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Martin’s 10 Rules of Lighting

Although most homes are poorly lit, they still use too much energy for lighting. Follow these rules to brighten up your home while lowering your energy bills.

Posted on Oct 21 2011 by Martin Holladay, GBA Advisor

Most homes use too much energy for lighting. According to the U.S. Energy Information Administration, the average American household uses 1,667 kWh per year for lighting, which amounts to 15.3% of residential electricity use. Ironically, this energy devoted to lighting is used inefficiently, so the usual result is a dim house with dark, depressing corners.

Although many electric utilities have subsidized the cost of bulb swap programs for years, the typical house still has far too many incandescent bulbs. Even people who have swapped their incandencents for compact fluorescent lamps (CFLs) often install their bulbs in terrible fixtures with opaque shades or dark lenses. Fixtures are often installed in awkward spots. The dark corners that are common in a poorly lit house become more noticeable as we all get older; to see well, older people need more light than younger people.

Finally, many houses have too few switches, so that homeowners have to make an all-or-nothing decision about whether to turn on all six bulbs in a track-light fixture.

Once you become aware of some basic lighting principles, you’ll be able to solve the lighting problems in your own home and the homes you build. There's only one downside to obtaining a lighting education: every time you stay in a hotel room, the bad lighting will drive you crazy.

Lighting basics

Lighting designers have their own jargon. They call light bulbs “lamps,” for example, and they call light fixtures “luminaires.”

Lighting designers often tell us that there are four different kinds of light: ambient, task, accent, and decorative.

Ambient light is the soft, general illumination that fills a room and softens shadows.

Task lighting is a focused source of light near a work surface, a countertop, or a book.

Accent lighting is a type of directed illumination used to spotlight an object — for example, a work of art or a houseplant.

Decorative lighting comes from a fixture chosen for its attractiveness — for example, a chandelier. (The purpose of decorative lighting is not so much to provide light as to draw attention to the fixture.)

The last two types of lighting — accent lighting and decorative lighting — fall into the realm of interior decoration. Although accent and decorative lighting can be important, I won't be discussing them in this article. If you’re a builder, you don’t necessarily have to master the intricacies of accent lighting and decorative lighting. But it is essential that you provide good ambient lighting and good task lighting in every room.

A single fixture is rarely able to provide both ambient and task lighting, so most rooms require several fixtures. It's no longer acceptable to put a single fixture in the center of the ceiling and call it good.

There are many ways to provide ambient lighting, but the best ambient lighting fixtures are designed to bounce light off the ceiling. This won’t work if your ceiling is finished with stained tongue-and-groove boards; that's why the best ceilings are finished with white-painted drywall.

Light fixtures that hang a few inches below the ceiling are often designed to send light upwards as well as downwards. This is a good design for an ambient light source. Ambient light can also be provided by fluorescent tubes located in coves, cornices, or ledges.

When it comes to task lighting, the key is to get the light source as close as possible to what you want to see. Task lighting doesn't have to be bright, but it should be close.

Color rendering index (CRI) and color temperature

Lamps are rated with two numbers related to color. The first is the color rendering index (CRI). The CRI scale goes from 0 to 100. Light sources with a high number render colors more accurately than light sources with a low number. Among the light sources that achieve 100 CRI are noon sunlight and incandescent bulbs. Many fluorescent bulbs have a CRI of 80, which is high enough to render colors accurately.

Lamps are also rated with a temperature rating in degrees Kelvin (K); this indicates the hue of the light source. Sunlight at sunrise, like an incandescent bulb, is considered a warm (orangey) light. (Confusingly, even though it is called “warm,” it is rated with a low number in degrees Kelvin.) Sunlight at noon, like a halogen lamp or some fluorescent lamps, is considered a cool (white or bluish) light; even though it is called cool, it is rated with a high number in degrees Kelvin.

