8 Irrigation Considerations for Soil-Based Living Walls

Green Walls are being touted as interiorscaping marvels and prime examples of biophilic design.

Green walls are being used to enrich client’s lives and boost ‘green’ marketability.  But the capacity for green wall products to validate the ‘green’ image they create depends on factors like irrigation.  In light of water resource concerns, is a green wall wasteful?

No.  By design, living wall systems can distribute water efficiently and effectively, and even utilize reclaimed water.  Systems are designed with special features and growing media to balance moisture levels to optimize plant health and minimize overall water use.  And some systems can be especially efficient.  For example, the water used by an interior Modulogreen living wall system per year, per square foot, can equate to the water a typical North American uses to shower per day!

Living walls generally use hydroponic systems or drip irrigation to distribute water.  In recent years, drip irrigation has developed into an effective tool for modern agriculture and water-wise landscaping (xeriscaping).  Green wall fabricators have adopted drip irrigation technology and engineered products that incorporate standard components.  Today, I focus on drip irrigation for soil-based living walls, although some considerations apply to hydroponic living walls.

If you are tasked by a client to design and install a soil-based, drip-irrigated living wall system, keep these considerations in mind to ensure things flow smoothly:    

  1. Water Source. It’s imperative to determine the water source for the living wall and if water is to be recirculated.  Either way, make sure the water connection and/or reservoir placement are negotiated early in the design phase.  Direct-source irrigation from a potable water supply is common for large living walls, or for places where water reservoirs aren’t feasible.  As a source, potable water is extremely stable.  However, without a reservoir, the potential for flow interruption exists (water supply disconnection within the building or via utility outage).  There’s not much you can do about the utility, but within the building, a dedicated water supply is recommended.Living walls that are reservoir-fed tend to be smaller, but are capable of efficiently recirculating potable, grey and/or rain water.  Of course, your client will need space nearby to store the water and additional pumping and filtration equipment to facilitate recirculation.  Also know that reservoir-fed systems tend to require more monitoring and service hours to maintain.  These systems may require periodic ‘flushing’ to introduce fresh water and fight nutrient/contaminant build-up.
  2. Irrigation Equipment. Irrigation systems vary from project to project, and product to product, but you’re going to need a little space for the irrigation controller, fertilization system, filter, zone valves, backflow preventer, etc.  Typically, irrigation works are situated in a utility room or in a cabinet close to the living wall.  You can be creative about hiding the irrigation works, but it needs to be readily accessible to maintenance personnel.

Irrigation-cabinet

 

-Example irrigation cabinet (Courtesy of Modulogreen)


Legend

A. Manual valves F. Pressure gauge
B. Automatic valves G. Backflow preventer
C. Timer H. Shut-off valve with purge
D. Fertilizer injector I. General filter with purge
E. Filter
    1. Water Filtration. Extra filtration is especially important for grey/rainwater sources and recirculating systems, otherwise sediment and other materials may clog drip lines and emitters.  Also, for potable source applications, filters are recommended to remove additives like chlorine to facilitate plant health.
    2. Water Pressure. Consider water pressure when specifying your supply line connection.  Ensure that water pressure is sufficient to get water to all parts of the wall, especially the top!  Consult with an irrigation specialist to be sure.
    3. Watering Zones. If you have a large living wall, it will likely span a variety of microclimates (some will be obvious prior to installation, some may become apparent later during a maintenance inspection).  Do your best to anticipate all climate and microclimates when delineating watering zones. To be safe, I recommend designing multiple watering zones within the irrigation design.  Also, water pressure might be a concern if you water the entire living wall at once.
    4. Installing Irrigation Equipment. Who does this depends on the size of the living wall and complexity of the system.  If instructions are clear, you might be comfortable installing the irrigation works yourself.  Just be clear in your negotiations with the client on who provides what (where connection terminates, who supplies backflow preventer, etc.).  And be smart about the plumbing.  You might feel comfortable installing the drip tubing and the supply lines, but it might be worthwhile to involve certified plumber and/or irrigation specialist.  Your client will feel safer, local code enforcement will be happy, and the risk for water damage is minimal.
    5. Waterproofing. Speaking of water damage, waterproofing liners and seals are recommended behind interior living walls.  Some systems profess to be completely water tight, but I would still invest in a heavy-duty waterproofing barrier.
    6. Testing. Once the irrigation is installed, test it before planting (depending on your system). Run the system to test the components and ensure proper function.  Inspect for any leaks, clogs, malfunctioning zones, water pressure issues, etc.  If modules are already in place, run the irrigation until the system is saturated and set initial timer programming.  If you implement sensors and remote-monitoring systems, test those, too.

 

Bottom Line: Be very prudent when designing and installing the irrigation component of a living wall.  It’s a matter of life or death for the plants!

(Many of these points were made or verified by Fred Collay and Nicolas Rousseau at By Nature Design.  Thank you to for sharing your expertise!)

 

Featured image courtesy of Modulogreen Vertical Solutions.

Mark is an accredited LEED Green Associate with a background in green wall research and product management and expertise in sustainability, ecology, green infrastructure, and green building. He currently works at Bela Flor Nurseries, a large wholesale supplier of annuals and perennials.

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