Do electric rooflights have rain sensors?

The part doing the work is a small pad mounted on the top of the frame, wired to the motor. Its surface is divided into two interlaced electrical tracks with a tiny gap between them. Dry, that gap does not conduct. The moment a raindrop bridges it, a trickle of current flows, the control board registers a contact, and it sends the close command to the actuator. There is no camera, no forecast and no guesswork. It is reacting to water landing on the roof, which is why it triggers within a second or two of the first drops rather than waiting for a downpour.

Because it is a contact sensor and not a moisture gauge, it also fires on things that are not strictly rain. Heavy dew, wet fog rolling in off the estuary, or a garden sprinkler catching the roof will all close the unit. That is the sensor doing its job rather than a fault. Once the pad dries out the contact breaks, though the rooflight does not reopen by itself. You reopen it deliberately, from the switch or the remote, which is the behaviour you want: the last thing you need is a rooflight swinging open again the second a shower passes while you are out.

It depends on how the unit is powered, and this is where the specification sheet matters more than the brochure headline.

• Mains-wired opening rooflights. These almost always ship with a rain sensor as part of the standard package. The motor is already drawing on a fused spur, so adding a sensor draws nothing extra and there is no reason for the manufacturer to leave it out.
• Solar-powered opening rooflights. The kind that run off a small photovoltaic cell and an internal battery, so they need no cabling. A rain sensor is standard on most of these too, and it is one of the main reasons people choose them, because the whole appeal is a rooflight that manages itself.
• Electric conversion kits on a manual rooflight. If you are motorising an existing manual unit with a bolt-on chain or spindle actuator, the rain sensor is a separate item you have to specify and pair. It is not automatically there just because there is now a motor.

So the honest answer to “does it have one” is: a bought-as-electric opening rooflight almost certainly does, a motorised manual one only has it if someone asked for it. When you get a quote, ask for the sensor to be named on the specification rather than assumed. “Electric opening” describes the motor, not the sensor.

The reason you open a rooflight in the first place is usually heat, not stuffiness. Southend faces south across the Thames Estuary, so the rear extensions and loft rooms that end up with opening rooflights are often the ones that run hottest through the afternoon. An opening unit at the highest point of the room lets the built-up warm air escape, which is the single most effective thing you can do once the sun is already on the glass. That is ventilation working with the physics rather than against it, and it sits alongside the glass specification as part of how we handle solar gain and overheating.

The problem with relying on that in south Essex is the weather turning fast. A bright, hot afternoon on the seafront can become a sharp shower in ten minutes. Without a rain sensor you either sit under the rooflight all day ready to close it, or you leave it shut and lose the ventilation you fitted it for. The sensor removes that trade-off. You open it on a warm morning, go to work, and it looks after itself if the weather changes. On a deep south-facing kitchen or a top-floor bedroom that bakes in summer, that is the difference between a rooflight you use and one you leave closed. If overheating is the actual issue, though, the sensor is only half the answer, because ventilation shifts warm air but it does not stop the sun getting in. The glass specification does that, and it is worth reading how a low G-value and an opening unit work together on our electric skylight installation page.

It is worth being clear about the limits, because a rain sensor is sometimes sold as if it solves everything.

It closes the rooflight, but it does not compress the seal to storm-proof it in high wind. A driven rain on a gusty estuary day can still push a little moisture at the gasket in the seconds before the unit is fully home, which is normal and not a defect. It also does nothing about wind loading itself. Many quality units pair the rain sensor with a separate wind sensor or an anemometer input so the rooflight also closes in a gale, but that is an additional function and you should check whether it is included rather than assume the two come together.

It will not reopen the rooflight for you. That is by design. And it is not a substitute for closing the unit properly before you go away for a week, because a flat battery on a solar unit or a tripped spur on a mains one means the automation is not watching. Treat it as a safety net for everyday use, not a reason to leave a rooflight open indefinitely.

On a factory electric unit the sensor is plug-and-play. It comes paired to the control board, and beyond siting the wall switch and, on a mains unit, running the fused spur, there is nothing for you to configure. The sensitivity is set at the factory to a level that catches real rain without firing on the lightest passing drizzle, and on most units it is not user-adjustable, which is fine because the default is well judged.

Where there is a decision to make, it is about integration. Many electric rooflights now speak to a home automation hub, so the rain-sensor close can sit alongside a timed morning vent, a room thermostat trigger, or a single button that closes every opening in the house at once. If you want that, it needs specifying at the point of order because it can change which control module goes in. Retro-fitting smart control to a basic wired unit later is possible but more work than choosing it up front. The wiring for a mains opening rooflight is a fused connection that a qualified electrician signs off, and the rest of the installation, the upstand, the flashing and the weathering, is the same careful job as any non-opening rooflight.

If you are choosing an electric rooflight, ask three questions of whoever is quoting: is the rain sensor named on the specification, is there a wind sensor as well, and is the unit mains-powered or solar. Those three answers tell you what the rooflight will actually do when the weather turns while you are out. If you are motorising an existing manual unit, ask specifically for a rain sensor to be added, because it will not be there otherwise.

If you would rather we worked it out with you, tell us which way the roof faces, whether the room runs hot in summer, and roughly how big the opening is, and we will come back with a unit, a glass specification and a price. Ring 01702 898232 or request a quote, and have a look at how the opening and the glass work together on our energy-efficient skylight installation page while you are deciding.