Field Test Results of Green Roofs, Cool Roofs, and

Field Test Results of Green

Roofs, Cool Roofs, and

Conventional RoofsCNY Engineering Expo

Oncenter, Syracuse, NY

November 9, 2015

Hugh I. Henderson, Jr. P.E

CDH Energy Corp.

Cazenovia, NY

Project Goals

• Side-by-Side Comparison of Different Roofing

Systems

– EPDM w/ 4 inches of foam (UNIT 1)

– TPO w/ 4 inches of foam (UNIT 2)

– Vegetative Roof with 4 inches (UNIT 3)

– TPO w/ 8 inches of foam (UNIT 4)

• Measure Performance Impacts

– Compare thermal losses / energy impacts

– Compare water retention performance

• Jamesville provided 4 similar roof applications

Four Different Roofs at the Same

Facility

Unit 1

EPDM, 4 in

Unit 2

TPO, 4 in

Unit 3

Veg, 4 in

Unit 4

TPO, 8 in

Approach

• Install dataloggers to continuously monitor performance

– Two independent measurement locations on each roof

– Collect data continuously at 15-minute intervals

– Directly measure temperature differences through roof assembly

– Measure weather conditions

– Direct measurement of HVAC energy use was not practical at this site

Roof Assemblies

Location Insulation Surface

Unit 1 4 inches Poly Iso1 foam board

(R22)

EPDM rubber2

Unit 2 4 inches Poly Iso1 foam board

(R22)

TPO White3

Unit 3 4 inches Poly Iso1 foam board

(R22 + vegetative laver)

EPDM w/ Vegetative

Surface

Unit 4 8 inches Poly Iso1 foam board

(R45)

TPO White3

Notes: 1- Polyisocyanurate foam board applied in 2 inch layers

2- Black EPDM (Ethylene Propylene Diene Monomer) single-ply rubber roof membrane

3- White TPO (Thermoplastic Polyolefin) roof membrane

Vegetative Roof

• Carlisle Roof

Garden System

• Light-weight

assembly

Instrumentation

Point Description Instrument Eng

Units

Locations

TRO Roof Temperature

(on top of insulation, under roof brd)

Type-T

Thermocouple

ºF At each station

TRI Roof Temperature

(under roof insulation, above deck)

Type-T

Thermocouple

ºF At each station

TAI Indoor Temperature

(just below the roof)

Type-T

Thermocouple

ºF At each station

Point Description Instrument Eng

Units

Locations

TAO Outdoor Temperature Type-T

Thermocouple

ºF Station 2A

ISH Solar Insulation

(horizontal)

Licor LI200x W/m2 Station 2A

TGR Green Roof Temperature

(in middle of soil layer)

Type-T

Thermocouple

ºF Station 3A

MGR Green Roof Moisture Content

(in middle of soil layer)

Campbell

Scientific CS616

0-1 Station 3A

RAIN Rainfall Texas

Electronics 525

Inches Station 2A

WF Water Flow from Green Roof

Mockup

Hydrolynx 5050 Gal/h Station 2A

Roof Sensor Location/Station

Thermocouple TRO Thermocouple TRI

Thermocouple TAI

Sensors Installed During

Construction

Insulation

Board

Thermocouple

Probe

Thermocouple on Top of Insulation

(station 1B)

Indoor Thermocouple

A & B Stations on Each Unit

1A

1B

Results for Sunny November Day

EPDM TPO

Unit 1: 4 in, EPDM

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

20

40

60

80

100

Tem

pera

ture

(F

)

Unit 2: 4 in, TPO

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

30

40

50

60

70

80

Tem

pera

ture

(F

)

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

0

200

400

Inso

lation (

W/m

^2)

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

-2

0

2

Heat

Loss

(B

tu/f

t^2-h

)

Unit 3: 4 in, Veg

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

30

40

50

60

70

80

Tem

pera

ture

(F

)Unit 4: 8 in, TPO

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

30

40

50

60

70

80

Tem

pera

ture

(F

)