Here are the degrees Kelvin and CRI numbers for a few light sources:

  • Incandescent bulbs: 2,700 K, 100 CRI
  • Cool white fluorescent tube: 4,100 K, 62 to 80 CRI
  • Noon sunlight: 4,500 K to 5,400K, 100 CRI

For thousands of years, people used candles or oil lamps for nighttime illumination. Eventually, most of the world switched to incandescent electric bulbs. All of these light sources — candles, oil lamps, and incandescent bulbs — are on the warm side of the temperature scale. By now, such warm light seems “normal.” But these warm lamps are a poor imitation of sunlight.

Sunlight is on the other end of the degrees Kelvin scale; it’s cool. Once you begin to notice the difference between cool light sources (for example, the light produced by a halogen lamp) and incandescents, you may begin to prefer cool lamps to traditional warm ones.

However, many people have strong opinions in favor of warm lamps. Fortunately, you can buy CFLs in almost any color temperature you want. Try a few different colors to see which color you prefer. If you’re in doubt, you won’t go wrong if you choose a lamp rated at 3,000 K with a CRI of at least 80.

Martin’s Ten Rules of Lighting

1. For now, screw-based CFLs are the best bulb choice for residential lighting. Bulbs with an Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. label are likely to last longer than cheaper unlabeled bulbs.

If LED lamps continue to drop in price and improve in quality, they are (eventually) likely to replace CFLs in many locations. If you care about energy efficiency, use linear fluorescent tubes (especially T-5 or T-8 lamps) in locations where they make sense, like kitchens. Don’t install any incandescent lamps.

Here is some information on lamp efficiency:

  • Indancescent bulbs produce about 14 to 17 lumens per watt.
  • Low-cost LEDs produce about 15 to 25 lumens per watt.
  • High-quality LEDs produce about 40 to 70 lumens per watt.
  • CFLs produce about 48 to 60 lumens per watt.
  • T-5 and T-8 linear fluorescent tubes produce about 98 to 105 lumens per watt.

2. It’s better to illuminate the ceiling than the floor. The U.S. is cursed by a plague of senseless recessed can fixtures. If you walk under a recessed can, it will cast strange shadows on your face. Why do people like these ridiculous fixtures?

Recessed cans do a great job of illuminating the floor, but they keep your ceiling dark. Some hotels use recessed cans to illuminate their hallways. As you walk down the hallway looking for your room, only one thought is going through your mind: “Ugly carpet. Ugly carpet.”

A good ambient lighting fixture works on a different principle from a recessed can fixture. If you use an ambient lighting fixture to bounce light off a white-painted ceiling, your ceiling will be brighter than your floor. This mimics the natural world; a bright sky makes us cheerful and optimistic. On the other hand, the combination of a bright floor and a dark ceiling feels ominous and unsettling.

Some people assert that recessed can lights can be used for task lighting, but I disagree. The ceiling is too far away from any task; that's why you need a pendant fixture or a wall-mounted swing-arm fixture for task lighting. The amount of light striking an object is inversely proportional to the distance from the light source squared. If you double the distance, you get only one-fourth as much light. If a lamp produces 64 lumens at 1 foot, it will produce only 16 lumens at 2 feet, and only 4 lumens at 4 feet. At 8 feet, you are down to 1 lumen.

The farther away your light source, the brighter it has to be to be useful. That's why the worst imaginable fixtures are recessed cans in a high cathedral ceiling.

3. Most homes need more task lighting. Almost every room needs at least one, and often several, task-lighting fixtures. Providing more lighting options usually saves energy. In an office, the most important light fixture is the task light over the desk. An adjustable desk lamp is fine; if you prefer a pendant, bring it low, close to the work surface. Remember: the closer the lamp to the work surface, the fewer lumens you need.

4. Every section of kitchen countertop needs task lighting. Such lighting can be provided by undercabinet lighting attached to the wall cabinets or by small pendant fixtures. Install them lower than you think. As long as the pendants don’t interrupt views through windows or across your kitchen, install them at eye level.

