Cool Roofs and Sustainability

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1 Cool Roofs and Sustainability Saleh A. Al-Zahrani Consulting Services Department Saudi Aramco The Saudi International Building and Constructions Technology Conference 2015

2 Building sector account for approx. 80% of KSA energy power consumption (SE 2013 annual report )

3 KSA Power Consumption 2013 Others 3.6% Commercial 15.1% Industrial 19.9% Governmental 12.4% Residential Industrial Governmental Commercial Others Residential 49.0%

4 Typical Home Annual Power Use 7% Refrigerator/ Freezer Water Heater 21% 7% Lighting 5% Appliances/Other Household HVAC 60% Air Conditioning/Heating Water Heater Refrigerator/Freezer Lighting Appliances/other Household

5 Skin load (Wall and Roof) accounts for 10-30% building energy usage.

6 Why Roofs Direct solar heat density w/m 2

7 OUTLINE What is Cool Roof? Cool Roof Basics Standard Roofing/insulation System Types, Benefits, Limitations Energy Standards Comparisons Saudi Aramco Projects References and Tools

8 Cool Roof

9 Cool Roof (ASHRE 90.1) 1. Solar Reflectance (0.55)* and Thermal Emittance (0.75) 2. Solar Reflectance Index (SRI) (64)* *3-year aged

10 Cool Roof (LEED) 1. Solar Reflectance Index (SRI) (78)* *3-year aged

11 Cool Roof (ENERGY STAR) 1. Solar Reflectance (0.5)* *3-year aged

12 What is Cool Roof A system that act to reduce direct sun radiation effects on the outer surface of the structural roof membrane. Reduced skin temperature will reduce heat load transmitted from the roof surface into the building.

13 Cool Roof Types 1. Permanent Shade 2. Reflective 3. Thermal Mass (Ballast) 4. Vegetated surfacing (Ballast) 5. Combination

14 COOL ROOF Basics Heat Transfer: Q=U*A*(To Ti) Q=U*A*CLTD (cooling load temperature difference) CLTD for roofs will depend on: 1.Location of the mass relative to the insulation 2.Presence of false ceiling 3.Total R value 4.Construction material used

15 Typical Roof CLTD T (out) = 44 C (111 F) Water proofing Insolation board Concrete roof R (total) Roof # (ASHRAE) T (in) = 24 C (75 F) Peaking Hour CLTD o C ( o F) To-Ti o C ( o F) Additional Heat Load (104) 20 (36) (96) 20 (36) (87) 20 (36) 2.4

16 SAES-M-100 (Saudi Aramco building Code) The preferred roof systems for new flat roofs with low slope (roof slope < 2:12) are: A. Loose laid ballasted single ply membrane systems B. Inverted, loose laid ballasted single-ply membrane systems C. Fully adhered and mechanically fixed single ply membrane systems

17 SAES-M-100 (Saudi Aramco building Code) AGGREGATE. In roofing, crushed stone, crushed slag or water-worn gravel used for surfacing for roof coverings. BALLAST. In roofing, ballast comes in the form of large stones or paver systems and is used to provide uplift resistance for roofing systems that are not adhered or mechanically attached to the roof deck.

18 SAES-M-100 (Saudi Aramco building Code) Ballasted shall be designed in accordance with ANSI/SPRI RP-4 Ballasted roofs shall have a separation layer installed below the gravel ballast. Ballasted roofs shall have a minimum of 19 mm washed gravel placed to a minimum thickness of 50 mm (2 ) Approx Kg/M 2 (15-20 lb/ft 2 )

19 SAES-N-004 Building Thermal Envelop

20 Cool Roof (Reflective) Source Lawrence Berkeley National Laboratory from Berkeley, CALIFORNIA

21 Cool Roof (Reflective) ageing Low-sloped roof color NEW AGED ( 3 YEARS) R E SRI T o C ( o F) R E SRI T o C ( o F) Bright-White (9) (28) Zinc/Al/ Steel (36) (65) Standard Gray (69) (69)

