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Let There Be Light

More to Fixtures Than Just Illumination

Article written by Jack Carr, P.E., R.S., LEED AP, Criterium Engineers
Published in Condo Media, March 2010

Exterior lighting is a common element found in every type of condominium complex, yet with many permutations of light fixtures, placement and site design, it is one of the most unique assets. With the net age of condominiums increasing, capital repair decisions related to light fixture replacement, function and location will be an agenda item for more and more buildings and grounds committees in the coming years. So, let's shed some light on the goals and issues to be considered in making any outdoor lighting design plan.

Local Codes

The first thing to do is inquire if your municipality has a policy governing site and exterior lighting. This code or design guideline will form the basis of any plan.

Knowing some of the technical jargon is often helpful when reading local lighting ordinances and talking with illumination professionals. The unit of "foot-candle" is used for measuring the amount of light falling on a surface where as the term "lumen" is a measurement of light energy emitted by a light source. The word "luminaire" is used to describe the complete light fixture including the lamp (bulb), lens and wiring of the fixture. Finally, some municipalities require a photometric plan, which lists not only all of the luminaires and their locations, but also describes the horizontal illuminance on the site and the vertical light trespass around the perimeter of the site.

Whether or not your committee will have to deal with the submission of a photometric plan in your location,  consideration should be given to several important issues in developing your lighting project's objectives. These issues include controlling glare, promoting effective security, minimizing light trespass onto adjacent properties, minimizing direct upward light emission and the avoidance of interference with safe motor vehicle operation.

Lighting Needs

When considering these objectives, the levels of illumination needed for the various areas on your site will come into question. During these deliberations there should be a constant mantra whispering in your ear: "less is more." The human eye needs very little light to function. A sunny day on Old Orchard Beach has more than 30,000 foot-candles while a cloudy day has 1,500, yet only .1 foot-candles is needed to read the fine print in the condo bylaws.

If one area of the complex is very bright it will create the illusion of the properly lighted area nearby to be under- illuminated. Competing light levels detract from our sense of safety and security, and defeat the very purpose they were intended to serve. For a feeling of security, it is often more effective to be able to see far ahead with clearly defined escape paths than have extremely bright lighting.

Reducing the level of illumination will save on energy, but there are many other means to this goal. Though the initial selection oflamp type, ballast, luminaire type, quantity and location can have a significant effect on lifecycle costs, the control strategy can be even more important. Not all outdoor lighting needs to be on full light output
all evening. Many methods are available to reduce the hours of lighting operation including timers, motion sensors, photosensors, curfew dimming and step switching.

The environmental concern of light pollution is getting a lot of visibility lately. The results of this problem are glare, skyglow and light trespass. They arise from improperly directed fixtures and inadequate lamp shielding.  Cutoff fixture is a term to describe a luminaire designed to focus light exactly where it is needed. When determining the height of a pole fixture, it is often better to have more fixtures at a lower level than fewer fixtures higher up. Tall fixtures tend to illuminate the area directly around the pole and not the area needing the light.

Glare also can be controlled by diligently locating fixtures. Uncomfortable and unneeded light can reflect off a wide range of surfaces, such as building windows, wet pavement and landscaping features. Glare and a lack of uniformly distributed light can temporarily reduce vision function, and create a sense of unease or confusion. This will not produce the curb appeal to make the condo shine in this market.

With the current trend to use hardscape design elements on the grounds of many condominium complexes, care should be taken to avoid uplighting landscape features. Instead, use of shielded fixtures such as path lights, bollards and post-top lights with minimum intensity levels is recommended. Effective lighting design is not only good for the environment, it also makes cents.


 
© 2010 CRITERIUM ENGINEERS