Green Roofs - Living Architecture Monitor - Winter 2010 - (Page 34)

GRHC UPDATE NEW CORPORATE GREEN ROOF ENERGY CALCULATOR AN UPDATE ON THE DEVELOPMENT OF A NEW TOOL FOR MEMBERS PLEASE JOIN US IN WELCOMING THE FOLLOWING TO THE GRHC COMMUNITY AS CORPORATE MEMBERS By Jordan Richie GREEN ROOF DESIGNERS TO COMPARE AND ASSESS THE ENERGY-USE IMPLICATIONS OF VARIOUS DECISIONS By David J. Sailor MOLLY MEYER LLC Molly Meyer LLC is a vegetated green roofing consulting company, advising architects, contractors and property owners on best practices for design, installation, and maintenance. Located in Chicago, we advise on projects nationwide. Our mission is to provide longlasting green roofs at reasonable budgets. ECOTEKT Ecotekt is a full-service architecture, interior design and consulting firm specializing in innovative design and client service, founded on principles of sustainability, integrity and design excellence. Our solutions to architecture, planning, and community design embody enduring standards of quality that examine the economic, ecological, and social consequences of design. ATLANTIS WATER MANAGEMENT Atlantis Water Management is the manufacturer of 95 percent-void structure products made of recycled polypropylene (D-Raintank, Flo-Cell panels) that are wrapped in specified liners for use in channelling, detaining, filtering and harvesting stormwater. The product’s high loadbearing capacity (H20) makes it a strong and flexible LEED® certified solution for surface or subsurface designs. CONSTRUCTION CONTROL INC. Established in 1972, Construction Control Inc. is a multidisciplinary firm of engineers, building scientists, LEED® Accredited Professionals, and certified Green Roof Professionals (GRPs) providing consulting engineering services across Canada and around the world. Our services include structural assessments, LEED® consultation, green roof design, project management, building science services, capital budget plans and due diligence support backed by our 38 years of experience. I n November of 2008, a group of researchers at Portland State University, University of Toronto and Green Roofs for Healthy Cities (GRHC) initiated a two-year project funded by the United States Green Building Council (USGBC) to create a green roof energy calculator. The purpose of the calculator is to provide an easy-to-use design tool for assessing the building energy-use implications of various green roof design decisions. A green roof designer could use this tool to compare the performance of roofs with different thicknesses of soil or with differing types of vegetation. Prior to the USGBC project, the researchers had created a sophisticated green roof energy model that is imbedded in the U.S. Department of Energy’s EnergyPlus building energy simulation software (see The plan for the calculator is to populate an extensive database of thousands of simulations and then create a graphical user interface that will allow the user to explore simple design options for a green roof by interpolating within the database. User options include a pull-down menu of more than 100 cities in which to locate the building. The user may also choose between residential and commercial building types. He or she may then specify growing media depth, and leaf area index (LAI) – a measure of vegetation coverage. Fixed prices for electricity and natural gas can also be specified or, alternatively, the user can simply allow the calculator to use the utility rate schedules that are available to EnergyPlus for the modeled city. With that information, the calculator then searches the database for the selected building type and city. Within the available data, the calculator will further interpolate to assess the energy performance for the soil depth and vegetation coverage specified by the user. The calculator then provides output regarding annual energy use and cost savings of the selected green roof design in comparison to the performance of two different types of conventional roofs – a typical membrane roof, and a highly reflective “cool roof” membrane. The calculator has limitations; it is not capable of exploring differences in types of soils or plants, nor does it take into account the specific geometry, construction, equipment or operations schedules of the building. Thus, the results in the output phase of the calculator must be considered as approximate. A key benefit of the calculator is that it requires no specific modeling expertise and has the capacity to provide a very quick assessment of the impacts of some fundamental design decisions. If the user desires more specific estimates of energy performance for a building, he or she may need to hire an energy modeler with expertise in using EnergyPlus. In the first year of this project, we have made incremental improvements to the underlying EnergyPlus simulation code so that the green roof module can be used with a wider range of EnergyPlus solution algorithms. We have also created a beta-version of the calculator interface and conducted a full suite of simulations for more than 40 cities. These simulations have been used to provide an initial set of data for the calculator database. These early simulations identify tradeoffs between heating and cooling impacts of green roofs. For example, a lush vegetation canopy provides shading that can reduce summertime air conditioning, but if the vegetation remains lush in the winter, the undesired wintertime shading of the roof can increase heating energy consumption. There are similar tradeoffs associated with the thermal storage and thermal insulating characteristics of thick (> 6 inches) soil layers. We are now finalizing the energy model simulations and anticipate making a final version available during the summer 2010. This calculator will reside on a website at Portland State University’s Green Building Research Center ( with web pages at University of Toronto and GRHC providing links to this site. D David J. Sailor is a professor in the Mechanical and Materials Engineering Department at Portland State University in Portland, Oregon. LIVING ARCHITECTURE MONITOR WINTER 2010

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Winter 2010

Green Roofs - Living Architecture Monitor - Winter 2010
Laying Roots for Green Jobs
Outstanding Student Design
Passing of a Legend
New Federal Stormwater Guidelines From EPA
Partnering Science with Service
On the Roof with...Eden Brukman, Reg. Arch., LEED(R) AP
The Leaf Effect
Who Owns the Green Roof?
Planting the Federal Inventory
Curb Appeal
Maintenance Matters
Professional Development Update
Professional Calendar
Congratulations New GRPS
Welcome New Corporate Members
Green Roof Energy Calculator
Doing No Harm

Green Roofs - Living Architecture Monitor - Winter 2010