An update on the development of an accelerated aging method for roofing materials

(1)

An update on the development of an

accelerated aging method for roofing materials

Mohamad Sleiman, Thomas W. Kirchstetter, Haley E. Gilbert,

Paul H. Berdahl, Hugo Destaillats, Ronnen Levinson

Lawrence Berkeley National Laboratory, Berkeley, CA

http://HeatIsland.LBL.gov

and Hashem Akbari

Concordia University, Montreal, Canada.

Asphalt Roofing Manufacturers Association

(2)

Heat Island Group, Lawrence Berkeley National Laboratory

Replacing a dark roof with a cool roof can help…

Reduce annual cooling energy use

by 5-20%

(Levinson et al. 2005)

Mitigate the heat island effect

(Rosenfeld et al. 1998; Akbari et al. 2001)

Delay global warming (10 tonnes of

CO

₂

offset by 100 m

2 _{white roofing)}

(

Menon et al. 2010; Akbari et al. 2009;

Oleson et al. 2010)

2

(3)

Making U.S. commercial building roofs white

would offer $11B in lifetime energy savings

Retrofitting 80% of

U.S. air-conditioned

commercial buildings

with conventional

white roofs would

annually save

$735M

6.2 Mt CO2

(=1.2M cars)

through energy

conservation

New York Times

_{, 30 July 2009}

(4)

Berkeley Lab’s Heat Island Group works

to cool buildings, cities and the planet

4 International

collaborations

• dissemination of cool roofing

technologies worldwide

Improve the performance of

cool roofing materials

• rating (CRRC), standards (ASTM, ISO)

• accelerated aging methods

• next gen materials (cool colored

pigments, retention of high SR)

Advance the science of

heat island mitigation

• mapping urban albedos using

aerial imagery

• satellite measurements of

radiative heat flows

Engage stakeholders

• smart choices about cool surfaces

(5)

Aging = soiling + weathering

wet deposition: soot, salts, organics

dry deposition:

mineral dust

microbiological

growth:

fungi, mold,

bacteria

2010

2012

Challenge:

speed the development of high performance building envelope

(6)

0.0

0.1

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1.0

0.0

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1.0 A

g

e

d

s

o

la

r

re

fl

e

c

ta

n

c

e

Initial solar reflectance

no change

CA Title 24

running mean

OHIO

(n=586)

Aging markedly decreases solar reflectance of

conventional roofs.

6 clay tile

concrete

tile

field-applied

coating

metal

roofing

single-ply

membrane

asphalt

shingle

factory-applied

coating

modified

bitumen

When a white roof’s reflectance falls to 0.60 from 0.80,

annual energy savings decrease by ⅓

Sleiman et al. (2011)

Solar Energy Materials and Solar Cells, 95, 3385.

OHIO

(n = 573)

(7)

-0.1 0 0.1 0.2 0.3 0.4 0.0 – 0.2 0.2 – 0.4 0.4 – 0.6 0.6 – 0.8 0.8 – 1.0 Florida Arizona Ohio

Mean absolute

loss in solar

reflectance

Initial solar reflectance

We observe significant differences between the

three CRRC sites…

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance

FLORIDA

no change CA Title 24 running mean (n=586) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance

ARIZONA

no change

CA Title 24

running mean

(8)

8

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance Factory-applied coating FLORIDA CA Title 24 running mean no change 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance Field-applied coating FLORIDA CA Title 24 no change running mean 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance Metal FLORIDA no change CA Title 24 running mean 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance Modified bitumen FLORIDA no change CA Title 24 running mean 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance Single-ply membrane FLORIDA no change CA Title 24 running mean 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A g e d s o la r re fl e c ta n c e

Initial solar reflectance Tile

FLORIDA

running mean

CA Title 24

no change

… and significant differences among product

-30

-20

-10

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10

20

30 F

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T

ile

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i

n

a

g

e

d

s

o

la

r

re

fl

e

c

ta

n

c

e

(

%

)

Florida

Arizona

Ohio

124

173

33

71

13

34

27 Number of samples

(R

_k

– R

_CRRC

)

R

_CRRC

Fluctuations in aged solar reflectance with

respect to CRRC 3-site average are moderate

Sleiman et al.

Solar Energy Materials and Solar Cells.

(10)

Development of accelerated aging method:

Purpose, objectives and approach

Problem Statement:

CRRC and Energy Star rating programs require three years of

natural exposure, delaying introduction of novel cool roofing materials.

R&D challenge: Develop technology to quickly rate roofing products, removing

barrier to innovation of energy saving roofing materials.

Impact:

Benefits to society and roofing industry by speeding prototyping and

introduction to market of high performance products.

Focus:

Develop and transfer technology that promotes advanced cool roofs. Wide

adoption of cool roofs is projected to yield annual net primary energy savings

of nearly 300 TBTU, worth about $2B/year, reduce CO

₂

emissions, and partially

mitigate global warming

.

