The aerodynamically effective opening area of a smoke and heat exhaust ventilation unit (RWG) is also referred to as AW and is calculated from the geometric opening area Ag of the RWG, e.g. a skylight, and the flow coefficient cv, which reduces the geometric opening area, e.g. by taking into account built-in components of the RWG such as rods and cylinders. So-called wind deflectors, which are attached to the outside of the RWG, can significantly improve the flow coefficient, which can reduce the number of RWGs required. Manufacturers use test certificates to prove the AW values for their products determined in the wind tunnel.
If required by project-related requirements, e.g. by a special building ordinance, an official requirement or a fire protection certificate, the AW value required for smoke extraction for a construction project is calculated according to fire load, e.g. according to DIN 18232.
For smoke extraction in stairwells in accordance with the requirements of the state building code, the dimensioning of the smoke extraction opening is usually not carried out with the aerodynamically effective opening surface, but with the geometric opening surface.
AW = Ag x cV
Unit: m2
Source: bauwion
