But there’s more to daylight than meets the eye. A house that’s optimized for daylighting helps us see better, think with more clarity, be safer, save energy, and makes our home a more enjoyable place to be.
Plenty of natural daylight creates a positive home environment and may even have health benefits, such as warding off seasonal affective disorder and other types of depression.
What is Daylight?
The light that comes into your house during the day is either direct sunlight or ambient light.
Direct sunlight is bright, hot, and cheery, but it creates glare and it’s everyday usefulness is limited until it turns into ambient light. Direct sunlight creates dark shadows.
Ambient light is reflected light. Sunshine that enters your house and hits a wall or floor turns into reflected, ambient light that fills interior spaces with a soft, pleasing glow. On a cloudy day with no direct sunlight, all the natural light inside your house will be ambient light. Good ambient lighting helps eliminate shadows.
Light intensity is important for doing tasks and setting the mood. Lighting psychology says that bright light creates a more positive and energizing environment; dark light calms and soothes.
Of course, too much bright light causes uncomfortable glare, and too little light makes it hard to read, clean, and find socks that match.
During the day, the goal of creating a well-lighted house is to control direct sunlight and maximize ambient light, supplementing as needed with artificial light.
What Makes Good Daylighting?
Good daylighting is a balancing act. In winter the sunlight that streams through your windows adds free solar heat that lowers your heating bill. In summer, you want to prevent direct sunlight from overheating interiors. All the while, you want to reduce harsh glare and create soft, ambient light that makes it easy to do everyday tasks (and relax when you want to).
Good daylighting is the interaction between lots of factors, including:
- House orientation.
- Proper window design and location.
- Light control (blinds, shades, etc.).
- Daylight requirements per type of room (living, bath, kitchen).
- Window shading.
- Interior design, such as the arrangement of furniture and paint colors.
- Reflective surfaces, both inside and outside your house.
- Supplemental (artificial) lighting.
How Much Daylighting Do You Need?
Light is measured several ways — one way is with footcandles (fc) — the amount of light that falls on one square foot. On a sunny day, the area outside your house gets about 10,000 footcandles; on a cloudy day, about 1,000.
Only a fraction of that enters your house as ambient daylight — from 1% to 10%. However, that’s generally enough for most needs:
- Living room: 10-20 fc
- Kitchen, general: 30-40 fc
- Kitchen stove: 70-80 fc
- Dining room: 30-40 fc
- Hallway: 5-10 fc
- Bathroom: 70-80 fc
But pinning down indoor daylight requirements gets tricky, as light shifts during the day and each set of eyes is different — children and older adults need more light than people who are between 15 and 50 years old.
Good daylighting really is a matter of personal preference — if you think your hallway is too dark, then it is — and you should find ways to add more light so that you’re safe and comfortable.
If you have a favorite nook for reading but it gets too much sunlight in the afternoon, then you’ll want to use a strategy to turn harsh light into softer ambient light.
In general, the more ambient light, the easier it is to see.
Getting the Most From the Windows You Have
The best way to control daylighting is to simply have your house oriented to the sun correctly. Best case: The largest facade of your house would face south and have the most windows.
Of course, you can’t do much about which way your existing house is facing, but knowing how natural light changes during the day and throughout the year can help you plan to control daylight effectively.
North-facing windows don’t get much direct sunshine, so in general they lose more heat than they gain. That means keeping north-facing windows to a minimum to reduce heat loss.
At the same time, north light is usually soft, pleasing, and free of glare — it’s the ideal ambient light.
A good compromise is to spend for well-insulated windows on the north side of your home. Energy-efficient windows with low-E coatings, argon gas insulation, and thermally resistant frames (such as wood and fiberglass) cost about 10% more than regular insulated windows, but they should pay for the difference in energy savings in two to six years. Plus, you’ll enjoy increased comfort.
East- and west-facing windows get lots of direct sunlight and can be difficult to shade. Morning east light is usually acceptable, even in summer, as it chases off darkness and adds cheery sunshine to interiors during the early part of the day.
But west light is more difficult to manage — in the summer it can be harsh and hot. To reduce the amount of western sunlight in the warmer months:
- Opt for low-E coatings on windows. To keep unwanted heat out, make sure the coating is applied to the inner surface of the outer pane.
- Shade windows with awnings. They’ll keep all but the very last sunshine out of interiors.
