Cool roofing-Important green building strategies

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Updated： 2013/7/11 21:21:36

Cool roofing-Important green building strategies

What is cool roofing?

Overall, cool roofs having high reflectivity and emissivity. In other words, it reflects sunlight and the atmosphere of the solar radiation is absorbed, not to the heat absorbed by the lower conductive construction. Unlike traditional black roofs that reflect sunlight and cool roof radiant heat. Heat is easily absorbed and penetrate into the roof inside the building, increased cooling costs. Instead, cool roofs can reduce cooling costs the hot summer months, thus energy-saving and cost reduction.

Next, cool roofs and cool roofs for non-analog comparator: Suppose in a hot day two people are wearing T-shirt, one wearing white, while the other one wore black. From everyone''s experience, in the summer, wearing a black T-shirt is not a wise move, because the black fibers absorb the sun''s rays, thereby heating the skin. Instead, wearing a white T-shirt who want to feel cool, because white T-shirt reflecting more sunlight and absorb less heat. Solar roofs like a white T-shirt, it makes the building interior cooler cooler.

However, cool roofs and white T-shirt is an important difference between a cold roof is not necessarily white. If, for aesthetic needs, architects have to be designed as a black roof construction, when the use of a sufficiently "cool" colors without sacrificing the building attraction. Cool Roofs latest trends in the market, including "cool color" products, such products using the dark pigment, dark pigment in the solar spectrum near-infrared (invisible) part has a high reflectivity. With the "cool color" technology development, and now have a cold roof green, red, blue and almost all of us to think of color.

In addition to color selection problems, cool roof product types in recent years has also been booming. Whether wall panels, tiles, asphalt, area with a coating, or a single-layer film, has a "cool" version to choose from to satisfy everyone''s aesthetic and energy needs.

For example:

* Reduce haze formation: the city because of the lower temperature reduces the photochemical reaction,

* Reduce greenhouse gas emissions: reduce air conditioning energy consumption is reduced because oil and coal power plant emissions

* To improve air quality and health standards: Because reduced haze and emissions,

* Reduce the urban heat island effect: Infrared reflection back into the atmosphere so that the urban core to keep cool.

Save Energy

The roof of cold heat of the sun reflected and radiated to the air, rather than below the heat to the building, thus cooling the surface of the roof can be obtained a lower temperature and reduce the heat conduction inside the building and reduce building cooling on a hot summer load. Lawrence Berkeley National Laboratory and the California Davis Energy Group, one study showed that cool roofs installed each building effectively reduce the peak temperature of the roof surface, and reduce the energy consumption of refrigeration equipment reached 52%. Using the measured data and the revision of the simulation program, the researchers estimated that in California all 16 climatic regions solar roof installation proceeds as follows: the average peak energy demand about 3.9 to 6.6 watts / square meter.

Many of the world''s climate zones, cool roofs can significantly reduce building cooling load energy consumption. China can benefit greatly from installing cool roofs. With the rapid development of the construction industry, in a hot climate zones will greatly increase the number of new building air conditioning demand, installing cool roofs will greatly reduce energy consumption, especially in southern China. There are some doubts whether the roof is cold in winter heating costs increase, in fact, even a slight increase in winter heating costs, which can increase the amount of summer cooling is offset by energy savings. Most northern climate zones in the cold winter, the sun is low in the sky, often cloudy and often snow-covered roof, so in the winter heat gain through the roof is usually negligible. As mentioned above, combined with the cold roof insulation measures to improve energy efficiency in buildings is the best way, and make the building in colder climates run better.

