What is the difference between a roof lantern and a skylight?
A lantern is a glazed structure standing above the roof, with sloping faces meeting at a ridge. A skylight, in ordinary use, is a single pane sitting in the plane of the roof. One adds height and collects light from several directions; the other is quiet, modern and cheaper. They are different products rather than better and worse versions of the same one.
The word skylight
Used loosely, and that is the root of the confusion.
People use it for a flat rooflight, for a roof window in a pitched slope, and occasionally for a lantern, so it is worth establishing which product is actually meant before comparing anything.
What a lantern is
A framed structure on a kerb.
Rafters rise from a perimeter beam to a ridge with glass in each face, and it stands proud of the roof by its full height.
The whole of it is on what is a roof lantern.
What a flat rooflight is
A pane on a kerb, in the plane.
A single sealed unit in a slim frame sits on an upstand and reads as part of the roof rather than as something on it.
That is on what is a flat roof rooflight.
What a roof window is
A different product again, for a pitched roof.
A framed opening window fitted between rafters in a sloping roof, flashed into the covering, which neither of the other two is.
That is on what is a roof window.
The height difference
The most obvious one and the one that decides most jobs.
A lantern is a metre or more above the roof on a decent size. A flat rooflight stands only the height of its kerb and frame.
On a low extension near a boundary that difference can be the whole argument.
What each does to the ceiling
Opposite things.
A lantern lets the ceiling continue upward into the structure, which makes a low room feel taller. A flat rooflight leaves the ceiling where it is and puts light through it.
What each does with light
Different qualities, similar quantities.
A lantern gathers from several directions and gives a brighter room earlier and later in the day. A flat pane gathers from directly overhead, which is the brightest part of an overcast sky.
How each looks from a bedroom window
Worth standing and looking before choosing.
Seen from above, a flat rooflight is a quiet dark rectangle in the roof and a lantern is a glazed structure. On a plain modern house the flat unit usually looks more considered.
How each looks from the garden
The opposite consideration.
From ground level a flat rooflight is invisible and a lantern is a feature, and on a period house that feature can be exactly what the building wants.
What each costs
A lantern is a step above.
More glass than plan area, more frame, a taller kerb and more making good, so the same opening is a larger job as a lantern.
The comparison is on how much does a roof lantern cost.
What each costs in heat
A lantern loses more for the same opening.
The larger glazed area and the greater length of frame both count against it, though good specification narrows the gap considerably.
The figures are on how much heat do you lose through a roof lantern.
Overheating
Both can, for different reasons.
A lantern faces several directions so no orientation describes it, and a large flat pane over a south facing room takes the high summer sun square on.
Solar control glass answers both, as on will a rooflight make my room too hot.
Cleaning
Different problems.
A lantern sheds rain off pitched faces and stays cleaner, but the ridge is out of reach. A flat pane is reachable and holds what lands on it.
Which suits a period house
Generally the lantern.
Victorian and Edwardian back additions had glazed lanterns, so the shape belongs to the building and a flush pane can look like an insertion.
Which suits a modern extension
Generally the flat rooflight.
A plain rendered box with a flat roof and large sliding doors is a composition that a flush pane joins and a lantern interrupts.
Which suits a pitched roof
Neither of the first two.
A pitched slope takes roof windows, and a lantern needs a flat platform built for it, which is rarely worth doing.
That is on can a roof lantern go on a pitched roof.
Having both on one house
Common, and it works when it is deliberate.
A lantern over the kitchen and flat rooflights over a utility or a hallway is a sensible specification, provided the frame finishes match.
Where the words matter practically
When you are getting quotations.
Three firms quoting for a skylight can be quoting for three different products, and the only way to compare them is to establish which of the three is on each quotation.
Asking for the product name and the plan size settles it.
What a builder usually means
Whatever they last fitted.
Trade usage varies by region and by generation, so it is worth confirming rather than assuming a shared meaning, particularly on a drawing.
What an architect usually means
Something specific, drawn.
Where a lantern or a flush rooflight has been specified on a drawing, the section will show which it is, and that is more reliable than the label on the plan.
The question we start with on a lantern
We ask what the room needs, height or light, before we recommend either, because those two answers point at different products and the price difference follows from the answer rather than leading it.
The whole picture is on the roof lantern installation page.
Thinking about this job? We survey across Worthing, West Sussex and the South Downs and give you a fixed price before any work starts, with a 10-year workmanship guarantee.