Ventilation number

A room’s overall air volume flow can also be determined as a first approximation by using the ventilation rates. This in particular is “only” permissible in ventilation systems who do not require any particular air conditioning regarding humidity and temperature and air replacement is mostly covered by a sufficient outdoor air rate.

The ventilation rate specifies how many times per hour the room volume is turned over (replaced). According to room use and the desire for air replacement, the ventilation rate varies (table).

Example
A double-axis office with a floor space of 26 m2 and a room height of 2.8 m has a room volume of 72.8 m3. The ventilation rate (see table) is selected as z = 5. This means an hourly air volume of 364 m3 to be turned over. Divided by 4 luminaires (equipped with 1 x 58 W fluorescent lamps each for an average working area illuminance of ca. 500 lx), the air volume flow per luminaire is 91 m3/h. The outdoor air rate with two persons in the room is 80 m3/h, i.e. the outdoor air portion is ca. 22%.