5. Task lighting fixtures should be controlled by separate switches rather than a single switch that energizes several fixtures at once. All-or-nothing switches that control several lamps at once are infuriating. To save energy, it's important to be able to control your lamps individually.

Resist the temptation to locate all of a room's switches in one location. Four switches all in a row are confusing. It's better to scatter the switches around the room; most switches should be located near the fixture that the switch controls.

6. Put reading lights where they belong. A reading light should be close to your book or magazine. In general, the light should come from over your shoulder or from the wall above the back of your head. A short table lamp on a low coffee table at the end of the sofa won't work; the light will be too low. Task lighting for reading should be provided for every piece of furniture in your living room. There shouldn’t be any armchair or any seat on a sofa where the lighting is insufficient for reading. In bedrooms, the best location for a reading light is on the wall above the headboard of your bed.

7. Most bedrooms have insufficient ambient light. If you're reading in bed, you don't really need any ambient light. But when you are getting dressed or packing a suitcase, you need plenty of ambient light. If your bedroom has insufficient ambient light, it's hard to find things.

8. Every bathroom needs at least two wall-mounted fixtures, located to the right and to the left of the bathroom mirror. If the light source is above the mirror, it can cast shadows on your face. Again, when fixtures are located in the right place, they can use bulbs of a lower wattage than are required for poorly placed fixtures.

9. Just say no to dark-colored shades and lenses. Evidently Jesus had a good grasp of lighting principles, because in Matthew 5:15 he gave excellent advice: don’t hide your lamp under a bushel basket, but put it on a lamp-stand. Unfortunately, far too many people hide their lamps behind dark-colored lenses or brown lampshades (the bushel baskets of our era). Since you want the maximum number of lumens per watt, it makes little sense to produce a bright light and hide it behind a filter that obscures 80% of the lamp’s output.

Choose fixtures with clear lenses, if possible. Don’t be afraid of fixtures with a modern design that incorporate a bare lamp.

10. Don’t forget to provide good lighting in basements, attics, and crawl spaces. You need more fixtures than you think, so provide lots of them. Remember to provide a separate switch for each fixture.

Last week’s blog: “Keeping Ducts Indoors.”


Tags: , , , , , , ,

Image Credits:

  1. Matthew Beckler
  2. Todd Hryckowian
  3. Brownlee Lighting
  4. Delray

1.
Fri, 10/21/2011 - 10:04

Edited Fri, 10/21/2011 - 10:06.

Controls
by Adam Flowers

Helpful? 0

Good read, it's great to keep some focus on those ever-important baseload energy users. One thing that I'd add to the conversation is the importance of controls, specifically occupancy sensors and dimmers. Occupancy sensors turn lights on when motion (or body heat, more specifically) is picked up, and turn them off after a preset amount of time. Many even have an on/off button that allows them to function as a standard switch, when the need arises. They're great in closets and bathrooms. And while it's not ideal (read "affordable") on CFLs, dimmers are great on LEDs and Incandescent fixtures. Wattstopper and Lutron are the industry leaders in both of these products. Thanks again for a great lighting article!


2.
Fri, 10/21/2011 - 11:09

Daylighting and more
by Doug McEvers

Helpful? 0

Good article, Martin

I would add this study as further reading for those interested.

http://www.swenergy.org/publications/documents/Lighting_Technical_Report...


3.
Fri, 10/21/2011 - 11:13

Response to Doug
by Martin Holladay, GBA Advisor

Helpful? 0

Doug,
Thanks for the link to the useful resource. I'm happy to add it to the other links in my "More Information" box.


4.
Fri, 10/21/2011 - 12:36

Daylighting, the free and potentially best lighting
by Brennan Less

Helpful? 0

Martin, I think that having not a single mention of daylighting in this article is a major mistake. I get that this article is about electric lighting strategies, but at least a mention of the use of daylight would be nice. Daylighting can be designed, just like passive solar design. It takes advantage of natural energy flows, links people to the progression of the day and the seasons, and if designed well, it works forever, never needing a new bulb. Granted, residential occupancy is probably more towards the night time hours, but major day time occupancy is still a reality.