Reduce urban heat island effect

Using cool roofs in the city, the energy saving effect can more significantly reduce urban heat island effect, compared with the nearby suburbs, urban heat island effect will raise the temperature of 1-1.5 ℃ (2-10 degrees Fahrenheit) 3. Urban heat island effect is due to focus on building the city and makes the city an endothermic temperature much higher than the enclosed area of the phenomenon. As the ambient temperature increased with increasing peak energy demand, and thus adversely affect the community, air conditioning costs, air pollution level rise, increased haze, heat-related illness increases. Including Beijing, many Chinese cities have been plagued by high temperatures, by the urban heat island effect of the storm. Cool roof is reflected back through the solar atmosphere and help to reduce the negative impact of the heat island effect.

Lower roof repairs

Study the surface solar roofs can effectively extend the service life of the roof. Day after day, ultraviolet radiation, infrared (IR) radiation, heat flux can be lossy material. By reflex, cool roof system ultraviolet radiation, infrared (IR) radiation slowed the rate of aging, and that the roof kept in a more stable temperature range. Extend the life of the roof can help reduce the maintenance costs, and reduces the amount of waste generated.

Recycled and non-toxic materials

Another important aspect of green building is the use of recycled popular and / or non-toxic materials. Many manufacturers have in their product formulations integrated solar roofing additional environmental benefits. For example, in some synthetic materials, metal materials and recycled components used for production. Moreover, some of the product itself designed to be fully recyclable, and then at the end of life recycling. Use of recycled materials means less time resources, thus reducing energy consumption and reduce waste generated pressure.

What is a cold Roof Rating Council?

Cool Roof Rating Council (CRRC) was established in 1998, is an independent, nonprofit rated entity, which measures the radiation characteristics of the roof surface of the product. By CRRC, roofing product manufacturers and distributors of their products can be measured radiation characteristics of credit by an independent testing laboratory CRRC (AITL) measurements, and the product listed in the CRRC rating online catalog site at www . coolroofs.org.

In addition to open, fair, accurate and trustworthy manner rating the energy performance of roof surface outside, CRRC''s mission is to support the roof surface radiation characteristics of energy-related research, and is keen to understand and compare different roofing people choose to provide education and target information. CRRC radiation characteristics roofing products provide third-party certification, an individual looking for a suitable roof is an important tool.

As green building as building owners, legal entities, architects and manufacturers central issue, so it is necessary to carry out product "green" certification. Individuals seeking product ratings may include architects, regulations makers, owners, building legal entity, energy service providers and community planners. Owners may want to verify that the product meets the regulatory requirements, the architect may want to get the Energy Efficiency Design (LEED ®) credit scoring points, while utilities may need accurate information in order to achieve the rebate program.

CRRC consists of two separate and distinct group composition: Licensees and membership. CRRC Licensees are those producing, selling roofing products or product components company. Once an authorized supplier of product ratings, the product will appear in the catalog rating and is authorized providers can use the material in their products CRRC product identification. CRRC members interested in forming and guiding the organization''s constitution all groups. CRRC members can vote on matters relating to the organization, to join a committee, a board of directors election duties. Membership is completely separated CRRC Product Rating Program, and includes ratings manufacturers, suppliers, distributors and roofing contractors, consultants, architects, non-profit organizations, government agencies, educational institutions, air quality committee, legal entities, energy service companies and other interested parties. (Http://www.coolroofs.org/crrcmembers.html)

Product rating process is how to carry out the work?

CRRC''s Product Rating Program allows the manufacture of commercial roofing and aging initial value identifies the different radiation characteristics of the roof surface products, and these are listed in the catalog rating. (Http://www.coolroofs.org/products/search.php)

Independent testing and certification

CRRC cool roof roofing products tested, not the roof installation. Similarly, a small group of roofing material samples were fully tested. CRRC using ASTM Test Method E1918, C1549 and E903 for solar reflectance test, but also with C1549 revision CRRC-1 Test Method # 1 measurement. Using ASTM C1371 for thermal emissivity measurements. CRRC also for the regional application of the coating thickness of sample testing to ensure products tested in the manufacturer''s recommended range of applications.

