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Roof Lantern Lighting: Bright by Day, a Black Hole by Night

Archlior
Roof Lantern Lighting: Bright by Day, a Black Hole by Night

By day, a roof lantern is usually the brightest thing in the room. It is often the point of the extension: a kitchen or living space flooded with light from above. After sunset, the same lantern becomes the darkest thing in the room, a hole in the ceiling filled with night sky and reflections of the lights below it.

A common fix is to shine light up into the glass. Little of that light comes back. The better answer, as our guide to conservatory lighting puts it, is to light the lining, not the glass: the solid, plastered sides of the opening are the part of a lantern best placed to reflect light back into the room.

Why Lanterns Are So Bright by Day

A roof lantern looks straight up at the sky, and on an overcast day the sky is brightest overhead. The CIE standard overcast sky, the model used for daylight factor calculations, is about three times brighter at the zenith than at the horizon. A window in a wall mostly sees the dimmer sky near the horizon, along with buildings and trees; a rooflight sees the bright sky overhead.

Manufacturers and governments put numbers on it. Velux says roof windows give at least twice as much light as vertical windows of the same size. The Australian Government's YourHome guide says a skylight or roof window can admit more than three times as much.

The same exposure works both ways. YourHome also warns that skylights can be a major source of unwanted heat gain in summer and significant heat loss in winter. A lantern that floods a room with light in March can overheat it in July.

Why They Turn Into a Black Hole at Night

After sunset, the opening that was full of bright sky is full of dark sky. Almost nothing comes in. Worse, the glass now reflects: glazing becomes a mirror wherever the room is brighter than the space beyond it, so the pendants, downlights and spotlights below reappear in the lantern as bright reflections against the dark.

That is why a lantern can make a well-lit kitchen feel dim after dark. The largest feature in the ceiling has gone from the brightest surface in the room to a dark one, and it is studded with reflections.

Light the Lining, Not the Glass

What follows is design practice rather than a standard, and it is consistent with the approach in our conservatory guide.

The glass of a lantern reflects some light and lets most of the rest pass straight through. Aim light up into it and much of it carries on into the sky. The lining, the plastered upstand that rises from the ceiling to the lantern frame, is different: it is solid, usually pale, and faces into the room. Light it and it glows, framing the opening, and the light it reflects comes back down where people are.

There are two ways to do it.

Washing up from the base

A concealed strip at the base of the lining, where it meets the ceiling, washes light up the plaster. The lining glows brightest at the bottom and fades towards the glass, which frames the opening softly from inside. The strip sits at ceiling level, so it is easier to hide and to reach than one higher up. Some of the light carries on past the top of the lining into the lantern, so the strip's beam and position matter.

Washing down from the top

A strip set just below the lantern frame, aimed down the lining, keeps more of the light inside the room. The lining glows brightest next to the glass, so the dark sky is framed by a bright edge rather than a soft one. The strip is harder to hide, because people look up into the lantern from below, and harder to reach for maintenance.

Either way, light all sides at the same level, or the lantern will look lopsided.

Hide the strip from every position

Check the detail from where people will actually stand and sit, including the far end of the room, not just from directly below. Our guide to cove lighting explains the same sightline test for coves, and our LED strip lighting guide covers profiles, dots and where to put the driver. A strip in a profile, set into a small recess or behind a lip, can read as a glow rather than a line of LEDs.

What Not to Do

Do not uplight the glass. Little of the light comes back into the room, much of the rest leaks into the night sky, and the neighbours see a glowing lantern.

Do not fix fittings to the lantern itself. Industry advice from glazing installers is not to screw lights into the roof lantern frame, because it can weaken the structure and cause leaks. Anything attached to the lantern should be agreed with its manufacturer.

Do not leave the lantern unlit. A dark opening above a bright kitchen is exactly the black hole the lining detail is there to prevent.

Do not forget the reflections. Bright points of light below the lantern will reflect in its glass after dark. Fewer, softer sources reflect less harshly than a grid of downlights.

The Island Under the Lantern

Roof lanterns are often placed over a kitchen island, and that creates a problem the daylight hides. By day, the lantern lights the worktop beautifully. After dark, the island loses its light at exactly the place it is needed most, and there is no solid ceiling directly above it to hang pendants from.

There are three ways round it, and the choice belongs in the design, before the lantern is ordered:

Offset the lantern so that the island, or part of it, sits under solid ceiling, where pendants can hang in the normal way. Our guide to kitchen island pendants covers heights and spacing.

Light the island from the solid ceiling around the lantern, with adjustable downlights aimed at the worktop rather than straight down, keeping the beams out of people's eyes.

Design a support across the lantern opening for pendants or a suspended linear light, agreed with the lantern manufacturer and the structural engineer.

For the rest of the room, our guide to kitchen lighting design covers layering task, ambient and accent light.

Blinds: A Ceiling at Night

A lantern blind, drawn after dark, turns the black hole into a surface. Pale fabric catches light from the lining and the room, stops the reflections, and keeps the lantern from glowing at the neighbours. Our conservatory guide makes the same point: the blind is a ceiling when it is drawn. Motorised lantern blinds are a specialist product, so plan the fixing and power with the lantern supplier.

