LPDs, As Low As We Should Go

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.

Xicato Publishes IES TM-30-15 Results for its LED Modules

In a first (as far as I know) LED manufacturer Xicato has published TM-30 results for some of its modules alongside the CRI results for Ra and R9.  Menko de Roos, CEO of Xicato, says “At Xicato we are very supportive of TM-30-15 overall and recognize the need for an improved metric system along these two dimensions.”  You can read the full press release and find links to the results here.

I’m excited to see this greatly improved color rendering metric being used by a major manufacturer, and hope to see more manufacturers releasing TM-30 results soon.  If you still haven’t looked into TM-30 there is an increasing number of resources available to you.  TM-30 is available for purchase here. You can also view the recording of a webinar sponsored by the DOE and the IES and presented by two members of the IES Color Rendering Subcommittee, Michael Royer and Kevin Hauser.

Light and Health Webinar, September 30

Almost as if on cue, Philips Lighting is hosting a webinar on light and health presented by Mariana Figuerro, the Light and Health Program Director at Lighting Research Center.  I attended one of her in-person seminars earlier this year and I can say that she does a great job of explaining what aspects of light and health we can integrate into our practice now, and what aspects need additional research.  You can read more about the webinar here, or go straight to the registration page here.

Use of LED Lamps To Improve Health

Today’s New York Times has an article on several manufacturers’ new LED products that are intended to improve wakefulness, sleep, focus, and other aspects of daily life and health. The article appears on both the business and technology pages, but not on the health page, and I think that’s appropriate.  Although there are testimonials by the consumers of some of these products, there’s no discussion about any peer reviewed science behind them.  In fact, about two-thirds of the way through the article the author finally gets to the fact that, “Researchers are still determining how spectrum and intensity of light affect the brain.”  So, the article is an uncritical look at new LED products that make health claims.  We shouldn’t rely only on the claims of the manufacturers, though – remember the claims of 100,000 hour lifetimes for LED lamps?

I’m not saying that we know nothing about how light affects us, because we know quite a bit.  The question is, “Do we know enough to properly and safely integrate that information into our design practice?” and there things become uncertain.  So, before accepting the claims of manufacturers, or making the same claims to clients, it’s important for designers to be up to date on the current state of research and to understand the strength of the findings, as well as how (and if) those findings can be folded into a design.

There are a few web sites that I find useful for keeping up to date.  The first is the Health and Vision page of the Lighting Research Center’s web site, which has links to many of their recently published research papers.  The second is the Research page of USAI Lighting’s web site.  This page provides links to a mix of newspaper articles and scholarly publications on a variety of topics connected to LED lighting.  The third is the Research page of the IES web site.  Finally, members if the IES can  download copies of Leucos, and non-members can purchase copies.

LEDs continue to revolutionize the lighting industry.  Most manufacturers have ended  research and development for incandescent and fluorescent products. OLEDs are increasing in efficacy and prices are dropping, while new technologies (such as light emitting plasma and quantum dots) are on the horizon or already here. To preserve their client’s money, the occupant’s health and safety, and their own reputations, designers need to make sure that they don’t get swept up in the possibilities that are marketed to them before the facts are in.

TM-30 and Color Gamut

You may be familiar with the idea of a color gamut from displays or from RGB LED fixtures. In both cases the gamut describes the full range of colors that the device can create. In TM-30-15 IES Method for Evaluating Light Source Color Rendition gamut (Rg) has a somewhat different meaning. It refers to the average color shift of the 99 color evaluation samples (CES) under the test light source when compared to the reference light source. The reference source used in Rg is the same source used when calculating color fidelity (Rf) (as opposed to a fixed reference source as has been proposed in other gamut metrics).

A gamut index of 100 means that, on average, the test light source doesn’t change the hue or saturation of the CES compared to the reference source. An Rg above 100 indicates that the test light source, on average, increases the saturation of the CES producing colors that are more vivid. An Rg below 100 indicates that the test light source decreases the saturation of the CES producing colors that are less saturated.

The addition of a gamut index is a huge improvement over the single CRI (Ra) number that we’re used to. With Ra, every shift from a match to the reference source, whether it increases or decreases saturation, is treated equally and the direction of the shift is not reported. However, this is important information. For instance, research has shown that in many situations most people prefer a slight increase in color saturation. With Rg designers know the direction of the color shift, and the TM-30 calculation tool also shows the shift by hue and for each of the CES.

What’s the relationship between Rf and Rg? If Rf is 100 (a match to the reference source) Rg must also be 100. If the Rf calculation doesn’t indicate a mismatch with the reference source then there is no change in saturation. As the Rf value falls the potential range of Rg above and below 100 (indicating an increase or a decrease in saturation) grows. The calculation tool includes a chart that shows this relationship and gives a visual indication of where the light source in question fits.

Another graphic, the Color Distortion Icon, is plotted on the CAM02-UCS color space. In this graphic both the reference source and the test source are shown, along with an indication of the direction and magnitude of the hue shift caused by the test source.  Finally, we can even look at the color shift for each of the 99 CES.

A designer using TM-30 now has three big picture metrics to evaluate a light source: color fidelity (Rf), color gamut (Rg), and correleated color temperature (CCT). The designer can use TM-30’s calculation tool to examine the Rf and Rg of a light souce in as much detail as the project merits, from a very broad overview to a very detailed, color by color, evaluation.

The one thing that TM-30 does not do is provide guidance on the significance of the values it calculates. It is a Technical Memorandum that describes two calculation proceedures, not a design guide for using the results of those proceedures. Guidance will come later in the form of a TM-30 addenda or a design guide prepared by the IES, or guides prepared by other parties. In the meantime designers can begin to build their own understanding by comparing Rf and Rg values to the their visual evaluation of the light source, and by sharing the results of their work with others.

The pubication date has not been set, but now that the TM has been approved by the IES board of directors it should be available soon.  Keep an eye on the IES bookstore and on trade publications for updates. In my opinion TM-30 is a huge improvement over CRI, and I hope that the industry enthusiastically adopts it.

Note:  This post was originally published on June 15, 2015 but was taken down when the IES contacted me and claimed copyright to all graphics produced by the TM-30 calculation tool.  This seems to me as absurd as Adobe claiming copyright to all pictures edited in Photoshop, but I didn’t have the time to argue.  I took down the original post and have reposted it here, without graphics, and edited the text to omit references to graphics.

Start of the Semester Fun

Tomorrow is my first day of class at Pratt, so here we go again.  I know that this shouldn’t become a thing, and I’m really trying but I can’t help myself!  Here’s another video of a song related to light and featuring frightening hairstyles.  This time it’s Styx singing Lights in 1980.   (And no, I can’t explain Tommy Shaw’s sailor costume so don’t ask.)