Sustainable green building water use

green building / sustainability / water efficiency / leed / living building challenge / breeam

Regulating green building water consumption

We all need reminding occasionally that water scarcity is, despite being inevitably local in urgency, is ultimately a global problem as it relates above all to the impact of climate change, resulting from our collective impact on the planet we call home.

The pattern of unsustainable water use in the built environment is therefore right up there, in green building terms, with energy efficiency and waste management.

Although water is of course used outdoors, most notably for irrigation purposes, 70% of building water use occurs indoors (LEED). Bathrooms, kitchens, and process water for manufacturing or industrial applications are the main sources of indoor water use.

Nobody is suggesting that a modern building should do without water, it simply isn’t an option but in order to reduce overall water use within buildings, an efficiency first approach can represent considerable savings.

Primarily this equates to installing water-efficient appliances, low or no irrigation planting strategies, alternative water sources (such as greywater and rainwater collection) and finally ongoing real-time water sub-meter monitoring to keep a close eye on exactly what is being used and when within the building in question.

Rather than architects, landscapers and engineers needing to work all of this out for themselves, sustainability standards such as LEED, BREEAM and the Living Building Challenge provide guidance and benchmark standards for all of the above. Let’s get into it!

Water use reduction in green buildings

Outdoors, more indirect green building strategies such as smart landscaping (or xeriscaping - using plants that require no additional irrigation other than the expected annual rainfall in each location) can have large impacts on building site water use. 

Indoors, green building water use reduction strategies such as the installation of efficient fixtures and appliances are crucial.

For bathrooms, green building technologies include ultra-low flow water closets and urinals, which use pressure-assisted flushes and dual-flush water closets, which distinguish between liquid and solid flush options. In addition, waterless fixtures can be implemented, such as waterless urinals or composting toilets (LEED). 

More generally, low-flow aerators can be installed at minimal cost, essentially a water flow constrictor that reduces water output from faucets. In outdoor contexts, strategies such as drip irrigation can be implemented, which is a more efficient strategy that delivers water directly to plant roots (LEED). 

When considering which types of green building appliances to install, benchmarking tools can a green building consultant’s best friend as a way to cut through any potential greenwashing and guarantee maximum impact in water reduction terms.

For example, the WaterSense label, a partnership with the United States Environmental Protection Agency (EPA), provides invaluable guidance on water efficient fixtures. Green building products with the WaterSense label are designated to be at least 20% more efficient that other appliances in that category.

In outdoor irrigation contexts, broader strategies that include location and site characteristics can be implemented. Rainfall and climate vary greatly based on location, so outdoor water use strategies will shift based on these factors. 

Native and locally adapted species can be implemented in landscaping plans to reduce the need for irrigation and, as a bonus to provide wildlife habitats, promoting biodiversity. In addition, xeriscaping uses a combination of soil improvements, native plants, and efficient irrigation to reduce water use (LEED).  

Alternative water sources in a green building concept

Within the United States alone, buildings account for 14% of potable water use (LEED). The Living Building Challenge’s Water Petal section suggests that no potable water should be used when it is not needed, ie, besides in the case of drinking water, potable water use in a green building should be avoided.

Rather, water reclamation systems such as greywater and rainwater recycling should be used to provide alternative water sources.  

As mentioned, understanding the relationship between site location and climate has a large role to play in any green building plan. In the cases where ample rainwater is available, rainwater capture systems can be an investment that pays off handsomely in the medium-term, especially in locations with limited water availability. Rainwater can be collected passively or actively then used for irrigation, process water, or flush fixtures.

Passive strategies such as rain gardens or dry ponds redirect water to planted areas and provide irrigation assistance. Active rainwater management systems capture, store, and transport water to a desired application. Active systems can be helpful as rain is weather dependent, providing greater flexibility to when and where the water can be applied (LEED). 

Graywater recycling is another alternative water resource that allows for reuse of otherwise discarded water. This process involves the collection, treatment, and storage of water discharged from kitchens, showers and other sources and can provide non-potable reuse applications (BREEAM). Most commonly, this water can be reused in flush fixtures and helps reduce water demand in buildings. 

The use of alternative water sources in tandem with more efficient appliances and water reduction strategies can greatly reduce building site water usage. 

Monitoring water performance in a green building

As with many sustainable building trends, monitoring and regulating performance is vital to ensuring success. Devices should be implemented to monitor water usage trends and identify any potential problems. 

Sub-meters are devices that monitor water leaks, measure usage, and provide the potential to make building improvements with the provision of this data (LEED). Leak detection systems are very important in the case of major leaks, which for obvious reasons could affect building water use and efficiency (BREEAM). 

It is vital that this water data is tracked and regulated by those who oversee the operations and maintenance of the building. In addition, if select information such as water use is displayed to building occupants, additional benefits from behavioral changes can be achieved. 

A concept known as the Prius Effect states that when presented with information, people tend to have a greater incentive to reduce consumption. The concept was derived from the Prius car, which encouraged drivers to further reduce gas consumption when efficiency information was made available. In the case of water usage, real-time water information can be displayed in places where people use water to encourage further reductions from a behavioral standpoint. 

The monitoring of water performance can feed back into the other strategies of water reduction, water efficiency, and alternative water resources. As design decisions are made, the reality of those decisions can be tracked in real time to provide further guidance on the most effective efficiency measures.