5.
Fri, 10/21/2011 - 15:04

Edited Fri, 10/21/2011 - 16:10.

Response to Brennan Less
by Martin Holladay, GBA Advisor

Helpful? 0

Brennan,
Fair enough -- I accept the criticism, and there is much to be said about daylighting, especially in offices and commercial buildings.

One reason that daylighting is less important in residential buildings than commercial buildings is that most U.S. homes are unoccupied during daylight hours -- especially from late September to early March, when the sun rises late and sets early.

In any case, when talking about homes rather than offices, daylighting has a humbler name. In my day, we always called them "windows."

Yes, every room needs at least one, and usually several, windows. And there is a lot to talk about there: where they belong, how big they should be, how to address sight lines, how to capture (or partially obscure, if you are Japanese) views, and avoiding glare. Not to mention glazing specification, a topic I have written about several times.

However, an hour after the sun sets, every home still needs to consider artificial lighting.


6.
Sat, 10/22/2011 - 02:15

one tiny fix
by John Klingel

Helpful? 0

Good article, but one minor "math" error. "...The amount of light striking an object is proportional..." should read "... inversely proportional".


7.
Sat, 10/22/2011 - 05:10

Response to John Klingel
by Martin Holladay, GBA Advisor

Helpful? 0

John,
Good catch. You're right, of course; I've made the correction. Thanks.


8.
Sun, 10/23/2011 - 01:40

Martin: I don't know a lot,
by John Klingel

Helpful? 0

Martin: I don't know a lot, but now and then I can be of use. Doug M: I just started reading that article. The first graph is quite informative; very hard to beat the sun, it seems. Thanks. j


9.
Sun, 10/23/2011 - 22:39

Edited Sun, 10/23/2011 - 23:20.

Fluorescents in the kitchen?
by Kevin Dickson, MSME

Helpful? 0

Martin,

Remember those big recessed flourescent fixtures in kitchens they built in the 70's and 80's? They were sort of like a dropped ceiling with the big 2'x4' lenses or egg-crates.

This article makes me believe they should come back for efficiency's sake.

Buyers and cooks hated them, and saw recessed cans as much more palatable.

Is there a good way to get T-8s back out of the garage and inside the home?

LED's may yet win the lumens/watt contest, here's one that cranks out 94.4l/w :
http://www.amazon.com/Incandescent-Replacement-Illumination-G7-Power/dp/...


10.
Mon, 10/24/2011 - 12:03

Night Lights and Stair Lights
by Richard Patterman

Helpful? 0

Don't forget night lights. I like to be able to walk into the bathroom or kitchen in the middle of the night without either stubbing my toe or blinding myself by turning on enough light to cook or shave.
LEDs in the toekicks of cabinets work well.

Building code addresses adequate stair lighting, but does not address the importance of proper switching. I lived in a three story where, when coming home in the dark, I had to turn on lights for lower stairs, go up stair, turn off lights for lower stairs and turn on lights for upper stair, go up upper stairs turn off lights for upper stair. Multi floor lighting should turn switch all stair lights from top and bottom of all stairs.


11.
Tue, 10/25/2011 - 11:00

Beyond the light fixture
by Buildingwell .org

Helpful? 0

Proper lighting goes beyond just the light fixture or bulb (luminaire/bulb). Proper wall coloring will also benefit your lighting pieces. Use lighter toned colors to help reflect the lighting around the room. Building off of Martin's statement regarding white ceilings, your walls act just the same way. By using a lighter color the room will not only feel more open but lighting will distribute better than if you used a deep/dark color. Also to build upon the daylighting discussion, installed light fixtures should be located deeper within a room rather than near a window. Utilize daylight for a majority of your lighting. Then have task lighting by this window areas for evening lighting. Otherwise, use switches for zone lighting throughout the room so an occupant does not have to turn on all lights at once but possibly just the more interior lights during daytime needs.


