As precious as it is, water is everywhere – which might be why so many people waste it daily, often unintentionally. In green building projects, designers tend to focus on efficient energy usage more than efficient water usage, but we need to focus on both as water availability and quality grows into a looming social issue.
All projects need to achieve a water balance.
Water balance means that the water that enters and leaves the site is balanced in an integrated fashion. For example, you’ve got toilets on one side and bioswales on the other. Is the bioswale the right size to manage the water coming out of the toilets? Is the cooling tower using the water that is collected on site?
- How much water falls?
- Where does it land?
- Where does it go?
- How much do site users need?
A simple calculation to address these questions is key:
rain falling on + water flooding in + potable supply
= toilets flushed + sinks filled + cisterns fed + cooling tower loss + outfall
Considered together, these questions identify the biggest variables in the equation – what project teams should focus on and why – to achieve perfect water balance.
Own the water balance
It’s hard to address or achieve water balance because water responsibilities are fragmented across multiple players in a building project:
- The mechanical engineer knows about toilets.
- The landscape architect knows about plant irrigation.
- The operations people know how much water the cooling tower needs.
- The civil engineer figures out where the water comes from and goes to.
- The architect controls how the water gets into the building and what people need it for.
These five teams will create five distinct design responses to the project’s water issue; and those five responses will often have no connection to one another. Each response also misses the opportunity to leverage the other four systems, which results in more missed opportunities.
For example, a civil designer might create a 100,000-gallon vault to catch storm water from a building’s roof. The mechanical engineer will pump 100,000 gallons of water up a tower to flush toilets. Between them, they are managing 200,000 gallons of water; the owner is buying water that doesn’t need to be bought; and water is unnecessarily being taken out of the watershed. On top of it all, the mechanical engineer might never learn that the civil engineer has all the water that she needs.
Building projects need a water champion.
Being the water champion and owning the water conversation requires integration skills, great project management, and a willing team. Most projects have some of these, but it’s rare to have all of them. As long as water is cheap, it seems like an inexpensive mistake to make and an easy win to overlook.
Showcase: projects with water in balance
The Las Vegas Springs Preserve is a 180-acre project initiated by the Las Vegas Valley Water District to restore the springs that once provided water to the Las Vegas Valley. The project consists of five buildings including an historical museum and desert-living center, low-water gardens, a desert wetland, and walking trails. All of the projects on the site demonstrate sustainable and low-impact landscaping and construction strategies to encourage water and energy conservation.
The desert living center cooling system used water to provide the cooling rather than electricity. Paladino recommended that the project use photovoltaics to pump a little bit of water to a wind tower, and run it through filter medium, i.e. a big sponge. Because the wetted air blowing through the medium is heavier than dry air, it falls into the building and cools it – like a giant swamp cooler.
One of only five Marriott Marquis properties in the world, Marriott Marquis Washington, DC is the largest hotel in the city. The $520-million, four-star hotel has 1,175 rooms including 49 suites and more than 105,000 square feet of function space, as well as five separate restaurant spaces. Paladino served as the green building consultant and the commissioning authority for this highly anticipated project. Its innovative wastewater management system collects stormwater and condensate in a 40,000-gallon tank for use in irrigation and cooling tower make-up water. The system—the largest in the city— provides 10 million gallons of reclaimed water per year. Not only does this reduce the amount of potable water required and the embedded energy associated with treating and pumping it, but it also reduces the amount of stormwater contributed to DC’s combined sewer/stormwater system, which can overflow into the Potomac and ultimately the Chesapeake during heavy rain falls.
After 28 years in Park Ridge, New Jersey, The Hertz Corporation announced plans to develop a new headquarters in Estero, Florida. Water flow is viscerally important to the health of the wetlands around the headquarters. Hertz limited the disruption of natural water flow by reducing its impervious cover like parking lots and driveways, and implemented onsite infiltration, reducing pollution and contaminants from stormwater runoff. A rooftop rainwater harvesting system collects rainwater and provides 100% of the water needed to flush toilets for the campus’ 850 workers. The mechanical design uses a central chilled water plant to ensure high efficiency, and a thermal storage system to reduce peak energy demand. And while not part of the water balance, the project uses ice as the thermal storage, proving that the balance concept can be applied to energy too.
One of the powerful roles of a sustainable company is to own the balance between buildings, design, and the environment. If the owner is interested in minimizing footprint and impact on a site, someone needs to hold all the demands and sources in balance. The sustainability team is ideal for that purpose.