What is the lifespan of a rooflight motor?

Most opening rooflights are not driven by a bare electric motor. They use an actuator, which is a small geared motor packaged with the part that does the pushing. There are two common types and they wear differently.

A chain actuator uses a stiffened chain that folds away inside a slim housing and pushes straight out to lift the sash. You find these on roof windows and smaller opening lights. A spindle or rack actuator turns a threaded rod or a toothed rack to drive the opening arm, and it is the usual choice on heavy glass, walk-on units and larger lanterns because it shifts more weight. Chain units are compact and quiet. Spindle units are stronger and generally hold up better under a heavy sash, which is the load that grinds gears down over time.

Whichever type you have, the part that actually ages is rarely the copper windings of the motor itself. It is the gearbox, the plastic and brass gears inside it, and the electronics that drive the whole thing: the control board, the capacitor on a mains unit, and the battery on a solar one. Those support parts usually decide the real service life, not the motor winding, which will happily outlive everything around it.

Cycle count is the honest measure, not calendar years. Every full open and close is one cycle, and the manufacturer’s rating is given in cycles for exactly that reason. Four things bring the count up faster or wear the mechanism harder than the raw number suggests.

• Sash weight against the actuator rating. A motor sized with little headroom over the glass it lifts runs near its limit every time it moves. Heavy double or triple glazing on a wide lantern is the usual culprit. A correctly specified actuator loafs; an underspecified one labours, and a labouring gearbox wears out years early.
• How often it moves. A rooflight wired to a rain sensor or a thermostat can rack up thousands of cycles a year on its own. Manual, occasional use stretches the same rated life over a far longer period.
• Heat in the roof void. Control electronics and capacitors dislike sustained heat, and the space directly under a south-facing roof is one of the hottest places in the house on a summer afternoon. A motor housing that bakes at 40 degrees or more, day after day, ages its own driver board.
• Salt-laden air near the coast. Along the estuary front, damp salty air finds its way into any housing that is not properly sealed and corrodes contacts, pins and exposed gear teeth. A unit half a mile inland has an easier life than one that looks out over the water.

The estuary angle ties two of those together. Southend faces south across the Thames Estuary, so on a great many rear extensions the opening rooflight is fitted precisely because the room overheats, which means the sensor or the occupant opens it far more often through the cooling season. More cycles, in a hotter roof void, in saltier air: the same conditions that make an opening light worth having are the conditions that work its motor hardest. Getting the glass specification right in the first place, so the room is not fighting solar gain, quietly takes load off the motor by giving it less reason to open. That is one of the reasons we treat orientation and G-value as part of the same decision, which our work on energy-efficient skylight installation goes into properly.

The two power routes age on different timetables, and it is worth knowing which you have.

A mains-wired actuator runs on a hard-wired supply or a low-voltage transformer, and its weak point over time is the capacitor and control board rather than any power source. Treated gently, the drive can reach the top of that 10-to-15-year window. A solar-powered roof window, such as the widely fitted VELUX solar units, carries its own small photovoltaic panel and a rechargeable battery, and the battery is the part with the shortest clock. Rechargeable cells typically hold useful capacity for around 8 to 10 years before they stop taking a full charge, at which point the window opens sluggishly or refuses to close fully even though the motor is sound. On those units the battery is a replaceable service part, and swapping it can give the original motor a long second life. If you are choosing between the two on a new install, that trade-off is one of the things we talk through in an electric skylight installation.

Rooflight actuators almost always announce themselves. Watch and listen for these before deciding anything:

• The sash opens more slowly than it used to, or hesitates partway and then carries on.
• The motor sounds rougher, louder or higher-pitched than when it was new, which usually points to worn gears.
• It closes but does not seal down tightly, so you feel a draught or find damp on the reveal after rain.
• The unit stops on its own mid-travel, or the wall switch and the remote disagree about what it should be doing, which more often means the control board than the motor.
• On a solar window, it works on a bright day and gives up on a run of dull ones, which is a tired battery rather than a tired motor.

Distinguishing a spent motor from a flat battery, a failed sensor or a loose connection matters, because they call for different things and only one of them means the drive is genuinely finished.

If the rooflight itself is sound and it is only the actuator or a solar battery that has worn out, the sensible route is a like-for-like drive or battery from the manufacturer, fitted by an electrician or the window maker’s own service. That keeps a good unit going and is not our trade.

Where the rooflight is dated, single-glazed, poorly insulated or the wrong glass for a hot south-facing room, a failed motor is the moment to weigh up replacing the whole unit rather than keeping an old one limping along. A replacement is our work, and it is the point at which you can move to a better-sized actuator, an upstand that seals properly, and a glass specification suited to the orientation. If the failing rooflight is a lantern over a kitchen, our roof lantern installation page shows what that swap involves, and the skylight installation costs page sets out where the money goes.

To buy for a long life first time: specify an actuator with real headroom over the glass weight, keep the number of forced cycles down by controlling solar gain rather than relying on the motor to vent the heat away, and choose a unit whose battery or drive is a stocked, replaceable part rather than a sealed assembly. If you would like us to look at an opening rooflight that is on its way out, tell us the orientation and the rough opening size and we will come back with a specification. Ring 01702 898232 or request a quote, and we will look at the whole roof rather than just the motor in it.