I see several threads attempting to get an answer on how one demonstrates controller efficiency and the most prevalent answer seems to be just use 1 because no other values can be substantiated by manufacturer documentation. Is that still the prevailing opinion?
It seems clear that a value of 1 is meant to reflect the default position of not using weather based smart controllers for irrigation. So it seems obvious that a weather based controller would be preferable and incentivized by a lower value. The USGBC guidance does not seem to suggest complex exceptional calculations are required in their reference to just provide manufacturer backup. Yet, they also suggest a possible range and do not just provide a default value to be used with such a controller.
Given that manufacturers do not seem to provide a CE in their documentation, do we actually believe that a high efficiency drip irrigation system with a weather based controller should have to use a CE of 1 and has to somehow find an exceptional way to achieve this credit? Or ultimately is it simply sufficient to provide normal product data backup that indicates a weather based controller is being used?
Carlie Bullock-Jones
PrincipalEcoworks Studio
LEEDuser Expert
220 thumbs up
November 25, 2014 - 11:26 am
Hi Michelle,
You are correct, if the irrigation system has no weather-based controllers or moisture sensor systems, a CE value of 1.0 should be used in the calculation (and no back up data is required).
Note that for projects registered after the February 2, 2011 Addenda, any percentage reduction in water use from controllers cannot exceed 30%; therefore, the CE may range from 0.7 to 1.0.
I am not aware of any default values that can be used for controllers. To claim the CE value utilized, data and/or supporting calculations from the manufacturer must be provided to verify the savings. If the manufacturer data states that the controller provides a range (for example, 20% – 30% efficiency) then I would utilize the lower value (0.8) in the calculations.
Hope this helps!
Michelle Rosenberger
PartnerArchEcology
519 thumbs up
November 25, 2014 - 11:32 am
Hi Carlie,
Thanks for the response. The manufacturer's data is not providing us with a helpful xx% efficiency claim. So I am trying to determine what "detailed calculation" done by the landscape architect would substantiate this.
Cynthia Estrada
LEED AP BD&CSDS Architects, Inc.
48 thumbs up
July 20, 2015 - 3:22 pm
I too have question about this; we just received preliminary design review comments on the credit citing the 2/2/2011 addenda. Does this mean that I have to set the CE value in the design case to .70 to comply with the 30% rule, even though the manufactures documentation indicates .56 CE? This is a bit confusing.