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

0

200

400

Inso

lation (

W/m

^2)

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

-2

0

2

Heat

Loss

(B

tu/f

t^2-h

)

Ambient Temperature, Top of Insulation, Bottom of Insulation, Indoor Temperature

Heat Transfer Analysis

TAO

TRO

TRI

TAI

Rinsulation q Insulation

Board

Concrete Deck

Veg roof (optional)

Deck Board membrane

Where:

Rinsulation - R-value for Insulation layer

(ºF-h-ft2/Btu)

q - Heat flux through the roof

assembly (Btu/h-ft2)

q = (TRI-TRO) Rinsulatiion

Insulation Layer

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

8 9 10

Nov

2009

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

He

at

Lo

ss R

ate

(B

tu/f

t^2

-h)

Unit 1: 4 in, EPDM

Unit 2: 4 in, TPO

Unit 3: 4 in, Veg

Unit 4: 8 in, TPO

Impact on Heat Transfer(solid line = station A / dotted line = station B)

q = (TRI – TRO)/Rins

Summer Sunny, 71F pkMay 29

Summer, Sunny, 71F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

28 29 30

40

60

80

100

120

140

160

Tem

pera

ture

(F

)

Summer, Sunny, 71F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

28 29 30

-4

-3

-2

-1

0

1

2

Heat

Loss

(B

tu/f

t^2-h

)

Summer, Sunny, 59F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

15 16 17

20

40

60

80

100

120

140

160

Tem

pera

ture

(F

)

Summer, Sunny, 59F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

15 16 17

-6

-4

-2

0

2

4

Heat

Loss

(B

tu/f

t^2-h

)Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Summer Sunny, 59F pkMay 16

Summer, Sunny, 71F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

28 29 30

40

60

80

100

120

140

160

Tem

pera

ture

(F

)

Summer, Sunny, 71F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

28 29 30

-4

-3

-2

-1

0

1

2

Heat

Loss

(B

tu/f

t^2-h

)

Summer, Sunny, 59F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

15 16 17

20

40

60

80

100

120

140

160

Tem

pera

ture

(F

)

Summer, Sunny, 59F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

15 16 17

-6

-4

-2

0

2

4

Heat

Loss

(B

tu/f

t^2-h

)

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Summer Cloudy, 44F pkMay 12

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Summer, Cloudy, 44F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

11 12 13

20

30

40

50

60

70

80

90

Tem

pera

ture

(F

)

Summer, Cloudy, 44F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

11 12 13

-2

0

2

4

Heat

Loss

(B

tu/f

t^2-h

)

Fall, Sunny, 38F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

1 2 3

0

20

40

60

80

100

Tem

pera

ture

(F

)

Fall, Sunny, 38F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

1 2 3

-2

-1

0

1

2

3

Heat

Loss

(B

tu/f

t^2-h

)

Fall Sunny, 38F pkNov 2

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Summer, Cloudy, 44F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

11 12 13

20

30

40

50

60

70

80

90

Tem

pera

ture

(F

)

Summer, Cloudy, 44F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

11 12 13

-2

0

2

4

Heat

Loss

(B

tu/f

t^2-h

)

Fall, Sunny, 38F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

1 2 3

0

20

40

60

80

100

Tem

pera

ture

(F

)

Fall, Sunny, 38F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

1 2 3

-2

-1

0

1

2

3

Heat

Loss

(B

tu/f

t^2-h

)

Winter Sunny, 3F pkJan 24

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Winter, Sunny, 3F, Min temp of -13F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

23 24 25

-10

0

10

20

30

40

Tem

pera

ture

(F

)

Winter, Sunny, 3F, Min temp of -13F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

23 24 25

1.0

1.5

2.0

2.5

3.0

3.5

Heat

Loss

(B

tu/f

t^2-h

)

Winter, Cloudy, 25F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

18 19 20

-10

0

10

20

30

40

Tem

pera

ture

(F

)

