Lavatory durations - justified deviation from "default" 30 sec?

Hi Joanna,
v4 no longer allows teams to take credit for metered lavs with shorter duration cycles. I believe the reason being that metered faucets with shorter duration cycles often encourage people to use more than one cycle per wash, negating the positive impact of the shorter cycle. A 30 second default must be used, unless the project team can provide published data/studies justifying an alternate usage duration. A 30 second default must also be used, regardless of a duration specified by the manufacturer as the manufacturer’s duration setting may not reflect typical usage patterns given variability in occupant behavior.
I hope this helps!

Kimberly,

Thanks for your response to the OP. Do you happen to know of any explanatory information from USGBC that discusses this topic?

I've spoken with reviewers a few times about these calcs. Their reasoning was basically what Kimberly said above. I also asked if they had updated the Additional Guidance doc for the WE credits from what is provided for v3, and they said no, but noted it as something that is needed (doesn't help us in the meantime, though). 

I've emailed GBCI just now asking if they can point me to an article or publication explaining the reason behind the change; I will post back here (and under all related rating system versions) if they respond with something useful. 

We're still all mourning the loss of this adjusted calc.

Here's the response I just got back from GBCI for Michael's question:

"Hi Emily, thank you for asking.

We have found that short cycle times typically result in multiple uses so are not an accurate reflection of water volume consumed.

This explanation is found in the 'Changes from LEED 2009' section of the reference guide. These sections in every credit/prerequisite - I find them very useful."

Emily,

Thanks for the leg work. I found a copy of the reference guide in our office. (Didn't know we had it) I found the section that was referenced. For the project I'm working on now, not being able to use the duration based savings caused us to go below the prerequisite of 20%. In order for us to get to 20% we have to go with .35 gpm faucets. 

Michael, sometimes the calculator can be a little tricky when documenting things b/c of the way GBCI wants to see the calcs done. Usually, though, it's not difficult for projects to meet the prereq % if they're using lower flow fixtures than the baseline, particularly for the flush fixtures. Do you have limited scope, or other fixtures that just aren't low enough?

If it makes you feel better, most of my projects use the 0.35 gpm fixtures these days, some to help with these points, but others just b/c it's become more standard.

Yeah its a medical office building with a bunch of exam sinks. the restrooms are all unisex with no urinals. There are also no showers. So our only savings come from 1.28 gpf water closets, .35 gpm lavs and one breakroom sink.

Pretty soon the lav gpm will be so low we will be misting our hands at the sink.

I've been told several times by reviewers that exam sinks (and even mother's room sinks) are considered process water, and therefore do not need to be listed in the calculator. I've also had projects include them where their inclusion was not noted by the reviewers either way. Not sure if you're including them there, but you may want to see how the calculator changes with and without them. 

Do you have your toilets listed as two separate line items, one for male and one for female, and 100% use assigned to both?

Emily, yes that's how I have it in the calc.

Yes for the exam sinks, as far as I've been told they are exempt in the calc. As a test I added them in. I chose "Kitchen faucet" that has a default of 15 duration and 1.5 gpm flow. The savings went up about .5%. I would hate to submit it that way and then it comes back as an invalid calc.

Yeah, I'd probably leave them out if you've gotten the same guidance. 

Sounds like y'all might just have to have the 0.35 sinks, or consider a 1.1 gpf, or 1.1/1.28 dual flush toilet. We've had good feedback and widespread use of an Afwall 1.1 version, including in our own office.