The Value of Reflective Wall Coatings
André Desjarlais
Oak Ridge National Laboratory
17 February 2011
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Presentation summary
Is energy efficiency in buildings and walls important? Some statistics……
What research is going on to measure energy benefits of “Cool” walls?
What are the energy savings of this technology?
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Energy is the defining challenge of our time
The major driver for Climate change National security Economic competitiveness Quality of life
Incremental changes to existing technologies cannot meet this challenge Transformational advances
in energy technologiesare needed
Critically dependent on the best science and technology
3 Managed by UT-Battellefor the Department of Energy
Global energy consumptionwill increase 50% by 2030
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 5 10 15 20 25 30
Per Capita Electricity (MWhr/yr)
Pe
r C
ap
ita G
DP
($
/yr)
United States
Chile
Canada
Czech Republic
Italy
Norway
Japan
China
Russia
Sweden
Source: Energy Information Administration and United Nations Statistics Division
North American countries can improve their efficiency
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Improvements in energy efficiency of the economy have been essential to the stabilization of U.S. energy consumption . .
Wood
Qua
drilli
on B
tu
Natural gas
Estimated energy savings
Petroleum
Coal
Non-hydro renewablesNon-hydro renewables
NuclearNuclear
HydroHydro
Source: Energy Information Administration, U.S. Bureau of Economic Analysis
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Buildings energy use is large and growing
Industry377 MMTC
(25%)
Buildings658 MMTC(43%)
34% of Natural Gas Directly (55% Incl. Gen)34% of Natural Gas Directly (55% Incl. Gen)
73% of U.S. Electricity73% of U.S. Electricity
40% of U.S. Primary Energy Consumption40% of U.S. Primary Energy Consumption(39% of U.S. Carbon Emissions)(39% of U.S. Carbon Emissions)
Source: 2007 Buildings Energy Data Book. Tables 1.1.3, 1.2.3, 1.3.3
0
500
1000
1500
2000
2500
3000
1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005
Sa
les
(B
illio
n k
Wh
)
Buildings
Industry
Source: EIA Annual Energy Review, Table 8.9, June 2007
Buildings Drive Electricity Supply Buildings Drive Electricity Supply InvestmentInvestment
0
5
10
15
20
25
30
35
40
45
1980 1985 1990 1995 2000 2005
Year
Qu
ads
Industrial
Transportation
Buildings Total
Buildings Energy Use Growing FastestBuildings Energy Use Growing Fastest
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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The building envelope is the key!!
Heating23%
Cooling13%
Lighting18%
Ventilation3%
Water Heating10%
Electronics7%
Appliances12%
Computers2%
Other12%
Has Impact on 57% of Existing
Loads
• 133 Billion $/yr• 13.9% US Energy• 3.5% Global Energy
▪ $133 Billion Annually
▪ 13.9% of U.S. Energy
▪ 3.5% of Global Energy
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Quiz
With Comfort and Energy Efficiency in mind, which car do you select to drive during the
summer?
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Proof of concept
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Solar energy spectrum
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Critical properties
ReflectanceReflectance ((solarsolar) E) Emittancemittance ((IRIR))
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Net Heat Flux into Building
solar It Reflected
solarIt Absorbed)
IItt
Total SolarIrradiation hair(tair-ts) IRR
Net InfraredRadiation
with R=(Ts4-Tsurr
4 )
Convection
solar and IR are both very important!