CRRC''s Product Rating Program also conducted random testing procedures, a certain percentage each year ratings randomly selected products for testing. Random test samples of products are on the market product transport contractor distributor or obtained, or obtained from the production site. The purpose of random testing procedure is to verify that products marketed a true reflection of the value of their ratings.

Initial and aged Ratings

Once the initial tests carried out, product samples and sent to the United States three different climatic zones of the test field test (hot / humid, cold / warm, hot / drying). Samples of each place three years to go through the wind and rain. The idea is to simulate how the product is aging and performance over time variations, such as by soot, algae growth, as well as other natural climatic conditions. Three years later, the removal of samples from the test site, in the case of not cleaning retest radiation characteristic values. After testing, the aging of the value added to the online catalog, making the directory user can see a three-year cycle of the product''s performance status. Currently, CRRC testing field and testing laboratories in the United States only, but the product has been rated by the CRRC production and sales in every corner of the world.

Energy Star

In the CRRC, the United States is just another cool roof rating process is the U.S. Environmental Protection Agency''s ENERGY STAR ® reflective roof program, which is the CRRC program supplement. ENERGY STAR logo is widespread consumer awareness of energy efficiency mark. Manufacturers can choose to use their products ENERGY STAR ratings, as long as the product meets ENERGY STAR for initial and aged solar reflectance minimum technical requirements on the line (low slope roofs initial value must be SR ≥ 0.65, aging is SR ≥ 0.50; The initial value of the high slope roofs must be SR ≥ 0.25, aging is SR ≥ 0.15). If the data are consistent with CRRC rating criteria, the ENERGY STAR program can also accept the manufacturer''s data.

Green building projects and regulations

Several green building projects and regulatory approvals cool roofs and the numerous advantages of creating a more sustainable building strategic significance. Well-known project is the Energy Efficiency Design (LEED ®) project of the U.S. Green Building Council (USGBC) leadership roles. The well-known title 24 - the California Energy Commission''s building standards and regulations, is applied to the cold roof building regulations a typical case. Title

USGBC LEED

USGBC LEED rating system for several different types of building an unofficial certification process, and is nationally recognized high-performance green building design, construction and operation of benchmarks. LEED use of solar reflectivity factor (SRI) to define their cool roof requirements. Online calculators (including USGBC provided a) to calculate SRI, the use of solar reflectance and heat radiation rate SRI. LEED 2009 is the latest version of the rating process, the program will come into effect in August 2009. When 75% of the roof covering to meet or exceed minimum SRI (low inclination = 78, high-inclination = 29) required materials, LEED for new buildings of the old version includes a cool roof credibility. LEED credibility retains this new requirement, but if more than 75% of the roof are covered, the SRI request to allow more than lower. LEED 2009 includes a new reputation for different point distribution. For a given project, and is currently a total of 100 possible points (previous versions may have only 69 points). Cool Roofs reputation value a single point, and can be used for each LEED, including for the school''s LEED, for existing buildings LEED, for the core and shell LEED, for families LEED.

California Title 24

California Energy Commission (CEC) in 1978, is located in residential buildings and non-residential building energy efficiency standards established in response to lower energy consumption in a California statute. Building regulations and standards of the latest edition is called Title 24, will be held August 1, 2009 to take effect. Title 24 constructed in accordance with the type of construction purposes, product density gradient and roof painted roof requirements. Title 24 also specifies CRRC radiation characteristics as roofing materials regulated entities, thus requiring CRRC certified roofing products must be approved by the CRRC labeling, or assume the default rating of aging reflectivity and emissivity. California Title 24 exemplary exposition of how the solar roof can be used for building codes, as well as how to CRRC as a useful tool to ensure accurate, independent and comparable rating.

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Tilting type	Minimum 3 years of aging solar reflectance	Low thermal radiation rate	Minimum solar reflectance factor (SRI)
Low inclination	0.55	0.75	64
High inclination <5 lbs / ft	0.2	0.75	16
High inclination ≥ 5 lb / sq ft	0.15	0.75	10