Harvesting the Future: Stormwater-Powered Living Walls
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In the realm of sustainable architecture and green building practices, pioneers and advocates worldwide are continually seeking innovative solutions to reduce the environmental impact while still preserving the aesthetic appeal of their designs. One such innovation that has gained significant attention in recent years is the use of stormwater collection as a primary source to irrigate Living Walls.
In this article, we’ll explore a compelling case study from our friends at Sempergreen Europe, that highlights the tremendous potential of Living Walls in transforming urban landscapes and promoting water conservation.
Enni Headquarters Moers, Germany. Photo: Sempergreen Europe
Living Wall System: Sempergreen
Location: Moers, Germany.
Client: Enni Headquarters
Enni, a germany based energy supplier, boasts a Living Wall that stretches across an impressive 650 square meters (about 7000 sq. ft) of their new office headquarters. What makes this design truly special, however, is not just its size but its skillful use of harvested stormwater as a primary irrigation source. In this article, we’ll review the unique features of this Living Wall project and the thoughtful design that keeps it going.
Harvesting the Storm: A Sustainable Source
At the heart of Enni's stunning vegetative facade is its primary irrigation source—harvested stormwater. In an era marked by increasing droughts and rising temperatures across Europe, relying on stormwater for a Living Wall might seem risky. However, this design includes a smart backup connection to the building's water supply. Meaning, when the cistern's water level approaches a critical low, an internal floater device triggers the switch to the building's water supply until the stormwater replenishes to a satisfactory level.
Enni Headquarters Moers, Germany. Photo: Sempergreen Europe
The Underground Reservoir: A 20,000-Liter Marvel
The backbone of this stormwater harvesting system is an underground cistern with an impressive capacity of 20,000 liters (5283 gallons). Strategically located outside of the building, this vast reservoir stores rainwater that is collected from the building's rooftops and surrounding areas. To ensure the cistern's effectiveness, it is placed a minimum of 2 meters below the soil level, providing both efficient storage and protection from everyday traffic.
Filtration and Recirculation: Ensuring Water Quality
Stormwater can contain impurities, including gutter rust and pollutants. To maintain water quality and protect the Living Wall, a robust pump sends stormwater through a comprehensive filtration system. This includes an initial filter to remove larger particles, followed by smart irrigation components that ensure precise and efficient distribution of water to the plants.
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Given that this Living Wall operates on a recirculating system, the importance of thorough filtration cannot be overstated. The gutters on the facade, designed to collect runoff, may accumulate rust, which needs to be removed before the water reaches the recirculating tank. This calls for another filter which further refines the water before it rejoins the tank, eliminating that rust and any residuall traces of fertilizers.
Water Consumption: How Much Water Does Enni’s Living Wall use?
On average, Enni's Living Wall needs approximately 2 liters of stormwater per square meter per day, equivalent to 1/2 gallon per 10 square feet daily. While this is an impressively low consumption rate, it is essential to note that hot summers can pose a challenge and change living walls consumption but also rainfall collected. Many variables can influence the amount of water used by Living Walls including wind impact, sun exposure, plant type and time of year.
During such periods, a freshwater building connection becomes critically important to supplement the stormwater supply and ensure the well-being of the plants.
Enni Headquarters Moers, Germany Photo by Sempergreen Europe
Collaboration and Expertise: The Role of Water Engineers
To bring Enni's innovative vision to life, collaboration with a water engineer was essential. In Germany, where comprehensive water collection, including blackwater, is a common practice, such coordination falls well within their expertise. The success of Enni's stormwater harvesting system highlights the importance of interdisciplinary collaboration in pushing the boundaries of sustainable architecture.
Monitoring and Maintenance: Incorporating Sensors
Enni’s Living Wall is equipped with moisture sensors to monitor plant health and track water consumption. These sensors provide valuable data for maintaining the lush greenery and ensuring the long-term sustainability of the Living Wall. Additionally, temperature sensors are employed to address the challenge of fluctuating water temperatures. When the water in the tank drops to 2-4 degrees Celsius (about 36-39 degrees Fahrenheit), an electric heater is activated to warm it to a plant-friendly temperature of 10 degrees Celsius (about 50 degrees Fahrenheit). This ensures that the roots remain healthy and unshocked by cold water.
Historically, Living Walls have been seen by the opposing voice as energy and water “divas”. So, their inclusion in the designs of net-zero or low impact buildings has often raised an eyebrow or two. However, this project is proof that with the appropriate Living Wall system and a sophisticated irrigation design, Living Walls can continue to rival alternative coatings and claddings being considered. Enni’s Living Wall serves as an inspiring example of how creativity, collaboration, and advanced technology can transform urban spaces into green oases, promising a greener and resilient future for all.
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Lily Turner, WELL AP, Director of Green Walls at Urbanstrong, which specializes in green walls. Reach out to Lily Turner at lturner@urbanstrong.com
