• Integration with other building systems An important overall design consideration is the integration of the green wall system with the rest of the building systems. Obviously such things as the building envelope type, windows and any window washing equipment will play into a green façade or living wall design coordination. Structurally, there is usually very little if any impact. In a well designed system, the modules in a living wall system are typically held in place with a series of supports extending at most up to 8 feet. Hence, there is never more than approximately 125 lbs. of weight on any given anchor on any point in the wall (assuming a 50 lbs/pcf soil is used, without a wind load). As a result, there is no practical limit to the height of the wall (no “stacking issues”), simply the height to which the client is willing to do maintenance on the system. From the standpoint of weather and waterproofing, the supports & modules of a living wall usually provide a minimum of 2.5 inches of clearance between the soil and the wall. You can expect humidity to be somewhat higher in the areas between the building wall and the green wall system.  Although there is no water running down the walls, the wall should still be waterproof. For concrete structures use elastomeric paints. For metal, wood frame and other structures consider rubberized or thermoplastic membranes (EPDM, TPO, etc.) or others as appropriate. In all cases, however, all penetrations for anchors, fasteners, or other uses must be fully sealed.

• Installation Direction. The assembly & installation of a green façade or living wall system is typically done by a local contractor, even one with little experience. The growing-in of plants takes place at a local nursery or grower’s facility, often using their labor for module assembly, soil filling, planting, growing, and any necessary acclimation. Either the grower or the installing contractor would transport the fully grown modules to the site. The contractor would execute the final steps. In a green façade, he would plant the modules or free growing plants as appropriate. In a living wall, he would fasten the framesets onto the modules, hang the units and install the final irrigation elements. Traditionally the installing contractor will be responsible for the first three months of maintenance on the living wall, and then the project is handed off to a maintenance contractor. Sourcing plants for custom living walls should begin a minimum of 12 months prior to installation to allow for seed collection, propagation in seed trays as plugs, and testing, especially if using native or custom plants. At least one month prior to installation, the building envelope consultant, architect or the project manager should inspect the structural wall for water tightness.  The general contractor should clean the wall and provide clear access to the site. When installing on a new building, always make sure that the green wall is installed last as it might get damaged by other trades.

Interior applications have a completely different set of requirements and horticultural conditions. Specifically, interior plants are typically subject to lower light levels than exterior plants, and need to be replaced due to decline more often than exterior plants. There are also issues with directional lighting and water that complicate matters. Often, rather than direct planting into a soil profile, a system that uses acclimated plants in modular grow-pots slid into cachepots without holes creates a system that is easy to maintain, and allows the irrigation system to be integrated into the frame.

When complete, a successful design process will address and overcome the top 5 challenges related to green walls:

• Improper irrigation (under- or over-watering, installation errors).
• Failure to consider the different microclimates between one part of a living wall and another part (different light, heat, humidity conditions).
• Incorrect plants specified by architects for climate/lighting.
• Incorrect growing medium used.
• Indoor applications with insufficient light for plant survival.

It should also be noted that most building codes do not make any provision for green walls and as such when undertaking one of these projects, a designer will most likely have to educate code administrators about the technology and its applications.

Maintenance Considerations

Maintenance should have been considered during the definition of the project’s scope and a preliminary maintenance plan should be established as a part of the design phase in order to ensure the long-term success of the project. Maintenance for green walls is different than for horizontal surfaces (i.e., green roofs). The vertical orientation of the vegetation may make maintenance access difficult and may require that maintenance personnel adapt traditional landscaping techniques, while bearing in mind that each plant has its own requirements. Therefore, it is important to manage client expectations by communicating the intricacies of the green wall, by pointing out the varieties of plant used and any seasonal changes called for, and to be specific about the anticipated maintenance plan and the associated costs.

