A skylight and a roof window do the same basic job, bring daylight through the roof, but they are not the same product. A skylight is a glazed unit fixed into the roof slope that either does not open or vents only a few inches, and it usually sits above arm’s reach. A roof window is an operable unit installed low enough to reach, so you open, clean, and often escape through it like a normal wall window. The fastest way to tell them apart: if you can reach out and open it by hand, it is a roof window; if it is out of reach on a high ceiling, it is a skylight.
This guide sorts out the full family of terms (skylight, roof window, rooflight, sun tunnel, and roof lantern), explains the US and UK naming gap that trips up most buyers, and shows where cost, ventilation, and leak risk actually differ. For product picks and pricing on specific units, see our companion guides linked throughout.
Skylight vs roof window: the core difference
The core difference is operability and reach. A roof window is designed to be opened and reached by hand on a pitched roof, so it doubles as ventilation and, in many cases, a fire escape. A skylight is mounted on the roof slope for daylight first, is often fixed or only vented, and frequently sits too high to touch. Both are glazed roof openings; the distinction is how you interact with them, not the glass itself.
Manufacturers and installers apply the terms loosely, and VELUX (the dominant brand in the category) markets operable units under both labels. Treat the table below as the working distinction rather than a legal standard, because usage varies by brand and by country.
| Feature | Skylight | Roof window | Sun tunnel |
|---|---|---|---|
| Opens? | Fixed or vents a few inches | Opens fully, operable by hand | No, sealed tube |
| Within reach? | Often out of reach | Installed low enough to reach | Ceiling diffuser only |
| Typical roof pitch | Flat to steep, curb or deck mount | Pitched roofs, flush mount | Any pitch, small opening |
| Primary purpose | Daylight, some ventilation | Daylight, ventilation, egress | Daylight in small or dark rooms |
| Can serve as egress? | Rarely | Often, if sized correctly | No |
What is a skylight?
A skylight is a light-transmitting glazed unit built into the roof to bring daylight into the space below. Most residential skylights are either fixed (sealed, no opening) or vented (open a limited amount for airflow). They mount on a raised curb on low-slope roofs or deck-mount flush on shingle roofs, and they are the term most Americans reach for regardless of whether the unit opens.
Fixed, vented, and tubular skylights
Skylights split into three common subtypes, and the one you need depends on whether you want airflow, budget, or light in a tight space:
- Fixed skylight: sealed glazing, no opening. The lowest cost and lowest leak-point option because there are no moving seals.
- Vented skylight: opens manually, by electric motor, or by solar-powered motor to release hot air and moisture. Common over kitchens and bathrooms.
- Tubular skylight (sun tunnel): a small reflective tube that channels daylight from the roof to a ceiling diffuser, made for hallways, closets, and windowless bathrooms.
If your existing unit is failing rather than new, our roof skylight replacement guide covers when to replace versus reflash and what the job involves.
What is a roof window?
A roof window is an operable glazed unit set into a pitched roof, positioned so you can open, clean, and often climb through it. It sits flush with the roof line and pivots or hinges outward, giving both daylight and ventilation. Because it is reachable and can be opened wide, a correctly sized roof window can also serve as an emergency egress in a converted loft or attic bedroom.
The practical test installers use: if the unit is low enough that you operate it by hand from the floor or a short reach, it is functioning as a roof window. VELUX and similar brands sell center-pivot and top-hung models specifically for this reachable, habitable-room use.
Rooflight, sun tunnel, and roof lantern: the rest of the family
Beyond skylights and roof windows, three more terms show up in listings and quotes. Knowing them prevents paying for the wrong product.
Rooflight
A rooflight is the same thing as a skylight, expressed in British English. In UK building terminology a rooflight (also written roof light) is any glazed opening that brings daylight through the roof. If you are reading UK product pages or importing a unit, read rooflight as skylight. Our overview of roof lights and the four things that term can mean untangles the decorative and off-road uses that also share the phrase.
