Design Options for Living Walls

Like most sustainable building components, there are different ways to include living walls and green infrastructure in buildings. While all may have different design, installation, and maintenance considerations, each of the following design options can help designers achieve both aesthetic and sustainability goals, including improved energy performance in buildings:

• Living Green Walls: Living wall trellis systems can be used to create soft-textured vine-covered seasonally changing surfaces, commonly referred to as “green facades.” Manufacturers of trellis systems used for this purpose generally offer engineered mounting accessories designed to hold trellis panels off the building surface. This protects the building’s cladding from direct plant attachment and transfers the weight of the plants to the screen structure and the wall attachments. Panels can be stacked side to side or top to bottom to cover larger areas.
• Fencing: Sometimes, instead of a wall, a separate, stand-alone vertical surface is desired for enclosure or fencing. In this case, lightweight but strong trellis panels can be placed between appropriate supports to “capture” plant material and provide the benefits of a living fence enjoyed from both sides. This approach can be simple, or complex based on the nature of the design, but modular components help facilitate easier installations.
• Infill/Overhead: Vegetated trellis panels can be placed overhead on traditionally built flat or curved frameworks to create a more immersive experience. This approach can create shade for an outdoor space, provide more privacy, and mitigate views based on the leaf canopy of the plant selected. The trellis panels can be used as infill and be custom tapered, notched, mitered, or curved for unique configurations using standard attachments.
• Columns: In some cases, free-standing columns that may support an overhead structure are the desired surface onto which to add vegetation. Standard column trellis panels are typically a 15 ½”-diameter column up to 14 feet high as a basic building element. Custom diameters and heights are possible by checking directly with manufacturers. Mounting clips or brackets may also be provided for attaching to the structure.
• Planters: For projects that require freestanding containers, trellis panels can be mounted to rectangular planters in multiple configurations. Some column trellis products also coordinate with cylindrical planters or can be adapted to posts or columns of various diameters. Planters can be incorporated onto rooftops, used as patio dividers, or help to define outdoor spaces.
• Custom: Living trellis panels are commonly based on a modular 2”x2” design which allows them to be easily customized to meet a wide variety of project requirements. At least one manufacturer uses such three-dimensional panels fabricated from a welded wire grid separated by a bent wire truss welded every 2 inches, resulting in rigid, yet lightweight and customizable panels. They can be cut at angles, mitered, notched, spliced, or curved. The panels can span openings or attach to support frames. In combination with standard or custom edge trim and engineered mounting hardware, unique applications are limited only by the imagination of the designer.

With this variety of design options, it is readily possible to incorporate living components into many outdoor spaces.

Photos courtesy of Greenscreen

Green features based on modular, trellis-type systems can be used in a variety of ways to create and define outdoor spaces.

DESIGNING WITH DIFFERENT TYPES OF POROUS PAVING

All porous paving systems are designed to transfer the weight of pedestrians or vehicles while maintaining the integrity of the surface, although some can carry more weight than others. Porous paving systems also have varying degrees of void space which means that the water will pass through at different rates. As noted earlier, there are four fundamental types of types of porous paving systems – 1.) Porous concrete or asphalt, 2.) concrete paving blocks, 3.) rigid plastic porous pavers, and 4.) flexible plastic porous pavers.

All systems have similar components after the site is excavated down to the existing subgrade soil as follows:

• Base Course: The specified base course of a permeable paving system is one of the most essential elements of the system itself. The recommended depths and composition must be sufficient to accommodate not just the load of the traffic, but the potential flood of stormwater without maintenance or future retrofitting. The deeper the base course, the stronger and greater space for water storage. The base course should be composed of at least 70% gravel/stone material, and the rest should be sand, for ultimate support and porosity. Base course depth recommendation will vary by use, some requiring a very shallow 2” for pedestrian and light stormwater capture – to depths of 12” for heavy stormwater drainage, and to satisfy Fire Departments for Heavy Fire Trucks.
• Void Space: Void space is what determines the flow rate – it equals the percentage of water or air that can pass through a product. The amount of void space is an important consideration when choosing a system because higher void space will create a faster flow rate. For example, porous asphalt may only have a 16 percent void space while flexible porous pavers can have up to 96 percent.
• Porous Paving: If porous concrete or asphalt is used as the final paving, then it is placed appropriately over the base course. If concrete paving blocks are used, they are placed and spaced as called for in the design. If porous plastic pavers are used, they are installed with structural fill in the form of gravel aggregate or soil and grass to create the final surface.

Photos courtesy of Invisible Structures

Plastic or concrete porous paver systems are laid over a base course with appropriate void space and then filled with a choice of gravel, grass, or other porous material.

All porous pavers are an environmentally better design choice than traditional concrete or asphalt. However, prioritizing the most important elements of a project can determine which type of paver is the best option. What makes porous paving products different from one another? The structures themselves vary in material, size, shape, and compressive strength. Manufacturers also provide slightly varying specifications of the porous base course and the structural fill as well. Porous asphalt is a good choice to help drain a medium-duty roadway or parking area to reduce standing water and flooding during rain events. Concrete paving blocks may be chosen for a certain design appeal. Flexible porous grass paving can maximize drainage, reduce heat islands, and can be installed easily on curved areas. Flexible porous gravel paving offers the benefits of a gravel surface with products that can include customized colors to blend with the gravel aggregate, helping it stay unseen from the surface.

Where Porous Pavers Are Being Used

Porous paving systems can be used in virtually any situation where other types of impermeable paving are used. Their use has become so well accepted that municipalities are regulating the use of impervious versus pervious surfaces in building construction and renovation to mitigate the effects of stormwater, particularly in commercial, industrial, and institutional applications. They are also very well suited for residential applications, both for single-family and multifamily developments and projects.

Commercial applications include common outdoor areas such as parking lots and access roads where drainage is always a concern. They are particularly well suited for overflow parking or fire lanes though since they can be disguised as a people and environmentally friendly grassy or lawn area and only used when needed for vehicular access. Homeowners and business managers alike have found creating useable parking that adds to the aesthetics, to be a more inviting and natural environment. Stadium operators find this multi-use surface particularly appealing for tailgate fans, turning grass parking areas into festival grounds.

Public monument and park facilities in particular are places that are well suited for accessible, porous paving for pedestrian access and for needed vehicular or specialty access such as helicopter and airplane landing pads. This includes places like botanical gardens, public parks, school campuses, stadiums, outdoor complexes, zoos, and museums. By meeting ADA requirements and other federal specifications, they have been installed in significant installations such as the Pentagon Memorial, Reliant Stadium, the National Botanic Gardens, and the Oakdale National Preserve.