High School Level 1 Energy Audit -- Chapter 4

CHAPTER IV - School Lighting Audit

There is significant potential for lighting system changes and dollar savings in most schools. These changes can save energy (and associated costs) and still provide occupants with the quality and quantity of light that is needed to perform their various tasks. A key finding in a study: Energy Efficiency Guidelines for Oregon Schools (1993) is that the first investments should be made in the lighting system and ventilation system controls of schools. If you want to look for ways to save energy in buildings look long and hard at LIGHTS.

A lighting system is just that -- a system. It is important to consider the impact of the different elements on the whole. Its many elements are interrelated just as the lighting system itself is interrelated with other systems in the building. While energy can be conserved by properly removing lamps (light bulbs) and light fixtures, such action should be taken only after the impacts on the complete system have been considered to be sure the changes will not cause a problem. While conservation of energy is important it must be achieved without the loss of safety, productivity, visual comfort, aesthetics and compliance with federal, state, and local laws and ordinances.

"You know, I don't think 10 lumens is gonna cut it"

An excellent initial step to save money through more efficient lighting is to reduce lighting levels consistent with the current use of the different spaces as identified during the building audit. In other words, how is the area being used and how much light is needed in the space for that use?

Controls: Turn off lights when not needed

Plan a program to turn lights on only when and where they are needed. The major advantages of such programs are that they can be tailored to the characteristics of the space, adjusted to the needs of its occupants, and implemented relatively inexpensively and quickly. The key element of a lighting use program is a lighting schedule related to occupant usage patterns. Personnel should be assigned, trained and made responsible for the efficient use of lighting according to the needs in the area. A light that is turned on is like a meter running in a taxi-cab.

"You mean I'm gonna have to pay the energy bills around here?"

Appropriate Lighting Levels:

Areas can have too little light and they can have too much light. In the latter case, they are "overlamped". Below are recommended Federal Energy Administration maximum lighting level standards. With a light meter, it is relatively easy to determine, the lighting level by area.

Task or Area	Foot-candle Levels	How Measured
Hallways or corridors	10	Measured average
Work and circulation areas	30	Measured average
Normal office work	50 (40-60)	Measured at work station
Prolonged office work	75 (55-90)	Measured at work station
Office work visually difficult	100 (80-210)	Measured at work station

A second source for recommended lighting levels is the Handbook of the Illumination Engineering Society. The following table presents specific values pertaining to schools from the IES Lighting Handbook.

Special Areas: Schools

ENVIRONMENT WHERE TASK IS DONE	TASK DONE	Foot-candles Recommended
ANY SPACE WHERE:	Reading printed material	30
	Reading pencil writing	70
	Drafting, benchwork	100
	Lip reading, chalkboards, sewing	150
CLASSROOMS
	Art rooms	70
	Drafting rooms	100
	Sewing room	150
	Cooking room	50
	Note-taking	70
LABORATORIES	Dissection, experiments, etc.	100
LECTURE ROOMS
	Audience area	70
	Demonstration area	150
MUSIC ROOMS
	Simple scores	30
	Advanced scores	70
SHOPS	Operate machinery	100
STUDY HALLS/LIBRARY	Study/typing	70

Source: Illumination Engineering Society, IES Lighting Handbook.

Comparing different types of Light Sources: You already know that the type of light source makes an enormous difference in energy usage. Recall that incandescent light bulbs have an efficiency of 5% as compared to fluorescent lights with an efficiency of 45%. Clearly you will save money every time you replace an incandescent lamp with a fluorescent lamp. However, all lights of the same type are not the same in terms of efficiency. With fluorescent lights, the type of ballast (provides the correct current and voltage to run the lamp) and design of the fixture is very important. For example, fluorescent lamps show considerable variation in terms of how many lumens of light they produce for one watt of electricity. The newer electronic ballasts significantly outperform the older magnetic ballasts.

