Download
1 / 56
560 likes | 669 Vues
AIA CES: Cool Roofing and Coating Systems. Disclosure - 1. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members available on request. Disclosure - 2.
E N D
AIA CES: Cool Roofing and Coating Systems
Disclosure - 1 • Credit earned on completion of this program will be reported to CES Records for AIA members. • Certificates of Completion for non-AIA members available on request.
Disclosure - 2 • This program is registered with the AIA/CES for continuing professional education. • As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. • Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Roof Coatings: Learning Objectives
Learning Objectives After this training power point, you will be able to: • Define a cool roof & understand the benefits of a cool roof. • Understand mitigating effects of Cool Roofing on Urban Heat Islands • Describe the options for “cool” roofing materials • Understand Energy Codes and Cool Roof Ratings systems • Investigate basic types of roof coatings and their compositions and benefits • Evaluate the condition of a roof to determine if the roof is suitable for coating. • Use rating guides to understand the best cool roofing option
Define a Cool Roof- Benefits of a Cool Roof Cool Roof 101
“Cool” Roof ? What is a “cool” roof? • A roof surface that stays relatively “cool” as compared to the ambient, or surrounding, temperature Or… • The roof surface temperature is usually only slightly higher than the air temperature
Cool Roof 101 - Introduction • Architects are specifying cool roof products for all types of roofs, hip, square, flat, etc. • Cool roofs come in a variety of materials and colors and can be applied to virtually any building or roof slope in any location. • The extent of the benefits will be related to the building’s location, type and use, as well as to the specific selected roofing product. • The broad range of locations in which cool roofs are proving to be a viable energy efficiency measure is growing. • Cool roofs are roofing products that integrate materials with greater spectral reflectance than their traditional, non-cool counterparts, and thereby minimize the transfer of heat to the building below.
Solar Reflectance Index (SRI) • Codes, standards and programs typically reference the Solar Reflectance Index (SRI). • SRI allows actual measured solar reflectance and thermal emitance values to be combined into a single value by determining how hot a surface would get relative to standard black and standard white surfaces. • The standard black roofing material has a high emitance value (90 percent) but a low reflectance value (5 percent). This creates a hot roof surface because even though the emitance is high, there isn’t enough reflectance to help cool the roof. As such, the standard black roof is given an SRI value of 0. • The standard white roofing material is highly reflective (80 percent) and has the same emitance as the standard black surface (90 percent). Its surface is much cooler and the standard white roof is assigned an SRI value of 100. Like solar reflectance and thermal emitance, a higher SRI value is synonymous with a cooler roof.
Thermal Effects on a Roof This diagram shows solar radiation on a roof surface. Image courtesy of Cool Roof Rating Council
Building Operations alone are responsible for 43.5% of all energy consumed in the United States, while Building Construction and Materials are responsible for an additional 5.5%.
77% of all Electricity generated in the US goes to operating Buildings .
Reduced Energy Costs Studies show that building owners can save 20-70% in cooling costs, according to a Department of Energy study. And it is quickly becoming a requirement, with recent legislation like Title 24 in California and the Chicago Conservation Energy Code.
Peak Energy Savings & Grid Stability • Because cool roofs reduce air-conditioning use during the day’s hottest periods, the associated energy savings occur when the demand for electricity is at its peak. • In addition, for building owners that pay for their energy based on the time of use, they save energy when it is at its most expensive – and save more money!
Cool Roofs – Big Benefits • COOL ROOFS EQUATE TO BIG BENEFITS TO THE OWNER AND THE ENVIRONMENT • Among the benefits to the building occupants and owner are: • Improved interior comfort • Reduced energy costs • Longer Mechanical Equipment unit life • Increased roof longevity • Decreased Life Cycle Cost
How “Cool” is a Cool Roof? Sacramento, CA; July 12, 2000 -- 89ºF, about noon, with local delta breeze EPDM single-ply 173 °F BUR topped with aggregate 159 °F BUR topped with capsheet 158 °F Courtesy Dan Varvais, Applied Polymer Systems
How “Cool” is a Cool Roof? Sacramento, CA; July 12, 2000 -- 89ºF, about noon, with local delta breeze Cool coating over BUR 108 °F Cool single-ply 121 °F Courtesy Dan Varvais, Applied Polymer Systems
Urban Heat Island Mitigation • Cities can be 2° to 8°F warmer than surrounding areas due to dark materials, including roofs, which absorb the sun’s energy as heat during the day and release it at night. • This phenomenon removes the opportunity for air to cool down at night resulting in higher temperatures being maintained longer. • By immediately reflecting solar radiation back into the atmosphere and reemitting some portion of it as infrared light, cool roofs help create cooler air temperatures for the surrounding urban area during hot summer months. • Through reduction of the urban heat island effect with the reduction of ambient air temperatures, cool roofs also improve air quality.
Row Houses – Absorb 95% of the Sun’s Heat + function as ovens
Confirming with Local or State Codes and Requirements • It would be prudent to first check with the local or state building codes to determine if there are specific cool roofing requirements that must be satisfied. • Such is the case with the ASHRAE Standard 90.1, California’s Building Energy Efficiency Standards, Title 24, NYCECC, as well as a number of other city building codes, including the Cities of Chicago, Houston, and Dallas. • In addition, voluntary green building programs, such as The U.S. Green Building Council’s LEED® program and the GreenGlobes™ environmental rating system, provide credit for cool roofs and several electric utility companies provide rebates.
