In order to effectively protect sun shading systems from excessive wind load, it must first be clarified how strongly the wind attacks on different facades. Naturally, this will be more the case at exposed
corners than in the middle of the façade. Inner courtyards are usually relatively protected as long as there are no large driveways or partially elevated storeys allow the wind to enter. By grouping areas of similar loads on the façade areas the respective zones are created. In this way, the actual wind control can be targeted to these areas.

Afterwards, the wind analysis and the associated zoning become part of a control concept for the sun shading systems. This concept also addresses other questions, such as the appropriate positioning of the sensors for decentralized or centralized control. If it is not yet clear whether centralized or decentralized control, the concept can also compare the effects of both possibilities.

Do you have questions? Please do not hesitate to contact us, because unfortunately there are still no standards or guidelines for these control concepts, and the state of the art is viewed very differently by different market participants.

The decentralized wind control of sun shading blinds is initially always based on a suitable zoning of the façade areas that are more or less exposed to the wind, see above. It may also be necessary to subdivide areas with different curtain qualities. The philosophy of a decentralized control system is to record the wind speed on the façade at one or two representative measuring points in each blind zone, which corresponds directly to the wind load on the blinds. If the local measured value is compared with the warranty limit value specified by the manufacturer, a decision can be made immediately as to whether or not the local blind zone needs to be raised.

Decentralized wind control is technically simpler than centralized wind control and decentralized wind measurement does not require any assumptions about the local wind field in the surrounding area, as measurements are taken directly in the area of the hangings. Subsequent changes due to the demolition or construction of additional buildings are also easily recorded at any time and do not require any reworking. The disadvantage is the larger number of (albeit simpler) sensors, which also have to be connected to the façades and, in case of doubt, maintained.

The central wind control of sun shading systems is a classic that many building practitioners have in mind and can also be implemented at a later date. The measurement is usually carried out centrally on the highest roof according to wind speed and wind direction. However, as the wind sensors must be exposed to a free flow, at least two measurement locations are usually selected, e.g. in opposite corners of a roof. At least one half-space of the wind flow can be measured near the corner without the need for a measuring mast that is too high. The measured values from both masts are then combined in the control system and evaluated together.

This evaluation can be carried out on a central computer, which then stores the exposure to the wind for all blind zones (see zoning) for each wind direction and can decide whether the local measured values at the sensor represent an exceedance of the warranty limits or not! Commands are then sent to the shading groups for raising or lowering from this central point via the building bus. Alternatively, more intelligent local actuators can also be used, which read the measured values on the roof via the bus and then decide locally for their curtain group whether it needs to be raised or not. For this functionality, the previously determined correction factors (also known as speed-up factors) are offset against the manufacturer's warranty limit values for their blinds, so that only one corrected limit value needs to be stored in the local actuator, which can then be compared directly with the measured value for the respective wind direction.

Central sun shading control systems can be set up very efficiently today thanks to combined sensors (e.g. based on ultrasound), but require additional effort in planning and implementation to determine the conversion from roof measurement to façade exposure per wind direction. This would also actually have to be adapted if the structural environment changes. If a wind tunnel test is already available for a building project, its results can easily be transferred to the conversion. If not, we will be happy to provide you with an expert opinion on the factors!