Green Material Alternatives for Plumbing Fixtures

Humans cannot live without water, but the western world’s practice of using exorbitant amounts of drinking-quality water to transport sewage is not a sustainable practice. This is becoming increasingly evident as the population grows, and water becomes increasingly scarce in the dry regions of the United States. Plumbing fixtures that use low or no water are available from a number of manufacturers. These include:

• Composting toilets, waterless urinals, and low-flow toilets (models range from 0.8–1.6 gallons per flush, including standard gravity-flush, pressure-assist models, and dual flush toilets, which can deliver either a 1.6 gallon or a 0.8 gallon flush, as needed).
• Low-flow showerheads (various models using less than 2.5 gallons per minute).
• Low-flow faucets (using less than 2.5 gallons per minute) and metered faucets (to ensure that faucets in public bathrooms will not be left on).
• Shutoff valves for kitchen faucets and showerheads that enable the temperature setting to be “saved” while the water is temporarily shut off.

Treating gray water like black water is not the most efficient strategy. Once-through gray water from sinks and washing machines can often be reused directly for toilet flushing or for subsurface irrigation (depending on regional codes). Gray water can also be used on (nonedible) plantings after treatment with a commercial filter or site-built sand filter.

For showers or other hot-water fixtures, gray water waste heat recovery systems can capture the heat from the hot water as it goes down the drain and transfer it to incoming water. These systems are especially effective in high-use shower areas, such as in locker rooms.

This technology produces both heat and electricity and makes use of them in a large building or campus system. Because the heat associated with standard electricity production is often wasted (simply exhausted into the atmosphere), cogeneration is a much more efficient process. In fact, cogeneration raises fuel utilization efficiency to more than 90% (compared to typically 35% efficiency for plants generating electricity alone) and reduces fossil fuel use by over half.

Instead of mixing high-velocity air from overhead ducts to “dilute” the stale air in a room, a displacement ventilation system supplies fresh, cool air from a pressurized floor plenum (similar to the access floors used for computer rooms) or from low, wall-mounted diffusers. The fresh air displaces the warmer, stale air, which is removed via a ceiling plenum.

Compared to a conventional system, a displacement system moves a larger volume of higher-temperature air at a lower velocity and lower pressure drop, thereby reducing required fan power. Low-velocity air is quieter and less drafty. Also, displacing rather than diluting the air results in better pollutant removal. Pollutants and heat from copy machines and other equipment, lights, and people tend to be drawn straight up in a “plume” rather than being mixed laterally in the conditioned air. Furthermore, the warmer supply air means the chillers are more efficient. Finally, the under-floor plenum can also be used for wiring, providing superior convenience.

Materials required for under-floor air distribution typically include an access floor system (usually covered with carpet tiles or resilient floor tiles) so that sections of floor can easily be removed to access the floor plenum. In applications where spills may be an issue, such as grocery stores, labs, hospitals, etc., displacement ventilation can be supplied low in the room, through millwork, rather than through the floor.

In conventional building operation a considerable amount of energy is used in circulating air for ventilation. Using natural forces to move air can result in effective ventilation without the energy input. Examples include providing cross ventilation to make use of wind, building chimneys to induce stack ventilation, and using water-evaporation systems in hot dry climates to induce cooling and air movement. (Humid air is more buoyant than dry air.)

Excerpted from Green Building: Project Planning & Cost Estimating, available through RSMeans.