What’s A Cool Roof

Common Measurements Of Cool Roofing: Solar Reflectance Emissivity & Sri

When designing a property with a more eco-friendly, cool metal roof or wall system, several measurement terms come up, including:

• Solar reflectance
• Emissivity
• Solar Reflectance Index

In the early to mid-2000s, legislation and regulations were established to reinforce sustainability and combat increasing problematic energy consumption. Thats how the three terms listed above came into prominence, as these measurements are how cool roofing is determined.

Lets dive deeper into the meaning of each.

What Is Reflective Pigment Technology

Reflective pigment technology is an energy-efficient roof coating that enables roofs to reflect heat in the summer, while providing superior insulation in the winter. This protection from UV rays can also help extend the lifespan of a roofespecially in areas that experience long, intense sun exposure.

Reflective technology is a key feature of most types of energy-efficient roofing. These pigments are primarily found in metal roofs, but can also be used in tiles and be implemented in asphalt shingles.

An alternative to reflective pigments are radiant heat barriers. These barriers are made by lining the inside of the attic with a highly reflective material, such as aluminum. This material will reflect heat absorbed from roof tiles, rather than allowing it to absorb into your homes ceiling or walls. Your roofing contractor should be well-versed in cool roofing materials and technologies, so be sure to discuss your energy efficiency goals ahead of installation.

What Is The Cool Roof Rating Council

The Cool Roof Rating Council was created in 1998 to develop accurate and credible methods for evaluating and labeling energy benefits associated with roofing products. It is the sole entity the California Energy Commission recognizes for certifying the solar reflectance and thermal emittance values of roofing products. If a product is approved by the CRRC, it is recognized as Title 24 compliant in the state of California. Only products listed within the CRRCs Rated Products Directory may be used to meet cool roof requirements.

CeDUR now offers Golden Cedar, a Title 24 compliant Cool Roof Rated product. Golden Cedar features the same product composition as our other product colors , passes the same high performance testing standards, but also offers a variety of energy benefits for your home. Golden Cedar has been Approved by the Cool Roof Rating Council and is Title 24 compliant by the California Energy Commission.

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What Is A Cool Roof For Residential Areas

The term cool roof refers to a roofing product with high solar reflectance and thermal emittance properties. Solar reflectance refers to a roofing materials ability to reflect the suns solar energy back into the atmosphere. Thermal emittance provides a means of quantifying how much of the absorbed heat is rejected for a given material.

Cool roofs are a somewhat unique kind of roof that is specially designed to reflect more sunlight, and therefore absorb less heat than the standard roof. Cool Roof materials were originally created for California residents as a method to decrease heat in populated areas. If white roofs or cool roofs are used instead of asphalt shingles and dark colored roofs it can reduce the temperature of a community as a whole.

Although it is greatly beneficial to populated areas, Cool Roofs are beneficial to virtually any type of building or urban environment where the urban heat island effect can come into play. However, although a residential cool roof offers many benefits, it is essential to consider various factors such as your areas climate, before choosing to install a cool roof. Areas of cooler temperatures, for example, would not benefit from a cool roof as warmer temperature-areas would.

Understanding Cool Roof Technologies

With all the focus on green building these days, the market is heating up with interest in cool roof technology. A cool roof is a roof that reflects more sunlight and absorbs less heat than a standard roof, lowering roof temperature and releasing less heat into the environment.

What Constitutes a Cool Roof?

Cool roof requirements vary by region but generally are based on solar reflectance and thermal emittance values which, collectively, create the metric for the solar reflectance index . Most regional requirements will have minimum values listed.

Many regional and green rating councils utilize three-year aging values for the previously mentioned parameters, but others will accept initial values if three-year aged data is not available. It is important to verify local cool roof requirements before selecting the best roofing system.

Solar Reflective Index

Solar reflective index is a calculation based on solar reflectance and thermal emittance in conjunction with ambient air temperature, sky temperature and wind factors.

Most SRI calculators utilize standard solar and ambient conditions as defined per ASTM E 1980. The solar reflective index is reported as a value from 0 to 130 ranging from least reflective at 0 to most reflective at 130.

Cool Roof Technologies Are Not the Same

Does Color Matter?

Yes, just like light-colored clothes are more comfortable to wear in hotter climates, a light-colored roof performs better than a black roof at cooling the building.

