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))