Lamp-Ballast System Comparison: Two-Lamp Open Air Systems

Ballast Type	Lumens Produced per Watt Efficacy
Magnetic (Standard)	61
Magnetic (Energy Efficient)	68
Electronic	85
Electronic IS	92

Source: Advanced Lighting Guidelines: 1993 (Revision 1) Electric Power Research Institute.

These are selected values, however, notice that the best electronic ballast fluorescent lamp (92 lumens/watt) is about 51% more efficient than the worst magnetic ballast fluorescent lamp (61 lumens/watt).

In choosing the most cost desirable option there are other factors to consider besides energy needed to run the lamp. How much do the lamps cost? How long will they last?

Performance Characteristics of Various Light Sources

Lamp Type	Efficacy (Lumens/Watt)	Average Life (Hours)
Standard Incandescent	5-20	750-1000
Tungsten-Halogen	15-25	2000-4000
Compact Fluorescent (5-26 watts)	20-55	10,000
Compact Fluorescent (27-40 watts)	50-80	15,000-20,000

Source: Lighting Fundamentals Handbook Lighting Fundamentals and Principles for Utility Personnel. Electric Power Research Institute Publication.

Problem: You are about to buy a light bulb for $5.50 that has a rated life of 850 hours. You then notice that you can buy a bulb that produces the same light for 18,000 hours but costs $62.00. Energy use is the same for each bulb. Which bulb is the better bargain?

_____ The $5.50 bulb_____ The $62.00 bulb

Hint: you will have to buy about 21 bulbs that live 850 hours to get 18,000 hours of service (21 X 850 = 17,850 hours). Those 21 bulbs will cost you $115.50!

Beyond the energy costs associated with selection of equipment, there are also maintenance costs. If you use incandescent lamps in your home with an average of 1,000 hours you will replace ten bulbs for every fluorescent lamp. If the change takes as little as six minutes you will have invested an hour of labor in "bulb changing". This idea also applies to building equipment. The maintenance costs for various building activities are listed below. Although your team will be concerned primarily with the energy costs associated with your school you may want to consider the labor hours that are saved by recommending equipment, especially lighting, that has longer lifespans and therefore do not need to be changed out as often. For buildings like your school the table below shows the relative maintenance costs of facility maintenance.

Relative Facility Maintenance Costs

Source: Washington State Energy Office. 1991 Facility Management.

In a recent presentation at a PGE Conference Center, a Resource Conservation Manager from the Eugene School District pointed out that the main reason why custodians liked switching to an energy saving exit light was that they had extremely long life spans. Even more important to them than energy conservation was that they did not have to change them as often. The law requires exit lights to be visible all of the time. The task of keeping on top of those that burn out and replacing them can be a rather time consuming and burdensome chore.

Lighting Surveys: You will notice that the amount of energy used to produce lighting depends on: 1) the type of device used to produce the light (incandescent vs. fluorescent), (2) the amount of light produced, (3) conditions in the space such as the color of walls, if any, and, (4) the amount of time that lights are on. The lighting survey is intended to provide information on these variables. Switching to a more efficient lamping system does not make much sense if the lights are then left on all the time, nor can it be economically justified if the lights are never used. In your lighting recommendations, consider whether it is more economical to switch to more efficient lights; add controls that switch lights off when not needed; or delamping areas where lighting is excessive.

Common lighting recommendations of building energy auditors include the following:

Utilize fluorescent energy saver tubes and/or ballasts when replacement becomes necessary.
Convert interior incandescent fixtures to energy efficient fluorescent lighting.
Convert exterior incandescent fixtures to higher efficiency lower wattage lighting sources, such as metal halide, or high or low pressure sodium. Consult a lighting specialist.
Lighting may or may not provide for additional security after hours. People don't "hang out" in dark unlit places. Consider delamping and evaluating the change.
Maintenance costs of electrical (lighting) ranks under HVAC, plumbing, and interior construction. Accordingly life span of the bulb is directly related to relative maintenance cost of a facility.

Source: Washington State Energy Office, 1991. "Facility Management".