Winter, Cloudy, 25F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

18 19 20

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Heat

Loss

(B

tu/f

t^2-h

)

Winter Cloudy, 25F pkJan 19

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Winter, Sunny, 3F, Min temp of -13F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

23 24 25

25

30

35

40

45

Tem

pera

ture

(F

)

Winter, Sunny, 3F, Min temp of -13F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

23 24 25

1.0

1.5

2.0

2.5

3.0

3.5

Heat

Loss

(B

tu/f

t^2-h

)

Winter, Cloudy, 25F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

18 19 20

25

30

35

40

45

Tem

pera

ture

(F

)

Winter, Cloudy, 25F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

18 19 20

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Heat

Loss

(B

tu/f

t^2-h

)

Spring Rainy, 41F pkApr 17

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

Spring, Morning, 41F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

16 17 18

35

40

45

50

55

60

Tem

pera

ture

(F

)

Spring, Morning, 41F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

16 17 18

0.0

0.5

1.0

1.5

2.0

Heat

Loss

(B

tu/f

t^2-h

)

Spring, Sunny, 49F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

13 14 15

0

20

40

60

80

100

120

140

160

Tem

pera

ture

(F

)

Spring, Sunny, 49F

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

13 14 15

-4

-2

0

2

4

Heat

Loss

(B

tu/f

t^2-h

)

Rain

Impact of

Snow &

Rain

30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nov Dec

0

20

40

60

Te

mp

era

ture

(F

)

30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Nov Dec

0.0

0.5

1.0

1.5

2.0

2.5

3.0H

ea

t L

oss (

Btu

/ft^

2-h

)

Unit 1: 4 in, EPDM, Unit 2: 4 in, TPO, Unit 3: 4 in, Veg, Unit 4: 8 in, TPO

30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

December

0.00

0.05

0.10

0.15

0.20

0.25

Wa

ter

(in

ch

es) Rainfall

Drainage

RainSnow

(no drainage)

Ambient

Daily Heat Loss

0 20 40 60 80 100

Outdoor Temperature (F)

-40

-20

0

20

40

60

He

at

Lo

ss (

Btu

/ft^

2-d

ay)

Unit 1: 4 in, EPDM

Unit 2: 4 in, TPO

Unit 3: 4 in, Veg

Unit 4: 8 in, TPO

Impact of

Snow Cover

Heat Loss

Heat Gain

Monthly

Heat Loss

Month

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

November-09 675.2 930.2 815.8 603.1

December-09 1,063.2 1,253.3 1,078.4 823.1

January-10 1,089.5 1,231.3 1,090.0 824.1

February-10 939.6 1,043.6 999.0 728.1

March-10 629.8 900.5 883.9 623.6

April-10 138.8 496.9 550.2 379.4

May-10 (178.1) 248.0 339.3 216.3

June-10 (261.0) 75.4 178.5 117.5

July-10 (437.9) (22.2) 135.8 59.6

August-10 (302.7) 34.4 174.5 83.6

September-10 (8.8) 306.7 313.3 221.0

October-10 394.8 641.0 621.6 445.9

November-10 724.2 946.5 874.8 636.2

December-10 968.7 1,101.0 1,013.5 729.2

January-11 970.8 1,178.0 1,035.6 734.1

February-11 879.4 1,074.0 942.2 679.1

2010 Htg Season 4,885.5 6,360.8 6,032.8 4,366.6

(Oct to April) 1,475.3 1,147.4 (518.8)

30% 23% -11%

2010 Clg Season (1,188.5) 642.2 1,141.3 698.0

(May to Sep) 1,830.7 2,329.9 1,886.5

Heat Loss (Btu/ft^2)

Monthly Heat Loss

(600)

(400)

(200)

-

200

400

600

800

1,000

1,200

1,400Ja

n-1

0

Feb

-10

Mar-10

Apr-

10

May-

10

Jun-1

0

Jul-10

Aug-1

0

Sep-1

0

Oct

-10

Nov-

10

Dec-

10

He

at

Lo

ss

(B

tu/f

t^2

)

