Adding a light kit to a tunnel

Why it is worth having

Because the rooms sun tunnels serve are internal, and they still need light at night.

Without a kit you need a separate ceiling fitting beside the diffuser, which means two apertures in what is usually a small ceiling and a visually busier result.

Fit it at installation

The tube is open, the ceiling is already being cut, and the electrical connection is made while everything is accessible.

Retrofitting means getting back into the loft, opening the tube and running a supply, which is most of the original job again.

Even if you are unsure, having the wiring run to the position at the time is cheap insurance.

How it looks

The lamp sits above the diffuser, so from the room you see the same illuminated panel. It is the tunnel lighting up rather than a downlight next to it.

Colour will differ from daylight. Most kits are warm white against the cooler daylight the tunnel delivers, which is only noticeable at dusk when both contribute.

Bathrooms

The fitting sits in a bathroom ceiling and must suit its zone with appropriate ingress protection. That is an electrician’s decision and belongs in the specification from the start.

Switching

Wired to a normal wall switch and it can share a circuit with existing lighting. In a windowless bathroom, wiring it with the extractor so both come on together is a sensible arrangement.

Lamp replacement

Worth asking how the lamp is accessed. On most systems the diffuser comes down. Where it does not, changing a lamp means loft access, which is worth knowing before rather than after.

Why a tunnel needs one

A sun tunnel tracks the day. It is brightest through the middle, dimmer at each end, and after dusk it gives nothing at all.

In a windowless bathroom, WC or hallway, which is where tunnels go, that means you still need electric light for a good part of the time you use the room. In winter that is most of it.

So the question is not whether the room needs a light, it is whether that light goes inside the tunnel diffuser or somewhere else in the ceiling.

What the integrated kit is

A lamp assembly that mounts within the diffuser housing, above the ceiling plate, so the light appears to come from the same disc that the daylight does.

It is switched separately from the daylight, on an ordinary lighting circuit, and from below it reads as one fitting rather than a tunnel with something bolted to it.

The case for fitting one

Ceiling space. The main practical argument. A small bathroom ceiling is frequently already carrying an extract fan, and adding both a tunnel diffuser and a separate light fitting leaves a cluttered ceiling with three discs in it.

One opening doing both jobs is neater and it leaves room for the fan where it needs to be.

Continuity. The light comes from the same place at four in the afternoon as it did at midday, which reads better than daylight from one point and electric light from another.

Avoiding a relocation. Where an existing light fitting would have to move to make room for the diffuser, the integrated kit removes the problem and the making good that goes with it.

The case against

Output. An integrated kit is a modest light source. It suits a WC, an ensuite or a hallway where you want to see rather than to work.

In a room where genuine light output matters, a kitchen, a utility room used for tasks, or a bathroom somebody applies makeup in, it will not carry the room on its own and you will want additional lighting anyway.

Access. Changing a lamp means getting to the diffuser, which on a high ceiling means a ladder. With LED assemblies rated for many years that is infrequent, and it is worth knowing rather than discovering.

Decide before the ceiling is cut

This is the part that matters practically.

The kit needs a cable to the diffuser position, and that is run while the ceiling is open and the tunnel is being installed. Adding it later means opening the ceiling again, which turns a five minute component into a half day job with plastering and decorating attached.

If you are undecided, have the cable run and capped. It costs almost nothing at the time and it leaves the option open indefinitely.

Photograph where the cable is before the ceiling is closed, because nobody will find it again by guesswork.

Bathroom electrical zones

Bathrooms and shower rooms have defined electrical zones, and any fitting has to be rated for the zone it sits in. A ceiling fitting directly above a bath or a shower has particular requirements.

That is settled at design stage with the electrician rather than on the day, so tell us at the enquiry if the tunnel is going over a shower. It affects which kit is suitable rather than whether one can be fitted.

The wiring itself is electrical work and needs to be carried out by a competent electrician and certified, and depending on the situation it may be notifiable under Part P.

Solar powered light kits

Some systems offer a light charged by a small photovoltaic panel at the roof end, storing energy through the day and running the lamp at night.

The attraction is obvious: no cable, no electrician, no ceiling opening for wiring.

