Brise Soleil Wind Load Considerations
The wind load is often the factor that is underestimated by external shading fins being structural elements and therefore being part of the main structure of a building.
Site Exposure and Building Height
Design wind pressure is determined by two main factors. The exposure of a site (how open it is to wind) and the reference height of a building (how tall it is). In urban locations with nearby buildings, wind pressure on a building façade is typically less than that experienced at exposed rural or coastal locations.
Uplift Is Usually the Critical Case
While face-on pressure is often the first consideration for wind load, negative pressure creates a suction force pulling fins out and up. This must be taken into account for the fixings and brackets of your external shading solution, and it is crucial that this is clearly distinguished from the lateral force in any structural specification.
Fin Geometry Multiplies the Load
A deeper fin or closer pitched fins create a greater area for wind to blow against the façade. Concentrated loads at bracket points of Brise Soleil systems are a function of fin depth and spacing. A slender fin at wide centres carries a lot less load per bracket than a deep fin at close pitch.
Applicable Standards
Wind loading on elements mounted to external faces of buildings is covered by BS EN 1991-1-4, Wind Actions on Buildings. Information on how to use this code is provided by the Institution of Structural Engineers in structural wind load guidance for façade elements.
What to Give Your Fabricator
Pass the calculated design wind pressure, the governing load case and the required fixing capacity to the fabricator before they start detailing the brackets and fixings. This will ensure that the bracket and fixings are adequately sized and not under-designed through lack of information.
Getting the wind load data right from the start can save a lot of work down the line.