LEED points vs water conservation
There is currently a high end shower system, Nebia, which advertises a remarkable 0.7 gal/min (2.65 L/min) flow rate, well below the 2.5 gal/min (9.46 L/min) standard shower in the U.S. The system atomizes the water to create a better distribution of water over your body. I read many reviews, from independent sources, and could not find anyone who disliked the product, which seems a bit too good to be true.
While I read, and in some case watched, online reviews, I learned a lot about the product, which does, indeed, sound like a good way to reduce water use, but I realized that 0.7 gal/min is not the rate of flow to be used in the LEED credit calculation. First, I noticed that in addition to the main fixed shower head there is also a separate hand held shower wand, which can be use simultaneously with the main head. Second, I also saw one reviewer comment about using a rinse mode (the company calls it “strength mode”), to facilitate removing shampoo and other soap products. Having worked with the LEED standard since 2009, I am well aware that, for purposes of water credit calculations, you need to use the “worst case” flow for faucets. That would be the sum of the rinse mode plus the flow through the wand. On the company’s website they show this number to be 1.3 gals/min, (4.92 L/min) almost double the 0.7gal / min. achievable in normal mode.
This is still an excellent number, but is it worth the price? Researching a bit more I was able to find shower heads that are rated at 1.5 gals/min (5.68 L/min) for about 1/8th of the price….so would I recommend the higher end, more efficient shower, to a client building a LEED project? If you look at an average family home; 3 bedrooms, 4 occupant, and assuming the same low flow facets, toilets, water efficient clothes washer and dishwasher, a 1.3 gpm shower head generate a monthly savings of 28.44% over the baseline water consumption. A 1.5 gpm shower head reduces this savings to 25.99%, but in both cases the home would earn 4 points in LEED indoor water use credit (4 points for 25% savings 5 points for 30% savings). There is something the makers of the Nebia system could do to perhaps tip the balance, ever so slightly more in their favor; namely design the system so the hand held wand and main shower head could not operate at the same time. This would change the worst case number from 1.3 gal / min to 0.9gal/min (3.41 L/min) and change the water savings in the above scenario to 33.34%, enough to earn 5 points. I have to say I’m a bit conflicted. In practice, the Nebia system’s flow rate will probably be somewhere between 0.7 and 1.3 gals/min, so in terms of pure water savings, it the best choice….notwithstanding the debate of whether or not extreme “low flow” actually leads to longer showers, but from a LEED points perspective, I’d still lean towards the lower cost, albeit slightly higher flow rate, option.