Approach:

(1) establish a network of industrial partners, (2) field exposure of 27

products, (3) develop lab method, (4) validate method with inter-laboratory

study, (5) develop ASTM and ISO standards for accelerated aging, (6) integrate

soiling in a commercial weatherometer to facilitate technology adoption.

(11)

We screened 100 roofing materials from 40 industrial partners

Selected 28 materials from the following categories:

Selection criteria: diversity of products & colors, market presence,

sample uniformity and availability of aged samples.

Used for laboratory (accelerated) and natural exposure

field-applied

coating

asphalt

shingle

concrete

tile

metal

roofing

clay

tile

single-ply

membrane

factory-applied

coating

modified

bitumen

Roofing products used in this study

(12)

Coupons of 27 products naturally exposed at the three

CRRC sites are collected & characterized quarterly

12

JANUARY APRIL JULY OCTOBER

2011 2012 2013

45 °

°

tilt

5 °

°

tilt

hot & dry

(Phoenix, AZ)

temperate

(Cleveland, OH)

hot & humid

(Miami, FL)

(13)

We measure radiative properties using

ASTM standards E903, C1371 & C1549

E 903 Solar Absorptance, Reflectance, and

Transmittance of Materials Using Spectrometer

w/ Integrated Spheres

C 1371 Determination of Emittance of

Materials Near Room Temperature

Using Portable Emissometers

C 1549 Determination of Solar Reflectance

Near Ambient Temperature Using a

(14)

We measure chemical and physical properties

of a subset of samples

14

0

500 1000

1500

2000

0

200

400

600

800 1000

C

o

u

n

ts

m/z

Florida

Ohio

SEM (morphology)

Water contact angle

(hydrophilicity)

Soot

Salts

Chemical composition of soiling

Laser desorption photoionization

TOF-mass spectrometry (ALS)

(15)

Some products reach CRRC’s 3-year-aged solar reflectance

after 1 year of natural exposure; others take longer

White single-ply membrane, 5 degree tilt

0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 0 3 6 9 12 15 18 21 24 27 30 33 36 S o la r R e fl e ct a n ce , B 8 9 1 M e th o d

Number of Months Exposed Since October 2010 Sample 1: White Single-Ply Membrane, 5 Degree Tilt

LBNL, Arizona LBNL, Florida LBNL, Ohio CRRC, Arizona CRRC, Florida CRRC, Ohio 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 0 3 6 9 12 15 18 21 24 27 30 33 36 S o la r R e fl e ct a n ce , B 8 9 1 M e th o d

Number of Months Exposed Since October 2010 Sample 2: White Single-Ply Membrane, 5 Degree Tilt

LBNL, Arizona LBNL, Florida LBNL, Ohio CRRC, Arizona CRRC, Florida CRRC, Ohio

Natural exposure:

• Seasonal variability

• Geographical (climate) variability

• Precision of aged solar reflectance measurements

(16)

GOALS

Develop a reliable lab method for accelerated aging that

can be readily adopted by industry

Incorporate this method in standards to

facilitate worldwide adoption of cool roofs

CHALLENGES

Method should be tunable to mimic accurately aging of

roofing materials in different climate zones

Method should reduce complex and variable

environmental signatures to a minimum set of parameters

16

(17)

Dust

28 – 66%

Soot

4 – 12%

Particulate

Organic

Matter

8 – 36 %

Salts

18 – 27%

Dust

53%

Salts

23%

POM

18%

Soot

6%

Favez et al,

Atmos. Environ, 2006

How to mimic natural

soiling in the lab ?

Chemical composition of soiling on building

envelopes

soot

core

salts and

organic

coating

(18)

Soot hydrosol

Salts

Clays + Iron oxide

Humic acid

Ozone

Methane diffusion flame

18 Soiling surrogates used in our laboratory

method

(19)

Spraying the soiling mix

(5 – 30 sec)

Drying w/IR lamp

(1 – 2 min)

Measurement of R

( 5 - 10 min)

Unexposed

Soiled

Soiling apparatus and laboratory method

Air

Soiling

mix

Pressure

Spraying vessel

Coupons of roofing products

(20)

Heat Island Group, Lawrence Berkeley National Laboratory 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 250 500 750 1000 1250 1500 1750 2000 2250 2500

r

(λ

)

Wavelength (nm)

organics

dust

20 Contribution of each surrogate to the

reflectance spectrum

soot

(21)

Correlation of soot loading with R/R

₀

0.75 0.80 0.85 0.90 0.95 1.00 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

R

/R

0

Deposited Black Carbon Soot (μg cm

-2

₎

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 250 500 750 1000 1250 1500 1750 2000 2250 2500

R

e

fl

e

ct

a

n

ce

Wavelength (nm)

Unexposed

0.12 μg/cm2

0.22 μg/cm2

0.4 μg/cm2

0.47 μg/cm2

0.76 μg/cm2

(22)

http://www.q-lab.com/QUV.html

QUV/Spray Weathering Tester (Qlab)

