LEED asks that the baseline and projected water use be evaluated at 60 and 80psi. How can we account for the fact that the pressure won't be that high?
Th project is a luxury hotel, which plans to use showerheads that have a 50L/min (13gpm) at 80psi. The water pressure in the bathrooms will be set at 44psi max, which would bring the showerhead max flow down to 7.4gpm. It remains too high but it would make a big difference to our water use value.
Would we have to find the equivalent standard flows at 44psi in order to compare baseline and projected flows?
Karen Blust
Green Building ConsultantThe Cadmus Group
124 thumbs up
May 14, 2010 - 5:18 pm
Here is an NCv2.1 CIR Ruling that you might find helpful: http://www.usgbc.org/LEED/Credit/CIRDetails.aspx?CIID=829
Josephine de Montmarin
Communication and Development OfficerMANEXI
26 thumbs up
May 17, 2010 - 3:25 am
Thank you but I don't actually have access to the ruling on the USGBC site. The project is not registered yet as we are trying to determine if it even worth pursuing certification. After all, if we can't meet this prerequisite we're stuck...
Tristan Roberts
RepresentativeVermont House of Representatives
LEEDuser Expert
11474 thumbs up
May 17, 2010 - 9:33 am
Below is the key paragraph from the "ruling" part of the CIR. Note that this CIR is from an older LEED rating system, and was given in 2004, but it should be able to give you some general guidance on how GBCI is likely to view this issue."The underlying assumptions used for calculating projected water use savings should remain consistent between the baseline and design case. Supply water pressure varies across the United States and within individual buildings (as you note in your inquiry). Flow rates at 80 psi are used for the calculations in this credit for consistency and to reward use of efficient fixtures. It is recommended that all projects use the flow rates reported by the manufacturer at 80 psi for comparison with the Energy Policy Act of 1992 flow rates. If you wish to use on-site tests to report the most accurate volume of water use, you must be consistent throughout all fixtures and test both baseline and design fixtures. It is not acceptable to use flow rates at 80 psi for some fixtures and actual flow rates for other fixtures. Measurement can also be used to account for the benefits of whole-building strategies, e.g., flow restrictors at the water service entrance."
Josephine de Montmarin
Communication and Development OfficerMANEXI
26 thumbs up
May 17, 2010 - 9:38 am
Thank you, that is indeed helpful (although unfortunate in our case). Testing the fixtures directly at the building's specific pressure might work, but how would one go about "testing the baseline fixtures"? Any ideas?
Thank you again for your help, this is much appreciated!