Light or dark rooms: how window size changes the choice

A small or dim room usually looks best in a light color, because light colors reflect more of the daylight that reaches them. That is the simple answer, but window size changes it considerably. A room with generous glass can carry a deep color that would feel heavy in a room with a single small window, and the right choice depends on how much light the room receives and when it is used.

Two questions guide the decision: how much daylight reaches the room, and how much time is spent there after dark. Answering both before buying paint prevents a common mistake, which is choosing a color that looks lovely in a bright store and disappoints in the room it was meant for.

What a light color does in a small or dim room

Paint manufacturers often publish a light reflectance value, or LRV, for each color. The scale runs from 0 for pure black to 100 for pure white, and a higher number means the color reflects more light. In a dim room, a higher LRV helps make the most of limited daylight, so the walls look brighter and the room feels more open.

Light colors have drawbacks too. A pale color with a cool or gray undertone can feel cold in a north-facing room, and a very bright white can make a dim room look starkly lit rather than cozy. A light color with a warm undertone usually solves the coldness, and a softer off-white avoids the glare.

What a deep color does and where its risks lie

Deep colors absorb more light, which can make a room feel enclosed, especially when the window is small or set high in the wall. In a small room, a dark wall can reduce the apparent size of the space, and strong contrast with a bright ceiling can make the edges of the room feel closer. Deep walls also show dust, scuffs and uneven application more readily than light ones.

These risks are not reasons to avoid deep color altogether. They are reasons to think about where it goes, how it is finished and how it will be lit. A deep color on a single wall, or on the trim and ceiling of a room used mostly in the evening, produces a different effect from a full room of dark walls with little light.

How window size and count change the answer

Window size matters because it sets how much daylight enters, relative to the amount of wall that daylight must cover. A room with large windows on a sunny side may have enough light to support a mid-depth or even a deep color, since the light keeps the walls from looking muddy. A room with a single small window on the north side will struggle to show the same color well.

Window count and orientation change the picture further. Two windows on different walls light a room more evenly than one, and a south-facing window gives more direct sun than a north-facing one in the Northern Hemisphere. Trees, neighboring buildings and overhangs can also reduce the light more than the glass size suggests, so check the room at the time of day it is used.

When a deep color can still work

A deep color can work in a room used mostly at night, such as a dining room, media room or study, because the lamps provide the light the walls reflect. The color will look different under lamps than under daylight, so judge it under the lamps that will actually be used. A deep color with a warm undertone tends to feel more inviting in the evening than a cool one of the same value.

A deep color can also work in a room with a strong architectural feature or several lamps. Painting only the walls that receive the most light, or using a deep color on built-in shelving or a door, adds depth without enclosing the whole room. Finish matters too. A satin or eggshell finish reflects a little more light than matte, but it also shows the condition of the wall more clearly, so the finish should suit the surface.

Deciding with a sample test

Test both a light and a deep option in the room rather than relying on the names on the chips. Use large samples, at least about 12 inches square, and place them on the walls where the room's light falls. View each one in the morning, at midday and in the evening, under the lamps that will be used. Compare how the two samples change through the day.

If neither extreme feels right, consider a mid-tone or a lighter shade of the deeper color. Many rooms look best at a value between the two extremes, where the color adds depth without absorbing the room's light. Whatever you choose, judge it in the room as it will be used, because the decision depends as much on the light and the hours of use as on the color itself. For many small or dim rooms, a light color with a warm undertone is the most dependable starting point, and a deep color earns its place when the room has enough light or spends most of its hours under lamps.