Taking the LEED in Water Conservation

While much of the focus of mechanical and electrical designers over the past few years has been on controlling energy operating costs, a shift in emphasis to controlling water costs can be expected as the decade unfolds. In drier parts of the country, such as the Southwest, water is already dear, but even in more humid sections of the country, such as the Pacific Northwest, a combination ...

By Jonathan Gray, C.I.P.E. and Jerry Yudelson, P.E., Interface Engineering, Inc., Milwaukie, Ore. March 1, 2002

While much of the focus of mechanical and electrical designers over the past few years has been on controlling energy operating costs, a shift in emphasis to controlling water costs can be expected as the decade unfolds. In drier parts of the country, such as the Southwest, water is already dear, but even in more humid sections of the country, such as the Pacific Northwest, a combination of factors is influencing designers to come up with innovative methods of water conservation and water-cycle management.

Some perspective on H2O

Price increases for water supply and wastewater/stormwater management are being driven by the rising costs of maintaining municipal infrastructure as well as the capital costs of system expansion due to increasing populations. In the Portland, Ore. area, for example, costs are increasing as a result of municipalities having to pay for alternative stormwater management systems. Because of these increased municipal costs, developers and building owners are being hit with system development charges —impact fees assessed on new construction. Therefore, considerable pressures exist to reduce the amount of water used on a project site and the amount of rainfall that runs off it.

The final factor driving water conservation is the advent of green building ratings from the Washington, D.C.-based U.S. Green Building Council. Its Leadership in Energy and Environmental Design (LEED) program has established a system that awards points to owners of new buildings or major renovations, based on the sustainable initiatives implemented in a project.

Five broad categories exist—siting; water efficiency; energy efficiency; materials and resource use; and indoor environmental quality. A minimum of 26 points—out of a maximum 69—is needed to earn certification for good environmental performance.

Interface is currently involved in three LEED projects, including Ecotrust’s Jean Vollum Natural Capital Center, one of the first buildings in the country to be certified as “gold”—in other words, achieving 60% of the potential 69 points. Ecotrust is a non-profit organization dedicated to supporting the emergence of a conservation economy along North America’s rain forest coast.

Interface provided M/E/P services for Ecotrust’s renovation and conversion of a 70,000-sq.-ft. historic warehouse into a modern office building and retail operation that houses a number of environmentally conscious groups, including outdoor clothing retailer Patagonia. For purposes of this article, the focus will only be on the facility’s water-related LEED initiatives.

The lowdown on LEED

The LEED system treats water use and water-cycle management in several sections. First, it deals with stormwater management, awarding credit points for developed projects that do not increase the rate and quantity of stormwater runoff from the undeveloped conditions, with the goal of improving the quality of water in surface streams. For existing facilities already more than 50% impervious, LEED asks that the quantity of runoff be reduced by 25% from existing conditions. In addition, LEED awards credit for projects in which 80% of total suspended solids and 40% of total phosphorous are diverted from the runoff. In both cases, LEED strongly supports on-site stormwater detention—to reduce peaks—and retention—recharging or otherwise using stormwater on site—typically via bioswales and rooftop gardens.

Mechanical designers interacting with roof garden development have to come up with a number of innovative ways to handle roof runoff for both detention and retention purposes. An excellent resource is the Texas Water Development Board’s “Texas Guide to Rainwater Harvesting,” available on line at www.twdb.state.tx.us/publications/reports/RainHarv.pdf .

Another two LEED credit points are available for projects that reduce or eliminate the use of potable water for irrigation. Normally the province of the landscape architect and civil engineer, mechanical designers are now being brought into the loop to provide expertise on supplying gray water.

Two further points are given to projects that reduce potable water use for building services 20% below the standards set in the 1992 Energy Policy Act, which, of course, set the current 1.6-gallons-per-flush water closet standard. Two additional LEED points are given if water use is reduced to 30% below the standard.

A final LEED credit point is awarded for reducing the use of municipally provided potable water for building sewage conveyance by a minimum of 50%. This goal is typically accomplished either through the use of composting toilets—which work, but are not commonly used in buildings—or by the construction of on-site biological wastewater treatment systems such as the Living Machines (visit www.livingmachines.com ).

