Noise, speed and how an electric rooflight feels to use

The sound an electric rooflight makes is a low geared whirr, not a bang. Most opening actuators sold for domestic rooflights sit somewhere between 40 and 52 decibels measured a metre from the unit while the motor is driving. For reference, a quiet suburban bedroom at night is around 30 dB, ordinary conversation is about 60, and a fridge compressor cycling on is roughly 45. So a well made rooflight actuator running is quieter than two people talking and about level with your kitchen fridge, for the thirty to sixty seconds it takes to complete its travel.

Where the noise comes from matters more than the headline figure. A cheap actuator makes a harsher, higher pitched sound because the gear train is running dry or the plastic housing resonates against the frame. A better one is geared down further, runs on a metal worm drive with grease that stays put, and the pitch drops to something you stop noticing after the first week. The other source is the seal breaking. A rooflight is compressed hard against a weather gasket when it is shut, and the first second of opening is the motor peeling the sash off that seal. You hear a brief rise in load, then it settles. That initial tug is normal and is not the mechanism struggling.

Ceiling height changes the experience completely. On a standard 2.4 metre kitchen ceiling the motor is close to your head and you hear every part of the cycle. Put the same unit in a loft conversion with a 3 metre pitch, or over a double-height stairwell in one of the taller Edwardian villas along the cliff, and the same 46 dB is a distant murmur you register only if the room is otherwise silent. The higher the aperture, the less the motor noise counts, which is one of several reasons electric units belong on ceilings you could never reach with a pole anyway.

Rooflight actuators are not fast, and that is deliberate. A fast motor would slam the glass and hammer the hinges, so the mechanism is geared for a slow, even travel that eases to a stop at both ends. Two things set the timing: how far the sash has to move, called the stroke or throw, and how quickly the actuator extends, its travel speed. Chain actuators, the most common type on domestic rooflights, extend at roughly 5 to 9 millimetres per second. Spindle and rack actuators, used on heavier and commercial units, tend to run a little faster but carry more load.

The table below gives typical figures for the size and type of unit you would actually meet on a house. Treat them as the shape of the market rather than a firm promise, because every manufacturer gears their motors slightly differently.

Half a minute to a minute is the honest answer for most homes. That sounds slow written down, and it is exactly right in use. You press the button on your way to fill the kettle and the room is venting by the time the kettle boils. The one moment the speed registers is the rain close, and that is why the good units close faster than they open, or trigger the close the instant a sensor is wet rather than waiting for you to notice the weather.

The rain sensor is the feature that changes an electric rooflight from a convenience into something you trust enough to leave open when you go out. A small sensor pad sits on the outside of the frame or on the roof beside the unit. The moment it detects moisture it sends the motor to shut, no matter what the handset last told it to do. From the first drops to a closed and sealed rooflight is usually a handful of seconds plus the travel time, so a unit that was fully open closes in under a minute, and one that was on a small night vent closes almost instantly.

A few things about sensors are worth knowing before you rely on one. They react to moisture, not to rain specifically, so heavy dew or a garden sprinkler can trip them, which is a mild annoyance rather than a fault. They shut the rooflight but they do not reopen it, by design, because you do not want a ceiling flapping open the moment the shower passes and the pad dries. Reopening is a decision you make. And the sensor needs an occasional wipe, because a build up of grime or leaf debris on the pad can make it either over sensitive or slow to react. On the exposed roofs along the estuary front, where salt and grit ride in on the wind, that wipe matters more than it would inland.

For anyone who leaves an opening rooflight venting through the day, the rain sensor is the difference between coming home to a fresh room and coming home to a wet carpet. It is close to essential on any unit you cannot see from where you work.

How a rooflight feels to use is mostly about how you tell it what to do, and there are three common ways, often fitted together.

The handheld remote

The handset is the default. Open, close, and usually a stop button so you can hold the rooflight at a part vent rather than fully open. Most run on a radio frequency rather than infrared, so you do not have to point it at the ceiling, and one handset can drive several units on separate channels. The obvious weakness is that a handset gets lost. If it is the only control, a flat battery or a misplaced remote means a rooflight stuck in whatever position it was last in. That is the argument for never relying on the handset alone.

The wall switch

A hardwired or wireless wall switch, fitted at the same height as your light switches, is the control that gets used most in practice because it is always in the same place. For a kitchen or a bathroom this is usually the one that earns its keep. It costs little to add at the wiring stage and it removes the hunt for the handset entirely. Wiring it in while the walls are still open, before the plaster goes on, is far tidier than adding it later.

The app and home automation

Newer units link to a hub that puts the rooflight on your phone and into a smart home system. That brings scheduling, so the roof can vent at set times, and it lets a rooflight join a rule with the heating or a room thermostat. It is genuinely useful for a unit you cannot reach and for anyone who wants the ceiling to open on a warm morning without being asked. It also adds a layer that can drop off the network and want reconnecting, so it is best thought of as a bonus on top of a physical switch, not a replacement for one. A rooflight should still open from a switch on the wall when the broadband is down.

The actuator hidden in the frame is the single biggest influence on how the whole thing feels, and there are two families of them.

A chain actuator pushes out a stiff, articulated chain that stays rigid in one direction, like a bicycle chain that can only bend one way. It is compact, it tucks neatly into a slim rooflight frame, and it is quiet. It is the right answer for the great majority of domestic flat rooflights and it is what most opening units in a house will have. Its limit is load and stroke: it is happiest on light to medium sashes with a modest opening.

