Green Roof Research at Michigan State University Bradley Rowe Michigan State University Department of Horticulture
Design Intent Intensive greening Extensive greening
Cantonel University Hospital, Basel
Rigi Kaltbad Edelweiss
Why Green Roofs?
Benefits Aesthetics Recovery of green space Biodiversity Water and air purification Longevity of roof Noise reduction Stormwater management Quantity and Quality Moderation of urban heat island Building insulation Carbon sequestration
Research at MSU Plant selection Stormwater Thermal properties Carbon sequestration
Stormwater Quality Retention Slope Substrate Depth Vegetation Type Instrumentation Curve Numbers
3 Hydrograph 10 mm rainfall Oct 4, 2002 Vegetation Reduced peak Rainfall or Runoff (mm) 2 1 Rainfall Gravel Media Vegetated Delayed total 0 0 1 2 3 Time After Initial Rainfall (h)
MSU Campus = 14.2 million sq ft of roof surface
If all MSU campus roofs were green 64,821,351 gallons = 8,665,354 cubic feet = 245,375 cubic meters...would have been retained (2003)
Niagara Falls - Canada 1 minute, 48 seconds
Curve Numbers Slope Curve Number (CN) 2% 84 7% 87 15% 89 25% 90 Traditional Roof CN=98
Photo Walbridge Aldinger
PSSB Roof 60 Top of Insulation 50 Temperature (C) 40 30 20 Ambient Air Vegetation Gravel 10 08/01/06 08/02/06 08/03/06 08/04/06 Date
Energy Efficiency Source: National Research Council, Institute for Research in Construction
Plant Evaluations Substrate depth and composition Nutrient requirements Rate of establishment Growth Survival and persistence Competition/Succession Environmental tolerances Plant stress Evapotranspiration Carbon sequestration
Growth and Coverage Survival Growth index Visual rating Biomass Image analysis Point frame Relative abundance Absolute cover
August 2001
August 2001
September 2002
May 2004
Sedum Crassulacean acid metabolism
Propagation 2 months
Competition #2
Quantifying drought tolerance Watering regimen Measurements Growth, survival, evapotranspiration, and chlorophyll fluorescence
Carbon sequestration Sampled Above ground biomass Below ground (roots) Soil carbon content Sample preparation Dried Weighed Ground to a fine powder
Carbon sequestration Total carbon concentration determined Carlo Erba NA1500 Series 2 N/C/S analyzer Carbon accumulation Multiply dry matter weight by total C concentration
Carbon sequestration Preliminary study (2006) 12 roofs in Michigan and Maryland 1 to 6 years in age 1.27 to 10.2 cm depth Sedum based Above-ground only
Results - Preliminary study Average: 162 g C/m 2 Range: 73.2-276.5 g C/m 2 500 y = 71.5 + (2.72 x Age in months) r 2 =0.32 400 Carbon (g.m -2 ) 300 200 100 0 0 10 20 30 40 50 60 Age of Green Roof (months)
Results - Preliminary study Mean above-ground carbon content of select extensive green roofs Location MSU Communication Arts Building East Lansing, MI Mean Substrate Depth (cm) Age (months) Carbon (g m - 2 ) 2.5 15 96.8 MSU HTRC East Lansing, MI Ford Motor Company Rouge Plant Dearborn, MI 2.5 39 143.5 2.5 48 196.3
Results - Preliminary study Mean above-ground carbon content of select extensive green roofs Location Mean Substrate Depth (cm) Age (months) Carbon (g m - 2 ) MSU HTRC East Lansing, MI MSU HTRC East Lansing, MI Renaissance Center South River Colony Edgewater, MD 5.0 39 158.7 6.0 52 224.2 6.4 48 276.5
Carbon sequestration MSU PSSB Depth = 6 cm Species Sedum acre Sedum album Sedum kamtshaticum Sedum spurium Substrate only Time to equilibrium Harvested three times during the growing season
Results - PSSB Mean carbon content at end of first growing season (October 2007) Species g C m -2 Above Ground Roots Soil Total S. acre 258.4 A 11.9 A 265.9 A 536.2 A S. album 291.6 A 15.9 A 381.9 A 689.4 A S. kamtschaticum 214.3 A 143.8 C 343.5 A 701.6 A S. spurium 228.8 A 83.5 B 296.2 A 608.5 A Mean 248.3 63.8 321.9 633.9 Mean separation in columns by LSD (P 0.05). Uppercase letters in columns denote differences among species (n=20).
Results - PSSB Mean carbon content at end of first growing season (October 2007) Biome Type Temperate Species forest g C m -2 Above Ground Roots Soil Total S. acre 258.4 A 11.9 A 265.9 A 536.2 A Cultivated Land Temperate Grassland S. album 291.6 A 15.9 A 381.9 A 689.4 A S. kamtschaticum 214.3 A 143.8 B 343.5 A 701.6 A Desert Scrub Plant biomass (g C/m 2 ) 8,000 1,400 3,000 300 Mean Soil Organic Matter (g C/m 2 ) 11,800 12,700 19,200 5,600 S. spurium 228.8 A 83.5 C 296.2 A 608.5 A Mean 248.3 63.8 321.9 633.9 Mean separation in columns by LSD (P 0.05). Uppercase letters in columns denote differences among species (n=20).
Carbon sequestration Detroit Metropolitan area Land area of rooftops 6,335 hectares - commercial 8,399 hectares - industrial 20% green roofs ~19,000 metric tons of carbon sequestered ~ 0.2% of the carbon emitted by Detroit s major electric utility in 2005
Results - PSSB 1000 800 Above Ground biomass Root Biomass Substrate Grams C per m 2 600 400 200 0 Jun Jul Aug Sep Oct Nov Month (2007)
Influence of design on function Aesthetics Native species/plant diversity Stormwater Energy Irrigation Transpiration rates Soil fertility Maintenance DEPTH
Stuttgart Office of Gardens, Cemeteries, and Forestry
Current status Germany 10-15% growth for past 10 years 12% of all new flat roofed buildings Govt. incentives Europe United States
Barriers to acceptance Lack of awareness Cost Data regarding benefits Technical information Standards FLL, ASTM, FM Global Incentives
Swiss Convention Center, Basel
MSU Green Roof Research (www.hrt.msu.edu/greenroof) GreenRoofs.com (www.greenroofs.com) Green Roofs for Healthy Cities (www.greenroofs.org)