Can you convert a manual rooflight to electric?

The short answer

Often yes, and the answer is decided by the model rather than by how much effort anybody is willing to put in. Current generation manufactured roof windows from VELUX, Fakro, Keylite and Roto mostly have a retrofit opening kit designed for them: an actuator that clips into the top rail of the existing sash, a control board, and a remote to pair it to. Where that kit exists for your unit, it is a short job from inside the room with no scaffold and nothing touched on the roof outside. Where it does not, the sensible comparison is a different one entirely. The deeper treatment of what is involved sits on the electric rooflight installation hub, and this page is the direct answer plus the checks that settle it.

The model code on the sash decides it

Every manufactured roof window carries a data plate with a type designation and a size code, and on most of them it is on a plate at the top of the frame, visible once the sash is rotated or the ventilation flap is opened. That plate is the whole answer. It tells you the range, the generation of that range, and the size, and from those three things it is a matter of looking up whether an opening kit is listed for it.

Manufacturers change their sash profiles every so often, and a kit made for one generation will not mount on the one before it. Two units that look identical from the room can be a decade apart and take completely different hardware. Which is why guessing from a photograph of the window is unreliable and a photograph of the plate is definitive. Send that plate image with an enquiry and the answer comes back the same week.

What a retrofit kit consists of, and where it mounts

A typical kit for a pitched roof window is three parts. There is the actuator itself, a chain drive in a shallow housing that screws or clips to the inside of the top rail of the sash, taking the place of or working alongside the existing opening bar. There is a control board with a radio receiver. And there is a means of powering the two.

Some kits also include a driven locking element so the sash is pulled properly closed against its gaskets rather than merely pushed to. That matters more than it sounds. A sash held shut only by the friction of the gaskets will whistle in a February gale off the escarpment above Cheltenham, and a motor without a locking drive can leave a unit that reads as closed and is not sealed. Where a kit does not include one, the manual handle stays as the primary closure and the motor becomes a convenience rather than a full replacement for it.

Solar retrofit kits, and why they win in a finished room

The kits worth knowing about are the solar ones. A photovoltaic panel is fixed to the outside of the top rail, a battery sits inside the sash with the actuator, and the whole assembly is self contained. No cable enters the construction, so nothing is chased, nothing is replastered and nothing is redecorated.

In an existing room that is almost always the difference between a morning’s work and a project. A mains conversion in a plastered loft slope means lifting boarding at the head of the opening, running the cable along a rafter, passing it through the vapour control layer at a proper grommet, then making good. A solar conversion means a person on a stepladder inside the room and a short spell on the outside face of the sash to fix the panel. On the Cotswold cottages through Painswick and Chipping Campden, and in listed Cheltenham town houses where consent covers work nobody outside will ever see, the solar route also avoids a conversation about chasing cables into historic plaster.

Sashes that predate the mounting arrangement

An older window is a different proposition, and it is worth being straight about why. A sash approaching or past twenty years old will typically have gaskets at the end of their life, a hinge set with some play in it, and a frame whose profile predates any current actuator mounting. Hanging a motor on that buys very little: the mechanism will drive a tired sash against tired seals, and the things that were already going to want attention still will.

There is a second point about geometry. Older frames were often made to different overall proportions, and even where an actuator physically fits, the stroke available may not open the sash to a useful angle. An opener that lifts a sash by a token amount is worse than the rod that was already doing the job, because it costs money and delivers less air.

Weighing a kit against a complete new unit

Where the existing window is recent and its kit exists, the kit is obviously right. Where the window is old, the honest comparison is against a new complete unit, and it is closer than people expect.

	Retrofit opening kit	New electric unit
What changes	Actuator, control, remote. Sash, glass and flashings stay as they are	Frame, sash, glass, gaskets, flashing kit and actuator all new
Access needed	Inside the room, no scaffold on a solar kit	Scaffold or tower, covering taken back around the opening
Glass performance	Unchanged, so a 1990s unit stays at 1990s numbers	Current values, with solar control and laminated options available
Rain sensor	Included on most kits	Included, and integrated with the locking drive
Blind compatibility	Limited by the existing channel profile	Current blind range, orderable with the unit
Perimeter detailing	Untouched, whatever condition it is in	Underlay, flashings and insulation brought to current detail

The last row is the one that decides it on an old installation. If the underlay around the frame was slit rather than dressed when it went in, motorising the sash does nothing about it. Replacement is covered on the replacing a failed or misted rooflight page.

Kerb mounted flat roof units, which convert differently

A manual opening rooflight on a flat roof is not converted the same way at all, because the mechanism does not live in the sash. The drive is a spindle actuator, a threaded rod extending out of a tube, and on an opening unit it sits inside the kerb below the glass line.

That means the conversion happens in the upstand rather than in the room. On a unit already fitted, the questions are whether the kerb was built deep enough to house an actuator, whether there is a route for a cable into it that does not cross a finished waterproofing membrane, and whether the manufacturer supplies a drive for that hinge arrangement. Where the unit is a manual vent with a stay, frequently there is no actuated version of the same frame at all. Where the answer is a cable surface run across a single-ply membrane on a rear extension in Longlevens, the sensible route is usually a new opening unit specified with the drive designed in, and the kerb detailing on the flat roof rooflight installation page explains why.

What stays the same, and what still needs checking

Converting a unit changes nothing about the roof around it, which is the good news and the caution in the same sentence. The flashings stay where they are, the underlay stays as it was dressed, and the upstand keeps whatever height it was built to.

Three things are worth checking before a motor goes on. The gasket line, looked at with the sash open, because the actuator will be driving against it several hundred times a year. The hinges, for play, because a sash with movement in it will not present squarely to the frame under motor closure. And the drainage channel in the bottom of the frame, cleared out, because a channel full of moss on a Forest of Dean slate roof puts water where the design never intended it. All three are quick, and all three are done as part of fitting rather than afterwards.

How the conversion question gets settled

It starts with two photographs: the data plate at the top of the frame, and the window from inside the room with something in shot for scale. From those, the range and generation are identified and the available kits checked, and an indicative range follows by email.

Where the unit is recent and the kit is a straightforward one, that can be most of the conversation. Where it is older, or where the position is over a stairwell in a tall Stroud valley house with no floor to stand on, a survey settles both the hardware and the access before any figure is fixed. Severn Skylights Gloucester fits new rooflights, replaces units that have reached the end of their life, and motorises existing ones where the model supports it, across Gloucester and thirty miles by road around it. Email info@severnskylightsgloucester.co.uk with the plate photograph and the answer starts there.