As lighting installations in office buildings and other facilities continue to become more complex, designers must address ambient, task, and security illumination solutions separately. Why? When you consider that today's state and federal energy requirements often define a maximum lighting power density for different types of new facilities, it seems energy-efficient lighting design has become a requirement for squeezing out the best value for every dollar spent on lighting. Businesses can no longer afford to miss out on the savings an energy-efficient lighting design affords them, so it's no wonder more and more electrical and lighting design professionals are looking to software for help.

Today's lighting design software programs are powerful tools that can solve a variety of problems. They can calculate lighting levels easier, faster, and more accurately; handle repetitive layouts; keep track of fixture counts; determine the electrical loads on feeders or branch circuits; and take you on a virtual tour through your design. However, to fully appreciate the advantages such software can provide, it's important to understand some of the challenges modern lighting installations present.

Not only are many lighting installations becoming more complex, several are coming into the second and third generation of retrofits. Though previous retrofits may have saved some energy dollars, many have also caused a diminished visual environment. In some cases, they even failed to provide adequate lighting. Providing high-efficiency, high-quality fixtures, and lighting controls for complete relighting efforts translates into big business for contractors today. This is especially true for fluorescent and metal-halide applications. In this market, the right lighting design software program can help turn a proposal into a sale.

The industrial plant lighting market is also ripe with opportunities. Most manufacturing facilities have their own spatial conditions and task requirements. With a lighting design program, you can prepare several designs using different lamp/system combinations to determine variances in performance and economics. Each design must include a return-on-investment (ROI) evaluation.

The increasing use of electric power-generating photovoltaic panels in buildings is another factor to consider. To make the most of solar-generated electricity, these buildings must be as energy-efficient as possible. So architects rely on skylights and clerestory windows to maximize daylight in the interior spaces. Lighting programs that feature day lighting modules are very useful on these projects. Now that we've looked at the characteristics of today's lighting design market and explored a few ways you can apply lighting design software, let's take a look at the software itself.

Not what it used to be

Evolution is the key word when it comes to lighting design programs. In the old days, designers used rudimentary programs to do only the complex calculating functions rapidly. Today's modern programs can take you on a virtual 3-D color tour of the lighted space. This makes your computer or workstation a video tool, allowing you to see how a proposed lighting design will look when the lighting equipment is installed. The result is a better design in less time with greater assurance.

Powerful as it may be, lighting design software (like any tool) has its limitations. The utility of a lighting design program usually depends on the training, experience, and judgment of the user.

Granted, a program user cannot create any of the dramatic images unless he or she has the knowledge and experience necessary to understand how light is produced and controlled. However, features like photometric data files, which demonstrate the way lamps and lighting fixtures distribute light, have increased the demand for these programs. As a result of its increasing popularity, photometrics is an important concept for designers to understand. Major lighting fixture manufacturers and photometric laboratories use the most popular formats to archive luminaire photometric data in databases.

Finding the right program.

The best source of information on computer software is the Illuminating Engineering Society of North America (IESNA), New York, which periodically conducts a survey on currently available products. The latest survey results (printed in the December 1999 issue of the association's monthly magazine, Lighting Design and Application) include 25 lighting design software programs.

The survey describes the specific features of indoor, outdoor, roadway, flood, and sports- and stage-lighting applications, and it divides the information into eight sections, including price, applications, hardware requirements, types of analysis, special features, user interaction, and photometry.

The section on types of analysis reveals whether a program offers point or plane luminance calculations or economic analysis, and the section on special features identifies programs that import or export CAD files and the maximum number of luminaries the program can handle. The user interaction section presents the methods of entering data in each program and the types of output the program can handle. For example, one program may generate gray-scale renderings, while another may allow output of the lighting design to E-size blueprint pages.

The price section provides a starting point for selection. One fixture manufacturer offers two free programs and another that costs $100. Programs offered by other fixture manufacturers cost only a few hundred dollars, and should satisfy most contractors and engineers. On the other hand, programs sold by independent software firms run anywhere from a few hundred dollars up to $10,000. Generally, higher priced products are recommended for individuals who require detailed analysis on a regular basis.

The survey also provides the following information about software products:

  • If it operates inside a CAD program.

  • If you can enter data into tables on the screen.

  • If it accepts input from a digitizer, a keyboard, a mouse, or a stylus.

  • If it has provisions for multilingual support or CIE calculations (European standards).

  • If you can view graphic photometric distributions on screen

  • If you can tilt light meters.

  • If it uses the zonal cavity or lumen method for indoor calculation of average luminance.

  • If it offers roadway luminance and day lighting capabilities.

  • If tech support is available.

  • If documentation is provided online or is available in a printed manual.

The special features heading lists particular capabilities of the program. For example, the automatic layout feature suggests a layout of the luminaries. A generate schedules function produces a luminaire schedule for the building. Building shadowing calculations take into account the shadowing effects of other buildings in outdoor analysis. A program with batch processing can run several analyses while the computer is unattended. Interior obstructions calculations take into account the effects of user-defined obstructions in interior spaces. And an economic analysis feature will calculate the cost considerations for the lighting system.

Practical examples.

What can a typical lighting design program accomplish? One popular $600 program (from an independent software company) offers a photometric library of more than 17,000 products from about 60 manufacturers. It provides a step-by-step checklist for producing a lighting layout. Other features include: CAD interfaces with import and export capabilities, gray-scale images, project file merging, and a variety of customized reports. It also offers predefined objects, such as partitions, tables, and chairs that you can add to a rendered space to provide a realistic view of the design. In addition, you can use a second software program to produce full-color, photographic quality images.

If you work on both interior and outdoor projects, you may need more than one program. For example, software that includes the ability to use exterior luminaire photometrics, a solar calculator, and a geographic location is very useful when working on exterior site lighting layout. It's important to find a program with these three capabilities because they aren't usually found in a program that also does interior-design work.

The big picture.

Keeping up with the changes in lighting installations can be a job in itself. Not only that, as systems continue to increase in complexity, designers must find new ways to design and implement innovative lighting for new facilities. Luckily, recent advances in lighting design software have brought new capabilities to the field and made this task a little easier to handle.

Lighting Standards

Since the 1970s, government regulations and users have promoted the need for lighting systems with energy-efficient designs that follow an energy budget. For that reason, a lighting designer should be familiar with the latest revision of the ANSI/ASHRAE/IESNA 90.1-1999 standard. The ASHRAE portion of this standard deals with heating, ventilation, and air conditioning, while the Illuminating Engineering Society of North America (IESNA) portion deals with lighting.

The new 90.1-1999, Energy Standard for Buildings Except Low Rise Residential Buildings, includes lighting power density (LPD) values for whole buildings and for spaces within buildings. The Lighting Subcommittee of the ASHAE 90.1 Standards Project Committee and the IESNA Energy Management Committee developed these LPDs.

The LPDs establish appropriate lighting energy-consumption limits that promote energy efficiency without sacrificing good design and quality lighting. For calculating the LPDs, currently available lighting characteristics, such as coefficient of utilization (CUs), light loss factors, lamp efficacy, and luminance values from the 8th edition of the IESNA Lighting Handbook were input. Professional design experience and the characteristics of typical buildings were also included in the data. Then, by applying this data, a modified form of the lumen method in lighting calculation was used to set up the LPDs for each of the various building types. For example, the standard lists 1.34W/sq ft as the average for an office, and 2.2W/sq ft average for a manufacturing facility. The LPDs assigned to all types of facilities are available on the IESNA Web site: (