Water Efficiency

By reducing potable water use consumption inside and outside, green buildings can reduce up to 40% of water use.

Since clean water is one of our most important and scarcest resources, it is important that green buildings reduce their impact as much as possible. Water Efficiency methods like smart Irrigation Systems, Storm Water Protection, Water Efficient Landscaping, Graywater Recycling Systems, Rainwater Catchment Systems, and Water Efficient Appliances and Toilets have all become increasingly more efficient and innovative.

On a building site, water is used inside and outside of the building envelope. It is important to reduce potable water use below the conventional use baseline across all building activities.

Water Efficient Landscaping

Many building owners pride themselves on beautiful landscapes, however, maintaining the outdoor area can be highly water intensive. Since 30% of building water is used outdoors, many strategies need to be taken in order to reduce water waste.

Free Water Efficiency Course

By planting drought tolerant species, less water is needed to maintain the landscaping. Designing outdoor areas for high plant density can also reduce water use. When it does come time to water these plants, using irrigation efficient technologies vastly limits water consumption.

Drip irrigation can direct water to the exact areas where the water is needed, and less water is lost through evaporation. To avoid wasting potable water, a source that is scarce and requires a lot of energy to create, graywater, rainwater, and treated non-potable water can be used in its place for landscaping purposes. Evapotranspiration, plant species, plant density, and the microclimate factor all contribute to water loss in landscaping.

Innovative Wastewater Technology

In buildings, toilets use the second highest percentage of potable water at 19%. Clothes washers use 15%, showers use 12%, and faucets use 11%.

In green buildings, it is of primary importance to reduce wastewater generation and potable water demand while increasing the local aquifer recharge. One strategy for reducing potable water use for sewage conveyance is by using water conserving fixtures like composting toilets and low flow faucets and fixtures or by using non-potable water like graywater, rainwater, or treated wastewater for flushing.

Water reduction from indoor water fixtures are measured against a baseline determined by the Energy Policy Act of 1992, the Uniform Plumbing Code, and the International Plumbing Code. By definition, low flow showerheads run at less than 2.5 gallons per minute and faucets run less than 2.2 gallons per minute for private homes and less than 0.5 gallons per minute for public building faucets. 

Just looking at the numbers used when modeling for LEED certification, it is assumed that women and men both take 3 trips to the bathroom per day. Using a traditional water closet, women take 3 water closet trips and 0 urinal trips, but with a dual flush toilet, they only use 1 big flush and 2 small flushes.

Men on the other hand take 1 water closet trip and 2 urinal trips in traditional water closets per day, but in water closets that include waterless urinals men take 1 water closet trip and 2 urinal trips with no water use. Since regular toilets use 1.6 gallons per flush and urinals use 1.0 gallons per flush, using dual flush toilets and waterless urinals can save a tremendous amount of potable water.

Water Use Reduction

Some green buildings go above and beyond water use reduction. The minimum requirement for LEED buildings is 20% less water than the baseline, but it is possible for some buildings to achieve 30-40% reduction of water use. This can be achieved by implementing more water efficiency technologies and behaviors.

Cooling Tower Management

Water Drops Credit: Lesley Wheat via FlickrA cooling tower is a heat rejection device for industrial use, which extracts waste-heat to the atmosphere though the cooling of a water stream to a lower temperature. The type of heat rejection in a cooling tower is termed "evaporative" in that it allows a small portion of the water being cooled to evaporate into a moving air stream to provide significant cooling to the rest of that water stream. The heat from the water stream transferred to the air stream raises the air's temperature and its relative humidity to 100%, and this air is discharged to the atmosphere.

Cooling towers can use a lot of water and the process often adds chemicals to potable water. Green buildings can reduce the wasted potable water by either managing the chemicals associate with cooling towers or use non-potable water sources in the cooling tower. Cooling tower management is a very important water saving tactic especially for the operations and management of existing buildings.

 
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