Short answer: Yes, an electric skylight with a rain sensor closes itself when the sensor detects water, whether or not anyone is at home. A skylight rain sensor does nothing on a unit that has no sensor fitted, so it needs to be specified when the unit is ordered. Solar units can carry one too, and a power cut or a flat battery is the case to plan for.
How the sensor knows it is raining
An electric rooflight rain sensor is a small plate or grid on the outside of the roof, wired or linked by radio to the controller. Dry, it sits quietly. When water lands on it, the moisture completes a tiny circuit, and the sensor signals the drive to close.
The plate is usually warmed slightly, so that dew, frost and a fine film of damp do not trigger it falsely and so that it dries soon after the rain stops. It reacts to water on its own surface, which means the first few drops can land before the glass starts moving. That is normal. The aim is to stop a shower becoming a puddle on the floor, not to predict the weather.
Some systems have the sensor built into the unit. Others use a separate sensor fixed nearby on the roof. Either way, it has to be on the roof, in the open, not under an overhang, or it will not see the rain. We position it at survey.
How quickly it closes, and what stays open
Closing takes as long as the glass takes to travel. A chain or spindle actuator moves at a steady, slow speed, so a unit open a hand's breadth closes quickly and one open wide takes a little longer. Read the maker's datasheet for the travel time of your model. That number tells you how long the gap stays open once the first drop lands.
A rooflight that is already open a small way can close almost at once. That is one more reason to use a small opening for ventilation when you are out, and keep the wide opening for when you are in the room.
Some units keep a small ventilation gap when closed, a narrow slot that lets air through while the weather keeps out. These are designed so rain does not enter the gap when the unit is shut. It is a feature of certain models, not all, so check the specification for the unit you are considering rather than assuming.
After closing, a unit does not always reopen by itself when the rain stops. Many controllers wait for you to give the command again. That is the safe default, because a shower can come back, and it is worth knowing before you set the unit to open while you are out.
Power cuts, flat batteries and solar units
A mains-powered unit with no backup stays where it was when the power fails. If it is open, it stays open, and the rain sensor cannot close it. This is the weak point of any electric rooflight, and it is rare. In practice, the answer is to leave the unit closed when you leave the house for a long time, and to ask whether the unit has a battery backup, which some controllers carry.
Ask how the unit can be closed if the power is out. Many electric units have a manual override or an emergency closing method, but the arrangement varies by make and model, so the instructions for yours should be given to you at handover.
A solar rooflight carries its own panel and battery, so a power cut at home does not affect it. What matters is the battery state. After a run of dull days, the battery can be low, and a low battery may not have the strength to close the glass. Some solar units are designed to keep back enough charge to close the glass, so ask whether the model you are considering does. Ask about that when you compare models, and see our comparison of electric, solar or manual opening rooflights for how the drives differ.
- Is a rain sensor included, or an extra?
- Does the controller reopen the glass after rain, or wait?
- Is there a battery backup for a power cut?
- How do you close the unit by hand?
Keeping the sensor working
A rain sensor is simple, and it still needs a little care. Leaves, bird droppings and moss on the plate can block it or make it slow. Wipe the plate clean once in a while, particularly in autumn, when leaves collect on a flat roof, and after a spell of windy weather off the Irish Sea.
You can also test it. With the unit open, dampen the plate with a damp cloth or a splash from a cup, and the glass should start to close. If it does not, check the plate is clean, then the batteries in a wireless sensor, then call us. A test twice a year is enough, and it is worth doing before the first autumn gales.
Ventilation is not a reason to forget the sensor. If you leave a unit open on a warm day to clear a kitchen, the sensor is the safeguard. The ventilation side is explained in opening rooflights for kitchen extension ventilation.
Electric opening rooflights are fitted and replaced by us throughout Merseyside, the Wirral and the nearby areas. Expect a survey first, followed by a fixed quote in writing, with our workmanship guaranteed for 10 years in writing. Browse the models on the Electric and Opening Rooflights page, then request a free quote when one catches your eye.
Rain sensor odds and ends
Will the sensor close the unit during light drizzle?
It will react to enough water on the plate to complete its circuit. Fine mist may not trigger it at once, and steady drizzle will. If you want it more or less sensitive, ask whether the controller allows adjustment.
Can I add a rain sensor to an electric rooflight I already have?
It depends on the make and model, because the sensor must be compatible with the controller. Message us the make and a photograph of the unit on WhatsApp, and we will tell you what can be done.
Does a manual rooflight close in the rain?
No. A manual unit closes only when someone closes it, so it needs a drive and a sensor to do the job without you.