What the motor and the sensor actually do
An electric roof window has a small motor in the frame that drives the sash open and shut. You control it from a wall switch, a handheld remote or a control panel, depending on the model. A rain sensor, where fitted, sits on the outside of the frame and sends a signal that closes the window when it detects moisture.
That is a convenience, not a seal. A sensor closes the window for you, but it does not make an old window watertight, and it works only while the system has power. Ask the supplier what the window does if the power fails, and whether the sash can be moved by hand.
Ventilation is the other thing to check. A window closed by a sensor stops ventilating the room, so a bathroom or kitchen loft still needs its own extract route. Our guide to roof window ventilation covers how much air a window moves and where the vents should sit. Think also about noise and morning light: a window that opens on a timer or a remote can be a help in a bedroom, and a nuisance if the control is set up badly.
Where a powered window earns its place
The case for a motor is reach. A manual roof window is operated from a handle at the top or bottom of the sash, and some positions put that handle where nobody wants to stretch. If the window is high on a landing, over a staircase or above a bath, a powered one saves a pole or a stepladder every time.
The case is weaker in a bedroom loft where the window sits at a normal height. Compare the options on a plain list:
- A window over a stair well or void, where reaching is awkward: a motor makes sense.
- A window above a bath or shower, where wet hands and a high handle do not mix: a motor makes sense.
- A window in a room used by someone who cannot reach or grip a handle: a motor can be the deciding factor.
- A low window within easy reach: a manual one works, and there is less to go wrong.
Price varies by size, covering and where the cable has to run, so it is quoted after a survey rather than guessed from a catalogue. A powered window also adds parts that can fail, which is worth weighing against the convenience.
Wiring is an electrician's job
A powered window needs a supply. Some use a mains connection, and others run from a low-voltage unit; the maker's installation sheet says which. Either way, the cable has to get from a power point or consumer unit to the frame, and in a pitched roof that usually means a route through the loft floor, a rafter bay or behind plasterboard.
The roofer fits the window, the flashing and the covering. The electrician connects and tests the supply. Keep them separate, and ask for the electrical work to be certified by the person who carried it out. This is also the stage where a roofer and an electrician need to talk, because the lining around the opening is closed up once the window is in.
Plan the cable route before the tiles come off. Opening the plasterboard afterwards to pull a cable through costs more and creates more redecoration than agreeing the route first. If the roof is being re-covered anyway, the window and its cable can be planned into that work from the start, with the loft side left open until the electrician has finished.
Checks to make before ordering
Four checks keep an electric window from becoming a disappointment.
- Where will the wall switch or control panel sit, and who can reach it?
- Where does the cable run, and does it pass through anything that is hard to open later?
- What happens in a power cut, and can the sash be opened by hand?
- Does the frame size and pitch suit the opening you already have?
If the window replaces an existing one in the same opening, the structure is already there, which keeps the roofing side simple. Our page on the roof window flashing kit explains the part that keeps the opening watertight, whether the window is manual or powered.
A new window in an existing house also has to meet the Building Regulations. Approved Document L sets the roof window row at a U-value of 1.4, or Window Energy Rating Band B as a minimum, so check the energy label on the model you choose. More on the wider choice sits on the roof windows and skylights page.