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Effect Of S On The Monthly Energy Loads

The hourly heat fluxes on the indoor surface were used to determine the monthly cooling and heating loads for wide ranges of ins, and s . As examples of roofing systems with different values of s and having ins of 2 , 4 , 6 , and 8 , Figures 5AD, respectively, show the monthly cooling loads and the monthly heating loads . In cold climates, the energy sources needed for heating the residential buildings are frequently fossil fuels while those needed for the cooling loads are electrical energy. Because of the difference in prices per thermal unit due to using fossil fuels and the electrical energy, the heating load and the cooling load must be specified individually . In hot climates such as that in Saudi Arabia, however, the energy sources for both heating and cooling loads are mainly electrical energy. So, the total load can be obtained as the sum of the heating load and cooling load for roofs having different values of ins.

Figure 5. Monthly energy loads for a wide range of s of roofing systems having insulation thickness of: 2.0, 4, 6.0, and 8.

Figure 6. Monthly total energy loads for a wide range of s of roofing systems having insulation thickness of: 2.0, 4, 6.0, and 8.

Is White The Only Color

When most people think about a cool roof, they often picture a white-colored one. However, today, we have cool roofs that resemble standard products even though they are more reflective in the infrared spectrum.

This means you do not have to sacrifice aesthetics to enjoy the benefits of a cool roof.

Such roofs utilize pigments that reflect solar radiation better. Here, you can have darker, richer hues such as brown and forest green. You can also find reflective coatings on metal, shingles, and tiles.

Another alternative to white-colored options is installing a green roof. This means placing plants on top of the roof. However, white roofs are often a more cost-effective option. Still, a green roof can offer other benefits other than saving energy like stormwater management. They also have a unique aesthetic appeal.

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What Purpose Does A Cool Roof Serve

Cool roofs serve environmental and financial purposes for invested parties. Commercial managers who invest in cool roof systems can reduce their carbon footprints. At the same time, these parties can cut their monthly expenses while keeping all visitors to their property comfortable.

But above all else, cool roof systems are highly beneficial to surrounding urban areas. This is because dense urban areas fall victim to what is known as the heat island effect. When a concentrated space becomes cluttered with heat-retaining materials and human waste, it rises in temperature. Thats why urban areas like New York City, Chicago, Houston, and other hubs can be notably warmer than their more suburban sisters.

This kind of heat produces a significant amount of CO2, which contributes to climate change worldwide. To reduce a citys carbon footprint, individual commercial building managers can reduce the amount of heat their infrastructure releases. Ergo, cool roofs have the potential to benefit not only individuals but entire cities.

Effect Of Ins On The Energy Performance Of Black Roofs

For black roofing systems of different values of ins, the results of the yearly cooling and total loads are provided in Figure 8. Because the yearly heading load for the case of a black roofing system is much lower than the yearly cooling load, the yearly total load is a little higher than the yearly cooling energy load . For small values of ins , Figure 8 shows that the yearly energy loads and the associated reduction rates in these energy loads significantly decrease with increasing ins. For example, the reduction rates in the yearly energy loads |dYCLB/d ins| and |dYTLB/d ins| were, respectively, 151, 72, and 30 /mm for ins of 0.5 , 1 , and 2 . However, for large values of ins , the yearly energy loads and the associated reduction rates in these energy loads slightly decrease with increasing ins. For example, for ins of 4 , 6 , and 8 , the values of |dYCLB/d ins| and |dYTLB/d ins| were, respectively, only 11, 6, and 4 /mm.

Figure 8. Effect of ins on: the yearly cooling load and reduction in this load, and the yearly total load and reduction in this load with respect to ins for black roofing systems.

For black roofing systems of different values of ins, the yearly cooling energy loads and the yearly total loads that are provided in Figures 8A,B, respectively, can be given as functions of in as:

Table 1. List of the coefficients a0 through a5 for the correlations given by Equations .

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Cool Roof Rating Council

Cool Roof Rating Council has created a rating system for measuring and reporting the solar reflectance and thermal emittance of roofing products. This system has been put into an online directory of more than 850 roofing products and is available for energy service providers, building code bodies, architects and specifiers, property owners and community planners. CRRC conducts random testing each year to ensure the credibility of its rating directory.

CRRC’s rating program allows manufacturers and sellers to appropriately label their roofing products according to specific CRRC measured properties. The program does not, however, specify minimum requirements for solar reflectance or thermal emittance.

Should I Install A Cool Roof

If youre aiming for increased energy efficiency and sustainability, you should absolutely consider installing a cool roofing system. Bridger Steel offers metal roofing and metal siding panels in approved cool roof colors. Theyre created with highly reflective paint to help the metal panels absorb less heat by reflecting sunlight. Our materials are also 100% recyclable, perfect for solar panels, and ideal for rainwater collection systems.

