The following is an excerpt from Green Lighting: How Energy-Efficient Lighting Can Save You Energy and Money and Reduce Your Carbon Footprint by Brian Clark Howard, William J. Brinsky and Seth Leitman (McGraw-Hill, 2011). The excerpt is part of Chapter 8: Lighting Best Practices and Daylighting.
While it’s possible to choose a lighting scheme based on detailed calculations of square footage, bulb output in lumens, angles of light, and other factors, it’s also true that lighting is highly intuitive. For the most part, it’s relatively easy, and affordable, to change the lighting in rooms. Simple adjustments include swapping out bulbs and shades, adding or subtracting floor lamps, or changing your curtains. In other cases, more intensive changes may be needed, such as rewiring fixtures or adding a window or skylight to let the free sunshine in.
In general, it’s best to light rooms with a number of sources rather than from a single lamp, whether it is an overhead or based on the floor or wall. By using several sources, you help to reduce glare and harsh shadows and have more flexibility.
Let’s take a look at some ways to maximize comfort and productivity, as well as energy savings, in your home or business.
Indoor Lighting Strategies
Here are some general tips for smarter, more efficient lighting:
• Use focused task lights as much as possible, reducing the need for general ambient lights.
• Use the lowest-wattage bulb you can for a given task.
• Turn off lights when you aren’t using them; sensors, timers, and other controls can help.
• Use light colors on walls, which will reflect more light and reduce your need to generate it.
• Maximize the use of windows and skylights, which is called daylighting.
• In retrofits and new construction, make sure that all lighting meets, or exceeds, applicable codes. This will improve safety, preserve your property value, maintain efficiency, and reduce your liability and risk of fines.
Know When to Turn Off Your Lights
Naturally, the surest way to save energy with lighting is to reduce the length of time that it is switched on. However, the actual cost-effectiveness of when to turn off lights depends on a number of factors, chiefly the type of light and the price of electricity. Turning off incandescent lights starts saving money after just a few seconds because they don’t require much to start up. Also, since incandescents are not appreciably degraded by turning them on and off, they can be switched on and off frequently without loss of life.
With fluorescents, on the other hand, it’s a bit more complicated. For recent fluorescent technologies, it takes only about five seconds of use to use the same amount of power that it requires to start up, according to the U.S. Department of Energy (DOE). However, since frequent switching does decrease the life of fluorescents, experts recommend shutting them off only if you won’t be using them for 15 minutes or longer.
To calculate precisely how much energy you are saving by turning a light off, follow these instructions from the DOE: First, determine how much energy the light consumes when on. Do this by locating the watt rating printed on the bulb. Multiply that number by the number of hours the light is on, and divide that by 1,000 to convert to kilowatt-hours. For example, for a bulb rated at 40 watts and used for 1 hour, this will consume 0.04 kilowatt-hour–or it will save 0.04 kilowatt-hour for every hour it is off.
Next, find out what you are paying for electricity. For some customers, this may vary based on time of year and peak or off-peak periods, so you can do the calculation multiple times to get more exact results. Look at your electric bill to see what the utility charges per kilowatt-hour, and multiply the rate by the amount of electricity saved by not using the bulb. With this example, if your electric rate is 10 cents per kilowatt-hour, the value of the energy savings would be 0.4 cent ($0.004) per hour. Of course, the value of the savings will increase with higher-wattage bulbs and as electric rates go up. If you know the cost of a replacement bulb and any labor costs changing it would require (for commercial managers), you can estimate when it is most cost-effective to make sure that lights are shut off.
As in most of life, too much of a good thing can be a problem. Too much lighting not only wastes energy, but it also can be uncomfortable to room occupants. No one, except maybe the occasional rock star or retro new waver, wants to wear sunglasses indoors. Overlighting can cause excessive glare and actually can make it harder to complete tasks.
Outdoors, overlighting can become light pollution, which disrupts wildlife, disturbs neighbors, and impedes the view of the starry sky.
Choose the Right Light for the Job
Low-pressure sodium lights may be efficient, but their poor color rendering and long startup times make them unappealing for most indoor spaces. Similarly, many cheaper compact fluorescent lamps (CFLs) have low color rendering indexes (CRIs) and harsh color temperatures and may not be ideal for living spaces, although they can work fine in utility areas, hallways, and the like. If you replace a 60- watt incandescent bulb with a 14-watt CFL and you don’t like the color or look of the light, try a different CFL. Sometimes, using a higher-wattage CFL will help to compensate for the difference, since it will produce more light.