- Plant deciduous trees that shade your house during the summer but lose their leaves and let sunlight through in the winter.
You want to stop hot summer light on the outside of your house before it enters. Shades and blinds on the inside can block harsh sunlight, but they won’t prevent heat gain.
South-facing windows are the best, providing ample ambient light during the day and inviting in warm sunshine during the winter.
That’s because the sun is high during the summer, and your roof’s eaves keep most direct sunlight out of south-facing windows. During winter, the sun moves low across the southern horizon, sending warming sunlight under eaves and into south-facing windows.
Optimum eave overhangs vary according to your location. The more north you are, the lower the summer sun is on the horizon and the more sunlight can hit your windows — so you’ll need larger overhangs for shade. For example, to completely shade a 5-ft.-tall window in mid-summer:
- Miami: 1.5-ft. overhang
- Dallas: 2-ft. overhang
- Chicago: 3-ft. overhang
- Fargo: 4-ft. overhang
If your eaves are too short, it’s impractical to add on to them. But if you’re going to be replacing your roof, you might consider extending eaves at the same time.
The alternative is to add awnings. A fixed, 4-ft.-wide awning is $250-$350. A retractable, 7-ft.-wide awning is $1,200.
Passive solar experts used to say that deciduous trees on the south side of your house helped control heat gain, but the latest solar planning says that the leafless branches of deciduous trees can block up to 40% of precious winter sunlight, so don’t plant them there.
You can add daylight by increasing the number and size of windows, but that’s not always practical or possible.
A good solution is to add skylights and solar tubes.
A skylight provides lots of light, about 30% more than a similar-size window. They’re best for general living areas, such as family rooms, and where you might want to combine extra light and privacy, such as a bedroom or bath. You’ll want to be cautious about adding skylights where intense sunlight and the resulting glare may be a problem, such as a kitchen or media room.
Some skylights come with low-E coatings, thermal glass, and mini-blinds that help control light intensity, heat gain, and heat loss.
A solar tube gathers light in a small rooftop dome, then channels it through a reflective tube down to a ceiling and a diffusing light fixture that creates ambient light. On a bright day, a solar tube with a 10-inch-diameter adds as much light as three bright LED bulbs, or enough to light a 200-sq.-ft. room.
They’re especially good for adding light to specific spots, such as stairways, hallways, closets, and laundry rooms.
Simple Ways to Maximize Daylight
To maximize ambient light, you’ll want to bounce it around. Interiors with bright colors help reflect light.
Paint colors are a primary source of reflected indoor light. In fact, some paint manufacturers rate their paints with an LRV — light reflectance value. You’ll find ratings on paint can labels.
An LRV of 0 is perfectly black; an LRV of 100 is total reflectivity. In reality, all paint colors are somewhere between. The brightest white paints approach an LRV of 85, with specially formulated paints reaching as high as 90. Yellow is the next most-reflective color.
Recommendations for LRV are:
- Ceilings: 60-90 LRV
- Walls: 35-60 LRV
- Flooring: 20-30 LRV
Avoid paints with a gloss sheen except for trim and in areas where splashes might occur — glossy paints create annoying glare.
Mirrors reflect almost all light that hits them. Put them in areas that have low natural light conditions, such as:
- Basement rooms.
Furniture arrangements may block light and create shadows. Keep large pieces of furniture away from windows and other natural light sources, and make sure your furniture arrangements have corridors that allow light to reach across rooms.
Venetian blinds are great at controlling light. By tilting them upward, you can direct incoming sunlight toward the ceiling, turning it into ambient light.
Curtains and shades are the ultimate low-tech lighting control. Translucent shades and sheer curtains block direct sunlight, turning it into softer ambient light. Some window coverings help save energy.
Daylight harvesting — also known as dynamic lighting — combines natural and artificial lighting to create ideal lighting conditions throughout the day.
It’s an automated system that uses light sensors to detect light intensity, and adjusts artificial lighting to keep lighting at a level that’s blended for optimum productivity and enjoyment.
Some systems include LED light bulbs that not only keep light levels constant — even when clouds move in — but will change their color temperature range throughout the day. That means the light the bulbs emit will shift from the cool light of morning to the warmer light of afternoon — mimicking the color shift of natural daylight.
Unfortunately for homeowners, the system isn’t in the residential market — yet. The technology is currently being developed for use in office buildings, so residential use probably isn’t too far away.