Lighting Audits
The first step to a successful lighting upgrade is the lighting survey or audit. In this stage, which is essential to proper planning, the lighting manager gathers and organizes information about the existing lighting system and how it is used.
Various software can serve as a valuable aid in collecting data. The U.S. Department of Energy provides a list of both free and paid software tools for this purpose.
Collect Financial Information
To conduct a full financial analysis that will be needed to justify an investment in upgrading the existing lighting system, gather data about the local utility rate structure and average charges for energy (kWh) and demand (kW).
Determine the availability of rebates from the local utility that may subsidize purchases of energy-efficient lighting equipment; also determine sources of financing and create assumptions for tax rates and inflation rates for materials and labor.
Collect General Information
Collect floorplans or reflected ceiling plans for the facility that show fixture locations and room dimensions (length in feet, width in feet, ceiling heights in feet and areas in square feet). Be sensitive that renovation work may have been performed over the years that has changed the original floorplans and/or reflected ceiling plans. If not available, create using graph paper.
Label each area (rooms, hallways, etc.) with a letter for future identification with sets of data that will be collected. Also label each area with a generic description (private office #2, lavatory #1, etc.). It may be desirable to put a sticker on each door hinge during the room-by-room survey that bears its identity that corresponds with the floorplan.
Also, gather as much information as possible about the building and its history; try to determine what future plans there are if any for the building.
Collect Occupant Information
A good way to learn about how occupants feel about their lighting system is with a survey, which can asks questions such as, “Do you have trouble with light reflecting off your computer screen?” An additional benefit of doing this is that it may help create “buy in” among building occupants for the new lighting system.
Should this path be taken, however, how caution in evaluating the answers; the occupants know little about lighting – – in fact, they rarely notice it unless something goes wrong. For example, an occupant saying there is too much light in an area probably is saying that it is too bright, which is an issue of glare, not quantity of footcandles.
Collect Lighting Information
For each area, identify:
- Hours of operation
- Type and size of fixtures
- Number of fixtures (hand-held mechanical counters can help)
- Number of lamps per fixture
- Number of lamps per ballast
- Type of lamps
- Type of ballasts
- Specular reflectors if already installed
- Fixture condition
- Whether fixtures are air-handlers, part of the air distribution system
- Availability of daylight
- Tasks that are performed in the space (with light level targets)
- Use of partitions
- Unique fixture types or physical features
- Area dimensions
- Height of the tasks
- Fixture mounting height
- Room surface reflectances and colors of major objects and room surfaces
Also determine lighting waste disposal regulations and costs.
Standardized forms can be created to help capture and organize information by area.
It may be desirable to plot existing light levels with a light meter, although this may result in misleading data because the condition of the fixture and point of life for the lamps may not be consistent from fixture to fixture. For this reason, it may be desirable to simply calculate existing light levels.
If the building is large, information can be extrapolated based on known data. For example, if the general lighting scheme is based on 2×4 fluorescent fixtures, and the spacing and room dimensions are known, an approximate number of fixtures can be extrapolated. Another method is to gather data for prototypical spaces, and then make assumptions for how other prototypical spaces are lighted (this method works best in large, homogenous spaces). However, when it comes to accuracy, of course, there is no substitute for a complete walkthrough.
It may be desirable to contact a lighting consultant or energy service company (ESCO) to help conduct the walkthrough and survey.
By Gary Turpen, inter.Light, inc.
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