Technology
Automating shading: blinds that follow the sun
Awnings, venetian blinds and roller shutters with a weather station and sun tracking: how the house stays cool in summer, safe in wind, and what can be retrofitted to existing motors.
Blinds operated by hand are usually in the wrong position: down too long in the morning, too late in the afternoon, not up at all in a storm. Automatic shading is the function our customers would least like to do without after a year.
What automatic shading needs
Three things: motors controlled by the smart home, a weather station on the roof or façade, and logic that connects the two. The weather station measures wind, brightness from several directions, rain and outside temperature; good devices additionally calculate the sun's position from date, time and location.
Awnings, venetian blinds, roller shutters: not the same thing
- Fabric awnings protect from sun but are wind-sensitive and retract first.
- Venetian blinds can be controlled in height and slat angle – the best choice for sun tracking, because daylight comes in while direct radiation stays out.
- Roller shutters close tightly, darken and insulate a little. Ideal for night and bedrooms, too coarse for daytime control.
Sun tracking
The controller knows the sun's azimuth and elevation and how each façade is oriented. If the sun hits a window and brightness exceeds a threshold – around 30,000 lux for the south side – the blind on that side comes down. With venetian blinds, the controller sets the slat angle so that direct radiation is just blocked while daylight gets through. As the sun moves on, the angle changes with it; after ten to twenty minutes without sun, everything goes back up. These delays matter, otherwise the system hunts with every cloud.
Summer heat protection
Through an unshaded south window, several hundred watts per square metre of glass enter the house on a clear summer day. External shading keeps most of that out; an internal curtain only a fraction, because the heat is already in the room. If the indoor temperature is taken into account, the house only shades in spring once it gets warmer than about 23 degrees inside – in winter the sun is allowed to heat.
Safety in wind
The most important rule: the wind alarm takes priority over everything. If the wind speed exceeds the value stated by the blind manufacturer – with fabric awnings often as low as 30 to 40 km/h – the blinds go up and stay up until the wind has dropped for several minutes. During that time manual commands are locked. In frost, the same applies to roller shutters, which would otherwise freeze solid.
Interplay with heating and cooling
Shading is part of the climate concept. In winter the south side stays open in sunshine and saves heating energy; in summer it closes so that cooling – often the heat pump in cooling mode – has less to do. That only works if shading, heating and room sensors are in the same system.
Retrofitting existing motors
Motors with a 230-volt connection can almost always be integrated: a blind actuator in the distribution board or a flush-mounted module behind the switch takes over control, and the old switch remains as a button. Somfy radio motors (RTS, io-homecontrol) are connected via a bridge. A weather station can be retrofitted as long as a cable or radio link to the roof is possible.
Conclusion
Automatic shading is unspectacular until the first hot summer comes. It needs a weather station, logic with delays and a wind lock nobody can bypass. We plan it together with your blind installer and electrician and explain how venetian blinds follow the sun.
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