What Is a Sun Tunnel?

The idea in one picture

Picture a drinking straw lined with a mirror. One end points at the sky. The other opens into a room that has never seen the sun. That is a sun tunnel. Light enters the clear dome on the roof, bounces down the polished tube and spreads into the room through a frosted panel set flush in the ceiling.

People also call it a light tube, a sun tube or a tubular skylight. Whatever the name, the job is the same: borrow light from straight up, where nothing blocks the view, and deliver it to a room whose walls have no useful window.

The parts, from roof to ceiling

Every sun tunnel is built from the same short list of parts, and knowing them makes a quote easier to read.

• The dome. A clear, domed cap fixed to the roof, which gathers daylight from the whole sky and not just from the sun itself.
• The flashing. A weatherproof collar that joins the dome to the roof covering, shaped for slate, tile or a flat roof so the join stays watertight.
• The tube. A highly reflective shaft that runs from the roof down to the ceiling. It can be rigid or flexible.
• The diffuser. The frosted ceiling panel that spreads the light so the room glows rather than shows a hot spot.

The roof opening is small, often a dinner plate in size or a little larger, so the structure above the room is disturbed far less than it would be for a full roof window.

Rigid or flexible tube

The tube is where sun tunnels differ most. A rigid tube is a straight, smooth metal shaft with a mirror finish, and it passes the most light because the light meets few surfaces on the way down. A flexible tube is a ribbed, bendable sleeve. It can curve round a rafter, a pipe or a duct, which makes it useful when the straight route is blocked.

When the drop from roof to ceiling is brief, a rigid tube is the natural choice. Where the loft is cluttered or the roof and the room do not line up, a flexible section lets the tunnel step sideways. Either way, a clean route with few bends keeps the room brighter, and the survey is where we walk the route and agree which suits.

Why the tube beats a bigger hole

Cutting a full roof opening means new timbers, a deeper reveal and more plastering. A tube sidesteps most of that. The opening is small, the framing around it is modest and the finished ceiling shows only a neat round panel. For a household that wants daylight on the stairs without a building project, that matters.

It also helps with the look of the roof. A dome is low and quiet from the street, so a front slope that you would rather leave untouched can still serve a dark landing behind it. If you live in a conservation area, ask the council's planners whether an Article 4 direction covers your street; the wider rules are in our planning guide.

Dust and condensation are worth a thought too. A well-made tube is sealed at the top and at the ceiling, so the air in the loft stays out of the shaft and the diffuser stays clear. That sealed build is part of what we check when we fit one.

Rooms a tube suits best

A sun tunnel suits rooms at the centre of the house: a landing, a hallway, a bathroom, a utility room, a walk-in wardrobe or a stairwell. These spaces share a problem. The side walls face other rooms, so there is nowhere to put a window. A tunnel solves that by coming in from above.

It also works in a room under a pitched roof where a skylight would be too large or too costly to justify, and in a flat-roofed extension that needs one extra pool of light. Our guide on where sun tunnels work best goes through the rooms one by one.

How a sun tunnel is installed

Fitting follows a clear order, and the inside is left finished.

1. We survey the roof and the ceiling, trace the route the tube will take and choose a rigid or flexible shaft.
2. A small opening is made in the roof covering, and the flashing is set so the join sheds water.
3. The dome is fixed to the flashing and sealed.
4. The tube is run down through the loft space to the ceiling.
5. The ceiling ring and diffuser are fitted, and the plasterboard around them is made good.

We look after Building Control sign-off wherever the work needs it, and the finished job meets today's Building Regulations. You get a free survey first, then a written quote that stays put, and a 10-year workmanship guarantee on paper.

A sun tunnel and a skylight side by side

A sun tunnel is a different tool from a skylight or rooflight, not a smaller version of one. A roof window gives a view of the sky and can open for fresh air. A tunnel gives light only, with no view, but it reaches rooms a window never could. If you are unsure which belongs in your room, read how a tunnel compares with a roof window.

To see how much brightness to expect, the brightness you can expect explains what changes the result. The wider picture lives on the sun tunnels hub.

A few more sun tunnel questions