A spindle or rack actuator drives a threaded rod or a toothed rack in and out, and it is stronger. It is what you want under a large glass roof lantern, a heavy double glazed sash, or a commercial vent that has to shift real weight against wind pressure. It tends to be a touch louder and it takes up more room in the frame, but it will hold a big sash steady in a gust where a chain would be working at its limit. On a large lantern over a south-facing kitchen extension, the sort of run of glass south Essex has an enormous stock of, the opening vent is usually spindle driven for exactly this reason.

Neither is better in the abstract. The mechanism should be matched to the weight and size of the glass and to the exposure of the roof, which on the seafront and the cliff top is not a small consideration. Getting that match right is part of specifying an electric skylight installation properly rather than fitting a motor to whatever unit was cheapest.

The motor runs for under a minute a few times a day. The glass sits over your head all year, and its own acoustic behaviour is a bigger part of how the rooflight feels than the actuator ever is. Two sounds dominate.

The first is rain drumming on the pane. A rooflight faces the sky, so it takes the full vertical fall of a downpour in a way no wall window does, and on a still night a hard shower on a large single glazed or thin flat rooflight can be loud enough to wake a light sleeper. Double glazing with a laminated inner pane, which overhead glass needs anyway under the safety rules, damps this noticeably because the laminate interlayer deadens vibration. If a bedroom rooflight sits under a south-facing loft slope in one of the terraces along the cliff, and the room is used for sleeping, the acoustic laminate is worth specifying for the rain as much as for the safety.

The second is wind. A rooflight that is fitted well is silent in wind. A rooflight that whistles or rattles in a blow is telling you something is loose: a worn gasket, a sash not pulling down evenly onto its seal, or a trim that was never fastened properly. A correctly compressed weather seal is what keeps a closed electric rooflight quiet when the estuary throws weather at it, and it is one of the things a proper installation gets right at the frame before the glass ever goes in.

An electric rooflight is not simply a manual one with a motor bolted on for the sake of it. It answers specific situations, and several of them are common across this stretch of coast.

The clearest case is height. Any rooflight over a stairwell, a double-height space or a tall loft pitch is out of reach of a winding pole, and an electric opener is the only sensible way to vent it. The taller Victorian and Edwardian villas along the seafront and around Clifftown throw up this problem constantly, with rooflights three or four metres above the floor that would otherwise never open.

The second case is heat, and this is where the aspect of the place does the deciding. Warm air stratifies and collects at the top of a room, so the hottest air in the house sits right under the ceiling, exactly where a rooflight is. An opening rooflight at the high point of a room dumps that trapped heat far faster than any window at head height, because it lets the hot layer escape upwards instead of trying to push it sideways. On a south-facing rear extension collecting sun off an open estuary horizon all afternoon, that upward vent is the mechanism that keeps the room usable in July.

But the opening only manages the heat that is already in the room. It does nothing about the heat still arriving through the glass, and on a south plane that flow is large. The vent and the glass are two separate jobs. The G-value of the pane controls how much solar energy gets in, and the opener controls how fast the resulting hot air gets out. Specify a low G-value solar-control glass for a south-facing unit and pair it with an electric opener, and you have both halves: less heat coming in, and a fast route for what does arrive to leave. Fit a clear-glazed electric rooflight on a south slope and you have bought a powerful extractor for a problem you could have halved at the glass. The motor is convenience. The glass is the answer. This is the same reasoning that runs through every roof lantern and rear extension we specify, and it starts with which way the roof faces.

Most of what makes an electric rooflight pleasant or irritating to live with can be settled before you order, in a short list of questions.

1. What is the motor noise figure, and where is it measured? A number quoted at one metre is comparable. Anything below about 48 dB is quiet in a normal room. If no figure is offered, that tells you something about the actuator.
2. Chain or spindle, and is it matched to this sash? A chain is fine and quiet on a light to medium unit. A large or heavy sash, or an exposed roof, wants a spindle or rack that will hold it steady in wind.
3. Is a rain sensor included, and does it fail safe? On any unit you cannot watch while you work, a rain sensor is close to essential. Check that a power cut leaves the rooflight closed rather than open.
4. Is there a wall switch, not just a handset? Adding a hardwired switch at the wiring stage is cheap and it is the control you will actually reach for. It removes the lost-handset problem for good.
5. Is the inner pane laminated, and is acoustic laminate an option? Overhead glass needs a laminated inner pane for safety anyway. Over a bedroom, the acoustic version also takes the edge off heavy rain.
6. What is the G-value on a south or west plane? The opener manages heat that is already inside. The glass decides how much arrives. On a sunny aspect, ask for the solar-control figure and the opener together, not one or the other.
7. Who handles the wiring and the Building Control notification? A powered rooflight needs a fused spur run to it, and new or enlarged rooflights are notifiable. We make that notification to Southend-on-Sea City Council, or the relevant local authority for your address, as part of the work.

Get those answered and the rest looks after itself. An electric rooflight that is the right mechanism, quiet, sensor protected and switched from the wall becomes something you use without thinking, which is the whole point of powering it in the first place. If you want it specified properly for your own roof, with the actuator matched to the sash and the glass matched to the aspect, ask us for a specification and we will set out the numbers plane by plane, actuator matched to sash and glass matched to aspect.