We are currenlty in the design process of a building targetting to be LEED certified under version 3.0. As per ASHRAE 90.1:2007 requirements for LPD is mandatory, in which luminare wattage is defined as follow:
The wattage of luminaires with permanently installed or
remote ballasts or transformers shall be the operating input wattage of the maximum lamp/auxiliary combination based on values from the auxiliary manufacturers’ literature or recognized testing laboratories or shall be the maximum labeled wattage of the luminaire.
The building façade lighting is designed with multi brightness levels, and accordingly with different power consumption based on the brightness level. The brightness level changes during the operation and in some occasions operates on the full wattage.
When calculating the LPD based on the full brightness the value exceeds the maximum permitted by ASHRAE90.1:2007, however, the system software has a facility to limit the brightness at any time to a maximum of certain value (i.e. 50% in our case) to maintain the LPD as per ASHRAE requirements.
Is lighting power reduction using the software acceptable by ASHRAE90.1:2007 and projects targeting LEED for new construction Version 3.0 or not?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5922 thumbs up
April 15, 2015 - 11:09 am
The LPD must be determined at the maximum brightness/full wattage.
In order to claim something less than that you would need to somehow provide assurances that the system setting will never change. Simply stating what the settings are and that they won't change may not be enough. How can you assure USGBC that the control setting cannot be changed in the future?
The best option is to design the system to comply and not have to rely on seeking a way around the requirements. Keep in mind that the exterior lighting is a mandatory provision and you must comply in order to meet this prerequisite. This is an area where you do not want to be cutting it close.