Sensor Faucets

Jennifer, are you saying the sensor faucets in question have an automatic shutoff after a certain duration?

My understanding of the calculations under LEED v4 is that the previous savings shown by the sensor faucets are not applicable any more - you really need to demonstrate savings using lower-flow (like a 0.35 GPM) faucet.  Under the v3 guidance document (https://www.usgbc.org/resources/water-use-reduction-additional-guidance) for auto-shutoff sensor faucets were treated the same.  Their guidance says that you use a calculation that shows a pretty significant savings by using the sensor - more than the 32% savings you reference above.  I assumed that this change under v4 was made because the previous calculation exaggerated the savings pretty significantly.  In my opinion, the new change underestimates savings - there's simply no way that a standard faucet where you turn the water on and leave it on while you soap up uses the same amount of water that a sensor faucet uses where the stream stops if you take your hands out of the sensor, and I'm hopeful that newer versions and or updates might address this - so it neither overestimates nor underestimates the savings.

Hi Jennifer,

I've actually had this conversation with GBCI reviewers for the water use reduction credit. In short, at this time, they are not allowing for any non-default calcs for the faucet types you describe. They are aware that there are some fixtures that likely do save significantly and use much less water than the standard 30-second duration currently required in the calcs. They told me that they do not have any approved deviations, however, and that all projects are so far still required to use the default. Officially, this is the response they sent:

"If the duration value of a lavatory fixture is modified, a narrative must be provided. Modifications cannot be based on manufacturer data. Published data or studies justifying an alternate duration may be submitted.

Unfortunately, there are currently no studies that USGBC is aware of to support duration-based savings for metering faucets, so we do not have an approved scenario to share at this time. In speaking with our in-house expert, some possible scenarios that would justify modifications include: special use applications (not the typical restroom lavatory fixture use), such an additional hand sink being used for non-restroom applications, or a study indicating that gym showers are actually used for X duration and more appropriate to project context, instead of LEED default shower duration. The WE TAG has extensively reviewed metering lavatory faucet research, and concluded that flow rate savings should be rewarded in LEED v4 (rather than duration savings) given the available research. In the absence of conclusive studies showing duration based water savings for metering faucets (also known as on-demand, auto-control, touch-free, or sensor activated faucets), metering faucets can continue to be included in LEED v4 using the flow rate in gallons per minute (GPM) and the default 30 second lavatory duration approved and vetted during LEED v4 rating system development. The default 30 second lavatory duration comes from public health source recommendations around hand washing to prevent the spread of germs, and USGBC has been hesitant about approving any shorter durations that may compromise public health. Project teams can still use metering lavatories in LEED v4, and can demonstrate flow rate savings over the 0.5 GPM baseline."

That probably answers your question, but if you do feel justified in using a non-default value, you'd likely need to contact GBCI with your specific project info for discussion prior to submission. 

For what it is worth, the study referenced is academic in that it was done by an undergraduate student at a school, but it definitely lacks the rigor necessary to use as a reference. They don't give study group demographics (how many people, male vs. female, etc.). They don't give the specific dates for each of their 14 day testing windows, which start in December - a month not known for standard occupancy at a school. They don't share the results of their randomized counting of occupants they claim confirms equal usage, but they do give the data showing that trial 2 (auto 0.5) and trail 3 (auto 0.35) had similar sensor trips (actually 6% different for men, not exactly equal but ignored) and somehow assert this proves the manual uses during trial 1 must be the same. They don't show where the meter was located to confirm if it was visible to occupants and impacting the study. The indicate they're comparing to a Delta 510 though the picture doesn't look like current models. The Delta 510 they indicate comes standard with a 1.5 gpm flow rate with an optional 1.2 gpm but they say it was 0.5 without showing a picture of the aerator to confirm. They don't indicate how old the existing one is or if it has been damaged at all over time to change flow. They don't give local water pressure. They don't tell us how long they set the activation times (must be the 3 second minimum based on the results). They say they put the metered faucets on the right hand side of the counter, which means there was more than one faucet available to users and they may have chosen not to use the new sensor faucets and thus artificially lowered their totals. The paper even starts with a review of the literature and mentions other studies that were much more robust that came to different conclusions, so it would be hard to reference this one with a straight face. Interesting project and I'm not in any way trying to be critical of the student who did it, but let's hope we can base our design decisions on something more substantial.