Design Criteria for Suspended Paver Systems
Some key design factors to consider when utilizing suspended paver systems are (1) maximize on the external tree trunk opening within the constraints of project budget, the local code and ADA compliance and (2) specify the tree opening appropriate to the tree being specified.

Suspended paver systems and tree grates are fabricated of recycled steel, which does meet LEED Materials and Resource Credit 4 and both must meet transportation engineering standards. Through these newer reduced opening tree grates and suspended paver systems, arboriculture and reforestation can be enhanced in the urban environment and this will assist in reducing the heat island effect and energy consumption.

Using Modular Decking to Green the Street

In addition to expanded tree grates and suspended paver systems, modular wood decking can be used to create seasonal green parks. Seasonal green parks can be set up or “popped up” along narrow streetscapes and then broken down if and when necessary. These seasonal parks are being used in Chicago, San Francisco, and other urban municipalities to “green the street” between spring and summer. The parks are then removed for winter storage. Private restaurants use the modular decking and planter systems of the seasonal green parks to create outdoor dining areas that are shaded and screened by small trees set in the modular planters. In Wheatridge, Colorado, a seasonal park system is being used to provide traffic calming. Although the planters provided as part of the seasonal green park system will only support shrubs and very small trees, this does provide added green space in tight urban areas.

The seasonal green “pop-up” park in San Francisco provides a means for greening an urban environment. Photo by: Matthew Roth; courtesy of Bison Innovative Products

 

These modular decking systems have been widely used in the United States for over a decade. There has been extensive testing done on these products and a few are now 100 percent made in the USA. The deck support system is gravity based and must have perimeter containment such as a curb or parapet walls, on all sides, and therefore does not require mechanical attachment to the pavement or the roof membrane for anchoring. Compared to traditional joist and plank installations the pedestal deck systems yield significant labor savings to the installer.

At ground level, these seasonal green parks systems add aesthetics to the street as well as adding a flexible type of urban green space that can be used either temporarily or long term.

Improving Urban Air Quality and Energy Efficiency

How do you expand urban green space and enhance the urban environment in tight areas? How do you obtain those LEED® and SITES™ credits and meet new development code requirements for stormwater management when there is no room for green infrastructure at street level? Dean Hill, ASLA, director of sustainability at greenscreen®, would suggest that you look up and consider green walls and green roofs. He considers vertical space as another layer in planting design. The incorporation of vertical vegetation through the use of green walls and green façade walls in particular can contribute to building energy efficiency, water efficient landscapes and the reduction of Urban Heat Island (UHI) effects. It can also provide landscape architects with an additional design dynamic to increase habitat connectivity, seasonality, native plant incorporation and the enhancement of overall planting designs.

Using Green Façade Systems and Green Walls

Vertical frame systems (green façades) help to expand the planting of vegetation in tight urban areas where there is no room for street trees. Green façade technology provides a direct interface between architecture and landscape architecture—between site and building—between grey infrastructure and green infrastructure. Rigid, green façade systems can stand independently away from a building or can be set back from the building façade through mounting clips. In both situations, the structural integrity of the building is maintained and waterproofing membranes are not penetrated or compromised.

A number of studies have been done with respect to green walls including a study completed by Thomas A. M. Pugh, A. Robert MacKenzie, J Duncan Whyatt and C. Nicholas Hewitt of Lancaster Environmental Centre, Lancaster University, Lancaster, UK on The Effectiveness of Green Infrastructure for Improvement of Air Quality in Urban Street Canyons. In a 2012 interview with BBC News, Professor A. Robert MacKenzie says “The benefit of green walls is that they clean up the air coming into and staying in the street canyon. Planting more (green walls) in a strategic way could be a relatively easy way to take control of our local pollution problems.” In addition, researchers in the UK found that trees were also effective in controlling air pollution, but “only if care is taken to avoid trapping pollutants beneath their crowns.

Green façade systems or green walls are being used throughout Europe and the United States in a variety of climates and settings to increase urban green space, mitigate stormwater runoff and assist in reducing energy consumption. In addition to having a direct interface with building façades, green walls are also being used on green roofs.

The Department of Public Works in Lexington, Massachusetts used wall mounted trellis panels to create a green wall that is part of a green infrastructure rain garden at a new regional office facility. This project received a Silver LEED® citation. In Oakland, California, large sections of trellis panels were placed on a multistory parking facility at the Kaiser Permanente Parking Lot. The trellis panels provide a support structure for vines that are part of a stormwater filtering rain garden. In the southwest, trellis panels were installed at the waiting stations throughout the Valley Metro Light Rail transit system in Phoenix, Arizona. The planted vines provide shade and reduce the heat from adjacent hardscape surfaces. In addition to use as independent green walls, green façade systems have been used in conjunction with on-site stormwater management plans such as the HOK design for the National Wildlife Federation Building in Washington, D.C.

When designing with green façades and trellis panels, consideration must be given to selecting appropriate plant materials (vines and herbaceous plants only) that are native to the area and providing regular maintenance for plant material and soil mediums. Landscape architects and architects are encouraged to reference regional plant lists and to consult with local nurseries regarding availability of recommended vines, hardiness of vines in windy urban areas, and solar requirements for the plant.