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No Light Matter

“The exterior lighting is terrible”.  So what do you do when the Board keeps getting complaints from the unit owners that they feel unsafe in the parking lot due under-illumination from the aging light fixtures; or the street lamps are leaning like Pisa’s tower; or the treasurer is reporting high electric lighting bills?  The simple answer might be to switch to LED’s but the devil is in the details and that is when the Board needs some guidance.

Guidance can come from interviewing:  1) local lighting contractors who can provide a design/build proposal for the needed upgrade; 2) local full service architectural/ engineering firms’; or 3) regional lighting specialists.  These types of consultants can answer the key questions of a) when/ where lighting is necessary; b) the right fixture for each application; and c) the correct lighting source.  Before initiating this process, the Board may want to do some preliminary research on the subject.

Knowing some of the technical jargon is often helpful in 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 the safe operation of motor vehicles.

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 in Portland has over 30,000 foot-candles while a cloudy day has 1,500 foot-candles, yet only 0.1 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.  In fact, 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 of course save on energy but there are many other means to this goal.  Though the initial selection of lamp type, ballast, luminaire type, quantity, and location can have a significant effect on life-cycle 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 ever growing problem are glare, skyglow, and light trespass.  Often these issues have common solutions.  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 can also 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 and to use shielded fixtures such as path lights, bollards, and post-top lights with minimum intensity levels.  Effective lighting design is not only good for the environment; it also makes cents.     

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Article written by Jack Carr, P.E., R.S., LEED AP, Criterium Engineers

Published in Condo Media, August, 2016

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