Project and Exercises

A. Do a Lighting Inventory

Take a lighting inventory for your school and complete the Room Lighting Checklist that follows. Your team will need a floorplan of the school, a light meter that measures footcandles of illumination, and a plan of attack. Lighting surveys can be completed in a couple of hours and at various times of the day when the school is in operation. It is important to find all of the lights (and ballasts if applicable and possible), both inside and outside as well as determining the type of controls that are used to turn them on and off. Most of the room lights are operated by a wall switch; some of the outside lights may be on timers or photocells.

Equipment needed:

1. Tape Measure	3. School Room Locator
2. Light meter (measure foot candles)	4. Lighting Survey Form (data collection)

Procedures: Inside Lights

Determine lamp type used to light the room space
Highlight areas with incandescent lights on the school floor plan
Take Light Level Readings (Foot-candles)
Note how many lights and their wattage
Note how lights are controlled
Note how many tubes per fixture (Luminare)
Where possible identify the type and make of the ballast

Outside Lights

Walk around the perimeter of the building noting outside lights on the floor plan
Note how lights are controlled
Locate the timeclock and read the on and off times
Note height of fixtures or mounting.

Room Lighting Checklist

Room Number	Room Use¹	Incandescent Bulbs #Watts²	Fluorescent Lamps # Watts² including Ballasts	High Intensity Discharge #2 and Wattage	Foot Candles³	Comments:⁴ (windows, skylights, reflector condition)

1. Room use: List primary activity such as Biology, office, art, music, conference, and home economics.

2. Bulb Count/ Watts: Identify the type and number of bulbs and wattage of each bulb. As appropriate, include ballast type and its wattage.

3. Foot Candles: The reading obtained from the light meter at representative work locations.

4. Comments: Does the room have windows, skylights? Are the reflectors dirty? Ceiling reflective?

B. Write a report analyzing how well your school performs relative to existing lighting standards.

Most lighting standards can be grouped into one of two categories:

1. The amount of electrical energy used, which includes such measurements as watts per square foot .

2. The measurement of light output, commonly the measurement of foot-candles or equivalent sphere illumination.

Understanding Watts/Square Foot

One common approach for developing a standard for lighting efficiency is watts per square foot or W/ft².

The technique uses a watts per square foot standard to establish a power limit for buildings. The assumption is that the reduction in allowable total wattage will require energy efficient lighting systems that produce adequate lighting. Watts per square foot is easily computed. If used as a single value for all areas of a building, one has only to total up the connected load of all lighting system components and then divide by total square footage in the building.

Is your school energy-conserving simply because it complies with codes? Not necessarily. The hours of operation of a lighting system have a great deal to do with the total energy consumed. For example:

Consider a 10,000 square-foot space lighted by a system rated at 20,000 watts or (20 KW). Its W/ft² rating is two (2). If the lights are used for 2,000 hours per year, total energy consumption is 40,000 KWH (kilowatt-hours). Now, consider the same space with a 10,000 W lighting system rated at one W/ft² used 5,000 hours per year. Total energy consumption is 50,000 KWH (10 KW X 5,000 hours).

Note that even though the lights are using less electricity, total consumption increased because the number of hours increased. In other words, the system with a one W/ft2 rating, which is only half that of the other, consumes 25 percent more energy because it is on longer. The above example points out that this method cannot indicate energy consumption or energy waste, only the relative energy requirement. Watts per square foot has been used extensively in establishing lighting budgets for buildings. Generally speaking, a "light budget" of two watts per square foot is acceptable.

The second type of standard deals with whether the light is sufficient for the type of task to be performed. Tables in this chapter contain recommended lighting levels from the Federal Energy Administration and the Illumination Engineering Society. How do the levels you measure for your school compare with these standards?

The light meter you will be using in this exercise measures light in foot-candles. Be careful where you take your measurements, the recommendations are based on light levels on task, as opposed to overall or general ambient light levels in the room.

1 Foot-candle = 1 Lumen/Sq. Foot

C. Based on your lighting inventory and analysis, recommend actions your school should take to improve lighting quality and efficiency.

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