The limitation is equally obvious. Output is modest, and it depends on how much charge the panel gathered that day. It suits a hallway, a landing or a WC where a low level of light is enough to orient by.

Where you need to see properly, mains is the right answer.

Control and dimming

Most integrated kits take a standard switched circuit and can be dimmed where the lamp allows it.

Worth considering in a bathroom used at night, where a low setting is more useful than full output. Also worth considering on a landing, where a dim setting can serve as a night light.

Where the tunnel serves a bathroom with an extract fan on the same circuit, check how the fan is triggered, because a fan wired to the light will run every time somebody turns the lamp on, which may or may not be what you want.

Lamp choice

LED in almost every case now, and two things are worth specifying rather than accepting.

Colour temperature. A warm white sits comfortably alongside daylight; a cold blue white looks wrong in a room whose other light source is the sky. Somewhere around 2700 to 3000 kelvin generally reads better in a domestic room.

Lamp life and replaceability. An integrated LED assembly that cannot be relamped means replacing the whole unit when it fails. On a fitting above a ceiling that is worth knowing at the outset.

Fitting one to an existing tunnel

Possible where the manufacturer offers a retrofit kit for that model, and the diffuser is designed to be removed for cleaning anyway, so getting to the housing is not the difficulty.

The difficulty is the cable. Into a finished ceiling that means either lifting flooring above, which in a bathroom means lifting a bathroom floor, or chasing and making good below.

Where a lighting circuit already runs nearby in the loft, it may be straightforward. Where it does not, a solar kit is frequently the pragmatic answer despite its modest output.

What to ask for

Whether the light kit is available for the specific tunnel model. Whether it is included or a separate item on the quotation. Whether the cable is being run as part of the installation. And where the tunnel serves a bathroom, confirmation that the fitting is rated for the zone it will occupy.

Four questions, and they cover everything people later wish they had settled before the ceiling was cut.

Why it is a neat idea

A sun tunnel in a windowless hallway delivers daylight through the day and nothing after dark. So the space needs a separate light fitting, and now the ceiling has two apertures a short distance apart doing the same job at different times.

An integrated light kit puts a fitting inside the diffuser assembly, so one aperture serves both. Cleaner ceiling, consistent light source position, and the room lit from the same place whatever the hour.

What it involves

A cable to the diffuser through the ceiling void, taken from a suitable circuit with a switch position that makes sense for the space.

That is straightforward at installation while the ceiling is open at that point anyway. Afterwards it means either surface trunking or opening the ceiling, which is why this is worth deciding before rather than after.

It is notifiable electrical work and needs certifying.

The detail that must not be compromised

The seal between the diffuser and the ceiling.

That seal is what stops warm damp room air entering the tunnel and condensing on the cold inner surface of the tube. Without it, water runs back down and drips at the diffuser, and it looks exactly like a leak.

A light fitting introduced into the diffuser is a potential breach of that seal. Which is why the answer is a manufacturer designed integrated kit rather than cutting a hole in a standard diffuser and fitting a downlighter into it.

And it is why the tube still needs insulating through the loft regardless. The light kit does not change the physics.

Where a separate fitting is better

In a bathroom, where the moisture load is highest and the seal matters most, keeping the tunnel sealed and putting the electric light elsewhere is the more robust arrangement.

Also where the tunnel is small and the room needs more light output than a diffuser mounted fitting can sensibly provide.

Choosing the lamp

Colour temperature matters more here than in a normal fitting, because it will be compared directly against daylight coming through the same aperture.

A cool white sits closer to daylight and makes the transition less jarring. A warm white looks better in the evening and looks obviously artificial beside the daytime light.

Where the fitting is dimmable, the compromise resolves itself: bright and cool early, low and warm later.

Access afterwards

Whatever kit you choose, establish how the lamp is changed. A fitting that requires the diffuser assembly to be dismantled from below, breaking the seal each time, is a poor design in a ceiling you cannot easily reach.

Switching arrangements

The light needs a switch in a sensible position, which in a hallway usually means it joins the existing lighting circuit and switch rather than getting one of its own.

Where the tunnel serves a landing with two way switching, the fitting has to work with that arrangement, and it is far easier to plan before the ceiling closes.