How to Chose a Cool Roof • A cool roof should be chosen based on the slope of the roof, energy savings goals, the project location and climate, local code requirement, as well as aesthetic preferences. • Designers who are seeking sustainable design credits may also want to consider the cradle-to-cradle aspects of their materials choices, including recycled content, end of life recyclability and use of toxic materials.
Product Rating Resources • Rated product databases can assist the designer in selecting an appropriate cool roof product. • These databases list pertinent product information that can be easily compared. • These allow the designer to search roofing products by the initial and aged solar reflectance and thermal emittance values as well as the slope application and type of roofing material.
Energy Star • While existing rating systems are complementary to one another, they do have slight differences in their requirements. ENERGY STAR, for example, aims to capture the most efficient products and set minimum requirements for both initial and aged solar reflectance. • In order for a product to be listed by ENERGY STAR, it must meet their minimum requirements as tested by CRRC (initial solar reflectance of 0.65 and three-year aged value of 0.50 for low-slope products and an initial reflectance of 0.25 and aged value of 0.15 for steep-sloped products).
What Is The Cool Roof Rating Council (CRRC)? CRRC’s work is limited to the top roofing layer , and the CRRC Product Label includes both reflectance and emitance data, for both initial and aged values. The CRRC uses three specific locations representing three key climate zones (hot/dry, hot/humid, and cold/temperate) to determine aged product performance over a 3 year period. CRRC does: • Rate, or measure, the radiative properties of roof products • Publish performance data on the directory CRRCdoes not: • Set a performance standard or define “cool”. • Energy Star and state standards “Certify” or “approve” roofing products
Understanding Cool Roof “Coatings”
Government Mandates • Dr. Steven Chu – mandated all Department of Energy Roofs – be coated with a “cool” white roof. He stated, the simple process of coating all roofs white globally with a “cool” roof, would have the same effect as removing all traffic off the streets for 12 years globally.
Coatings – Prolong Roof Life • Roofs wear out because of: • Sunlight • Heat • UV • Freeze/Thaw • Roof Deck Movement • Oxygen • Precipitation • It is more cost effective to maintain rather than to repair or replace (read: BIG $$)!
Liquid Applied Coatings Reduce Life-Cycle Costs • Applied over existing roofs without costly tear-offs or landfill waste. • Crews achieve much higher productivity versus installing BUR. • Your money goes into safe, "sustainable technology" materials, not excess labor. • Extends roof life, lowers cooling energy demand and lowers life-cycle costs. • Each coating becomes more and more cost effective.
Ingredients of (Roof) Coatings Basic Components of Coatings • Pigment • Binder • Additives • Liquid Solvent
Dimensions Defining Quality in a Coating • Pigmentation (think: very tiny “rocks”) • provides whiteness, color, hiding, bulk • Binder (think: glue) • binds pigment; provides adhesion • Other Ingredients / Additives • improve coating and improve specific properties. • Solids Content • proportion of pigment-and-binder to liquids that evaporate when the coating dries.
Pigments • Pigments: microscopic “rocks” • Provide Whiteness, Opacity, Color, Hiding, Bulk • Prime pigments: • provide color, UV blocking • add in hiding, makes coating opaque • Extenders: • provide bulk and economy
Elastomeric Roof and Wall Coatings: The Theory • Think “springs (polymer)” and “rocks (pigment)” • The higher the polymer level, the higher the elongation (and lower tensile strength) • The higher the polymer level, the better the adhesion. Pigment Pigment Polymer Think: “springs (polymer)” and “rocks (pigment)”
Acrylic Coatings • Known for higher elongation/ lower tensile strength • Waterborne • Usually one component • Excellent UV durability • Excellent price/performance balance • Wide range of roof and wall coating applications
Polyurethane Coatings • Known for High Tensile Strength and Exceptional Wear resistance • Outstanding Waterproofing ability enables it to withstand long exposures to water • Higher initial cost balanced by long term capability of the product • Extremely effective in High Rise construction where roof square footage is small in comparison to overall building square footage.
Coating Possibilities • Roofing technologies include the traditional built-up roof (BUR), plus newer systems, such as various types of single ply and modified bitumen sheets and spray-applied polyurethane foam with a protective coating. • Coatings are firmly established as an integral and required part of the urethane foam roofing system. • The type of polyurethane used to make the foam is not durable if left uncoated and will begin to powder and degrade within weeks of application. • Moreover, polyurethane foam is rather brittle and its skin can be cracked from impact with falling debris, heavy foot traffic, or severe hailstorms. Coatings protect the foam from these potential mishaps.
Extremely Light Weight • Some liquid-applied coatings have also proven their utility over other substrates, and can be used to protect, restore, and prolong the life of aged existing built-up or other conventional roofing systems. • Unlike re-roofing alternatives, they are extremely lightweight, adding virtually nothing to the load on the roof deck or supporting members. • In fact, roofs may be re-coated several times without contributing significantly to the load. • Once a roof is coated properly, it becomes a renewable system.
Highly Flexible • By definition, they are liquid applied, fully adhered, elastomeric functional membranes formed in-situ on the existing roof. • In the sense of being adherent to the substrate to which they are applied-in this case, the existing roof-they are paint-like. • However, their elastomeric feature, which distinguishes them from paints, means they are also flexible.
Cool Roofs / Roof Coatings Is a Roof Suitable for A Cool Coating
New Roof or Coating ? • For roofing jobs on existing buildings, the question faced by the roofing professional still remains the same: • Should an expensive new roof be installed or is there a roof replacement alternative which will prolong the life of the existing roof? • The answer may be a liquid applied membrane over the existing aged roof.