Light Spill and Neighbours

A lit lantern is visible from neighbouring gardens and upstairs windows, and any light aimed up through it adds to the glow of the night sky. DarkSky International's principles for responsible outdoor lighting include one that applies here directly: direct light so it falls only where it is needed. Light the lining rather than the sky, put the lantern lighting on its own dimmer, and draw the blind late at night. Our guide to dimming and lighting controls covers the controls side.

For Architects: Size, Heat and the Regulations

The size of a lantern is not only a design decision. In England, Approved Document L has for years limited the total area of windows, roof windows, rooflights and doors in an extension to 25 per cent of its floor area, plus the area of any windows or doors the extension covers up, unless the extra glazing is compensated for elsewhere. Council guidance on the 2022 revision says the limit still applies, with slightly stricter conditions. A large lantern uses up much of that allowance.

Overheating is the designer's problem, too. Approved Document O, the Building Regulations' overheating requirement, applies only to new residential buildings: the government's guidance says it does not apply to extensions or conservatories added to homes after they are built. Nothing in it will stop a large lantern overheating a kitchen extension, so solar control glass, blinds and ventilation need to be designed in.

And the lighting needs to be designed with the lantern, not after it: the recess or lip for the strip, the cable route and an accessible place for the driver all have to be in the build-up before the lining is plastered.

Checklist

Daylight and heat

  • Lantern size checked against the glazing limits that apply to the project
  • Summer heat gain considered: solar control glass, blinds, ventilation
  • Lantern position decided with the island and furniture layout in mind

Night

  • Lining lit, not the glass
  • Strip position chosen: base of the lining washing up, or top washing down
  • All sides of the lining lit at the same level
  • Strip hidden from every likely position in the room
  • Island task light planned: offset lantern, angled downlights or a designed support
  • Blind considered for night-time use

Practicalities

  • Nothing fixed to the lantern without the manufacturer's agreement
  • Recess, cable route and driver access built in before plastering
  • Lantern lighting on its own dimmable circuit
  • One colour temperature throughout the room
  • Mains connections made by a qualified electrician

Five Mistakes

  1. Uplighting the glass. Little light comes back, and the rest lights the sky.
  2. Leaving the lantern dark. It becomes the darkest thing in a bright room.
  3. Putting the island under the lantern without planning its light. There is nothing above it to hang pendants from.
  4. Screwing fittings into the lantern frame. Installers advise against it because of the risk to the structure and to the seals.
  5. Adding the lighting after plastering. The recess, cables and driver access have to be designed into the lining.

Frequently Asked Questions

How do you light a roof lantern at night? Light the lining, not the glass. A concealed LED strip at the base of the plastered lining washing up, or just below the lantern frame washing down, makes the lining glow and frames the opening. The lining is solid, so it reflects light back into the room, while light aimed up into the glass mostly escapes into the sky.

Can you put LED strip lights in a roof lantern? Yes, in the lining rather than on the glass or frame. Set the strip in a profile, in a recess or behind a lip so it is hidden from below, and plan the cable route and driver access before the lining is plastered.

Can you hang pendant lights from a roof lantern? Not from the lantern itself without the manufacturer's agreement; installers advise against fixing into the frame. Hang pendants from the solid ceiling around the lantern, or from a support designed across the opening with the lantern maker and a structural engineer.

Why does my roof lantern look like a black hole at night? Because the opening that was full of bright sky by day is full of dark sky at night, and the glass reflects the lights below it. Lighting the lining gives the opening a bright frame, and a blind, when drawn, gives it a surface.

Do roof lanterns let in more light than windows? Usually, yes, size for size, because they face the bright sky overhead. Velux says roof windows give at least twice as much light as vertical windows of the same size, and the Australian Government's YourHome guide says a skylight can admit more than three times as much.

Do roof lanterns make rooms too hot? They can. Roof glazing faces the summer sun, and YourHome warns that skylights can be a major source of unwanted heat gain in summer and heat loss in winter. In England, the overheating rules in Approved Document O do not apply to extensions, so it is down to the design.

What colour temperature should roof lantern lighting be? The same as the rest of the room, so the lantern reads as part of the ceiling rather than a separate feature. Warm white is a common choice for kitchens and living spaces in the evening. Our guide to colour temperature explains the options.

More on Light From Above

Notice

This article is published by Archlior for general information and educational purposes. It is written for architects, interior designers and homeowners as an introduction to lighting roof lanterns and rooflights.

It is not professional lighting design advice, structural advice, or a statement of compliance with the Building Regulations for any project.

Building Regulations guidance is summarised from the sources listed and may change; check the current Approved Documents and consult building control for your project. Manufacturer and installer advice is labelled as such. The sections on placing light describe design practice, not rules.

All mains electrical work should be carried out by a suitably qualified electrician working to the regulations in force locally. Nothing should be fixed to a roof lantern without the manufacturer's agreement.

Archlior accepts no liability for any loss, cost or damage arising from reliance on the information in this article. Readers act on it at their own discretion.

Last reviewed: October 2026.

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