Wind loading on a porous roof

Wind loads on a porous roof are found to be lower than those on a similar non-porous roof because air flows through the porous surface into the internal volume, tending to equalise the mean pressures and attenuating the peak pressures across the roof, both of which can reduce the total wind loading on the roof. The effects of porosity and internal volume on the mean, standard deviation and peak pressures on a porous surface in a pressure field similar to that for a roof or wall of a building have been measured. Reduction factors based on wind loads on a similar non-porous roof have been evaluated so that design wind loads on a porous roof can be estimated from external pressure coefficients given in existing wind loading codes.