22 Cool Roof (Reflective) Benefits: Reduced HVAC energy use, even after aging Available in wide variety (coating, solid/liquid membranes, shingles) Economical, especially for integrated reflective membranes (membranes with high SRI) Reduce heat island effect (urban)

23 Cool Roof (Reflective) Current Limitations: Reduced performance over time Cleaning and maintenance may be expensive & difficult Glare to windows and heat to nearby buildings Not effective in cold climates. (raise winter heating costs)

24 Cool Roof (Vegetated) Vegetative Roof Systems creates an insulated layer, provide partial shading, create evaporated cooling surface that makes roof surface at a lower temperature than ambient air. ASTM E standard Guide for vegetative (Green) roof Systems ASTM E Standard Guide for Selection, Installation, and Maintenance of Plants for Green Roof Systems

25 Cool Roof (Vegetated) Benefits: Reduced HVAC energy use: absorb heat and act as insulators for buildings, reducing energy needed to provide cooling or heating. Reduce ambient air temperature, heat island effect Manage storm water runoff from roofs Provides UV protection and shields the roof from wind and hail damage Provide natural habitat for many species/birds Provide pleasant view w/wide variety of plants available Require as little as 50 to 100 mm of planting medium

26 Cool Roof (Vegetated) Limitations: Additional roofing membranes to accommodate increased maintenance traffic Additional roofing membranes to resist root penetration and water management. Continuous maintenance Fire / wind resistance is uncertain (Code limit) 1. ANSI/SPRI RP-14 Wind Design Standard for Vegetative Roofing 2. ANSI/SPRI VF-1 Fire Design Standard for Vegetative Roofing

27 Cool Roof (Ballasted) (Thermal Mass) a layer of stones, pebbles, paver or slabs is required to held in place and protected roof loose laid membrane and insulation boards. Like the old buildings, roofs utilizes a mass of earth materials that provide a heat barrier and absorb solar energy during the day, delay transmission, and then emit the heat back into the sky at night.

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29 Cool Roof (Thermal mass)

30 Cool Roof (Thermal mass) Physical separation limit heat transfer by conduction Air gaps/windows and allow heat carryout back to atmosphere by natural convection Mass heat capacity absorb solar energy during the day, delay transmission, and then emit the heat back into the sky at night. Structural roof surface membrane temperatures very much lower that exposed surface.

31 Cool Roof (Ballasted) Compared to a white membrane with a reflectivity of 0.78, the thermal performance of the 10-pound ballast (code min.) is within 30% the 24-pound ballast was within 5%.

32 Cool Roof (Ballasted) Black Roof/Standard Ballast/ White Roof/ Heavy Ballast/ Concrete Pavers Source: Oak Ridge National Laboratories Envelope Systems Research Apparatus

33 Cool Roof (Ballasted) Benefits: Energy efficiency, reduce cooling and heating loads (17 Ib/ft 2 = energy star) Provides UV protection and shields the roof from high temperature, wind and hail damages Constant performance Economical/Quick installation Fast Construction in all conditions Easy Maintenance Reusable materials Natural looking Durable

34 Cool Roof (Ballasted) Limitations: Building must be designed to accommodate additional ballast weight. Additional Code requirement in high-wind regions/building height: ANSI/SPRI RP-4 Wind Design Standard for Ballasted Single-ply roofing systems

35 Cool Roof (Permanent Shaded) Oldest and simplest heat protection technique from direct sun radiation Well recognized in architectural engineering Well recognized in HVAC engineering Physical separation eliminate the direct effect of sun on roof surface resulting in a cool roof with temperatures not exceeding ambient air temperature.

