Bradley RoweMichigan State UniversityDepartment of Horticulture
Green Roof Research atMichigan State University
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 selectionStormwaterThermal propertiesCarbon sequestration
Stormwater
QualityRetention
SlopeSubstrate DepthVegetation Type
InstrumentationCurve Numbers
Time After Initial Rainfall (h)
0 1 2 3
Rai
nfal
l or R
unof
f (m
m)
0
1
2
3
RainfallGravelMediaVegetated
Hydrograph10 mm rainfallOct 4, 2002
VegetationReduced peakDelayed total
MSU Campus = 14.2 million sq ft of roof surface
64,821,351 gallons =
8,665,354 cubic feet =
245,375 cubic meters
If all MSU campus roofs were green…
...would have been retained (2003)
Niagara Falls - Canada
1 minute, 48 seconds
Curve NumbersSlope Curve Number (CN)2% 847% 8715% 8925% 90
Traditional Roof CN=98
Pho
to ©
Wal
brid
ge A
ldin
ger
PSSB Roof
Top of Insulation
Date08/01/06 08/02/06 08/03/06 08/04/06
Tem
pera
ture
(C)
10
20
30
40
50
60
Ambient AirVegetationGravel
Energy Efficiency
Source: National Research Council , Institute for Research in Construction
Plant EvaluationsSubstrate depth and compositionNutrient requirementsRate of establishmentGrowthSurvival and persistenceCompetition/SuccessionEnvironmental tolerancesPlant stressEvapotranspirationCarbon sequestration
Growth and Coverage
SurvivalGrowth indexVisual ratingBiomassImage analysisPoint frame
Relative abundanceAbsolute cover
August 2001
August 2001
September 2002
May 2004
SedumCrassulacean acid metabolism
Propagation 2 months
Competition #2
Quantifying drought tolerance
Watering regimen Measurements
Growth, survival, evapotranspiration, and chlorophyll fluorescence
Carbon sequestrationSampled
Above ground biomassBelow ground (roots)Soil carbon content
Sample preparationDriedWeighedGround to a fine powder
Carbon sequestration
Total carbon concentration determined Carlo Erba NA1500 Series 2 N/C/S analyzer
Carbon accumulationMultiply dry matter weight by total C concentration
Carbon sequestration
Preliminary study (2006)12 roofs in Michigan and Maryland 1 to 6 years in age1.27 to 10.2 cm depthSedum basedAbove-ground only
Results - Preliminary study Average: 162 g C/m2
Range: 73.2 - 276.5 g C/m2
y = 71.5 + (2.72 x Age in months)r2=0.32
Age of Green Roof (months)
0 10 20 30 40 50 60
Car
bon
(g.m-2
)
0
100
200
300
400
500
Results - Preliminary study
Location
Mean Substrate
Depth (cm)Age
(months)Carbon (g•m-
2)MSU Communication Arts BuildingEast Lansing, MI
2.5 15 96.8
MSU HTRCEast Lansing, MI 2.5 39 143.5
Ford Motor Company Rouge PlantDearborn, MI
2.5 48 196.3
Mean above-ground carbon content of select extensive green roofs
Results - Preliminary study
Location
Mean Substrate
Depth (cm)Age
(months)Carbon (g•m-
2)
MSU HTRCEast Lansing, MI 5.0 39 158.7
MSU HTRCEast Lansing, MI 6.0 52 224.2
Renaissance Center South River ColonyEdgewater, MD
6.4 48 276.5
Mean above-ground carbon content of select extensive green roofs
Carbon sequestration
MSU PSSBDepth = 6 cmSpecies• Sedum acre • Sedum album • Sedum kamtshaticum• Sedum spurium• Substrate only
Time to equilibrium• Harvested three times during the growing season
Results - PSSBMean carbon content at end of first growing season (October 2007)
g C•m-2
SpeciesAbove 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 - PSSBMean carbon content at end of first growing season (October 2007)
g C•m-2
SpeciesAbove 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 B 343.5 A 701.6 A
S. spurium 228.8 A 83.5 C 296.2 A 608.5 A
Mean 248.3 63.8 321.9 633.9
5,600300Desert Scrub
19,2003,000Temperate Grassland
12,7001,400Cultivated Land11,8008,000Temperate forest
Mean Soil Organic Matter (g C/m2)
Plant biomass (g C/m2)Biome Type
Mean separation in columns by LSD (P≤0.05). Uppercase letters in columns denote differences among species (n=20).
Carbon sequestration
Detroit Metropolitan areaLand area of rooftops
6,335 hectares - commercial8,399 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
Month (2007)
Jun Jul Aug Sep Oct Nov
Gra
ms
C p
er m
2
0
200
400
600
800
1000
Above Ground biomassRoot BiomassSubstrate
Influence of design on functionAestheticsNative species/Plant diversityStormwaterEnergyIrrigationTranspiration ratesSoil fertilityMaintenanceDEPTH
Stuttgart Office of Gardens, Cemeteries, and Forestry
Current statusGermany
10-15% growth for past 10 years12% of all new flat roofed buildingsGovt. incentives
EuropeUnited States
Barriers to acceptanceLack of awareness
Cost
Data regarding benefits
Technical informationStandardsFLL, ASTM, FM Global
Incentives
Swiss Convention Center, Basel
MSU Green Roof ResearchMSU Green Roof Research((www.hrt.msu.edu/greenroofwww.hrt.msu.edu/greenroof))
GreenRoofs.comGreenRoofs.com((www.greenroofs.comwww.greenroofs.com))
Green Roofs for Healthy CitiesGreen Roofs for Healthy Cities((www.greenroofs.orgwww.greenroofs.org))
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