Tubular skylights: daylight without the hole

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.

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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How tubular skylight installation actually works

1. 1

   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 forA 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.

2. 2

   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 forSizing 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.

3. 3

   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 forA 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.

4. 4

   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 forFingerprints, 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.

5. 5

   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 forA 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.

6. 6

   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 forNo 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.

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 →

If the number is the problem, here are the ways people pay for it →