Natural ventilation and automation with manual overriding are health solution.

The need for individual control with manual overriding combined with controlled natural ventilation is discussed. It is made plausible that with these two facilities problems related with the Sick Building Syndrome can be avoided. This principle is applied in a so-call led passive climate system. A system is devised setting the level of heating and ventilation by controlling motors fitted to radiators, ventilation openings in windows, Venetian blinds and outside shading. Moreover, it will switch on the lighting when natural lighting is inadequate. The system comprises a weather station on the roof, a network of sensors and controllers in each room hooked up to a control computer. The room controllers can be overridden manually by the occupants. With computer simulations it has been demonstrated that through nocturnal air cooling with opened windows and predictive control a comfortable indoor climate can be realized year round, provided that the internal load lies between 15 and 20 W/m2. Higher loads require additional mechanical cooling. Moreover, it is shown that a proper combination of controlled natural ventilation and mechanical cooling leads to an enormous reduction in energy consumption. It can be reduced to 20% of the amount that is normally required in buildings with closed facades. Moreover, the capacity of the cooling room unit can be reduced with 50%. The ability to remove internal heat and the costs of the passive climate system is compared with that of more conventional systems. It has been shown that the passive system is very promising and that the option with the additional cooling unit is superior to all the other systems.