LPDs, As Low As We Should Go

October 3, 2015 in Codes

ASHRAE has released a series of changes to Standard 90.1 in preparation for the 2016 update.  Among those changes is the further tightening of LPDs (click here) in all space and building types.  In my opinion, these changes should be rejected by the lighting community.

Rather than provide tight, but reasonable, limitations on the power consumption of lighting systems, the LPDs proposed in the revision of Table 9.5.1 are so low that they clearly favor LED technology almost to the exclusion of all others.  They also strongly imply that energy efficiency is the most important criteria of a lighting system, regardless of the application.  Neither of these positions is appropriate for this document or the organizations that develop and maintain it.

The proposed LPDs are nearly impossible to meet by lighting designers who wish to exercise their best judgement, or meet client requirements, by selecting project appropriate sources of light other than LED.  In some cases this imposes an avoidable financial burden on the owner.  For example, LED luminaires with a combination of high output and smooth dimming to zero (such as those required for theatres, cinemas, houses of worship, etc.) are substantially more expensive than halogen alternatives, and may require more expensive control systems as well.  Clients requiring excellent color rendering (such as high end retail, art schools, museums, and health care facilities) are also compelled to purchase premium priced LED fixtures.

The only way that these low LPDs (and the even lower LPDs we assume will be proposed in the future) make sense is if they are paired with hours of usage to arrive at a time weighted limitations.  Even then, the LPDs should be high enough to permit designers and owners a choice in the technology that they use for a given application.  The proposed LPDs come very close to eliminating that choice.

I’m not saying that all buildings should be illuminated with incandescent light, or that LPDs should be abolished. I am saying, however, that the ever tightening of LPDs cannot go on forever, and that we have reached a tipping point where these limitations are having unjustifiable impacts on designs and budgets.  In my opinion, LPDs should not be further reduced for the foreseeable future.