Sun tunnel (tubular skylight)
A sun tunnel is a reflective tube, capped by a weatherproof dome on the roof and a diffuser in the ceiling, that carries daylight into small or hard-to-reach rooms. It is also sold as a sun tube, solar tube, light tube, or tubular skylight. It brings light without a large roof opening, so it is cheaper and lower risk than a full skylight, but it does not open and does not offer a view.
Roof lantern
A roof lantern is a raised, multi-pane glazed structure that sits above a flat or low-slope roof, common over extensions and orangeries. It is a daylight feature more than a window, does not typically open, and costs more than a standard skylight because of its framed, pitched glazing.
US vs UK terminology: the naming gap most guides skip
The single biggest source of confusion is that the US and UK use different words for the same products, and cross-border product listings mix them freely. A “rooflight” quote from a British supplier is a skylight; a “roof window” means an operable unit in both markets but is used far more consistently in the UK. Match the term to the market before you compare prices.
| Product | Common US term | Common UK term |
|---|---|---|
| Fixed glazed roof opening | Skylight | Rooflight / roof light |
| Operable reachable roof unit | Skylight or roof window | Roof window |
| Reflective daylight tube | Sun tunnel / tubular skylight | Sun tunnel / sun pipe |
| Raised multi-pane glazed feature | Skylight / roof lantern | Roof lantern |
How much do skylights and roof windows cost in 2026?
Installed cost depends mostly on whether the unit opens and how it is powered, not on the skylight-versus-roof-window label. Per 2026 cost guides such as HomeGuide, VELUX units run roughly $150 to $2,000 for the unit alone and about $1,350 to $7,300 fully installed, with fixed units cheapest and powered vented units highest. These are reported national ranges; your quote varies by roof material, pitch, access, and region.
| Type | Reported installed range (2026) | Notes |
|---|---|---|
| Fixed skylight | About $3,000 to $5,000 | No moving parts, lowest leak risk |
| Manual vented | About $3,200 to $5,900 | Opens by hand crank or pole |
| Electric vented | About $4,350 to $7,250 | Motorized, wired to power |
| Solar vented | About $4,250 to $7,150 | May qualify for tax credits, verify current rules |
Many homeowners report paying roughly $1,650 to $3,800 for a single medium fixed skylight on an asphalt shingle roof, per the same 2026 guides, with sun tunnels typically the cheapest option because the roof opening is small. For brand-level pricing, see our VELUX skylights price guide and our ranked list of the best skylight brands and models.
Do skylights and roof windows leak?
Neither product leaks inherently, but every skylight or roof window is a penetration cut into the roof, so any of them can leak if the flashing is wrong or the seals age out. Industry sources are consistent that most leaks trace to installation and maintenance rather than the unit itself. Proper step and counter flashing that directs water around and past the frame is what keeps a roof opening dry.
VELUX, for example, backs skylights installed with its own flashing kits under a 10-year installation warranty against leaks, which signals how central flashing is to the outcome. Fixed units carry the fewest leak points because they have no operable seals, while older acrylic domes and failed gaskets are common culprits on units past their service life.
Which one should you choose?
Pick by how you want to use the opening, then match the term to the market you are buying in. A short decision path:
- Want daylight only, tight budget: a fixed skylight or, for a small dark room, a sun tunnel.
- Want daylight plus ventilation, unit is high up: a vented skylight, manual if reachable with a pole, powered if not.
- Want to open, clean, and possibly escape through it in a habitable loft: a roof window sized to meet local egress rules.
- Buying from a UK supplier: read “rooflight” as skylight and confirm whether the unit is fixed or operable before comparing prices.
Whatever you choose, the leak outcome rides on flashing and installer quality more than on the product name. Compare installed quotes on the same unit type, and confirm the flashing kit matches your roof material.
Reviewed by The Roofing Brief Team. Last reviewed July 2026.