To get something like sunlight into a room with no windows, light it brightly from the ceiling and put that light on a schedule: cool and bright in the morning, warmer and dimmer through the afternoon. With no window, the ceiling provides all the daylight there is, and nothing outside tells your body what time it is. Sunday Light, the artificial skylight we make in London, gives 34,500 lumens from the ceiling and runs that schedule by itself.
What a room with no windows takes away
The first loss is brightness. Most homes sit at 100-300 lux and a well-lit office at about 500, while outdoors is 50 to 100 times brighter than a typical room. A window, even a small one, lets some of that in. A windowless room has only what its fittings give.
The second is the clock. The body's internal clock runs on a cycle of about 24.18 hours on average (Czeisler et al., Science, 1999), so it needs a daily light signal to stay in step with the day. A window delivers that signal whether you notice it or not. In a small study of office workers, those with windows got more light during the working week and slept an average of 46 minutes more per night than those without (Boubekri et al., Journal of Clinical Sleep Medicine, 2014).
How bright, and on what schedule
The 2022 consensus from circadian researchers (Brown et al., PLOS Biology) recommends at least 250 lux of melanopic light at eye level through the day, no more than 10 in the three hours before bed, and no more than 1 overnight. Melanopic lux weights light for the cells in the eye that set the body clock. The same paper notes that common indoor light sources reach those cells substantially less efficiently than daylight, and that an office lit to the standard 500 lux usually gives under 200 melanopic lux at eye level.
So a windowless room needs more daytime light than an ordinary office, and a firm wind-down. In practice: cool light around 5000-6000K, as bright as you can get it, from the start of the working day; warmer and dimmer through the afternoon; and low, warm lamps in the evening. With no sunset outside to prompt you, the change has to happen on a timer, and in a room like this the schedule matters as much as the brightness.
Your options
Smart bulbs are the cheapest way to get a schedule. Philips Hue's 1,600-lumen White Ambiance bulb (£49.99 in the UK in October 2026) goes from warm to cool white, and Hue's Natural light scene shifts it through the day automatically. Three of them give 4,800 lumens, about the output of one bright ceiling light.
A light box gives a strong dose in a short session. The Carex Day-Light Classic Plus ($169.99) gives 10,000 lux at 12-14 in, and Carex suggests 20-30 minutes each morning. Lumie's Vitamin L (£99) gives 10,000 lux at 20 cm and 2,500 lux at 50 cm. Both light the person in front of them; the rest of the room stays at whatever the ceiling gives.
Sky panels such as Philips Skylight (3,800-5,300 lumens) and Govee's Sky Ceiling Light (7,000 lumens) look like a patch of sky and follow a daily schedule, which suits a room with no window. Their output is that of a bright ceiling light. The four kinds of artificial skylight compares them with recessed systems and with Sunday.
A skylight where there is no window
Sunday is an artificial skylight that hangs like a chandelier, so it goes into a windowless room with no roof work. The LED sits at the bottom of the arm and shines up at a sheet 120 cm across. The sheet scatters the bluer light and reflects the warmer light, the same Rayleigh scattering that happens in the atmosphere, so you see a sky glow with a warm centre and the room gets soft, indirect light. Sitting under it you get 5,000 lux and more, reaching 10,000 lux at 60 cm from the sheet, with a CRI of 97+. It emits visible light only, with no UV, and it is flicker-free.
Set a schedule once in the app and the light follows the sun on its own: cool 6000K daylight in the morning, then warmer and dimmer through the afternoon towards 2650K. We recommend having it off by around 6pm. The Sunday Remote, which comes with it, changes brightness and colour whenever you want something different. Water flows through the tubes in the arm to cool the LED, which is what lets it hold this brightness through a working day.
It needs a ceiling of 240 cm or more, and below about 260 cm it should hang over your desk rather than a walkway. Any qualified electrician can fit it in 1-2 hours. A solid concrete ceiling is no obstacle, and if the room has no ceiling light point, it can be powered by a cable run to a wall socket. At full brightness it costs about 10p an hour to run.
Sunday Light, our sunlight fixture, is £5,900 in the UK, $6,900 in the US and €6,900 in Europe, with free worldwide delivery. We install it for £450 in London and $450 in New York, Los Angeles, San Francisco and Seattle. The full specification is on the sunlight ceiling light page. If your trouble is the mid-afternoon slump, bright light for afternoon focus covers what the research shows.
