Skylights · Service

Tubular skylights: daylight without the hole

A reflective tube from a small roof dome to a ceiling diffuser. No rafters cut, no shaft to build, no framing headers — and no view and no ventilation either. Here is when that trade is the right one.

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In short

What is tubular skylight installation?

A tubular skylight — also sold as a sun tunnel or light tube — captures daylight in a small dome on the roof and carries it down a highly reflective tube to a diffuser in the ceiling below. Because the tube fits between rafters and joists, nothing structural is cut and no light shaft is framed, so installation is usually a half-day job with no interior drywall work. You get daylight. You do not get a view, ventilation, or the sense of open sky a real skylight gives.

Triggers

Signs you need tubular skylight installation

You have a windowless interior room — a bathroom, a walk-in closet, a pantry, a hallway, a laundry — that is on the lights at midday
You want daylight and would rather not cut and header a rafter, or pay for the framing and interior finishing that follows
The room below is a floor down from the roof, or the attic run is awkward, and a conventional shaft would be long, angled and unattractive
You are on a budget where a conventional skylight is out of reach but daylight is genuinely the thing you want
A stairwell or landing is dark and there is no wall available for a window
You want the daylight without the solar heat gain that a large glazed opening brings into a room that already runs warm

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The job

How tubular skylight installation actually works

Find a clear route between the roof and the ceiling

The whole feasibility question. Someone gets into the attic and traces a path from a suitable spot on the roof down to the ceiling position, between framing members and around ducts, wiring, plumbing vents and stored belongings. Rigid tubes need a reasonably direct route; flexible tubes bend around obstacles at a real cost in light delivered.

Watch for: A survey done from the ground and the room below only. If nobody has been in the attic, the route is an assumption, and the obstruction gets discovered with two holes already cut.
Choose the diameter for the room, not for the budget

Tube diameter is the main determinant of how much light arrives. A small tube in a large room reads as a bright spot on the ceiling rather than as daylight in the space. Manufacturers publish room-size guidance for each diameter, and it is worth being at the generous end of it, because the difference in installed price between diameters is small next to the difference in result.

Watch for: Sizing pitched at the smallest unit that will fit between your rafters. It is the cheapest quote and the most common source of disappointment with this product.
Cut the roof opening and set the dome

A round opening is cut between rafters — no rafter is severed and nothing is headed off — and the dome is set on a flashing base matched to your roof covering, interleaved with it in the same way a conventional skylight flashing is. On a low-slope roof a curbed flashing base is used instead.

Watch for: A dome sealed onto the covering with mastic instead of properly flashed. Small round penetrations are easy to fudge and slow to reveal the fudge, and the leak arrives years later at a spot nobody suspects.
Run the tube and seal the joints

Tube sections are assembled and sealed between dome and ceiling. The interior surface is the product — the reflectivity is what carries light down a run with minimal loss — so it is handled clean, never dented, and never left with a joint that lets attic air or dust in.

Watch for: Fingerprints, dents and unsealed joints. Every one of them costs you light, and every unsealed joint is a path for humid attic air into the tube, which then condenses on the cold interior and drips onto the diffuser.
Cut the ceiling opening and fit the diffuser

A round opening in the ceiling takes the diffuser, which spreads the light and determines the character of it — some diffuse softly and evenly, others let more direct sun through and produce a brighter, harder pool. The trim ring covers the cut, so there is little or no making-good.

Watch for: A diffuser placed for convenience directly over a bed or a desk. Direct-sun diffusers can be genuinely uncomfortable at certain hours; place it where you want light, not where the tube happens to land.
Insulate and air-seal at the ceiling plane

The tube passes through the insulated ceiling, so the penetration is air-sealed and the tube insulated where it runs through cold attic space. This is the step that prevents condensation inside the tube and stops the assembly becoming a chimney for warm household air into the attic.

Watch for: No mention of air sealing at all. In cold climates this is what determines whether you get drips on the diffuser in January, and it is invisible once the ceiling is closed.

Money

What does tubular skylight installation cost?

A tubular skylight is typically a few hundred to low four figures installed per unit, well under a conventional skylight, because there is no framing, no light shaft and almost no interior making-good. Larger diameters, long or bent runs and add-on light kits raise it. See the skylight cost guide.