A complete copy of the LEED scoring system, along with documentation requirements, can be downloaded at www.leedbuilding.org . Additional information is contained in the LEED Reference Guide, available at www.usgbc.org .

Going for the gold

At the Ecotrust Building, the plumbing design team was asked to come up with 30% calculated water savings—compared with a typical code-compliant building—to secure the two available LEED points for water-use reduction. Designers, to meet this credit, typically use high-efficiency fixtures and consider the use of collected rainwater, as well as gray water, for non-potable applications such as toilet and urinal flushing. In some jurisdictions, designers are even specifying waterless urinals. For this historic renovation, completed and occupied in September 2001, all water-consuming fixtures were selected for their capacity to conserve water and provide durability for long-lasting service.

For example, showers, installed for those who commute by bicycle or those who work out at lunch, are fitted with 2.0-gpm shower heads and lavatory faucets with 0.5-gpm aerators. Interior faucets, except lavatories, were fitted with 2.0-gpm flow control devices.

Overall, the project is calculated to achieve an annual 32% reduction in water consumption over a typical or code-compliant office building (see table, this page). It should be noted that to achieve this total, 40,000 gallons of recycled water were subtracted from the total use, based on calculations for expected stormwater reuse.

A great green roof

A second LEED project in Portland, this one striving for Silver certification—obtaining 33 to 38 of the possible 69 LEED credits—illustrates the lengths to which designers are being pushed to accommodate environmental sensibilities.

The project involves the renovation and retrofit of an older bank building into a new office building for Multnomah County.

The project stands out for two reasons: It involves a green roof; and it includes a functional sculpture that doubles as a water-pumping system to irrigate the roof garden (see image above).

The county is pursuing the green roof for several reasons: Based on current energy prices, it believes it can save about $2,500 annually in heating and cooling costs as the result of better insulation; the green roof is expected to extend the life time of the roof itself owing to its protection from ultraviolet rays; and finally, about 27% of the project’s overall costs will be cut as the county expects to obtain nearly $90,000 in immediately available sponsorships and grants for pursuing this particular sustainable technology.

From a plumbing perspective, the design challenge was to find a way to contain and collect roof runoff so that it could be used later in the year for irrigation water. Despite its rainy reputation, there is little rain in Portland from July through September, so plants do need supplemental water.

Further, as with many public projects, 1% of the budget was dedicated for art for the building. But in a twist on the norm, one of the artists commissioned, Noel Harding, developed the notion of a windmill sculpture that could also be used to pump water to irrigate the garden (see “Art Meets Engineering to Help the Environment,” p. 48).

Harding gained notoriety in Canada with a similarly unusual project in his hometown of Toronto, where a roadside sculpture composed of recycled plastic actually served as the receptacle for an artificial aquifer that helps the city’s watershed. His proposal for this project meant a water pump from the windmill would have to be incorporated into the storage tank and irrigation system. To say that this was an unusual assignment would be an understatement.

In concept—the county is still contemplating the scheme—the fifth-floor green roof will receive rainwater captured in storage tanks at the penthouse level. Rainwater would then be transported via the water-pumping windmill—which includes a custom-built irrigation system—through both the green structure on the penthouse level and the lower-level garden roof.

Like his Toronto project, Harding’s windmill and its related system will aid a municipal watershed and water treatment load, as it is expected to capture about one-third of a two-year intensity rain event that will be treated prior to being released into the city stormwater system.

As far as its actual operation, the 50-ft. windmill will pump stormwater from the second of two storage tanks, routing it to a pneumatic pressure tank and irrigation controls. Stormwater will be gathered by the existing roof-drain system at the penthouse level and intercepted to flow into the tanks.

Two overflow systems will protect the overall system: One routes excess water to existing storm drain conductors, while the other routes water to the building exterior for emergency drainage. The windmill would then draw water from the second tank and pressurize the irrigation system, distributing water to the adjacent hill of native flora as well as the green roof below.

Two tanks will be necessary because of structural constraints. The tanks also have to be rectangular to fit through an existing opening, and will be connected by routing water from one to another through the emergency generator room. The design, of course, required significant interaction with the existing equipment layout, but the greatest challenge in the scheme was taking the drainage back to the existing rain drain leaders, 70 to 80 ft. from the second tank.

