Green Roofs Take Root In Pavers

While Joseph Hagerman’s research fellowship with New York-based Rafael Violy Architects aims to advance green roof technology, his work may serve as well


While Joseph Hagerman’s research fellowship with New York-based Rafael Vi“oly Architects aims to advance green roof technology, his work may serve as well to expand concrete applications by cultivating green roofs as part of the larger urban infrastructure. Given his emphasis on integration of building components Û roof insulation, overburden, and drainage layers Û within a modular system to optimize energy and water management, concrete stands to contribute significantly to Hagerman’s design. Using concrete as a modular green roof component offers real advantages by reducing the number of plastic parts needed to build a green roof, he observes, while increasing the roof membrane’s long-term durability and ease of inspection.

Recently awarded a master of science degree in Civil Engineering from Columbia University, Hagerman studied under Professor Christian Meyer, chairman of ACI Committee 555, researching the use of municipal incinerator ash in concrete. In 2005, he designed Biopavers, a system of interlocking concrete pavers with phytoremediating plant cores, i.e, plants that absorb pollutants, delivered by means of compost within biodegradable, nontoxic bio-plastic formwork (fabricated from waste agricultural starches or wood fibers) in each unit. A ÎgreenÌ solution to stormwater management, Biopavers satisfy the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) rating requirements. The design is compatible with any commercially available open-cell paver, Hagerman affirms, so distributors or installers can conveniently add Biopaver’s patent-pending biodegradable core before or after paver installation.

Expanding the Biopaver model to reconfigure green roofs as urban infrastructure essential to environmental stewardship, Hagerman’s fellowship with the Rafael Vi“oly Architects (RVA) Research and Training Program involves formulation of an innovative green roof design Û with the help of Pittsburgh Corning Corp. Û and its implementation atop RVA’s New York office building. To my knowledge, he asserts, this project entails the first use of concrete pavers as the basis for a modular green roof product, opening doors to life-long, ÎgreenÌ building solutions.

RVA’s construction of the second-largest green roof in the U.S. Û for the Howard Hughes Medical Institute’s Janelia Farm Research Campus in Ashburn, Va. Û was instructive in highlighting the need for a more flexible and advanced green roof system to satisfy diverse design and environmental requirements. Accordingly, Hagerman’s work leverages RVA’s experience to develop a single modular system suited to multiple demands:

  • Accommodation of both shallow extensive roofs (growth medium < 6 in.) and deep intensive roofs (growth medium > 6 in.)
  • Accessibility for roof inspection and repair without damage or loss to plants, soils and support layers
  • Reconfiguration of plants after initial placement
  • Installation of mature plants late in the construction process to reduce construction management difficulties
  • Incorporation of key elements of the building’s water management system via multiple drainage planes, in contrast to conventional green roof structures laid directly atop completed roofs
  • Thermal performance sufficient to reduce the need for insulating materials or the size of HVAC mechanical systems

Thus, according to Hagerman, an ideal modular green roof comprising integrated building layers for long-term performance, plus easier construction and inspection, would include: Pittsburgh Corning Foamglas insulation, protective membranes, and growth-medium containers set in 12- _ 18-in. concrete roof pavers. Thermal bridging and heat transfer within the assembly would be minimized by Foamglas insulation as well as concrete’s thermal mass.

Regarding the ultimate goal of his fellowship, Hagerman says, If I can help define civic architecture’s responsibility to the environment as being an active component, then this opportunity will be successful. A call to action for paver producers, he adds, This is a great opportunity for the concrete industry to be at the forefront of the green building movement Û promoting green roofs as essential environmental infrastructure.
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  1. A roof membrane system is applied to the structural deck.
  2. Foamglas modules placed on top of the roof membrane are assembled to create an uninterrupted layer of insulation.
  3. After inspecting the assembly to minimize air spaces, a geo-textile mat is rolled out across the roof, overlapping as needed for proper coverage.
  4. Planting trays and vegetation are installed in concrete pavers. The planting tray system provides options of a green roof that remains in manageable sections or grows into a monolithic assembly.