Why You're Not Going to Get the Extra Point(s) for WEc1, Water Efficient Landscaping

I've had an issue come up multiple times in the past few weeks that I hope in telling will prevent you from similar headaches. In multiple projects that I've been involved in, we have situations where 100% of the water used for landscaping is being supplied by non-potable sources, yet in every case we will not be earning the 2nd point (v2 rating systems) or the other 2 points (v3 rating systems) for WEc1, Water Efficient Landscaping... Why, you ask?

Read Carefully

Read Carefully!

The issue with WEc1 is that the basic requirements listed in the rating system omit a very key statement which can only be found buried deep in the reference guides. Here I'm quoting from the LEED-NCv2.2 reference guide, but I checked and the v3 edition has the same problem:

"If the Percent Reduction of Potable Water is equal to or greater than 50%, WEc1.1 is earned."

So far, so good... nothing unexpected... but wait!

"If the Percent Reduction of Potable Water is 100%, you must also calculate the Percent Reduction of Total Water (Potable plus Reuse) according to Equation 7 […the long one where you have all the landscape coefficients and such]. If the Percent Reduction of Potable Water is 100% and the Percent reduction of Total Water is equal to or greater than 50%, WEc1.2 is earned in addition to WEc1.1.

The problem here is that the rating systems (the requirements you get to view for free) make no mention anywhere of the fact that TOTAL water use, not just potable, must be reduced by 50% along with the 100% potable water reduction in order to earn the additional point(s). It only shows up deep in the "Calculations" section of the reference guides...

If you have ample supply of non-potable water sources for a project, it is less likely that the design team has examined in detail the total water consumption of the landscaping as performing these calculations is time-consuming (read: costly).

Why this requirement isn’t stated upfront in the credit language is lost on me, but the fact remains we must not only reduce potable water use completely but also total water demand based on the LEED calculations. Had I recognized this before the latest update, I would certainly have suggested an amendment to the rating system during the public review. Let's all make an effort to correct this during public comments for the v4 rating systems!

Disagree with my interpretation? Did you slip one by a review team and get the extra points without anyone noticing? Let us know by leaving a comment!

7 comments:

Craig said...

Wow, there it is in black and white in the Ref. Guide. Thanks for the tip! Related question - anyone heard about any exemptions for turf grass athletic fields that require irrigation? Nothing in CIR's. If your project can't reuse non-potable/ harvested water does it basically disqualify you from achieving WE-c1.2?

Sarah said...

I think the issue is confusing because you're looking at WEc1.2 as a separate credit from WEc1.1 when in fact they're just one credit in which you can earn one or two point (v2.2, let's say).

So in essence, 50% reduction of total potable water is required for 1.1 and a prerequisite for 1.2.

If you look at the credit submittal template, Option 3, you have to enter the calculated baseline irrigation water consumption, calculated design case irrigation water consumption and non-potable water supply (all in gal). Percent Reduction in Total Water (according to the template) is calculated as(Baseline-Design Case)/Baseline.

So even though the credit requirements for WEc1.2 don't specifically mention total water reduction, it does reference WEc1.1 which requires 50% reduction of potable water, so you're already on your way, I assume.

I agree it's confusing in terms of the wording, which is probably why in the v3 Reference Guide, they added a subscript on the summary page for Option 2. But I've worked on projects where we didn't do the 'total water' calculation up front and still managed to earn the credit. Just my two cents.

Tristan Roberts said...

I agree this can be confusing. Here at LEEDuser, we diagrammed the WEc1 requirements in a way that may be helpful for people wrapping their minds around this.

On the athletic fields question, we had a similar question come up in our WEc1 user forum.

To briefly sum up the answer given there -- there is some precedent for excluding athletic fields, but then you have to be consistent across all credits, including open space credits.

NUNG said...

We don't really need these additional confusions in addition to what we already have in current building and planning codes.I think all these are designed to fatten someone bank's account.
Most clients are not really interested in paying for additional time/services for us to sort out all these added mandates.

Bill Swanson said...

I saved the 2009 public comments and responses. Here's a couple of the responses about this credit.

"Thank you for your comment. The overall goal of the LEED program is to increase the efficiency of resource use, in this case water resources (potable or non-potable).The intent delineates the goal of reducing potable, natural surface and subsurface water resources on or near the project site. Non-potable harvested rainwater would not be considered a natural surface or subsurface source and is not discouraged by this credit."

and

"Thank you for your comment. Credit 1.1 provides for two points and does not create additional points for additional potable or natural source reductions or substitutions. The intent of connecting 1.1 to 1.2 in this fashion is to provide points for non-irrigated landscape or use of only alternative site sources such as harvested rainwater, recycled wastewater, greywater, or water treated and conveyed by a public agency specifically for non-potable uses for irrigation."

mmr said...

You need to review the CIRs for this credit. Achieving the second point is very doable.

Christina said...

I'm not sure if you came back to this post at all and addressed it at a later time, but I'd like to help. I've figured it out by looking at some of the different submissions. And may I say thanks for posting about projects that published their documentation!

The total amount of landscaped area must be the same for both the design case and baseline. However, usually your turf grass SF in the baseline is more than in your design case. Again, TOTAL must be the same. The assumption is that if you weren't being "sustainable" you would use more turf grass in your design. So anywhere that you aren't required by local zoning to have ground cover, shrubs, or trees (like buffer or forest conservation requirements), can be compared in the baseline to a design that plants those areas with turf grass. Because if you weren't going after LEED, or be sustainable, you would have to plant those required numbers no matter what.

For example, lets say your design includes 100 SF of turf grass, 200 SF trees, 300 SF shrubs and 100 SF groundcover. That's a total of 700 SF of vegetated space. Lets assume that the trees, and 100 SF of the shrubs are required by the city. So your baseline would read 400 SF of turf grass, 200 SF trees, and 100 SF of shrubs. This totals 700 SF, just like the design case. You are doing the calculations correctly.

LEED shows this in their example calculation, but doesn't spell it out very well. Check it out. But since turf grass uses more water according to their calculations, your plantings will easily meet the credit requirements of reducing water requirements by 50%.

On the other hand, let me know when you figure out how to properly put in the amount of potable water used for irrigation from a cistern. You can't just put the volume of the cistern, that assumes one use from completely full to completely empty. I haven't seen any evidence for this from a project that successfully achieved all four points, without omitting all irrigation.