Artists and crafters have known for a long time that full-spectrum and high-CRI lights can help them to better see colors and details. This is also why paint mixers often work under full-spectrum lights–to better see the “true color” of the pigments. Grow lights for indoor plantings are also often full spectrum or nearly so to maximize the benefits to vegetation. Similarly, anyone who has ever kept reptiles knows that the animals are healthier if their caretakers use lamps that are formulated to more accurately replicate natural environments.
Along these lines, some manufacturers tout full-spectrum lights for phototheraphy, which is used primarily to counter seasonal affective disorder (SAD), a type of depression that seems to result from reduced exposure to sunlight during the winter. However, the role of artificial lighting in reducing SAD is not well understood, and some research suggests that white or blue light (or just simply the amount and timing of light) may be the crucial part of prevention.
Lighting Room by Room
The lighting needs of each room can be a bit different depending on how the space is used primarily, as well as its size, orientation, color, and relationship to other rooms. Still, there are some general guidelines that can help to get you started:
• Entryways. Ideally, lighting in foyers should offer a transitional level of brightness between the outdoors and indoors to help welcome visitors and guide them further inside. Notice that many fine apartment buildings and hotels use indirect lighting in entranceways, creating a soft, warm air of elegance. Wall sconces and overhead lights work well together. In private homes, these lights are rarely left on for long periods, so in that case they often aren’t good candidates for fluorescents.
• Kitchens. The kitchen is the heart of a home, so it should get lots of light. It also is a prime candidate for efficient technology because people spend a lot of time in their kitchens, and those lights are among the most used. A central fluorescent overhead fixture often works well for ambient lighting, paired with some additional features. Keep in mind that higher ceilings will demand brighter light bulbs, as will darker colors, including dark marble countertops.
Undercabinet lighting is becoming increasingly popular and is a great way to focus light right where you need it–on the counters where food is prepared. Light-emitting diode (LED) strip lights work well for this, as do small clusters of bright white LEDs made especially for this purpose. Fluorescent undercabinet fixtures are also widely available, and the housings tuck away neatly out of sight. Undercabinet lighting can make a kitchen feel bigger, as well as more contemporary. Another popular place for indirect lighting is at the tops of cabinets, which can give the room a soft glow, as well as highlight artwork. Don’t forget to make sure that any fixtures that could come into contact with water are protected by a ground-fault circuit interrupter to prevent electric shocks.
Another way to add interest to a kitchen is with hanging pendants, many of which are quite colorful and which often work great with CFLs. Pendants also can be placed over high-use areas to provide more light when needed, or they also can be used to divide up, as well as decorate, different sections. They are often used over eating areas.
Ceiling fans are popular in kitchens, as well as in bedrooms and other areas. Note that fan vibrations can decrease the life of CFLs, so it can be a wise investment to get models that are designed for the purpose. You also can choose Energy Star-registered fan-light combos, many of which are specifically designed for CFLs.
• Dining rooms. Traditionally, the centerpiece of a dining room is a large hanging light, whether it’s a classic crystal chandelier or a bold avant-garde statement piece. For the best effect, the fixture generally should be at least 12 inches narrower than the table and should hang a minimum of 30 inches above the table’s surface to avoid glare, not to mention collisions with taller guests. As with all rooms, light should not be from only one source; a chandelier should be augmented by one or more adjustable downlights or wall lights.
• Living rooms. Think layers of light, which you can apply in succession as needed. This can include some overhead ambient lighting, task lighting for reading or other activities, and accent lights–such as recessed low-voltage fixtures–to add a sense of depth and show off parts of the decor.
• Bathrooms. Bathrooms also should be well lit, although, unfortunately, many aren’t. It’s usually easiest to install a single light above the mirror, and this is what builders often do in apartments or older homes. But this scheme produces harsh shadows and high glare. It’s much better for putting on makeup or shaving to have lighting coming from either side of the mirror, ideally 35 to 40 inches apart and at head level (think about the dressing rooms of stars shown in classic movies). Pair this vanity light with an overhead, ideally something built into an exhaust fan unit.
• Bedrooms. Soft, warm light is best for bedrooms, and dimmers are particularly effective. With overhead lighting, reduce harshness and glare by using recessed downlights that focus toward the foot of the bed or toward the sides of the room. Pendants and wall scones also can add beauty and comfort. Pair these with table or directional lighting for reading on either side of the bed, as well as task lighting for closets.
People want their bedrooms to be cozy, and many are reluctant to consider CFLs because of their past associations with offices and cool temperatures. This is where new extrasoft CFLs shine and where it pays to use a good fixture that moderates the light. “People generally don’t like to look at CFLs. I mean let’s face it, they aren’t the prettiest looking things,” Bergman explained as he showed off the diffusing fixtures in his own bedroom. “So I make sure you can’t see the bulb.” Bergman’s bedroom is decidedly cozy and is lit with CFLs set in his fixtures.
