Hello, I was just wondering if anyone knows the reference or basis of the numbers used in Table 2. Default Fixture Uses, by Occupancy Type in the LEED manual? Example; The default for residential occupants is 5 uses per day of water closet and lavatory faucet, 1 shower, and 4 kitchen sink uses. Cheers, Neshat Sakeena

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Charles Nepps

NH Green Consulting

LEEDuser Premium Member

80 thumbs up

Mon, 12/05/2016 - 14:03

I think it's just a best guess of typical household fixture usage in the U.S. On the commercial side they assume 3 WC visits per day, per occupant, so maybe that is the base daytime usage and then you add a morning & evening visit to the WC to get to 5? ) The numbers were derived (somehow) just to create a basis for comparison. Regardless of the number of actual uses, what's important is the water savings your project achieves over the baseline.

Neshat Sakeena

Sustainability Consultant

Ramboll

LEEDuser Basic Member

2 thumbs up

Mon, 12/05/2016 - 14:19

Thanks for your response Charles. I am actually trying to overlap MEP water demand calculations with the LEED Water calculations for a Hotel project. The MEP water demand calculations are almost twice of that of LEED water baseline (IPC/UPC) numbers. Thus my interest in reference standard (if any) for the Default fixture uses. I understand water demand calculations also account for a safety factor but 50% discrepancy is too high.

Charles Nepps

NH Green Consulting

LEEDuser Premium Member

80 thumbs up

Mon, 12/05/2016 - 14:36

Are you just comparing fixture usage in both cases? Remember LEED (v2009) doesn't address things like dishwashers, clothes washers, bathtub usage, process water, etc.

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Tue, 12/06/2016 - 08:57

From memory the rates and uses per day are from the IPC (international plumbing code). In MEP design both anual usage and peak (or design) rates are considered. The designer needs to size equipment (pumps, filters, pipe dimensions) to deal with peak demand rates that are subject to ratios of concurrent usage, AND caluculate the annual water usage based on daily usage. The two are however not the same.

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