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THREE STEPS TO A BETTER LIGHTING RENOVATION

Many times throughout my career, I’ve heard stories of renovations that didn’t meet the expectations of  the architect, designer or owner because the new lighting was  inadequate, mostly due to light levels that were lower than promised or  anticipated. It’s a frustrating experience for everyone involved. After  all, how could new lighting be inadequate? It usually comes to this: the conditions of the  space weren’t properly documented beforehand, so every step that came  after was based on inaccurate assumptions. 


So,  how is this remedied so that anticipation doesn’t turn into  disappointment? Here are three steps a lighting designer will take to  ensure a better lighting renovation:


1. Don’t Guess in the Dark

In fact, there shouldn’t be any guesswork. It’s always a good idea to be knowledgeable about the  existing light sources AND light levels. Whether designing to maintain  the current light levels, or increasing them, knowing the current  footcandle levels is crucial and a good starting point to any lighting  retrofit.
 

2. 80/50/20—A Good Rule to Break

All  too often, these type projects are initiated with only room  measurements and replacement fixture selections. Calculations are  quickly performed using the default reflectance values of the lighting  software and inaccurate light loss factors. 80/50/20 cannot be used for  every application. What is 80/50/20? These are the default reflectance  values incorporated into most lighting calculation software programs.  The software assumes that the finishes selected for the ceiling, walls  and floor will have light reflectance values of 80%, 50% and 20%  respectively. This is a faulty assumption and should almost always be  modified since white ceilings and white walls are no longer commonplace.  
 

3. Light Loss Factor (LLF) – What happened to the light?

Most  fixture manufacturers run photometric tests on the luminaires they  introduce to the market. These photometric tests are then used for  reports and specification sheets, and for producing IES files used for  evaluating the performance in lighting calculations. The light output of  the luminaire is measured in “initial lumens”. Initial lumens represent  100% light output of a new luminaire. There are a number of  environmental influences that will affect the light output of a  luminaire (dirt, temperature, etc.), and over the life of the  installation, initial lumens will diminish. These conditions need to be  applied to the initial lumen output to simulate the expected loss of  light. 



The  first calculation of a renovation or retrofit project should be an  effort to recreate the original conditions. This is accomplished by  modifying reflectance values to match the space and by making  adjustments to the light loss factor until the model calculations are in  line with the footcandle readings recorded at the site. The lighting  designer will now apply the percentage adjustments to the new luminaire  with considerations for the physical properties of the source.


When  using Google Maps to reach a destination, one needs to know where they  are to get where they are going. Likewise, to achieve a good lighting  renovation (destination), the lighting designer (1) must first know  where he is by visually inspecting the site and recording the current  light level readings and fixture locations, (2) know the actual finishes  so that the true reflectance values can be considered, and (3) factor  in environmental conditions that affect light output. By taking these  three steps, the designer can now proceed with confidence that the  lighting design will reflect expectations and receive approval. 

 

Danny  Streit is an independent lighting designer, lighting educator and  advocate, residing in Nashville, TN. As design principal of DHS Lighting  Design, he is Lighting Certified (LC) through NCQLP, is an Associate  Member IALD, Member AIA, USGBC, and past President of IES Nashville. You  may reach him directly at danny.streit@dhslightingdesign.com 

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