Maintenance can be divided into three elements:

• Building/structure inspections will ensure that the green wall doesn’t cause significant damage to the building by catching problems before they become critical. Typically the wall and its surroundings, including drains and gutters, should be inspected a minimum of once per year. Random modules should be removed from the rails to inspect the wall and rails behind. The condition of the wall and its waterproofing, the rail anchors, the rails, drains and gutters should be checked.  Should a significant problem exist, a thorough inspection (removing all modules) may be called for. Clogged drains and gutters should be cleared.
• Irrigation inspections are recommended several times per year. The valves and fertilizer injectors should be checked for function, and the irrigation pipes checked for leaks. The modules should be examined for plant health, as a proxy for irrigation function. Should the plants in a module look out of the ordinary, check the emitters during a watering cycle to ensure that they function properly. Consult with the original irrigation specification to determine the proper end-of-season winterization (if required), or suggested maintenance schedules. The original irrigation specification should also include a recommended initial irrigation frequency and time, based upon the season and plant requirements.
• Regular maintenance to the plants will be required once they are removed from the nursery and planted in the ground or hung on the rails until they stabilize. This may require weekly inspection/correction for the first few weeks, extending to monthly, then assuming that the plants specified thrive in the wall, should be an infrequent (bi-monthly or quarterly) affair. Issues to look out for include pest infestations, plant disease, weed growth, over- or under-fertilization, and soil erosion. The plants may require some pruning to prevent overgrowth. Should an entire module of plants suffer decline (due to a broken drip emitter, for example), it may be easier to replace an entire module than attempt to replant and grow in the field. The same frameset may be used with a new module.

Case Study: Interior Wall Rooftop Lounge With Green Walls

Location:  San Diego, CA Green wall type:  Interior living wall system (uses plants in 6”/1 gal nursery pots) Completed:  March 2010 Cost:  $20,000 Maintenance:  weekly attention   Site Analysis:  A highly unusual site – an open-air rooftop lounge, with walls on 4 sides but open to the sky. Because of overhang, plants will likely receive no rain, not much direct sunlight. Team chose interior living wall system for this reason.  Plant List:  Living wall utilized sub-tropical plants acclimated to medium light levels. These would typically be used in interior applications.  Because of the sub-tropical climate of San Diego, these plants will thrive even in exterior conditions. Irrigation:  Plumbed line from a main water source. The system utilizes plants in their grow pots, dropped into cache pots with no holes. The irrigation water is fed into the bottom of the cache pot, and a felt wick takes up the water into the roots of the plants.  While there were initial issues with the multi-outlet drip emitters not being pressure-compensating, the contractor was able to dial the system in by changing to individual drip emitters of different flow rates. Maintenance Program:  Initially the contractor visited the site twice weekly. Once the irrigation system was stabilized the frequency was reduced to weekly, with the intention of further reducing it to a bi-weekly maintenance cycle. Lessons Learned:  The contractor shared these lessons from installation: The complexity of installing a living wall between 8’ and 16’ high should not be underestimated. It complicated the entire project, and took more time than imagined. Gain experience on the system prior to doing it in a client’s location. By acquiring a green wall frame and putting it through its paces prior to installation, the contractor was able to better understand how the plants would react in the project, and reduce the problems once the job moved to the maintenance phase. Nevertheless, the communication lines between installation crew and maintenance crew need to be more open. There were many small changes and accommodations that should have been communicated to those doing the maintenance. Critically, the design needs to be considered not just for the initial presentation, but how it will be several years down the road. The plant selection, combined with maintenance needs to be carefully considered in the context of the installation long before the project goes in.

Conclusion

A well designed green wall will add notable benefits to the building and community where it is located. Proper design using the input of numerous related professionals can help assure an end result that everyone is proud of.  With proper inspection and maintenance, a green wall system should be able to easily last 10 to 20 years or more. Incorporating this very green technology into a building project can help achieve some notable green building design objectives, contribute to the value of the project, and improve the health and welfare of the people who use or inhabit the building for years to come.

Peter J. Arsenault, FAIA, NCARB, LEED-AP is a practicing architect, sustainability consultant, and free-lance writer based in New York State focused on work related to design, sustainability, and technology solutions nationwide. He can be reached at  www.linkedin.com/in/pjaarch

 

Tournesol Siteworks is a national leader in products that connect landscape and architecture. Since 1979 they've manufactured pots, planters, irrigation systems, site furnishings, and most recently living wall and green building components for commercial construction projects. With a wide variety of manufacturing capabilities, they customize standard product platforms to realize any designer's vision for the urban environment. Let them be your link between landscape and architecture. tournesolsiteworks.com