Reducing Over-heating of Buildings by use of White Reflective Roof Coatings (WRRCs)

Transcription

1 Reducing Over-heating of Buildings by use of White Reflective Roof Coatings (WRRCs) The Middle East Conference on Sustainable Building Materials, Dubai, Feb 23rd 2011 Brown Joseph The Dow Chemical Company

2 Why Coat a Roof? Ingression of water Mechanical stress & strain Sunlight Movements Roof Coatings are critical to extend the life of a roof

3 White Reflective Roof Coatings (WRRC s)

4 White Reflective Roof Coatings (WRRC s) Agenda Theory of reflective roof coatings Standards for roof coatings From the roots until today Performance requirements for WRRC s Binder solutions for WRRC s

5 Physics behind the Cool Roof Ideal Cool Roof Reflectance = 100% Emissivity = 100% White Cool Roof Reflectance = >88% Emissivity = >90%

6 Why Coat the Roof White? Solar Reflectivity of Coated vs. Uncoated Roofing Substrate Black Asphalt Aluminized Asphalt White ERC: ARM91-1 (initial) Solar Reflectance 5% 41% 88%

7 Why Elastomeric Roof Coating? Roofs can develop cracks due to : Movement Vibration Stress Shrinkage Coatings with Elastomeric Property is necessary to bridge the cracks

8 Regulations and Standards for Roof Coatings ASTM D6083 American Society of Testing Materials Standard sets the bar for a high quality coating Commonly specified by architects, specifiers, building owner, etc. for roofing projects California Energy Commission (CEC) Title 24 A state standard loosely based on D6083 Contains energy components Solar Reflectivity Emissivity Exemption for coatings already D6083 compliant Energy Star Solar Reflectivity & Emissivity requirements VOC: SCAQMD rule is 50 g/l

9 Other Global Cool Roof Initiatives Green Globes ( The Green Globes system is a revolutionary building environmental design and management tool European Cool Roof Council ( Canadian Energy code ANSI/ASHRAE/IESNA etc.

10 Comparison Chart for Regulations & Standards Tensile & Elongation Properties Performance Spec ASTM Method D6083 Requirement Title 24 Requirement Energy Star Requirement Tensile Strength, initial, RT (73 F) D psi 100 psi Tensile Strength, initial, LT (0 F) D psi Elongation, initial, RT (73 F) D % 200% Elongation,, initial, LT (0 F) D % Elongation, G hrs, RT (73 F) D % 100% Elongation, G hrs, LT (0 F) D % Mandrel Bend - Alternate to T&E at RT & LT (-18degC) D522, Method B Pass ½ Mandrel Pass 1 Mandrel

11 Comparison Chart for Regulations & Standards Performance Properties Performance Spec ASTM Method D6083 Requirement Title 24 Requirement Energy Star Requirement G156, WOM 1,000 hours D4798 Pass/Fail Pass/Fail Permeance, Face Down D Water Swelling Resistance D471 20% Adhesion C794, D pli (wet) Tear Resistance D lbf/in Fungi Resistance G21 0 Rating

12 Comparison Chart for Regulations & Standards Energy Properties Performance Spec ASTM Method D6083 Requirement Title 24 Requirement Energy Star Requirement Solar Reflectivity, initial C % 65 % Solar Reflectivity, 3 years C1549 None today, proposed % in % Emissivity, initial C % Emissivity, 3 years C1471

13 It all started with a birdhouse 1981

14 Mississippi houses Control White roof Insulation One year period Energy saving White roof: - 22 %, 2.1y pay back Insulation: - 29%, 3.1y pay back

15 Further Studies Philadelphia Lower energy consumption Reduced mortality due to lower ceiling temperature Continuous energy saving programs sponsored by Dow Others Less energy consumption Most effective in hot climate Development of mathematical models

16 Key Properties of a WRRC High elongation while maintaining good tensile strength Has to be flexible enough to move as the roof systems moves; Yet has to be tough enough to walk on Excellent adhesion in dry and wet conditions Varied geographies means extremes in heat, cold, wet & dry Temperature: -15 C to +80 C Direct sun; water, ice, snow; dirt; foot traffic; equipment, tools Excellent long-term dirt pickup resistance Maintaining solar reflectivity longer-term energy savings Excellent water resistance properties Water swelling, blistering, and ponding water resistance Excellent UV resistance

17 Elongation/tensile strength PRIMAL EC-1791 E provides good flexibility even at low temperatures Elongation in % Elong. 43% PVC Elong. 35% PVC Tensile 43% PVC Tensile 35% PVC Tensile Strength in MPa Temperature in C

18 Durability of WRRC PRIMAL EC-1791 E keeps its good properties over years 400 Elong. 24 C Elong. -18 C Tensile S. 24 C 7.0 Elongation in % Tensile S. -18 C Tensile Strength in MPa Outside Exposure Time in Years

19 Adhesion to multiple substrates Concrete PRIMAL EC-1791 based formulation # ARM 91-1 ASTM D-6083 Requirement Polyurethane foam, Dry, pli 4.2 F not applicable Polyurethane foam, Wet, pli 2.7 F 2.0 pli min. Galvanized steel, Dry, pli 2.4 A not applicable Galvanized steel, Wet, pli 1.9 F 2.0 pli min. Polyurethane Foam A= adhesive failure mode and F= cohesive failure mode Asphalt Galvanized Steel Special binder technology required to achieve adhesion on multiple surfaces

20 Dirt Pick Up Resistance Improves Whiteness Critical property for maintaining high solar reflectivity

21 Binders for WRRC Composition choosing the right binder is critical Parts (w/w) Pigment 4 9 % Filler % Binder (wet, 55% solids) % Binder (based on solids) % Properties are determined by the binder

22 PRIMAL EC-1791E : High Adhesion Polymer 100% Acrylic Meets ASTM D6083 Adhesion to PUR Foam, metal, Hypalon, EPDM rubber, aged asphaltic Excellent exterior durability (up to 20 years) Numerous formulations available Energy star certified formulations for energy savings

23 LIPACRYL MB-3640 Very Hydrophobic, 100% Acrylic Designed for adhesion to asphaltic surfaces Excellent water resistance (up to 6 months!) Adhesion to other substrates Very low perms

24 Binders for WRRC LIPACRYL MB 3640 improves adhesion of fresh asphalt Developed for good adhesion on fresh asphalt Other good properties kept

25 International hospital in Kuwait develops green strategy Al Salam International Hospital Kuwait used WRRC for the roof restoration work in 2010 Product supplied by Insulation Coating Company U.S.A contractor : Burgan One General Trade and Contracting Company

26 Al Salam International Hospital Kuwait A 14 degc difference in temperature between coated roof and the uncoated

27 Satyam Computers Hydrabad, India Approx. 8% energy saving on total air conditioning Roof surface temperature dropped from 52degC to 32degC Increased interior comfort levels

28 81 Banks Alizona Banks Saved 33% energy consumption

29 Conclusion White Reflective Roof Coatings Reduce Temperature in Buildings less energy consumption decreased CO 2 emissions reduced mortality Chemical Industry offers Tailored Binders for WRRC different substrates new technologies for quick setting improved properties

30 Thank you for your attention!