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Light, Action, Savings...And Sustainable Living

Submitted by Fritz on Thu, 2010-01-21 13:51

Buildings are the largest single consumers of energy in North America. For a typical commercial building, lighting use accounts for 28% of this energy load. For buildings which rely on incandescent bulbs and "dumb" energy management systems, much of this is pure waste. But new lighting technology offers opportunity for huge savings in operating and maintenance costs, and may even improve lighting quality. You can also reduce your carbon footprint. For every 1,000 kWh that can be saved, your building will reduce 1,100 pounds of CO2 emission emitted.

Nonetheless, implementing a change in your lighting strategy is not a decision to be made quickly or lightly. For best success, you should:

  • Plan beforehand to avoid problems with lighting savings projects.
  • Have the board and building managers meet to establish goals for the project including payback, aesthetics desired, lighting levels, maintenance standards, and installation schedule.
  • Have a professional perform a comprehensive energy audit.
  • Implement the plan and then test the results, so you can confirm your savings.

At the meeting prior to the energy audit, focus on the human element: is your current lighting adequate to meet the needs of all occupants? Are there dark spots or locations which are lit unnecessarily? What are the patterns of use? Should systematic changes be considered, beyond a simple increase or decrease in foot-candles, as part of the project’s plan?

The energy audit, once performed, becomes the master plan for how to proceed. It documents your current systems and benchmarks items such as lighting level, hours of operation, lighting color, task lighting uses (appropriate lighting levels are different for walking down a hallway than for reading documents at a desk), opportunities for daylight harvesting, presence of (or lack of) occupancy sensors, ease of maintenance and temperature…lighting creates heat and will impact air conditioning. Professionals arm themselves with a light meter, tape or digital measure, digital camera and notepad (or computer), and the energy audit is ready to proceed.

Once the data is gathered on the existing lighting, a spreadsheet is created to model the current costs, and a financial benchmark is set. The actual electric rates should be used and not averaged…many utilities charge different rates depending on what time of day, or what time of year, the electricity is being used. Your local utility or provider should be able to send copies of the past year's worth of bills if you don’t have them in hand.

To get the full advantage of lighting opportunities, you should become familiar with new lighting technologies and the principles of how each technology fits into your goals. Lighting technologies convert electricity into light and heat at various efficiencies, and over the past 10 years there have been significant improvements in lighting efficiency and options. The old, familiar incandescent bulb converts only 10% of the electricity it receives into light, with the other 90% thrown off as waste heat! Fluorescent, HID (high intensity discharge), induction and LED (light emitting diodes) convert much more electricity into visible light, which saves you money. A professional will know which technologies will fit your building’s needs.

Lighting 101: Things you should know about your lights.

Two measurements are most commonly used to describe the amount of light a lamp produces: Lux and lumens (a lux is about 1/10 of a lumen). Output is measured against energy consumed: how many lumens produces for how how many watts used. The higher the lumens per watt, the lower the electric bill…and the easier it will be to meet the new energy codes that restrict watts per square foot. Compare lumens per watt and you quickly see how your technologies stack up. A typical 4-foot T8 fluorescent lamp produces almost 2,900 lumens while consuming about 30 watts of electricity, which gives you a rating of approximately 100 lumens per watt. This compares to about 70 lumens per watt for compact fluorescents and about 20 lumens per watt for an incandescent bulb.

When light hits a surface (or the light meter) the result is measured in foot-candles. One foot-candle is equal to one lumen spread across one square foot. Lighting in most situations is a combination of direct and indirect lighting. Direct lighting is the light that shines directly from the fixture to an object. Indirect lighting reflects off another surface before hitting the object. Direct lighting is more efficient, but less pleasing to the eye. There are standard foot-candle levels for spaces based on the tasks that are typically performed there.

There are various shades of white light. Incandescent bulbs tend towards yellow, fluorescent towards blue. The new LED lamps can produce whites that are very close to a "pure" white. The measure of the whiteness of light is called its color temperature – which, in this case, has nothing to do with heat! Higher temperatures are richer in the blue spectrum and lower temperatures are more yellow-orange. Color temperature is an important factor in measuring the effectiveness of lighting, because the color within the light affects how we see the colors of the objects we are viewing. The more accurate the colors are, the better. This is known as the lamp's Color Rendering Index (CRI), and the higher the CRI, the closer the lamp comes to lighting true color. Normal room lighting should have a CRI of 70 or higher.

In comparing lighting options, we want to consider all three measurements: lumens per watt for efficiency, foot-candles for total output, and CRI for the overall "quality" of the light produced. Depending on the efficiency of the existing lighting, you should generally aim to reduce energy consumption from 10% to 50% with a payback from 2 to 4 years, depending on your electric rates.

Some options to consider:

  • Look at 4-foot T12 fluorescent bulbs. Ever wonder what all that "T" business is all about? Fluorescent bulbs are measured by diameter, in 1/8 inch increments. A T12 bulb is 12/8 inch, or 1.5 inches in diameter. A T8 is one inch in diameter, and a T5 slightly more than 1/2 inch. When you switch from incandescent to fluorescent, a 40% reduction in energy consumption can be achieved while maintaining lighting levels. Newer fluorescent bulbs have a lower color temperature, because people tend not to like the bluish tint older bulbs give the space they light. Fluorescent bulbs will require additional effort when it comes to disposal: it is not legal to dump them into your garbage bin, because they contain mercury. Check for a local disposal site.
  • Incandescent bulbs can also be converted to compact fluorescents, which provide 70% energy reduction. You'll also enjoy great savings in maintenance, since the typical CFL will last 10 to 15 times longer. Look to purchase from stores that will take back CFLs to recycle when they burn out.
  • Occupancy Sensors are a great solution in areas where lights can be turned on and off based on whether someone is in the room. Conference rooms and bathrooms are good sensor locations. Make sure that the sensor has a clear path to recognize when someone is there.
  • For indoor parking, make sure the lighting choice will operate over the extreme temperature ranges that can be experienced in a parking structure. Low temperatures can severely affect the life and operation of some bulbs.
  • For outdoor parking lot lights, induction lighting can provide a 40% reduction and have an expected life of 100,000 hours for huge maintenance savings.
  • Seek opportunities for daylight harvesting and reducing energy consumption based on the amount of light coming into a room. There are special controls and ballasts needed for this technology, but there can be huge savings.
  • Since exit signs are on 24 hours per day, using new technologies can cut energy consumption and stop the constant need for staff to replace a bulb. Do make sure the exit sign you pick meets all local code requirements.
  • If you have a large number of lights that can be turned off for extended periods of time, you may be able to participate in your utility’s Demand Response (DR) program. With a DR program, you get paid for reducing your demand if the utility calls for a power savings event. You are paid even if no event is called for since you are committing to “stand-by” in case the utility grid is under duress…you are, in effect, on retainer. Typically a minimum of 100 kW load shed is required. In some cases, lighting reduction could be combined with HVAC controls and a standby generator. This is definitely something to ask your energy professional about.

It is critical that, after you have commissioned the lighting retrofit and the installation is done, you go back to test that the controls and light output meet your original goals. The energy savings for basic lamp fixtures can be calculated from spec sheets but you do want to confirm the light levels. The completed lighting document then gets handed over to the maintenance department with all of the lamp and ballast specifications. Tell maintenance not to deviate from the specifications listed in the document. Purchasing different bulbs or ballasts than the ones specified will impact the energy consumption, foot-candles, CRI and could also reduce the life of the lighting components.

Lighting choices can have a significant impact in lowering your bills and benefiting the environment, and can also provide one of the fastest payback items in energy savings for dollars invested.