Light as a Material: Designing Daylight in an Apartment

Light is the only material you cannot buy and bring to site. It is either there or not, and everything we do with plan and finishes is a way of taking more of it — or, sometimes, of softening it. So my project begins not with a picture but with three questions: where do the windows face, how deep is the room, and what will the light reflect from.

Where the windows face

South gives an even, high light for most of the day — easy to dose. East is low morning sun: good for a bedroom and a kitchen, where the day begins. West means long warm evenings and summer overheating: living room and the place for dinner. North is shade without direct sun, the most stable and honest light: a study, a workshop, anything where colour matters.

In the city the surroundings join the compass: the building opposite, a tree, a courtyard well. In historic St Petersburg a south window onto a courtyard well can be darker than a north window onto a wide street. So I always look not only at the compass but into the window itself — ideally at different times of day.

How deep the room is

There is a simple working rule: daylight does its job to a depth of roughly twice the height of the window head above the floor. A window with its head at 2.4 m "lights" about 4.5–5 m in; beyond that is dusk that has to be lit by day. Hence the consequences: in deep rooms, what needs light goes by the window (a desk, a kitchen worktop), and what lives under artificial light goes deep (wardrobe, bathroom, storage).

The second consequence: if a wall stops light going deeper, it is worth opening it — with glass, a wide opening, a cut under the ceiling. That is how the kitchen-livings in my projects work: one volume instead of three rooms, first of all for the light, not for fashion.

What the light reflects from

Half the light in a room is reflected. A white ceiling and a pale floor return it into the depth; a dark floor takes it away. Matt pale surfaces give soft diffusion; gloss gives glare and fatigue. So by the window in my interiors there are almost always pale tones and matt textures, and depth and colour further in, where they do not steal light.

Window reveals are reflectors too: splayed inward and painted white, they add noticeably more light than square, dark ones. A free decision people forget.

Light as a planning tool

Once the orientation and depth are known, the plan almost assembles itself: morning to the east, evening to the west, work to the north, private rooms where the sun does not wake you. Then artificial light as a continuation of daylight: warm and low where evenings are lived, even and high where people cook and work. It does not argue with the window; it takes over when the sun leaves.

Below is a small tool I use at the first meeting: it shows when direct sun enters your room and how deep daylight reaches. It is no substitute for an insolation calculation, but it is an honest first conversation with a window.