilation in a hot climate.

'Fan in wall' is a new ventilation system under investigation for hot and humid climate to assist natural ventilation. Temperature, relative humidity, air velocity, and thermal radiation affect thermal comfort of a person in hot climate. Installation of an air conditioner reduces air temperature and relative humidity to reach a certain level of thermal comfort. Under favourable conditions, increasing air velocity at unchanged temperature and humidity can result in the same perception of thermal comfort. We want to compare the required energy to obtain the same thermal comfort, first, by increasing air velocity and second by lowering temperature and relative humidity. The 'Fan in wall' system provides cooling by increasing air velocity in the occupied zone. In that respect, its action is similar to that of a ceiling fan. The main difference is that outdoor air is forced to flow through the living space. The resulting air change rate is much higher than what is needed for maintaining indoor air quality. The advantage is that even small temperature differences between indoors and outdoors can be used for cooling. At 29 Deg. C outside temperature, the room temperature can be reduced from 34 Deg. C to perhaps 30 Deg. C, depending on cooling load and wall temperatures, if the air change rate is high enough. In addition, this temperature may be perceived as comfortable at a high air speed. The occupant can turn on the electric fan to increase air motion if natural ventilation alone is insufficient. The combination of natural and mechanical is called hybrid ventilation. This is a progress report on an ongoing project that addresses questions of airborne dust, control, night cooling and interaction of several ventilated units facing the same ventilation shaft.