12.
Wed, 10/26/2011 - 21:54

Re Daylighting in Residential
by Peggy Deras

Helpful? 0

Besides windows for daylighting, there is the Sun Tunnel/SolaTube option as well. Some even come with lighting so they work day and night. While they simply light the floors the same way recessed lights do, they don't cost watts. Also great for daylighting hallways and other rooms with no windows.

You also forgot to explain the term "light layering", though you defined it. Very important to have separate switching to achieve functional layering. For instance: I put the ambient lighting in a kitchen on two switches, to give a low and high level of ambient light.
Then I put task lighting for each work area on its own switch. Decorative and accent lighting are usually switched separately as well.

Kitchens with ceilings over 8' high are candidates for lighting on the tops of upper and tall cabinets. Also rooms with attic space over them can have the ceilings lifted to accommodate uplighting.

Here's a kitchen remodel I did a couple of years ago with 100% fluorescent lighting (except for a couple of LED recessed lights not shown in these images.

http://kitchen-exchange.blogspot.com/2009/09/100-fluorescent-kitchen-lig...

No reason why energy efficient lighting can't be drop to your knees dramatic too. The designer just has to be committed to do it that way and able to convince the client that it will be great.


13.
Thu, 10/27/2011 - 16:44

Exposed Lamps / Daylighting
by Bill Burke

Helpful? 0

Martin,
I have to disagree with one comment. "Choose fixtures with clear lenses, if possible. Don’t be afraid of fixtures with a modern design that incorporate a bare lamp." To my eye, a fixture with a clear lens exposing a bare lamp makes no sense. If it's in your field of vision, it produces glare and compromises your ability to see. And if it's not in your field of vision, why have a lens? If you want a lens, it is possible to find diffusing glass that is as transmissive as clear glass.

Regarding daylighting, I agree completely. I always tell people that if they need to 'daylight' a residence, it's typically a sign that the house is too big. During daylight hours, even a marginally competent design should provide adequate illumination through windows such that there is no need to turn on electric lights.


14.
Thu, 10/27/2011 - 17:05

Edited Fri, 10/28/2011 - 03:30.

Response to Bill Burke
by Martin Holladay, GBA Advisor

Helpful? 0

Bill,
I am very sensitive to lighting anomalies and bad lighting design, but I am delighted with my Delray T-5 fixture (shown in the last photo on this page). It has a bare bulb. The great thing about it is that it is bright -- even though it doesn't draw many watts. To my eyes, there isn't any glare.

If you start paying attention, you'll notice such fixtures in many modern office buildings. I saw some at Harvard University a couple of weeks ago. There really is no objectionable glare from such fixtures.

Open your mind to new possibilities and experiment. Of course, opinions differ -- plenty of people like diffusers and shades.

Below is a photo of the Delray fixture I spotted in a Harvard meeting room:

Harvard lighting - low res.jpg


15.
Mon, 01/02/2012 - 03:18

Cathedral ceiling lighting
by milton pyron

Helpful? 0

What do you recommend for lighting great room with cathedral ceiling?


16.
Mon, 01/02/2012 - 08:32

Edited Mon, 01/02/2012 - 11:46.

Response to Milton Pyron
by Martin Holladay, GBA Advisor

Helpful? 0

Milton,
These rooms are difficult to light well, which is one reason that I'm not a fan of great rooms.

1. Make sure that you have good task lighting for reading at every chair or sofa. You can use table lamps, floor lamps, or wall-mounted swing-arm lamps to accomplish this.

2. For ambient lighting, you can use long linear fluorescent tube fixtures mounted on projecting shelves or cornices. The shelves should shield views of the bare tubes; the light should be aimed upwards toward the ceiling.


17.
Thu, 11/08/2012 - 12:05

In defense of recessed cans
by Andrea Lemon

Helpful? 0

Hi Martin,

This article was my bible when we designed the lighting for our house, and it served us well. But we also got advice from a lighting consultant, and he talked us into installing some recessed cans roughly 24" from the wall. Instead of lighting the floor, they illuminate the (light-colored) walls, which bounce quite a lot of light into the room.