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Camouflage invisible to night vision
Near Infrared FilmConventional Film
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Conventional vs. infrared pigments
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Regal White Rawhide Slate Blue
Brick Red Charcoal Gray
Hartford Green
Slate Bronze
Standard SR .67
Cool SR .72
Standard SR .47
Cool SR .56
Standard SR .21
Cool SR .33
Standard SR .25
Cool SR .30
Standard SR .14
Cool SR .28
Standard SR .11
Cool SR .28
Standard SR .08
Cool SR .26
Higher reflectance without sacrificing color choice
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Solar energy spectrum
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Overview: scope of work
Compare thermal performance of walls with cool (high infrared reflectance) and standard colors
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IR coating on right stud space and upper half of middle; Non-IR coating on rest except for strip of uncoated primer at bottom
ORNL test site
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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ORNL test site Data acquisition continuous for three years
Check consistency of data with program to estimate wall properties from temperature and heat flux measurements. Data very consistent from month to month
Behavior of solar radiation control on vertical walls more complicated than low-slope roofs. Difficult to generalize simply
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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30
50
70
90
110
130
ORNL test site: Non vs IR -- summer day
Hours into July 25, 2005
0 4 8 12 16 20 24
Heat Flux,
Solar/100
[Btu/(h·ft²)]
-1
0
1
2
-2
Temper- ature (°F) Air temp warmer
but wall solar lower vs 4/16/05
Behavior of Non and IR again same at night
Peak temps again consistent with coatings over primer
Non OutsideNon InsideIR OutsideIR Inside
Wall Solar
Non Heat Flux
IR Heat Flux
Air
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Model for wall behavior Seek a model that can be generalized to give
results for whole buildings
Have done extensive validation of a model in DOE 2.2 for a 1100 ft² ranch house
Conventional Wood-Framed Construction Heat/cool with heat pump: 68°F winter; 76°F summer; size heat pump for climate
Occupy with 3 people + Building America energy use profiles
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Model for wall behavior To validate model, generate climatic data from ORNL
weather station records for year of test Use properties of wall materials along with
construction details for test section
Extra gypsum layer(only for validation)
Gypsum wallboard
Fiberglass batt (R-11)
Stucco (1 in.)
Non-vented air space
Oriented strand board
Texcote coatings with different solar reflectance
Measured heat flux
Measured temperatures
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Model generalizations Building America Performance Analysis Resources at
http://www.eere.energy.gov/buildings/building_america/pa_resources.html gives energy use profiles for three occupants (3 BR home). Choose to heat and cool with air-to-air heat pump (76°F cooling; 68°F heating; no setup or setback)
Choose seven different climates to show response of typical house to cooling and mixed climates of interest
0
500
1000
1500
2000
2500
3000
3500
4000
4500
MiamiPhoenix
Las Vegas
Bakersfield
Richmond
Knoxville
Sacramento
CDD65 (°F-day)HDD65 (°F-day)Average Daily Solar (Btu/ft²)
Cities arranged by decreasing cooling degree days
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Model generalizations IR reflective coating on conventional walls saves
cooling energy. Savings are 4% to 9% compared to non-IR reflecting walls
Miami
Phoenix
Las Vegas
Bakersfield
Richmond
Knoxville
Sacramento0
1000
2000
3000
4000
5000
6000
4.25.0
5.3
6.2
7.1 7.6 9.0
Annual Electricity for Cooling (kWh)
Non Walls
IR Walls
Walls: Wood Studs + R-11 Batts
% Savings for IR Walls
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Model generalizations IR reflective coating on CMU walls shows larger savings
of cooling energy. Savings are 6% to 13% compared to cooling energy with non-IR reflecting walls
Miami
Phoenix
Las Vegas
Bakersfield
Richmond
Knoxville
Sacramento0
1000
2000
3000
4000
5000
6000 Annual Electricity for Cooling (kWh)
Non Walls
IR Walls
6.46.9
6.7
8.6
10.4 11.013.0
Walls: 8 in. CMU + R-5 Foam
% Savings for IR Walls
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
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Project summary
Full year of ORNL data validated DOE 2.2 model
Complexity of real wall applications (different orientations, shading and construction) makes generalization very difficult
DOE 2.2 whole building annual energy estimates for ranch house show that IR reflecting pigments save 4% to 13% of cooling energy
The Value of Reflective Wall Coatings
Questions or comments?
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