36 Cool Roof (Tent Shaded)

37 Cool Roof (Shaded) PV Photo Curtesy: Solar Advantage

38 Photo courtesy Green Roofs for Healthy Cities

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40 Why COOL ROOFs Reduce HVAC energy use. Reduce peak electric consumption Reduce Urban Heat Island Effect Minimal cost compared to alternatives Long-term benefit with minimal maintenance (even after aging and with reduction in actual reflectivity) Perfect for retrofit renovation tasks Extend structural roofing system life

41 Energy Standards Comparisons Low Rise residential: 1. SAES-A-504 (2015) 2. ASHRAE 90.2-(2007) 3. CA building energy efficiency Title 24 High Rise Building (Commerc. and Resident.): 1. SAES-A-503 (2015) 2. ASHRAE 90.1-(2013) (2010) 3. CA building energy efficiency Title 24

42 (SAES-A-503) (SAES-A-504) Energy Efficiency for Buildings Minimum of 75% of the roof area shall have Solar Reflectance Index SRI of 78 The SRI values should be determined by a nationally or internationally recognized accreditation organization, in accordance with ANSI/ CRRC-1 standard ASTM E1980

43 SAES-A-503 Energy Efficiency for Exceptions: Buildings Roofs with a minimum stone ballast of 85 kg/m 2 (17 lbs/ft²) Roofs with a minimum pavers ballast of 112 kg/m 2 (23 lbs/ft²) Roofs shaded by permanent structures Roofs over ventilated attics or over semiconditioned spaces.

44 ASHRAE 90.1 (high rise) (2013) Roofs in Climate Zones 1 through 3 shall have one of the following: minimum aged solar reflectance of 0.55 and minimum aged thermal emittance of 0.75 minimum aged Solar Reflectance Index of 64 Increased insulation levels (R-33 or R-34)

45 ASHRAE 90.1 (high rise)(2013) Exception: Roofs with a minimum stone ballast of 74 kg/m2 Roofs with a minimum paver ballast of 117 kg/m 2 75% covered Vegetated roof systems that has minimum thickness of 63.5 mm of growing medium with durable plantings 75% shaded roof by permanent components (PV, Solar collectors, structures etc)

46 ASHRAE 90.2 (low rise Res.)(2007) Set Minimum R-Values EXCEPTION (cool roof) minimum aged solar reflectance of 0.65 and minimum aged thermal emittance of 0.75 minimum aged Solar Reflectance Index of 75 Allow reduced R-values Only wood and steel structures

47 CA building energy efficiency Title 24 (high rise)(2013) minimum aged solar reflectance of 0.63 (0.55)* minimum aged thermal emittance of 0.75 minimum aged Solar Reflectance Index of 75 (64)* Exception: Roofs with a minimum stone ballast of 120 kg/m 2 (25 Ib/ft 2 ) *(high rise residential and hotels)

48 CA building energy efficiency Title 24 (low rise Res.)(2013) minimum aged solar reflectance of 0.63 minimum aged thermal emittance of 0.75 minimum aged Solar Reflectance Index of 75 Exception: Roofs with a minimum stone ballast of 120 kg/m 2 (25 Ib/ft 2 ) Roofs with integrated PV panels or Solar thermal Panels (shade).

49 Energy Standards Summery Buildings (residential) Low Rise residential 90.2 (2007) SAES-A (2010) - - R-15 (R-20) 90.1 (2013) R-20 (R-25) SAES-A-503 R-20 (R-25) R-19 R Reflectance Emittance SRI Ballasted N N Y Y Y Vegetated N N Y Y N shade Y N Y Y Y

50 King Abdullah University of Science and Technology (KAUST), Thuwal

51 King Abdullah University of Science and Technology (KAUST), Thuwal

52 King Abdullah Petroleum Studies and Research Center (KAPSARC), Riyadh

53 King Abdullah Petroleum Studies and Research Center (KAPSARC), Riyadh

54 AL-MIDRA TOWER, Dhahran

55 Additional Resources Lawrence Berkeley National Laboratory Oak Ridge National Laboratory

56 Available Softwares DOE Cool Roof Calculator EPA Roofing Comparison Calculator EnergyWise Calculator Energy-10 EnergyPlus equest Roof Saving Calculator

57 Q&A