LEED water calcs: Recent developments
By Timothy Allinson, P.E.,
Murray Co., Long Beach, Calif.
Have you ever noticed that just about the time you are starting to feel expert in something, the rules are changed, you discover something new or a law is created that turns everything sideways? This seems to be happening with increasing frequency, especially with ever-growing environmental consciousness and litigation.
Take LEED water calculations as an example. I have a project registered under LEED v2.2. Achieving maximum water conservation points in this relatively old version of LEED is not hard because the baseline assumes 1.6 gpf toilets, 1.0 gpf urinals and 2.5 gpm flow fixtures such as lavatories, showers and sinks. The use of “standard” UHE (ultra high efficiency) fixtures was usually enough to max out the water credits and possibly get an innovative design credit to boot. Such was the case on the project referenced at the top of this paragraph. Then the third-party LEED credit auditor got involved, and everything went sideways.
When the LEED calcs on this project were first done, floor plans were under development and little attention had been given during the calculation process to the fixture matrix on the project. When the LEED credit auditor reviewed the plans and the water calcs the comment was, “Where are all the urinals you have included in the calculation?” At first confused, I realized that the auditor was correct; the project had hardly any urinals. There were only two medium-size public toilet rooms with a total of six urinals. All of the other toilet rooms – 209 to be exact – were single occupancy unisex toilets with only a water closet and lavatory. I was stunned. I never realized that we had so few urinals. So, the assumption in the calculation that the male FTE (full time equivalent) staff would each use a pint-flush urinal twice a day was way off base and the LEED calc didn’t work.
To quote Bloat, the blowfish in Finding Nemo who utters the final line, “Now what?” Well, clearly every problem has a solution: It’s just a matter of determining the most practical one.
First I proposed to the LEED consultant that it stood to reason that male FTE staff members might each use a urinal once a day rather than twice, either on their way into the building in the lobby toilet, in the cafeteria toilet at meal time or in the lobby toilet on their way home. The LEED consultant said there was no precedent for such an assumption, so it was shot down.
Now I was in a bind. I tried running the calc assuming that all the FTE males used just the water closets and no urinals; that caused the water savings to drop below 40%, the magic number we had to maintain. I called the flush valve manufacturer (American Standard) to see whether they had a 1.28/1.1 gpf hard-wired flush valve and was told they did not. A call to the factory, however, revealed that they did, in fact, have a newly released product which was just that. This could be my salvation.
I reran the water calcs with the dual flush WCs, still assuming that the transient population would use the urinals in the lobby and cafeteria toilet rooms. The combined effect pushed us back up to 43.4%! Interestingly, the combined effect of 1.28 dual flush toilets for both men and women is nearly as effective as 1.28 regular WCs and pint flush urinals for the men.
If you do the math, four uses of the 1.28 WC plus two pint flush urinals totals 5.37 gallons for each male/female pair. Two uses of the 1.28 WC plus four 1.1 gallon flushes total 6.96 gallons per couple. The baseline calculation produces 8.4 gallons for the bathroom behavior of this same couple. So you can see that the savings are 36% and 17% respectively. Combine the 17% savings with the savings from the flow fixtures and you are in business to the tune of 40% +.
Things get a little more complicated when you are dealing with a LEED 2009 (v3.0) project. Since the baseline flow value for lavatories was reduced to 0.5 gpm for 30 seconds, the benefit of low flow lavatories is greatly reduced. However, with the development of modern sensor lavatory controls, there is room for savings even against the 0.5 gpm baseline.
The latest lavatory faucets (American Standard again, as an example) have flow rates as low as 0.35 gpm, and flow duration can be adjusted as low as 7.5 seconds per cycle. Using these numbers, lavatory usage reduces from the 0.25 gallon baseline to 0.044 gallons per person. This is a significant savings. And while low flow water closets are considered by many to be a slippery slope, creating dry drains and carry distance issues, for public lavatories 0.044 gallons per use is a fairly practical minimum, since most people just give their hands a quick rinse before dashing out of the room. Even for the more fastidious user, who spends time soaping up like a surgeon preparing for an operation, the water will stop running as the lathering takes place, saving water in the process.
The down side of taking water savings at lavatories to its limit is the issue of hot water delivery. With so little water used per cycle, the hot water rarely, if ever, reaches the user. This gets into another subject that is beyond the scope of this month’s article, but it is one of the challenges associated with water conservation facing today’s engineer.
When it comes to showers and sinks, again I believe that there are practical minimums. No matter how much you reduce the water flow at a kitchen sink, the pasta pot still requires six quarts of water to get the job done right. This is a simple law of Italian nature that will never change. Or will it? It wouldn’t surprise me if I were to find in the grocery store tomorrow a box of “sustainable” spaghetti marketing itself as requiring less water to cook. (Of course, it’s the same pasta with different instructions that cause it to cook as a sticky glob.)
With showers, a woman with long hair still requires a certain amount of water to rinse out the shampoo. Of course, the sustainable female should shave her head to reduce the water demand made by her hair, but that might have ramifications on the sustainability of our species. Kidding aside, there is a practical minimum to how much water a shower should flow, and I personally think it shouldn’t fall below 1.75 gpm.
I think that the next step for LEED in water conservation might be to start including dishwashers and washing machines in the calculation process. This will get manufacturers to start focusing more intensely on the water conservation of these appliances. I know there have been certain advances in this area already, but the appliance focus still seems to be more on energy consumption than water conservation. Surely that will change soon.
Timothy Allinson is a senior professional engineer with Murray Co., Mechanical Contractors, in Long Beach, Calif. He holds a bsme from Tufts University and an mba from New York University. He is a professional engineer licensed in both mechanical and fire protection engineering in various states, and is a leed accredited professional. Allinson is a past-president of aspe, both the New York and Orange County Chapters. He can be reached at email@example.com.