22

(23)

Effect of conditioning on initial solar reflectance

-0.04

-0.03

-0.02

-0.01

0.00

0.01

0.02 Field applied coating (n=6)

Metal/Factory applied coating (n=4)

Tile (n=4)

Single ply membrane (n=2)

Asphalt shingle (n=2)

Modified bitumen (n=1)

Mean gain in initial solar reflectance

24h

72h

(24)

Effect of conditioning on soiling

24

0.00

0.05

0.10

0.15

0.20 Asphalt shingle (n=2)

Metal/Factory applied coating (n=4)

Tile (n=4)

Modified bitumen (n=1)

Single ply membrane (n=2)

Field applied coating (n=6)

Absolute loss of solar reflectance

Soiling

Weathering + Soiling

Conditioning + Soiling ≤ Soiling

Soiling

(25)

Effect of weathering on solar reflectance losses

0.00

0.05

0.10

0.15

0.20 Asphalt shingle (n=2)

Tile (n=4)

Modified bitumen (n=1)

Metal/Factory applied coating (n=4)

Single ply membrane (n=2)

Field applied coating (n=6)

Absolute loss of solar reflectance

Weathering + Soiling

Weathering + Soiling +Weathering

Conditioning + Soiling + Weathering ≤ Conditioning + Soiling

Conditioning +Soiling

(26)

Effect of conditioning & weathering

duration: 1 week

26 No additional

effect by

prolonging

conditioning nor

weathering

y = 0.9927x

R² = 0.9911

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.2

0.3

0.4

0.5

0.6

0.7

0.8 S

R

(

C

S

W

-7

d

a

y

s

o

f

C

&

W

)

SR (CSW - 1 day of C & W)

No change line:

y = x

(27)

Specific surface characteristics (chemistry, rugosity)

determine soiling retention

n = 6

different

coatings

Coating 1

Coating 2

Coating 3

Coating 4

Coating 5

Coating 6

0.64

0.66

0.68

0.7

0.72

0.74

0.80

0.82

0.84

0.86

0.88 S

o

la

r

re

fl

e

ct

a

n

ce

a

ft

e

r

la

b

e

x

p

o

su

re

(C

+

S

+

W

)

(28)

Conditioning (QUV – ASTM G 154)

• 24h total duration (2 cycles)

• 8 h of UV (0.89 mw cm

-2

_{), temperature: 60 ˚C}

• 8 h of water condensation: temperature: 50 ˚C

Soiling (Spraying )

• Spraying of a mix of soot, humic acid dust and salts

• Total mass of soiling deposited is 0.7 – 0.8 g

• Evaporate water by heating with IR lamp

Weathering (QUV – ASTM G 154)

• 1 week total duration (14 cycles)

• 8 h of UV (0.89 mw cm-

2 _{), temperature: 60 ˚C}

• 8 h of water condensation: temperature: 50 ˚C

28

(29)

Our method reproduces CRRC’s 3-year-aged

solar reflectance ratings in 3 days

Field applied

coating (n=7)

Metal or

factory-applied

coating (n=8)

Single-ply

membrane (n=11)

Clay tile

(n=2)

Asphalt

shingle (n=4)

Modified

bitumen (n=3)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 Field-Applied Coating

Factory-Applied Coating

Single-Ply Membrane

Modified Bitumen

Shingle

Tile

Metal

Solar Reflectance

y = (1.02 ± 0.03) x - (0.01 ± 0.02)

R

2

=0.96

A

c

e

le

ra

te

d

a

g

in

g

(

L

B

N

L

)

(30)

Discussion and development

of accelerated soiling standards

June 2012 & Dec 2012

• Draft standard

presented at ASTM

• Created Task Group D08.20.45

(Test Method for Accelerated

Aging of Solar Reflectance of

Roofing Materials)

September 2012

• Draft standard presented at ISO

• TC-163: Thermal performance

and energy use in the built

environment

30 International Workshop on

Advances in Cool Roof Research

Berkeley, July 28-29, 2011

(31)

Perspectives and items for discussion

simple & reliable tunable method that mimics in just 3 days:

CRRC 3-year average of three sites; AZ exposure; OH exposure

not intended to test resistance to microbial growth or long-term

mechanical durability

Validation by inter-laboratory tests underway

Integration in laboratory weathering hardware underway

Future work:

1) Florida exposure: can it be predicted with this method?

2) Anti-soiling properties: can be predicted with this method?

(32)

U.S. Department of Energy (DOE/EERE/BTO)

Our industrial partners

CRRC: Sherry Hao and Jessica Clark

ORNL: André Desjarlais

LBNL team:

Chelsea Preble, Sharon Chen, Olivier Rosseler,

Amandine Montalbano,

Sarah Quelen, Lea Marlot,

Mike Spears, Vasileia Zormpa,

Tosh Hotchi, David Francois.

32