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NC-2009 SSc8:Light Pollution Reduction

Exterior Lighitng: Facade Lighting

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Saud Abdul Rasheed
Sustainability/Energy Engineer, CEM, PMP, LEED AP BD+C, LEED AP O+M, Estidama PQP
LEEDuser Basic Member
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Hello All, My question may be simple but still I want to be clear about it. When we are calculating the exterior lighting, in LEED Reference Guide as well as ASHRAE 90.1 2007 we have the units either as "watts per linear foot/metet" or "watts per square feet/square meter"?. For example in the latest addendum of the ligthing credit in SS it says for LZ2 the LPD for Facade lighting is 0.1W/ft2 or 2.5W/linear meter. How can I calculate these do I need all the Facade area for both calculations? and how I can convert from linear meters to square meters or vice verse?

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Lourdes Salinas
THREE Consultoría Medioambiental
LEEDuser Basic Member
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Fri, 11/30/2018 - 22:54

Hello Saud  Attending to your question, to calculate the lighting power allowance in facades there are two options, I would advise you to check which is the purpose of the proposed lighting before going forward, for example if the lighting would have the purpose to light a facade, i would use 2.5 w/linear foot for each illuminated wall or surface, if the lighting purpose is to light an specific area, for example an entrance, i would use 0.1 W/ft2 for each illuminated wall or surface. Regards 
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Bill Swanson
Sr. Electrical Engineer
Integrated Design Solutions
LEEDuser Expert
516 thumbs up

Mon, 12/03/2018 - 13:25

"How can I calculate these do I need all the Facade area for both calculations? and how I can convert from linear meters to square meters or vice verse?"
It is an "either" "or" option.  I suspect some regions of the world prefer area calculations and others prefer linear calculations.  Or as Lourdes noted, it could be based on how you are lighting the façade.  This is to provide you with options.  There is no conversion needed.    

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