See the full tubular skylight installation cost guide — by material, size and region →

Straight answer

When tubular skylight installation is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

You want a view or a sense of sky. A tube delivers light through a diffuser and nothing else — you cannot see out of it, and the ceiling reads as a light fitting rather than an opening. If the appeal of a skylight is looking up, this is the wrong product and you will feel it immediately.
You need ventilation. Tubes do not open. In a bathroom with a moisture problem, the daylight is nice and it does nothing for the humidity — you need extraction or a venting skylight instead.
The run from roof to ceiling is long or has to bend several times. Every bend and every extra foot costs light, and a heavily bent flexible run into a large room can deliver disappointingly little. Get the route confirmed in the attic and be sceptical of a quote that promises the same result down a difficult path.
You have a cathedral or vaulted ceiling. With no attic space to run through, the tube has nowhere to go and the case for a conventional skylight — which is at its cheapest and simplest on a vaulted ceiling anyway — is much stronger.
You are trying to daylight a large open-plan space with one unit. Tubes are excellent at bringing a windowless small room up to usable daylight and poor at lighting a big room. Multiple units, or a real skylight, is the honest answer.
You expect it to replace electric light at night or on grey days. Output tracks the sky. In a genuinely windowless room you still want a light fitting, which is why many manufacturers sell an integrated electric kit for the same diffuser.

Your options

Types of tubular skylight installation

Tubular versus a traditional skylight

The core decision — light versus light plus view and ventilation. Set out in full on the comparisons archive.

Rigid versus flexible tube

Rigid delivers more light; flexible negotiates obstacles. The route decides it more than preference does.

Integrated electric light kit

The same ceiling diffuser doubling as a light fitting after dark.

Conventional skylight instead

If a view, ventilation or a large amount of daylight is the real requirement.

Compare skylights options side by side →

Before you sign

What to check when hiring for tubular skylight installation

Have you been in the attic to confirm the route?

The entire feasibility of the job. Ducts, stacks and framing are what stop these, and they are only visible from up there.
What diameter are you proposing and what room size is it rated for?

Under-sizing is the number one regret with this product. Manufacturers publish guidance — ask to see where your room sits in it.
Rigid or flexible tube, and how many bends?

Rigid, straight and short delivers the most light. Every bend is a real loss, and a quote that is cheap because it takes an easier bent route is buying you less daylight.
How is the dome flashed into my specific roof covering?

Small round penetrations are the easiest place to substitute sealant for flashing. You want a flashing base matched to shingle, tile, metal or membrane.
How will the ceiling penetration be air-sealed and the tube insulated?

This is what stops condensation inside the tube in cold weather, and it is invisible once the ceiling is closed up. Ask before, not after.
Which diffuser is included, and can I see what the light looks like?

Diffusers differ a lot — soft and even versus bright and directional. It is the part you will actually look at every day.
Is an electric light kit or a dimmer available for this unit?

In a windowless room you still need light after dark. Fitting it at installation is far cheaper than adding it later, and it keeps one clean fitting in the ceiling.

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Local pros

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FAQ

Tubular Skylight Installation — questions people ask

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How much light does a tubular skylight actually give?

Enough to make a windowless bathroom, closet or hallway comfortably usable in daylight hours without switching anything on — that is the job it does well. It is not equivalent to a window or a conventional skylight in a living room. The variables are tube diameter, the length of the run, and how many bends there are: a short straight run in a generous diameter is dramatically better than a long bent one in a small diameter.

Do tubular skylights leak?

They have less to leak than a conventional skylight — a small round penetration with a factory flashing base, rather than a large framed opening with interleaved step flashing on four sides. The failure mode when it happens is the same one: a dome bedded in sealant instead of properly flashed into the roof covering. Ask specifically how the flashing base suits your covering.

Can a tubular skylight be installed in any room?

It needs a clear route between framing members from a viable spot on the roof to the ceiling position, so it needs attic space. Rooms under a vaulted or cathedral ceiling generally cannot take one, and rooms two floors down from the roof usually cannot either. Obstructions — ducts, plumbing stacks, wiring runs, chimneys — can also block an otherwise straight path, which is why the attic survey comes first.

Do they cause condensation?

They can, and it is an installation issue rather than a product one. The tube passes through cold attic space, so if the joints are not sealed and the assembly is not air-sealed and insulated at the ceiling plane, humid household air reaches a cold surface inside the tube and the moisture ends up on the diffuser. Correctly sealed and insulated units in cold climates do not do this.

Will a tubular skylight overheat the room?

Much less than a conventional skylight of comparable brightness, because the opening in the roof is small and the diffuser is not a large area of glass radiating into the room. That is genuinely one of the better arguments for them in hot climates and on south- and west-facing roof planes. It is not zero — the dome is still a hole in an insulated roof, which is why the insulation detail at the ceiling matters.

How long does the installation take?

Commonly a half-day per unit where the attic route is clear, and with very little disruption inside — the trim ring covers the ceiling cut, so there is normally no drywall repair, taping or painting to wait for. That absence of interior making-good is a large part of why it costs so much less than a conventional skylight, and why several can be fitted in a day.