Natural Light and Healthy Home Lighting
There is good evidence that natural light is good for you, physically and mentally, and some evidence that electric light which mimics daylight can help too. When you plan a home, that makes light one of the things worth designing for, not an afterthought once the walls are up.
This guide covers how to get real daylight into the rooms that need it, and how to choose electric lighting that reads like the sun once the daylight goes.
Daylight is the starting point, and orientation controls it
The best light in any home is free and comes through the windows. Getting the right daylight into the right rooms at the right time of year is the heart of passive design, and it starts with orientation. Living areas on the north catch the low, warm winter sun through the day and are easy to shade in summer, which is exactly the light you want where you cook, eat and relax.
A simple planning rule helps here. Keep a window within about 6 metres of any part of a room, because daylight and natural ventilation both reach roughly 6 metres in. Past that the room turns dark and airless and you fall back on lights and fans.
Choose electric light that looks like daylight
When the sun goes down, the quality of your electric light matters more than most people realise, and the average Australian home has around 37 light bulbs, so it is worth getting right. Colour is described two ways, and it helps to keep them apart. Correlated colour temperature, measured in kelvin, is the shade of white, warm and yellow at the low end, cool and blue at the high end. The colour rendering index, or CRI, is a different thing entirely: it measures how truthfully the light shows colour compared with daylight. Sunlight scores 100. Aim for LEDs rated CRI 95 or higher, and 99 if you can find them, so skin, food and materials look the way they should.
Brightness matters too. Aim for around 1200 lumens in living areas, because brighter, high CRI light is easier on the eyes and makes everything clearer at night. For the colour of the light, warm white under 3000 kelvin suits a home, and dimmable or colour tuneable fittings let you soften it in the evening.
The details that stop good light going wrong
Cheap LEDs flicker, and flicker causes headaches and eye strain even when you cannot consciously see it. Use dimming controls matched to the LEDs, and fittings with high frequency control gear, to avoid it. Shield the lamp itself so you are not staring at a bright point, and bounce some light off the walls and ceiling while keeping enough downward light for tasks like cooking.
It is worth being honest that the science here is not fully settled. The evidence points strongly to the value of real daylight, and of brightness, variability and avoiding flicker, while the evidence on colour rendering alone is more mixed. The safe reading is to prioritise real daylight first, then choose electric light that is bright, warm, flicker free and high in CRI.
Common questions
What CRI should I look for in a light?
Aim for CRI 95 or higher, and 99 if you can source it. Daylight is 100, so the closer you get, the more natural colours look indoors. Many cheap LEDs sit around 80, which makes rooms and skin look flat and grey.
How far can daylight reach into a room?
About 6 metres. Both daylight and natural ventilation reach roughly 6 metres from a window, so keeping every part of a room within that distance of glass is a good planning rule. Deep rooms need windows on more than one side.
Does the direction a window faces change the light?
Yes. North light is the prize, steady and warm through the day and easy to shade in summer, which is why living areas belong on the north. East light is bright in the morning, west light is harsh in the late afternoon, and south light is soft and even but cool. Dudils shows each plan with north up so you can see where the good light lands.