Bridger Steel is proud to offer products that have earned and received the governments ENERGY STAR label. This label represents products that help businesses and homeowners save money and protect our climate by utilizing superior energy efficient products.

If youre interested in learning more about cool roof systems and how you can take a step towards being more eco-friendly, talk to a Product Specialist today. Our team of experts will work directly with you to help you choose the right panel profile, gauge, and color/finish needed to make your project a success.

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Thermal Emittance Ability To Cool Down By Emitting Heat That Is Absorbed

Installing A Cool Roof

Depending on the shape and slope of your propertys roof, it may be more suitable to opt for alternative methods of cool roofing. For example, low and steep sloped roofs are more suited to a metal sheeting installation, available in various finishes of different levels of reflectivity. Regardless, always take the time to consider your propertys climate and environment, how well insulated your roof is, and the efficiency of your interior temperature control systems.

Cool roofs are great for the environment, your wallet, your comfort, and the overall well being of your property. At Roofmaster, we can provide exceptional service quality and the assistance of our team of dedicated and knowledgeable professionals. If youre interested in switching over to a cool roof, contact us for a free estimate and to book our services.

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Across The Us Federal Government

In July 2010, the United States Department of Energy announced a series of initiatives to more broadly implement cool roof technologies on DOE facilities and buildings across the country. As part of the new efforts, DOE will install a cool roof, whenever cost-effective over the lifetime of the roof, during construction of a new roof or the replacement of an old one at a DOE facility.

In October 2013, the United States Department of Energy ranked Cool Roofs as a 53 out of 100 for a cost-effective energy strategy. “Climate issues can affect cool roof performance. Cool roofs are more beneficial in warmer climates and may cause energy consumption for heating applications to rise in colder climates. Cool roofs have a lower impact the more insulation is used. The Secretary of Energy directed all U.S. Department of Energy offices to install cool roofs, when life-cycle cost-effectiveness is demonstrated, when constructing new roofs, or when replacing old roofs at DOE facilities. Other Federal agencies were also encouraged to do the same.”

How Does Energy Efficient Roofing Help To Decrease Energy Bills

Heating and cooling typically account for about half of a homes total energy consumption costs. That said, installing an energy-efficient roof can make immediate impacts on your utility cost and produce a great return on investment. In fact, they can lower your utility bills by as much as 25%thats $300 to $500 annually for the average home.

Homeowners can also benefit from credits and rebates offered for installing energy-efficient roofing. These can be available at the federal, state, or municipal level.

Beyond the immediate utility cost savings, a new energy-efficient roof can pay for itself in as little as 5 to 10 years (depending on the material and home size. This can help you make the most of your investment. They can also increase your property and resale value.

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Choose Feldco For Your Roof Replacement

As one of the biggest investments youll make in your home, roof replacement needs to be completed with quality materials, extreme care, and a deep attention to detail. At Feldco, weve got you covered. We make your roofing project as simple as possible by listening to your needs and providing you with the best options to bring your new roof to life. With a wide variety of roofing options, styles, and colors, youll be able to create a look for your home that provides both comfort and great curb appeal.

Brief Descriptions Of The Hygrothermal Model

The previously developed hygrothermal numerical model was used in this study to conduct numerical simulations in order to assess the energy and moisture performance of the roofing system shown in Figure 2 for wide ranges of insulation thickness and short-wave solar absorption coefficient of the rooftop. In the various material layers of different building components, this model solves simultaneously the time dependent 2D and 3D moisture transport equation, energy equation, surface-to-surface radiation equation , and air transport equation. The air transport equation is the Navier-Stokes equation for the airspace layers , and the Darcy equation and Brinkman equation for the porous material layers. With and without moisture transport, the model was extensively benchmarked against experimental results from the evaluation of a number of different building component assemblies . Saber et al. provided a summary of model validations against experimental data.

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On Costs And Energy Efficiency

Cool roofs dont always cost more than non-cool roofs if you are installing a new roof. And converting standard roofs in good shape to a cool roof can be costly.

However, a cool roof doesnt always cost more than a non-cool roof. Especially if you are installing a new roof or replacing an existing one.

Converting a standard roof thats in good condition into a cool roof can be expensive. Thats because roof costs typically cover materials and labor, maintenance, including cleaning, repair and recoating.

Cool roofs cut costs with energy savings, rebates, HVAC equipment and they extend the life of your roof.

How Do Cool Roofs Work

Cool roofs repel a significant percentage of the suns heat. The combination of light colors and a unique molecular make-up helps these roofs bounce UV rays back out into the wider world, reducing the amount of warmth that the roof and building retain.

Some of the most common cool roofing materials include:

• EPDM roofing membranes

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