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What is a solar tube? How it works and where it leaks

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A solar tube brings daylight through the roof without a big skylight. It also adds a hole to the roof, so it is worth knowing how it is sealed.

A solar tube is a small, round skylight. A clear dome sits on the roof, a shiny tube runs down through the attic, and a diffuser panel on the ceiling spreads the light. It lights a room with daylight and no electricity. Despite the name, it makes no power and has nothing to do with solar panels.

How a solar tube works

The dome catches daylight. The tube has a mirror-like lining that bounces that light down toward the ceiling. The diffuser at the bottom softens it so the room glows instead of glaring.

Because the tube is narrow, the hole in the roof is small. That is the appeal. You get light in a hallway, closet or bathroom where a full skylight would be too much.

Why it is a leak point

Every opening in a roof needs flashing, and a solar tube is no exception. A metal or plastic collar sits under the shingles on the upper side and over them on the lower side. The dome clips onto that collar.

Water gets in where that overlap fails. The collar may have been set wrong, the sealant around the base may have dried and split, or the dome may have cracked in the sun. The same overlap rule applies here as everywhere else on a roof, which is explained in what is roof flashing.

Leak or condensation?

Many drips from a solar tube are not leaks at all. The tube runs through a cold attic and carries warm, damp air from the room below. Moisture condenses on the cold metal and drips from the diffuser.

The clues are different. Condensation shows up on cold mornings and in winter, with no rain. A leak shows up during or right after rain. If you only see drips on cold, dry days, read skylight condensation before calling anyone.

What to check from the ground

Use binoculars from the yard. Look at the dome and the base around it.

  • A cracked, yellowed or cloudy dome.
  • A gap between the dome and its collar.
  • A thick smear of tar or caulk around the base.
  • Shingles lifted or missing next to the collar.

Inside, look at the tube and the ceiling around the diffuser. A brown ring, a bubble in the paint or a wet patch on the drywall are all worth a photo. In the attic, shine a flashlight at the tube from the walkway or the joists. Do not lean on the ceiling between them. Look for dark streaks on the tube or wet wood where it passes through the sheathing.

Is a solar tube worth it?

For a small dark room, often yes. For a room that already has a window, rarely. The honest trade-off is one more roof opening to keep sealed for the life of the roof. If you are planning a re-roof anyway, that is the natural moment to have the collar replaced along with the shingles.

Why we do not show the repair

Fixing a solar tube means walking the slope and lifting shingles around the base. We do not publish those steps. Take your photos, note when the drip appears, and ask a roofer to show you what failed before they quote anything.

Frequently asked questions

What is a solar tube?

A solar tube is a small round skylight. A dome on the roof and a reflective tube carry daylight down to a diffuser on the ceiling.

Does a solar tube make electricity?

No. It only carries daylight. It is unrelated to solar panels, which turn sunlight into power.

Why is my solar tube dripping?

It is either a leak at the roof collar or condensation inside the tube. Drips on cold, dry days point to condensation. Drips during rain point to a leak.

How can I check a solar tube without going on the roof?

Look at the dome and base with binoculars from the yard, then check the ceiling around the diffuser and the tube from the attic walkway.

Can I reseal a solar tube myself?

We recommend against it. The work is on a sloped roof with shingles lifted. Ask a licensed roofer to show you what failed.

Sources

What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.

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