Architectural louvres, fins and sun-screens

BS EN 13030 tests a louvre with 13 m/s wind and 75 l/h/m2 of water while air is drawn through at face velocities from 0 to 3.5 m/s. Rain penetration is graded from A (best) to D at each velocity, and airflow by a discharge loss coefficient class. A plant-room louvre feeding air handling units needs a class suited to its design face velocity, as well as enough free area.

Geometric free area is the open fraction of the louvre face, often around 50 percent for a standard weather louvre. Two louvres with the same free area can pass very different airflow, so compare aerodynamic free area. The mechanical engineer specifies the airflow and allowable pressure drop, and the blade is selected to suit.

Yes. Fins and blades are cladding elements under AS/NZS 1170.2, with high local pressure factors and, on long blades, vibration and fatigue checks. The structural engineer certifies the brackets back to the slab or sub-frame. On Type A and B buildings the fins fall under C2D10, which lists aluminium among the materials accepted where non-combustibility is required.

Fixed fins are set at the angle the facade engineer's shading study gives. Operable fins rotate on motorised axles controlled by the building management system or sun sensors. They cost more, need maintenance access and a power and control package, and their wind-lock position has to be designed.

External shading cuts solar heat gain through glazing, and Section J calculations credit it. The facade engineer models the fin depth and spacing, and the fins have to be built as modelled.