I agree that mid-room recessed cans are not useful, and recessed cans on a cathedral ceiling are a terrible idea, but a well-placed can does quite well.


18.
Thu, 11/08/2012 - 12:17

Response to Andrea Lemon
by Martin Holladay, GBA Advisor

Helpful? 0

Andrea,
Ultimately, lighting design is in the realm of aesthetics. De gustibus non est disputandum.

I'm glad that you are pleased with you lighting choices. (I feel confident that you didn't install those recessed cans in an insulated ceiling -- right?)

Certainly, it's easier to make an aesthetic error with recessed cans than it is with most other types of fixtures. But if you know what you're doing, and you like the effect they create, they have their uses.


19.
Thu, 11/08/2012 - 12:37

Insulated ceilings
by Andrea Lemon

Helpful? 0

Martin,

Ha! You are correct that we didn't install recessed cans in the insulated ceiling. Indeed, we didn't install any lights in the insulated ceiling upstairs -- it's all wall sconces and indirect lighting up there.


20.
Mon, 12/09/2013 - 20:28

Angled recessed cans on a horizontal ceiling?
by Bill L

Helpful? 0

I'm thinking of using angled recessed cans (originally designed for use in cathedral ceilings) on a horizontal (uninsulated) ceiling, in order to bounce light off of high walls. This seems a lot more efficient than those recessed fixtures which direct light toward the wall by shielding half of the opening to the can.
Has anyone tried this?
thanks,
Bill


21.
Tue, 12/10/2013 - 08:52

Response to Bill L.
by Martin Holladay, GBA Advisor

Helpful? 0

Bill,
You can do that if you want.

It's also possible to possible to buy recessed fixtures that are designed to be directional and adjustable. These are called "recessed eyeball" fixtures. You can Google them to learn more.


22.
Wed, 02/12/2014 - 16:14

where to find CRI for bulbs?
by Erica Downs

Helpful? 0

Where does one find the CRI for CFLs? I've looked on packaging for many brands, and it seems lucky to find the degrees K -- I've never found the CRI. Thanks!
Erica



24.
Mon, 04/07/2014 - 02:40

Ambient and accent lighting in bedrooms
by Vara Ramakrishnan

Helpful? 0

Hi, We're in the middle of new construction in California, and our electrical plans call for recessed adjustable lights to wash ceilings and walls for ambient and accent lighting. I saw your comment to Andrea Lemon "I feel confident that you didn't install those recessed cans in an insulated ceiling -- right?" and am wondering what I'm supposed to use instead. We have flat roofs, so there's only about 12 inches of insulation possible at most, so I'd love to not eat into that in a lot of spots, thereby reducing the overall R-value. How else can I accent art on the walls? Track lights wouldn't be pleasant. Thanks!


25.
Mon, 04/07/2014 - 06:03

Response to Vara Ramakrishnan
by Martin Holladay, GBA Advisor

Helpful? 0

Vara,
Installing recessed can lights in an insulated ceiling is an unmitigated thermal disaster. You don't want to do it. For more information on why, read Recessed Can Lights.

The usual way to hide recessed can lights in your type of ceiling -- in a way that is responsible from an energy perspective -- is to build a false ceiling about 10 inches below your real (insulated) ceiling. Of course, that means that you need to start with a house that has been framed for 9-foot or 10-foot ceilings.

If your architect or designer doesn't know these facts, that's a sign that your designer is not very energy-savvy.

If you are stuck with 8-foot ceilings, it's hard to drop your ceiling any lower. One way to do this is to build soffits around the edge of your room. Of course, you lose some ceiling height at those soffit areas, but at least you don't lose the ceiling height in the entire room. If you go this route, make sure that your ceiling plane is airtight before the soffit framing begins -- otherwise this type of soffit will be a disastrous air leak in your air barrier.


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