A roof window opens by hand, by mains powered motor, or by a solar powered motor. The choice is decided mostly by reach, partly by what the room is for, and entirely before the ceiling closes if there is any cabling involved.
Reach is the first question
Everything else follows from whether somebody can get to the window.
A control bar at the top of a window within comfortable arm’s reach is operated by hand with no mechanism to age and nothing to go wrong. Above that, an operating pole extends the range to a point. Above that, it is a motor or it is a window nobody opens.
The measurement is taken at survey with somebody standing where they would actually be, rather than estimated from a drawing.
Manual
What it is
A control bar or handle on the sash, operated directly or with a pole. On a centre pivot the bar is at the top, which is why the pivot action suits a high window: the bar comes toward you as the sash rotates.
What it suits
Any window within reach, and any high window on a centre pivot where a pole will do. It is the cheapest option, it needs no power, there is nothing to fail, and it works in a power cut.
The limits
A pole gives usable reach up to a point and becomes awkward beyond it. It also has to live somewhere, and in a small loft room a two metre pole is a genuine nuisance. And a manual window is one nobody opens on a cold morning, which matters if it is the room’s ventilation.
Electric, mains powered
What it is
A chain actuator on the sash, wired to a supply, operated by a wall switch or a remote. The motor drives a chain that pushes the sash open and pulls it closed.
What it suits
Any window out of reach, any window that needs to be operated frequently, and any installation where a rain sensor is wanted. It is the strongest option, it closes reliably, and it integrates with a home system where one exists.
The catch
It needs a cable, and the cable route is decided before the ceiling closes. Retrofitting a supply to a finished ceiling means lifting boards or chasing plaster, and it turns a simple change into a disruptive one.
Solar powered
What it is
The same actuator, powered by a small photovoltaic panel on the window itself charging an internal battery. No mains supply, no cable, no chasing.
What it suits
Precisely the situation that catches people out: a finished room where the ceiling is closed and nobody wants it opened again. It is also the answer where a supply would have to cross a fire compartment or a structural member.
The trade
It costs more than a mains unit as a product, and considerably less than a mains unit plus the cabling on a retrofit. The battery needs light to charge, which on a north facing slope in a Sussex winter is less than on a south facing one, and it is generally adequate for the small number of operations a domestic window sees.
The comparison
| Manual | Mains electric | Solar | |
|---|---|---|---|
| Cable needed | No | Yes, before the ceiling closes | No |
| Rain sensor | No | Yes | Yes |
| Works in a power cut | Yes | No | Yes, on battery |
| Retrofit to a finished room | Yes | Disruptive | Yes |
| Out of reach installation | Pole only | Yes | Yes |
| Long term maintenance | Almost none | Motor and controls | Motor, controls, battery |
The rain sensor
A rain sensor closes a powered window automatically when it detects water, and on this coast it earns its place more than it would inland.
Weather here arrives quickly off the Channel. A clear morning that becomes a squall in twenty minutes is ordinary, and an open rooflight in an empty house is a wet floor.
It is worth knowing what a sensor does and does not do. It responds to water on the sensor, so it closes once rain has started rather than before. And in a sea fret, which is fine wet air rather than falling rain, behaviour varies: some sensors trigger on the moisture and some do not, which is covered on its own page.
Cable routes, decided early
This is the practical heart of the decision and it is where most of the regret comes from.
A mains powered window needs a supply at the head of the frame. That cable runs through the roof construction, and the moment to install it is when the roof is open and the ceiling is not yet on. At that point it is minutes of work.
Afterwards it is boards up, plaster chased, or a surface run somebody will look at every day. Which is why we ask about powered operation at survey even where the customer has not raised it, and why solar exists.
Where powered operation earns its place
- A high window in a loft room or over a stairwell, where a pole is impractical.
- A bathroom or shower room, where ventilation matters and hands are frequently full.
- A window above a fixed obstruction such as a bath, a worktop or a bed.
- Anywhere a rain sensor is wanted, which on an exposed coastal roof is most places.
- A household where somebody would find a pole difficult, which is worth thinking about for the long term.
