Green Roofs: The move to sustainable roofs in commercial real estate Ben Murray MSRE 517 February 25 th, 2014 University of San Diego MSRE Program
Table of Contents What is a Green Roof? Construction Benefits Risks/Challenges Costs Types of Green Roofs Local Example Future of Green Roofs References
What is a Green Roof? A roof that is partially or completely covered in vegetation How does it work? Evapotranspiration: Combination of evaporation and transpiration
Construction Choice of vegetation depends on the type of roof, weather, sun exposure (very localized) The basic build of a green roof can be divided into vegetation, filtration, and drainage
Benefits Benefits of a Green Roof Mitigates urban heatisland effect Reduces utilities costs More than doubles the service life of the roof Improvement of the aesthetic environment Improves water quality Controls storm water runoff, erosion & pollution Increased property value Creates a wildlife habitiat Improves air quality CSR (Corporate Social Responsibility) Marketability Density bonuses (LEED points) Rainwater harvesting
Benefit Decrease of Urban Heat-Island Effect The heating up of an urban area due to the absorption of heat by the dark surfaces (i.e. roofs, streets, parking lots) Roofs make up about 25% of urban areas
Benefit Density Bonuses: LEED Credits Sustainable Sites SS Credit 5.1 Site Development Protect or Restore Habitat (1 point) SS Credit 5.2 Site Development Maximize Open Space (1 point) SS Credit 6.1 Storm Water Design: Quantity Control (1 point) SS Credit 7.2 Heat Island Effect: Roof (1 point) Water Efficiency WE Credit 1 Water Efficient Landscaping (Potential: 2-4 Points) Energy and Optimization EA Prerequisite 2: Minimum Energy Performance (Required) EA Credit 1 Optimize Energy Performance (Potential: Up to 19 Points) Materials and Resources MR Credit 3 Material Reuse (Potential: 1-2 Points) MR Credit 4 Recycled Content (Potential: 1-2 Points) MR Credit 5.1 Regional Material (Potential: 1-2 points)
Risks/Challenges Challenges of a Green Roof High upfront cost Fire safety issues Long wait time to recuperate initial cost Weight issues (possible need to renovate structural support system) High maintenance cost Possible leakage issues
Challenge - Cost Initial Cost Extensive roofs: $5/SF - $25/SF Intensive roofs: $25/SF - $40/SF Traditional roof: $5/SF - $12/SF Maintenance Costs Estimated to be $0.75/SF/yr - $1.50/SF/yr Possible Tax Credits State & federal legislation are in place to support the installation of green roofs Reduction of Energy Costs Savings are estimated to be $0.20/SF/yr Lifecycle Green Roof: 40 50 years Traditional Roof: 15 20 years
Type 1: Extensive Green Roof Lighter weight 13 lbs/sq ft dry weight 26 lbs/sq ft saturated weight Requires less structural support due to lighter weight Less maintenance required for upkeep Less irrigation Plant selection: sedums, succulents, drought tolerant Can be placed on higher sloped roofs Retains less storm water
Type 2: Intensive Green Roof Higher weight load on structure 34 lbs/sq ft dry weight Up to 100 lbs/sq ft saturated weight Higher initial investment due to more structural support needed Plant selection: no limit, bushes, trees, more water needed to support these plants High maintenance cost Limited to less sloped roofs
Historical Growth: North America
Palomar Medical Center: Green Roof 1.5 Acre green roof Drought tolerant specific plants Incorporation of Solar Tubes (see right) Andy Hoang, Will recover costs of green roof within seven years Purpose of green roof was for patients, environment and value 11-story Medical Center $956M Project 740,000 SF
Palomar Medical Center: Continued
Future: Solar Green Roofs Cooler air surrounding solar panels allows PV cells to work more efficiently (3% - 16%) Shade provided by solar panels allows green roof to work more efficiently as well Higher initial cost More sophisticated drainage system (see next slide) More efficient irrigation system (see next slide)
Solar-Green Roof
Questions?
References Interviews Ryan West ReCon Native Plants http://www.reconnativeplants.com/plants.html Site Visits Palomar Medical Center Escondido, CA Websites http://www.ranacreekdesign.com/projects/palomar-medical-center/ http://news.theregistrysf.com/more-green-roofs-arriving-to-san-francisco-2/ http://www.greenrooftechnology.com/solar_pv_greenroofs http://www.epa.gov/hiri/resources/pdf/greenroofscompendium.pdf http://www.empowermagazine.com/hyper-segregated-cities-at-greater-riskof-urban-heat-island-effect/ http://myplantconnection.com/green-roofs-legislation.php http://www.greenroofs.org/index.php/resources/2012-green-roof-industrysurvey http://ga.water.usgs.gov/edu/watercycleevapotranspiration.html
References Continued Websites Continued http://www.libertyapplianceservice.com/dishwasher-wont-fillwith-water/ http://www.epa.gov/hiri/ http://www.greenrooftechnology.com/leed/leed_greenroofs http://www.palomarhealth.org/contentpage.aspx?nd=32&ne ws=295 http://agrowingpassion.com/big-jump/ http://legistar.cityofmadison.com/attachments/32ef4bb8- b9d7-4b80-adae-cea76ccc712c.pdf http://koivu.luomus.fi/users/tiedotus/viherkattoraportti_2013.pd f http://www.utsandiego.com/news/2010/nov/19/green-roofnew-hospital-more-cover/ http://www.drawingontheland.com/?p=1399 http://www.buildinggreen.com/auth/article.cfm/2012/11/29/g reen-roofs-improve-solar-panel-effciency/