Do electric rooflights need a socket in the roof?
No. There is no socket at the rooflight and there should not be one. What arrives at the head of the unit is a thin extra-low voltage cable, usually 24V direct current, terminated into a small block inside the frame. The mains side stops well before that, at a transformer or a control unit sited somewhere accessible such as a cupboard, a landing or an accessible part of the roof void.
The question comes up because people picture a motor and assume a plug. The arrangement is closer to a doorbell than to an appliance. The wider subject sits on electric rooflight installation.
Where the transformer actually lives
The 230V supply ends at a transformer or a combined control unit, and where that box sits is a decision worth making deliberately rather than by default.
It needs three things. A mains supply, which usually means a fused spur. Somewhere within cable reach of the rooflight, since the low voltage run has a maximum length before voltage drop becomes a problem. And permanent access, because it holds the electronics, often the radio receiver, and sometimes a backup cell, all of which will want attention at some point in the next twenty years. An airing cupboard, a utility, or the side of a joist above an accessible loft hatch are all sensible. Above a plastered ceiling with no access is not.
The cable that does reach the unit
From the control unit onward it is a two core low voltage cable of modest size, often no thicker than a speaker cable. It runs to the head of the rooflight and terminates in the frame, and on a factory-built electric unit the terminal block is already there waiting for it.
Two practical points follow. The cable is small enough to run through a drilled joist or along a rafter void without any building work. And because it is extra-low voltage, terminating it at the unit is part of fitting the rooflight rather than notifiable electrical work. The dividing line between the two halves is set out on whether electric rooflights need an electrician.
Why a socket in a roof void is the wrong answer
Occasionally someone proposes a standard socket in the loft with the transformer plugged into it. It appears to solve the problem and it introduces several.
A roof void is a dusty, unheated space with a large temperature swing and, in a cold roof, moisture moving through it. A plug in a socket up there is a connection nobody will look at again, in a location where a loose terminal has insulation on either side of it. There is also the practical point that anything plugged in can be unplugged by someone moving boxes about, and the first anybody knows is a rooflight that has stopped answering. A fixed connection into a spur is the cleaner arrangement in every respect.
Fused spur or new circuit
| Supply arrangement | When it applies | Notifiable |
|---|---|---|
| Fused spur from an existing circuit | Circuit nearby, outside a special location | No, but tested and recorded |
| New circuit from the consumer unit | No suitable circuit, or several units to feed | Yes, under Part P |
| Solar unit | No cable route available | No mains work at all |
The spur is by far the commonest on a domestic job with a single opener. A new circuit appears where a whole run of glazing is being driven, where the existing circuits are already loaded, or where the electrician is rewiring anyway as part of an extension.
Warm decks, and roofs with nowhere to hide a cable
A cold roof has a ventilated void between the ceiling and the deck, and a cable runs through it easily. A warm deck flat roof does not. The insulation sits above the structural deck, the ceiling is fixed directly to the joists or to the underside of the deck, and there is no void at all.
On a new build-up this is planned in: the cable goes in at first fix, before the ceiling is closed. On a finished warm roof there is often no concealed route without lifting work that was already paid for. This is common on the newer rear extensions across Chelmsford, Braintree and Beaulieu Park, where the roof is built warm as a matter of course. It is also the single most common reason people end up specifying solar.
Solar removes the question entirely
A solar opener carries its own photovoltaic panel on the outside of the frame and a rechargeable cell inside it. There is no transformer, no spur, no low voltage run and nothing to site.
On a Victorian terrace with a converted loft, or a weatherboarded cottage in the Blackwater villages where chasing anything through historic fabric is best avoided, that removes the whole electrical conversation. The trade is a ceiling on sash weight, because a cell has a finite budget per cycle. What that means in daily use is set out on whether solar powered rooflights are any good.
Feeding more than one unit from one place
Where a room has two or three openers, they generally share a single control unit rather than each having their own. One mains supply, one transformer, one receiver, and a low voltage cable branching out to each rooflight.
That is cheaper, tidier and easier to live with, and it also means the whole group closes together on one rain signal. It has a limit, set by the total current the control unit will supply and by the length of the low voltage runs, and how far that stretches is covered on how many electric rooflights one switch can control. A motorised blind on the same unit will usually take its power from the same place, which is the argument for doing both at once.
What to run at first fix even if the motor comes later
This is the useful conclusion. If there is any chance a rooflight will end up motorised, the cable wants to go in while the ceiling is open, whether or not an actuator is ordered now.
Run the mains to a sensible control unit position and leave it terminated in a box. Pull a low voltage cable from there to the head of each rooflight position and coil the spare in the frame. Add a second one if a blind is even a possibility. At first fix that is a few metres of cable and half an hour of somebody’s time. Afterwards it is a plastered ceiling coming down. Sunspire settles the routes at survey and turns a range by email into a fixed written figure, with the Building Control notification for the rooflight handled as part of the job.
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