Sun tunnels and where they beat a rooflight

1. There is no roof directly above

The decisive one. An internal hallway, landing, bathroom or WC with a floor or a loft between it and the sky.

A rooflight cannot reach. A tunnel can, and it is the only product that can.

2. The building is listed and a rooflight is refused

The roof collector is small and sits low. On a sensitive roof a tunnel is sometimes acceptable where a rooflight is not, because the intervention in the fabric is far smaller.

Worth raising with the conservation officer as a fallback if a rooflight proposal is turned down.

3. Disruption is the constraint

A tunnel is half a day to a day with one neat ceiling aperture. A rooflight is a structural opening, days of work, and a reveal to plaster and decorate.

In an occupied house where the room is in daily use, that difference matters.

4. The room is small and the budget is real

A tunnel costs substantially less. For a windowless WC or a utility room, a rooflight is over-specifying.

Where a rooflight wins

Everywhere else. Far more light, a view of the sky, ventilation if it opens, and a genuine change to how a room feels rather than simply how bright it is.

Both

Common in a single storey extension: rooflights over the main space, and a tunnel into the internal WC or utility off it.

Five situations where the tunnel wins

A sun tunnel is not a compromise version of a rooflight. In these five cases it is straightforwardly the better answer, and we recommend it over a rooflight regularly.

1. The room has no roof above it

An internal bathroom, WC, hallway, landing or utility room with no external wall and no available slope. There is no rooflight solution for a room like that, and a tunnel brings genuine daylight into a space that has never had any.

This is the classic case and it accounts for most of what we fit.

2. A bungalow, where the run is short

The tube drops straight from the roof into the ceiling below, frequently under a metre. Light loss compounds with length, so a short straight run performs at the top of what the product can do.

Every room in a bungalow is under the roof, which means the daylight can go where it works best rather than where it fits.

3. Where a rooflight will not be consented

A sun tunnel is the least visible daylight option there is. The roof component on a low profile unit sits close to the covering and reads as a very small rooflight, and on a rear slope it is frequently invisible from any public vantage point.

The intervention in historic fabric is one opening between rafters rather than a trimmed structural opening, and it is largely reversible. On a listed building that is an argument worth putting to a conservation officer, and we have seen tunnels consented where rooflights were not.

It still needs consent. It is not exempt for being small.

4. Where the budget will not stretch

It is the cheapest daylight in this trade by a wide margin, because the roof component is small and most of the work is from inside, so the access that dominates a rooflight quotation barely features.

5. Where privacy matters absolutely

There is no line of sight through a mirrored tube. In a bathroom that is daylight with complete privacy, and no blind to get wet.

Where the rooflight wins instead

Any room where you want a view, ventilation, a sense of sky, or a lot of light. A tunnel gives none of those. What it gives, on a dull afternoon in a windowless room, is enough daylight not to reach for the switch.

How to tell which you need

Look up. If there is a roof slope directly above the room and you want a view, ventilation or a lot of light, you want a rooflight.

If there is no slope above the room, or the room is internal, or the only available position is on a slope a conservation officer will not accept, you want a tunnel.

Send us a photograph of the room and one of the loft space above it, and tell us what the room is used for. That is enough for us to say which product suits and what diameter or size to aim at, without anybody visiting.

Where the honest answer is that a tunnel will not give you what you are hoping for, we will say so. It is a good product within its limits and a disappointing one outside them.

The cases where a tunnel is the better product

An internal room with no external wall and no roof directly above it. A hallway, a landing, an internal bathroom, a windowless utility. A rooflight cannot serve these at all because there is a floor or a room between them and the sky. A tunnel can.

Where the ceiling cannot be opened up. A tunnel needs a circular hole between joists. A rooflight needs a structural opening, a trimmed reveal and frequently structural work.

Where the roof position is constrained by consent. A small dome is a far easier proposition on a sensitive roof than a rooflight, and takes up much less of the roof plane.

Where cost is decisive. A tunnel is a fraction of the price of a rooflight installation, because there is no structural work, no trimmed reveal and no substantial making good.

Where a rooflight is the better product

Quantity of light. A rooflight delivers far more, and a tunnel cannot approach it.

A view and a sense of the sky. A tunnel gives light, not outlook, and that difference matters in a room people spend time in.

Ventilation. Standard tunnels are sealed and passive.

Any room with a ceiling directly under the roof. If a rooflight is possible, it is usually the better answer.

The honest summary

A sun tunnel is not a small rooflight. It is a solution to a different problem: getting daylight to a place a rooflight cannot reach, cheaply and with minimal disruption.

Judged as a rooflight it disappoints. Judged as the alternative to a light burning all day in a windowless hallway, it is excellent.