Can a sun tunnel be added to an existing hallway?

Why hallways suit them

They are usually directly under a loft, so the run is short. They are small, so a 250mm tunnel does the job. And they have no external wall, so there is no alternative.

What is involved

Half a day to a day. The roof is opened, the collector flashed in, the tube run through the loft and insulated, the ceiling cut, the diffuser fitted and the collar sealed, and the ceiling made good ready to decorate.

One neat circular opening in a ceiling and some dust. We sheet up and clear up.

Position

Centrally along the length rather than in a corner, so light reaches both ends. In a landing, above the point people move through rather than directly over the stairwell.

The route usually has views of its own: joists, tanks, pipework and cables all live up there. Where the ideal position and a straight run disagree, take the straight run and move the diffuser a metre. A straight tunnel delivers materially more light than a bent one.

Landings above stairwells

Worth mentioning. A tunnel above a stairwell lights both floors to a degree, and the diffuser is high and hard to reach for cleaning. Position it over the landing rather than the void where you can.

Add the light kit

So the same fitting works after dark and the ceiling has one aperture rather than two. Far easier at installation than afterwards.

What to expect

Not a rooflight. Daylight in a space that had none, and a light switch you stop reaching for in the afternoon.

Yes, and hallways are among the best rooms for one

Internal hallways and landings frequently have no window at all, so the light is either borrowed from adjoining rooms or entirely artificial. A sun tunnel changes that for a fraction of the cost of anything else.

Because a hallway is a circulation space rather than a room you sit in, ambient daylight is exactly what it needs, and ambient daylight is exactly what a tunnel gives.

What decides whether it works

The route. There has to be a way from a clear patch of roof to the ceiling position. Purlins, tanks, soil pipes, steels and cables all live in loft space, and every bend in the tube costs light.

Moving the ceiling position by half a metre to get a straight run is frequently the better trade, and in a hallway there is usually latitude to do it.

Which floor. An upstairs landing is a short drop and performs very well. A ground floor hallway in a two storey house means running through the loft and then a first floor void, which is a longer run and needs more diameter to compensate.

Diameter. Output goes with area rather than width, so 350mm passes roughly twice the light of 250mm. For a hallway, 350mm is the sensible starting point and 530mm gives genuinely bright light.

Two rather than one

In a long hallway, two smaller tunnels spaced apart give even daylight along the space. One larger tunnel in the middle reads as a spotlight with the ends still dark.

Where two are fitted in the same visit the second costs meaningfully less, because the access, protection and setting up are shared.

What it will not do

Ventilate, or give a view, or provide any light after dark. Specify the optional light fitting inside the diffuser so the same ceiling opening does both jobs, and settle that before the work rather than opening the ceiling again.

The details that prevent trouble

Insulate the tube where it crosses the cold loft and seal the ceiling ring airtight. Without both, warm room air condenses inside the tube and the water arrives at the diffuser looking exactly like a leak.

What to send us

A photograph of the hallway ceiling and one of the loft above it. Between those we can usually confirm the route and recommend a diameter without a visit.

Why hallways are the ideal case

A hallway or landing is usually the darkest space in a house, because it is internal, has no external wall to put a window in, and is surrounded by rooms that have taken all the daylight.

It is also the easiest place to run a tunnel. The ceiling is normally directly below the loft, the route is short and straight, and there is rarely anything in the way beyond a joist or two.

A short straight run is what makes a sun tunnel perform. Light loss increases with every bend and with every metre of tube, so the hallway case, where the tunnel goes almost straight up, delivers far more light than a long dogleg run.

What to check before committing

The loft above the intended position, for water tanks, cabling, and any structural member that cannot be moved. A tank is the most common obstruction and it usually sits precisely where the hallway is.

The ceiling construction. A plasterboard ceiling is straightforward. Lath and plaster is more work and more mess, and on a listed building it may be part of what is protected.

And which slope the dome will sit on, because a front slope in a conservation area is a consent question even where the ceiling below is trivial.

Getting the best from it

Insulate the tube through the loft and seal the ceiling diffuser, so warm damp air from the house cannot get into the tunnel and condense.

And position the diffuser where the light is wanted rather than where the tunnel is easiest, if the two differ by a manageable amount. A short offset is worth it.