Mar 2013

A Sunday Factoid

Lighting accounts for only 5% to 7% of the total electricity usage in the average American home.

Mar 2013

Some Qualities of Light That You Should Know

Before my first posting about light bulbs (sources of light) there are some qualities of light with which you should become familiar. Different sources of light exhibit different characteristics that influence which light bulb to use in different situations.

Color Temperature is a term that refers to the color of light, commonly expressed as warm or cool. Technically it is expressed in degrees Kelvin (K) with lower numbers being warmer than higher numbers. For example 1,700K is the color of a flame, 2,700K is the color of an incandescent light bulb, 3,000K-4,500K is the color temperature of fluorescent and LED light sources and 6,500K is the color temperature of the sun on an overcast day. For residential lighting purposes most color temperatures are compared to incandescent light.

Notice the smooth transition from
red to violet for the
incandescent light bulb.

Color Rendering Index, expressed as CRI, is a measure of how good colors look. All light bulbs are compared to an incandescent light bulb which is deemed to have the best CRI. CRI is expressed by a number from 1 to 100, 100 being the CRI of an incandescent light bulb. CRI’s between 82 to 100 are judged to be satisfactory while CRI’s below 80 are not. Most of the new fluorescent light bulbs, including CFL’s, are mid 80 or higher. LED’s currently range from about 65 to 88. In the photo to the left you can see the full spectrum in the light of the incandescent light bulb earning it it’s 100 CRI rating.

As humans our eyes see color as the reflection of the color in the light source. If part of the color spectrum is missing from a light source, red for example, you will not see red. Some of the early highway lighting had such bad CRI that at an accident scene the police could not differentiate between blood and oil.

There is a lot to learn about light, how we see light, how contrast affects how we see, how glare interferes with our vision and what kind of light is best for different situations. I strongly urge you to download the Underwriters Laboratory app “Light Smart” at the App Store. It has lots of great information about lighting.

Please visit my website, FoggLighting.com.

Mar 2013

The Cost of Recessed Lighting

Examples of Recessed Lighting

Recessed lighting can be a cost effective way to light some of the rooms in your house. The fixtures range in price from about $25 to $500 depending on aperture size, light bulb used, features, components and manufacturer. Electricians will typically charge anywhere from $50 to $250 to install each fixture depending on the complexity of the installation.

The most common and least expensive recessed fixture is the 6″ can with a white baffle trim. These are usually lamped with a BR (Bulge Reflector) light bulb which gives a wide glow of light but which also causes glare because the bottom of the light bulb is level with the plane of the ceiling. Other commonly used residential recessed fixtures are the 3″, 4″ and 5″ aperture models which used CFL’s, A-Lamps (regular light bulbs), LED’s, PAR16, PAR20, PAR30 or MR16 light bulbs. Prices of these models depend primarily on the internal components which influence photometrics and aiming ability.

LED recessed lights are among the most expensive. They come in many variations. Some have a dedicated LED light source built in, some have LED inserts that can be removed. There are also LED light bulbs that can be used in existing recessed fixtures if you want to conserve energy. These range in price from about $25 to $75. The payback period on LED’s is generally measured in years. The latest figure I heard was anywhere from 5 to 7 years. As LED prices come down, which they will, the payback period will become shorter and shorter.

I will discuss more about recessed lighting in my next posting. In the meantime please visit my website. Thank you.