Unit 1: 4 in EPDM

Unit 2: 4 in TPO

Unit 3: 4 in Veg

Unit 4: 8 in TPO

Heat Gain

Heat Loss

Seasonal Cost Analysis

• Heating Season Assumptions:

– 80% efficient, $1 per therm

• Cooling Season Assumptions:

– 0.9 kW per ton, 12¢ per kWh

Heating and Cooling Costs

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

4.9 6.4 6.0 4.4

61.1 79.5 75.4 54.6

61$ 80$ 75$ 55$

(18)$ (14)$ 6$

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

152.6 194.2 157.2

137.3 174.7 141.5

16$ 21$ 17$

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

(2)$ 7$ 23$

COOLING

COMBINED

Savings per 1000 sq ft

Reduced Cooling (ton-hrs/yr per 1000 sq ft)

Reduced Cooling Power (kWh/yr per 1000 sq ft)

NET Savings per 1000 sq ft

Annual Gas Use (therms per 1000 sq ft)

Annual Cost per 1000 sq ft

Savings per 1000 sq ft

Annual Heat Load (MMBtu per 1000 sq ft)

HEATING

Water Retention

Testing

Long Term Retention Impacts

0 2 4 6 8

Rainfall (in)

0

2

4

6

8D

rain

ag

e (

in)

Retention Rate

is about 75-80%

Vegetative Roof Provides

Evaporative Cooling

22: 0: 2: 4: 6: 8: 10:12:14:16:18:20:22: 0:

40

60

80

100

Am

bie

nt

Tem

pera

ture

(F

)

22: 0: 2: 4: 6: 8: 10:12:14:16:18:20:22: 0:

0.0

0.2

0.4

0.6

0.8

1.0

Insola

tion (

W/m

^2)

22: 0: 2: 4: 6: 8: 10:12:14:16:18:20:22: 0:

0

5

10

15

20

25

Soil

Mois

ture

Conte

nt

(%)

22: 0: 2: 4: 6: 8: 10:12:14:16:18:20:22: 0:

60

65

70

75

80

Roof

Tem

p (

F)

July 20, 2010

July 27, 2010

More Recent Work

• Is simplistic heat transfer model accurate?

– Does heat transfer into roof deck = heat into space

• Longer term results (2009 to 2015)

– Impacts of aging

• Snow Retention on roof compared to ground

– Are the roof surfaces different?

A More Detailed Heat Transfer Model

• Developed EnergyPlus (E+) model of roof assembly

with finite difference option (not default CTF)

– Provides temperatures within layers

– Provides heat flux at both inside and outside surfaces

• Massive concrete layer confounds simple method

74

76

78

80

82

84

86

88

90

92

1 2 3 4 5 6 7 8 9

Tem

pe

ratu

re (F

)

7/1/2014 12:00

Insulation Layer

Tro

Tri

Comparison of Heat Loss through Concrete and Insulation layers

-200 -100 0 100 200 300

Concrete Layer Heat Loss (Wh/m2-day)

-200

-100

0

100

200

300

Insu

latio

n L

aye

r H

ea

t L

oss (

Wh

/m2

-da

y)

NRMSE=31.%

An Approximate Correction

• Use a simple mass

correction for the

concrete layer

• Demonstrated to work

with E+ results

• Applied correction to

the field data

Comparison of Heat Loss through Concrete layer, R22

-300 -200 -100 0 100 200 300

Energy Plus Model (Wh/m2-day)

-300

-200

-100

0

100

200

300

Sim

plif

ied M

odel (W

h/m

2-d

ay)

NRMSE=0.49%

Impact of Applying CorrectionUnit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

