Windowless rooms: lighting a space with no daylight

In a windowless bathroom, hallway, storeroom or basement room, artificial light does all of daylight’s work. A lighting scheme that keeps such a space from feeling cramped and gloomy.

Homes have more windowless rooms than we tend to think: bathrooms, toilets, hallways, dressing rooms, storerooms, and sometimes a study or guest room created by a new layout. Basement rooms in houses often have no natural light either. In these spaces artificial light works all day, not just in the evening, and has to do everything daylight would. Set up badly, the room feels cramped, dull and tiring.

The problem: daylight’s three jobs

Daylight does three things in a room, and in a windowless room each one needs its own solution.

• Overall light level. Light from a window fills the room evenly during the day.
• Lit ceiling and walls. Daylight falls on surfaces, so the room feels spacious and open.
• A sense of time. Light changes colour and brightness through the day, and people sense the hour.

A single ceiling light solves only the first of these, and only partly.

Light the ceiling and walls

The most effective way to open up a windowless room is to send part of the light onto the ceiling and walls. The brain reads bright ceilings and walls as open space. For this, use:

• wall lights or floor lamps aimed at the ceiling;
• concealed lighting along a ceiling cove;
• spots that wash a wall from above, or linear light along a wall;
• pendants that send light both down and up.

A single row of downlights, by contrast, lights the floor, leaves the ceiling dark and makes a windowless room feel like a cave.

Light, matt surfaces

In a windowless room, surface colour decides where the light goes. Light, matt walls and ceilings reflect it evenly, so lamps do more with less power. Dark walls soak light up, and glossy surfaces show reflections of the lamps and create glare.

A mirror is especially useful in a windowless room: it reflects light and makes the space look larger. Place it where it does not reflect a light source directly.

Colour temperature and the daily rhythm

Without daylight, the colour of the light matters even more. There are a few approaches:

• By the room’s function. Warm or warm-neutral light is comfortable in bathrooms and hallways. In a windowless study used for work or reading, neutral white light helps concentration.
• By time of day. Tunable systems can give more neutral, brighter light during the day and warmer, dimmer light in the evening. In a windowless room where someone spends long hours, this partly imitates the changes of daylight.
• Consistency with neighbouring rooms. If a windowless hallway links rooms with windows, its light colour should not contrast sharply with theirs.

For anyone spending long periods in a windowless room, sufficiently bright light during daytime hours also matters: staying in dim light all day adds to fatigue.

Comfort: glare and shadows

With no distant window view for the eyes to rest on, glare and hard shadows are more bothersome in a windowless room. To reduce them:

• keep bare bulbs out of sight, using opal shades or diffusers;
• split the light between several softer sources rather than one powerful point;
• add light from the side at a workplace so your hand does not shadow the work.

Bathrooms and toilets

The most common windowless room is the bathroom. Along with general ceiling light, it needs light around the mirror that lights the face from the front. In a humid environment, fittings need an ingress protection (IP) rating suited to the zone; defining those zones and installing the fittings is a job for a qualified electrician. A motion sensor also stops lights being left on in a windowless toilet.

Because lights in windowless rooms run all day, this is where LED bulbs make the biggest difference. Sensors in hallways and storerooms and zoned switching in living spaces cut unnecessary burning hours.

In a windowless room, Zəfər İşığı E27 and E14 bulbs can handle general light and GU10 or G5.3 spots can add direction. Before choosing a colour temperature, the simulator on this site is worth a look.