Where manual is the right answer
It is worth saying, because powered operation gets recommended by default.
A window at head height in a bedroom, opened twice a year, does not need a motor. Neither does a window in a room with plenty of other ventilation. Manual is cheaper, simpler, has nothing to fail, and works in a power cut.
The honest question is how often the window will actually be opened, and by whom.
Fixed, the fourth option
Not every roof window needs to open at all, and a fixed unit is worth considering where ventilation comes from elsewhere.
A fixed window is cheaper, quieter in rain, better sealed against air leakage, and has no mechanism to age. Where a room has adequate ventilation, no escape requirement, and the window is high in the roof where nobody would open it anyway, fixed is frequently the better specification.
It is rarely offered and it is worth asking about.
Escape windows and powered operation
Where a window has to serve as a means of escape in a habitable loft room, the operation is part of the requirement.
An escape window has to be openable by a person leaving the room, without a key or a tool, and the clear opening has to be unobstructed. A powered window that opens only on a remote control that is somewhere else in the house is not obviously satisfying that, and the arrangement has to be discussed with Building Control rather than assumed.
This is settled at survey, because it decides the product rather than being an accessory to it.
Retrofitting a motor to an existing window
A common question, and the answer is that it depends on the window rather than on the motor.
Some models are designed to accept an actuator retrofitted to the existing sash and frame, with the mounting points already there. Where that is the case it is a straightforward upgrade and the window itself stays. Where it is not, the frame has nothing to mount to and the honest answer is a new unit.
The data plate settles it, because the type code identifies the model family and whether an upgrade kit exists for it. It is worth checking before assuming either way, and it is a case where the cheap answer is sometimes the available one.
Two windows on one control
Where a room has more than one powered window, they can usually be operated together from a single control, and that is worth thinking about rather than accepting by default.
Ventilation is better with two openings than one, and opening both together is what you want on a warm afternoon. Against that, closing one and leaving one open is sometimes exactly what a room needs at night, and a single grouped control removes that choice.
Most systems allow both: a group command and individual control. Setting it up that way at installation costs nothing and is fiddly to change later.
Noise, and what a motor sounds like
An actuator makes a noise when it runs, and in a bedroom that is worth knowing about in advance.
It is a low mechanical hum for the few seconds the sash is moving, not a continuous sound, and modern units are considerably quieter than older ones. What people notice more is the rain sensor closing the window at three in the morning, which is the system working correctly and is still a surprise the first time.
Where a window is over a bed, it is worth operating one before choosing, and it is the sort of thing that is easy to arrange.
Controls and integration
Powered windows come with a remote, and most systems will take wall switches, timers and integration with a wider home system.
Where a home system already exists, it is worth establishing what protocol it uses before choosing a window, because compatibility is decided by the control system rather than by the window. Where none exists, a simple wall switch beside the light switch is what most people actually use.
What a motor needs over its life
Very little, and knowing what little helps.
The chain runs on a track and benefits from being kept clear of dust and debris. The gaskets are what seal the window when it is closed and they age like any gasket. On a solar unit the battery has a service life and is replaceable. And a mechanism that is never operated seizes, so running a powered window fully open and closed a few times a year is worth doing.
Salt, on this coast
Everything mechanical on a coastal roof is in salt laden air, and an actuator has more moving parts than a manual catch.
The specification response is stainless fixings and mountings, isolation where dissimilar metals meet, and the same annual fresh water rinse that benefits every other exposed component. It is also an argument for exercising the mechanism, since a chain that sits still for years in salt air is one that binds.
How we measure it on a VELUX
We measure the reach with somebody standing where they would be, ask how often the window will actually be opened, and raise the cabling question before the ceiling closes rather than after. Where a room is finished and a motor is wanted we specify solar rather than proposing to chase a ceiling. On the coast we specify a rain sensor as a matter of course and stainless throughout.
The cable is the decision. Everything else can be changed later.
Thinking about this job? We survey across Worthing, West Sussex and the South Downs and give you a fixed price before any work starts, with a 10-year workmanship guarantee.