Sun in the Morning, Stars at Night

A skylight is a window in the roof: you see sky through it, it opens on some models, and it needs a straight shot from the roof to the ceiling. A sun tunnel is a small dome on the roof feeding a reflective tube down through the attic to a flush light in your ceiling. You don't see sky through a sun tunnel, you just get daylight. The tube can bend around ductwork and framing, which is why a sun tunnel works in a hallway, a closet, or a windowless bathroom where a skylight can't go at all.

That's the case sun tunnels exist for. Interior bathrooms, hallways, stairwells, laundry rooms, and walk-in closets are the rooms nobody can put a window in, and they're the rooms where the difference is most obvious. The tube runs from a dome on the roof down through the attic to a flush fitting in your ceiling, and it can bend around framing and ductwork on the way. The one thing we need is a route through the attic, which we check before quoting anything.

There are three jobs behind that question and they're priced nothing alike. A sun tunnel is the cheapest by a wide margin, because the hole is small and nothing gets reframed. Setting a new unit into an opening that already exists comes next. Cutting a brand new opening costs the most, since it means altering framing and building a shaft down through the attic. After that it's what sits between your roof and your ceiling, and then the unit itself, fixed or venting or solar.

A unit facing the wrong way can, and it's worth talking about before you pick a spot. South and west exposures take the most summer heat, and that's what low-E glazing, factory blinds, and venting models are for. A venting skylight can also work the other way and pull hot air out of an upstairs room on a summer evening. We'll tell you which exposure you're dealing with before anything gets cut.

Twenty to thirty years for the unit, and less than that for the seal on older models. What usually fails first isn't the glass, it's the seal between the panes and the flashing around the frame. Fogging or moisture between the panes means the seal is gone, and that's a replacement rather than a repair. If yours went in with your last roof they're the same age as it, which is usually the first time anyone thinks about them.

Almost always the flashing, not the glass. Skylights get blamed for leaks that are really a failed flashing kit, a seal that's aged out, or shingles that were cut in around the curb instead of woven properly. There's a fourth cause that isn't a leak at all, and it's the most common one we get called for: condensation. We check that first, because it changes what you need and what it costs.

Condensation shows up on cold mornings, sits evenly along the bottom edge of the glass and the frame, and stops once the day warms up. A leak shows up when it rains, runs in a track rather than beading everywhere, and usually stains the drywall on one side of the shaft. Condensation is a ventilation and humidity problem, so the fix is in the attic. A leak is a flashing problem, and the fix is on the roof. We'd rather tell you it's the first one than sell you the second.

We do both, and the honest answer usually depends on the seal. Flashing failures, cracked or aged sealant, and shingles cut in badly around the curb are all repairable, and a repair is the right call when the unit itself is sound. Once there's moisture between the panes the seal is gone and no amount of work on the outside fixes it. If the roof over it is near the end anyway, it's worth asking whether you want to pay for the access twice.

It depends on which job you're doing, and the two are treated differently. Swapping an existing unit for one the same size doesn't change anything structural. Cutting a new opening does, because it means altering roof framing, and that's the kind of work jurisdictions look at. We confirm what your county or city requires before we schedule, and you'll know whether a permit is part of the job before anyone starts.

On a commercial building, yes. On a house, no, because we don't take flat residential roofs at all, and that's a firm boundary rather than a case-by-case thing. On a sloped residential roof, skylights and sun tunnels both work on shingle, and pitch mostly affects how the light falls through the shaft rather than whether the unit can go in.

If they're more than about fifteen years old, yes, and it's the cheapest they will ever be. The flashing that seals a skylight is woven into the shingle courses around it, so replacing a unit later means opening a roof that's already finished and reworking somebody else's watertight detail. The labor is nearly free while the shingles are off. Doing it three years later is a separate job with its own setup.