Ventilation requirements and demand controlled ventilation.

In order to avoid demage to the health of occupants, annoyance or reduction in amenity and demage to the building fabric the concentration of indoor air pollutants has to be held below pollutant specific levels. One appropriate measure for the control of concentration is ventilation. In several national and international activities in the past, among others in the IEA's Annex IX "Minimum Ventilation Rates" and standardization efforts in Germany and other countries, ventilation rates have been defined which should meet both indoor air quality (iaq) requirements and energy conservation. The necessary air flow rates are, depending on the type of pollutant and national conditions, usually based on an average occupancy of persons in the room; they vary in a range of 30-40 m3/h and person. For comfort reasons the minimum ventilation rate necessary to maintain acceptable indoor air quality (iaq) depends on many influencing factors especially on the number of persons, seasons, time of the day etc.. Ventilation rates exceeding the real and actual demand are not energy economic. A general view of iaq requirements is given. Natural ventilation systems are compared to the requirements of the proposed ventilation strategy. A state of the art is given for the use of simple ventilation devices. For conditions in the Federal Republic of Germany the arguments and the advantages for a ventilation strategy consisting of a basic ventilation for non-occupied rooms with an additional rate depending on the number of persons and their activity are outlined. Dominant influence factors for both basic ventilation and additional ventilation are pointed out.