During the summer, the system will be backed up by city water about once a month to keep foliage alive. In the winter, the system will be in continuous use—provided there is wind—to pump rainwater through the roof prior to release into the stormwater system.

Portland State

The final corner of the triumvirate of LEED-related projects—Portland State University’s new six-story Birmingham Student Housing Center—combined a gray-water system with energy conservation. Interface was asked to draw water from showers and laundry facilities, and then transfer it to a tank equipped with a heat-recovery system. Incoming cold water is then pre-heated and sent to the building’s water heater, where it is finally used as domestic water, reclaiming some of the heat from the original hot water and reducing the project’s use of energy.

Additionally, this project is located in a stormwater quality area of the city, meaning rooftop drainage needs to be detained in a storage tank for a two-year intensity rain event. Rainwater is collected and drains into a 5,600-gallon tank. Over the course of the year, water is drained and refilled numerous times, and the captured rainwater is used without further treatment as gray water for both flushing water closets and urinals in the first-floor public restrooms. As a further use of the gray water, excess water is also pumped out of the storage tank and used for on-site irrigation (see figure above).

Be a leader

LEED, first introduced in March of 2000, has become the de facto U.S. green building standard. In fact, nearly 300 projects—totaling almost 6% of all new commercial and institutional building floor area in 2001—have registered their intent to become LEED certified as of February 2002. Because of this surge of interest in LEED, we believe that mechanical and electrical designers should—and must—play a leading role in assisting their clients achieve LEED-certified buildings.

H2O Consumption Comparison

Fixture Type Daily Water Use – Ecotrust Bldg. (gal.) Daily Water Use Base Case (gal.)
Flush (W/C and Urinal) 660 660
Lavatory 45 179
Shower 119 149
Janitor Sink 16 16
Total Daily Volume 840 1,003
Annual Volume (260 days) 218,303 260,845
Allowance for Stormwater or Graywater Reuse on Site (40,000)
Annual Volume (Net) 178,303 260,845
Percentage Reduction 31.6%

Art Meets Engineering to Help the Environment

Art and engineering may come together to provide an unconventional method for irrigating a green roof in Portland, Ore.

Inspired by Canadian artist Noel Harding, Interface Engineering, in conjunction with Carleton Hart Architecture, Portland, is working to turn a 50-ft.-tall windmill sculpture into a functioning water-pumping system.

In fleshing out the design, the team has come up with a 3-in. cylinder capable of pumping 420 gallons per hour in a 10 mph sustained wind, and approximately 470 gallons per hour in a 15- to 18-mph sustained wind. These calculations are based on a rain event equal to one-third of a two-year intensity, which equates to approximately 7,300 gallons over a 24-hour period on the penthouse roof.

The windmill idea was brought to Portland by Harding, a Toronto artist noted for his work with the Plastics + Art initiative, which promotes the use of plastics in art. Harding’s work was selected during a juried competition to provide 1% of the project’s budget for art, a requirement for all public projects in Portland. His design also features a large tree-covered hill adjacent to the windmill. The hill would be placed in a giant tub that slowly rotates as the windmill turns. Harding says the building is really a great demonstration project, as it is clearly visible from the city’s main points of entry, including its bridges. The whole point of the rotating trees, he says, is to catch people’s attention and get them thinking about green roofs and the benefits they provide.

Capturing rainwater from the Multnomah County building will also provide a significant environmental benefit. Presently, raw sewage from the building dumps into the Willamette River every time it rains more than 1/10 in., because the building is in a combined sewer/stormwater overflow area. Existing pipes are at capacity with sewer flows alone. When stormwater is added, the overflow directly enters the river, bypassing the treatment plant. This occurs more than 70 times in an average year.

Another benefit of the green roof, according to Amy Joslin, assistant director of sustainability for Multnomah County Dept. of Sustainable Community Development, is that it will act as a “carbon sink,” absorbing carbon dioxide—the biggest contributor to global warming.

The particular green roof proposed for the project utilizes the existing 5-ply roofing system for the waterproof membrane, and then adds a root barrier layer, a drainage layer, a 4- to 6-in. soil layer and a plant layer featuring low-maintenance, drought-tolerant native species.

Harding’s art has raised controversy, however, and more than a year after the competition, the project is only now going through the city’s design review process.