2010 Htg Season 4885.5 6360.8 6032.8 4366.6 4905.3 6364.3 6047.2 4320.5

(Oct to April) 1475.3 1147.4 -518.8 1459.0 1141.9 -584.8

30% 23% -11% 30% 23% -12%

2010 Clg Season (1188.5) 642.2 1141.3 698.0 (1217.8) 639.3 1140.3 714.4

(May to Sep) 1830.7 2329.9 1886.5 1857.1 2358.2 1932.3

2011 Htg Season 3958.3 5725.5 5153.8 3407.3 4790.9 6557.0 5935.2 4156.3

(Oct to April) 1767.2 1195.5 -551.0 1766.1 1144.3 -634.6

45% 30% -14% 37% 24% -13%

2011 Clg Season (1204.4) 476.7 1009.4 558.8 (1244.9) 459.4 1004.9 559.3

(May to Sep) 1681.2 2213.8 1763.3 1704.2 2249.8 1804.2

2012 Htg Season 4483.5 6478.7 5942.2 4089.5 4496.8 6464.9 5964.3 4108.0

(Oct to April) 1995.2 1458.7 -394.0 1968.2 1480.8 -375.5

45% 33% -9% 44% 33% -8%

2012 Clg Season (1333.5) 568.1 1178.2 627.6 (1352.7) 570.4 1191.6 643.8

(May to Sep) 1901.5 2511.7 1961.1 1923.1 2544.3 1996.5

2013 Htg Season 5333.6 7179.9 6507.5 4937.1 5357.4 7202.5 6509.8 5000.0

(Oct to April) 1846.4 1174.0 -396.5 1845.1 1152.4 -357.5

38% 24% -8% 34% 23% -7%

2013 Clg Season (943.2) 1050.3 1408.7 881.6 (928.6) 1082.1 1422.5 888.6

(May to Sep) 1993.5 2351.9 1824.8 2010.7 2351.0 1817.2

2014 Htg Season 4472.2 6128.9 5503.6 4258.0 4381.0 6095.1 5510.5 4251.6

(Oct to April) 1656.6 1031.3 -214.2 1714.0 1129.5 -129.5

37% 23% -5% 39% 26% -3%

2014 Clg Season (1036.9) 802.5 1292.9 833.2 (981.1) 822.9 1278.2 818.5

(May to Sep) 1839.4 2329.9 1870.2 1804.0 2259.3 1799.6

Heat Loss (Btu/ft^2), No Thermal Mass Heat Loss (Btu/ft^2), With Thermal Mass

Impact of Applying Correction

HeatingUnit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Avg Annual Heat Load (MMBTU per 1000 sq ft) 4.6 6.4 5.8 4.2 4.8 6.5 6.0 4.4

Annual Gas Use (therms per 1000 sq ft) 57.8 79.7 72.8 52.6 59.8 81.7 74.9 54.6

Annual Cost Per 1000 sq ft 58$ 80$ 73$ 53$ 60$ 82$ 75$ 55$

saving per 1000 sq ft (22)$ (15)$ 5$ (24)$ (17)$ 3$

Reduced Cooling (ton-hrs/yr per 1000 sq ft) 154.1 195.6 155.1 155.0 196.0 155.8

Reduced Cooling Power (kWh/yr per 1000 sq ft) 138.7 176.1 139.6 139.5 176.4 140.2

Savings per 1000 sq ft 17$ 21$ 17$ 17$ 21$ 17$

Net Saving per 1000 sq ft (5)$ 6$ 22$ (7)$ 4$ 20$

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Unit 1

4 in EPDMCombined Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Heat Loss (Btu/ft^2), No Thermal Mass Heat Loss (Btu/ft^2), With Thermal Mass

Cooling Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Unit 1

4 in EPDM

Unit 2

4 in TPO

Unit 3

4 in Veg

Unit 4

8 in TPO

Conclusions

• TPO or “cool roof” is energy cost neutral in

Central NY: benefit in summer, penalty in

winter

• Vegetative roof has cooling season benefit

(due to evaporation)

• More insulation is better (especially in the

winter)

• Vegetative roof retains 75-80% of rainfall