• Offices. Since most offices–including home offices–are frequented for many hours at a time, fluorescents pay for themselves rapidly. Fluorescents also provide bright light that facilitates good visual acuity. To decrease reflections, avoid placing ceiling fixtures in front of a desk. Instead, light should come over the shoulders of the desk’s occupant. For more natural, comfortable lighting, use the fluorescents in indirect settings. Pair them with wall and accent lighting for variation, and provide task lighting as needed.
• Corridors. Hallways should be neither a lot brighter nor dimmer than adjoining rooms so that moving through them is not jarring to the eyes. Yet they should have enough illumination for safety, particularly in commercial settings. One general rule of thumb is to place a fixture every eight to 10 feet, either wall- or ceilingmounted. Fluorescents aren’t usually ideal in private residential hallways because the lights don’t need to be on much, although they can make a lot of sense in commercial buildings. LED strip lights can work well in nearly any hallway, as the Hageman family discovered in their green Rhode Island dream house.
• Stairs. For obvious safety reasons, stairs must be well lit, particularly in commercial buildings, where liability is a serious concern. David Bergman established a welcoming, diffuse light in the exposed-brick stairwell of his Manhattan condo building by placing a large, wall-mounted CFL fixture from his Parallel Universe series at each landing. Large commercial buildings are also increasingly installing recessed LEDs low to the ground, which illuminate each step. In typical homes, it’s common to use a single close-to-ceiling fixture or a chain-hung fixture at the center of the stairway.
• Basements. Good lighting can produce surprising transformations in basements, which often seem more dank, dreary, and inaccessible than they need to be. If possible, drive sunlight into your basement. If you can’t put in a few windows, consider tubular skylights. For artificial lighting, fluorescent ceiling fixtures provide a lot of light for low cost. To make your basement seem larger, light an entire wall with recessed lights mounted on the ceiling. The lights should be spaced at an equal distance from each other and the wall. If you have a workbench, desk, or sewing machine in your basement, use task lighting, as you would in other areas.
• Accents. If you have a fine painting, family portrait, or other type of wall covering you want to highlight, consider a dedicated picture light or recessed low-voltage light. This can be especially impressive in formal dining, living, or sitting rooms or in corporate lobbies. Recessed low-voltage lights or LEDs can beautifully illuminate china cabinets and hutches. If you want to emphasize or set something off, such as a table, buffet, or artwork, place wall fixtures on either side of that element. Place a light on a wall behind a plant to set off its silhouette.
We may not necessarily give it as much thought, but outdoor lighting is an important part of property management, and it provides safety, security, and aesthetics. Studies are inconclusive on whether outdoor lighting actually decreases crime, although most security experts believe that motion-tripped lights probably help. Unfortunately, outdoor lighting also results in significant energy use, and it can contribute to light pollution, which can disrupt wildlife and the sleep cycles of other people.
As stated earlier, it’s important not to overlight your yard (you also can look for fixtures that have been certified to reduce light pollution by the International Dark Sky Association). Outside, a little light can go a long way. Focus on the areas where you actually need illumination (driveways, pathways, and porches), and then add one or two areas to highlight, such as a sign or attractive tree or key part of the building. Remember to use controls to maximize utility but minimize energy use.
Here are common outdoor lighting strategies:
• Uplighting. Lights are placed at ground level and are aimed up toward a focal point, such as a sign, wall, or tree. The fixtures are often floodlights or spotlights.
• Downlighting. As the name implies, elements are lit from above, often with spotlights or floodlights.
• Spotlighting. A strong beam focuses on an object, such as a flagpole.
• Pathlighting. Lights are placed low to the ground to illuminate a path or a driveway.
• Backlighting. Lights are placed behind objects, such as plants, and fixtures are concealed.
Here are some additional outdoor lighting tips: Installing outdoor lighting can require some of the same thinking that goes intoother aspects of landscape design, especially the need to keep future changes in mind. “Install conduit under driveways or patios before paving or bricking, and have the ground-fault circuit interrupter (GFCI) receptacles installed before getting started,” Randall Whitehead, a landscape lighting designer in San Francisco, told Popular Mechanics magazine. He added, “Buy fixtures with more wattage capacity than you need, [and] then increase wattage in the future by replacing smaller wattage lamps with higher-wattage ones [within the capacity of the transformer] as the plants mature.” To avoid a monotonous look, mix and match fixtures and spacing.
Reprinted with permission from McGraw-Hill.