The Value of Reflective Wall Coatings André Desjarlais Oak Ridge National Laboratory 17 February 2011

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 2 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?

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 3 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 technologies are needed  Critically dependent on the best science and technology 3Managed by UT-Battelle for the Department of Energy Global energy consumption will increase 50% by 2030

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 4 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 5 Improvements in energy efficiency of the economy have been essential to the stabilization of U.S. energy consumption.. Wood Quadrillion Btu Natural gas Estimated energy savings Petroleum Coal Non-hydro renewables Nuclear Hydro Source: Energy Information Administration, U.S. Bureau of Economic Analysis

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 6 Buildings energy use is large and growing Industry 377 MMTC (25%) Buildings 658 MMTC (43%) 34% of Natural Gas Directly (55% Incl. Gen) 73% of U.S. Electricity 40% of U.S. Primary Energy Consumption (39% of U.S. Carbon Emissions) Source: 2007 Buildings Energy Data Book. Tables 1.1.3, 1.2.3, Source: EIA Annual Energy Review, Table 8.9, June 2007 Buildings Drive Electricity Supply Investment Buildings Energy Use Growing Fastest

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 7 The building envelope is the key!! 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 8 Quiz With Comfort and Energy Efficiency in mind, which car do you select to drive during the summer?

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 9 Proof of concept

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 10 Solar energy spectrum

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 11 Critical properties Reflectance (  solar ) E mittance (  IR )

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 12 Net Heat Flux into Building  solar I t Reflected  solar I t Absorbed ) ItItItIt Total Solar Irradiation h air (t air -t s )  IR  R Net Infrared Radiation with  R=  (T s 4 -T surr 4 ) Convection  solar and  IR are both very important!

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 13 Camouflage invisible to night vision Near Infrared Film Conventional Film

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 14 Conventional vs. infrared pigments

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 15 Regal WhiteRawhideSlate Blue Brick RedCharcoal 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 16 Solar energy spectrum

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 17 Overview: scope of work  Compare thermal performance of walls with cool (high infrared reflectance) and standard colors

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 18  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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 19 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY ORNL test site: Non vs IR -- summer day Hours into July 25, Heat Flux, Solar/100 [Btu/(h·ft²)] 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 Outside Non Inside IR Outside IR Inside Wall Solar Non Heat Flux IR Heat Flux Air

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 21 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 22 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 23 Model generalizations  Building America Performance Analysis Resources at 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 Miami Phoenix Las Vegas Bakersfield Richmond Knoxville Sacramento CDD65 (°F-day) HDD65 (°F-day) Average Daily Solar (Btu/ft²)  Cities arranged by decreasing cooling degree days

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 24 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 Sacramento Annual Electricity for Cooling (kWh) Non Walls IR Walls Walls: Wood Studs + R-11 Batts % Savings for IR Walls

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 25 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 Sacramento Annual Electricity for Cooling (kWh) Non Walls IR Walls Walls: 8 in. CMU + R-5 Foam % Savings for IR Walls

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 26 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?