cool metal roofs Archives

Metal Roof Skylight Benefits

Posted on April 14, 2023May 2, 2023 by Randy Tweedt

The beauty of metal roof system skylights can be a real benefit to the aesthetic value of a metal building project. Beyond looks, though, the proven benefits of daylighting are many: building occupant satisfaction from natural lighting, mold, mildew growth prevention, and, of course, energy savings, to name a few. In fact, once the decision has been made to go with metal for the roofing material, a skylight is often a natural tie-in when it comes to sustainable design—for both form and function. To make the most of the design choice, there are a few key considerations to bear in mind during the specification and pre-installation phases of the process.

Types of Metal Roof System Skylights

Common metal roofing skylight installation involves one of two types of skylights, Light Transmitting Panels (LTPs) and Curb Mount Skylights. Both metal roof system skylights supply natural light into the building and provide similar benefits.

LTPs, which are formed from a translucent material and come in many different panel profiles can be used not only in metal roofs but as an accessory for metal wall panels, too. One of the key benefits of LTPs is that the panel is formed so that it matches the configuration and characteristics of the system into which it is installed, and therefore can work seamlessly with specific metal roof systems.

Curbed (curb mount) skylights include a raised structure (“curb”) formed around the roof opening where the skylight will be attached. Curb skylights come in many shapes and styles.

In addition to the general “type” of the skylight, another consideration is selecting the best orientation for the skylight—which we will look at next.

Skylight installation Metal Roof Placement, Orientation, and Climate Factor

Placement and orientation are some of the most crucial factors in getting the maximum benefit from metal roof system skylights. During the planning phase, determine the best location to achieve optimal light and avoid obstructions (such as HVAC, plumbing, electrical, and vent pipes) below the skylight. In terms of getting the most out of the skylight from an energy-savings standpoint, climate, and exposure are also key factors. For example, with southern exposure, skylights provide an excellent level of passive solar heat during the colder winter months, while keeping cooling costs down during the summer heat. On the other hand, a skylight with western exposure will increase cooling costs if the structure is in a warm climate.

Skylights and Light Transmitting Panels supply natural light into the building as shown above.

Installation Planning and Timing

Metal roof skylight installation can be installed during or after the roof has been installed, but it is in the best interest of the project to plan for a skylight from the initial stages of the design phase to best accommodate and prepare for the addition of the skylight.

Safety Concerns, Responsibility, and Compliance

Skylights and LTPs should be guarded to protect from fall through the metal railing, nets or some other protection method. Last but certainly not least, it must be stated that it is the user’s responsibility to ensure that the installation and use of all light transmitting panels comply with State, Federal and OSHA regulations and laws, including, but not limited to, guarding all light transmitting panels with screens, fixed standard railings, or other acceptable safety controls that prevent fall-through.

For additional information about skylights for metal roofs, please contact MBCI at (877) 713-6224.

Reducing Peak Demand Costs with Cool Metal Roofs

Posted on May 9, 2017 by Candy McNamee

Among the many benefits offered by cool roofs—including a decrease in urban heat island effect or increased roof system longevity—perhaps the most significant is a reduction in peak demand energy usage which directly affects building expenses.

Peak demand is the highest point in the day at which a building draws electrical consumption. A facility’s monthly utility rates are largely determined by the power usage level at this time, so anything that can be done to drive usage down will significantly reduce utility costs. As evidenced by their test values, cool roofs are an effective way to decrease air conditioning loads during peak demand times.

Cool roof values are expressed in terms of solar reflectance and thermal emissivity. The combination of these values is used to determine how hot a surface will become by its ability to reflect solar energy and radiate heat away from itself. Cool roofsare capable of reflecting solar heat away from a building by more than 70 percent. In fact, the U.S. Environmental Protection Agency estimates that ENERGY STAR® qualified roofing products can lower roof surface temperatures by up to 50°F.

According to Jeff Steuben, executive director, and Carolyn Richter, communications manager, Cool Roof Rating Council (CRRC), in a recent Florida Roofing article, “Building occupants can experience improved comfort as compared to a conventional dark roof, as the building’s interior is subject to less thermal flux and stays cooler during warm seasons,” and, “Reduced indoor temperatures lead to energy savings from reduced cooling energy loads.”

Along these lines, contractors can also access a CRRC-provided listing of cool roof rebates, codes and voluntary cool roof programs at: www.coolroofs.org/resources/rebates-and-codes.

Cool Roofing Longevity

In addition to energy efficiency, cool metal roofs are known for extended durability and longevity, with most products offering a 40-year finish warranty.

In fact, a well-noted extensive study, Natural Exposure Testing in California, conducted by the Oak Ridge National Laboratory, found that pre-painted metal roofing maintained higher levels of reflectance, over a three-year period, due to its ability to shed particulate matter, as compared to conventional roofing materials. Further, pre-painted metal roofing has been found to retain 95 percent of its initial solar reflectance over this same three-year period.
Increasing performance and energy savings, solar reflective pigments in cool metal roofs offer higher total solar reflectance and thermal emittance, even in darker colors. With cool roof technology, the ability for the roof to store heat and radiate that heat into the building after sundown is dramatically reduced.

Heitmann Residence featuring a Cool Metal Roof

Cool metal roofs are proven to deliver environmental and performance benefits, of which the most significant to building owners is their contribution to the bottom line. Although savings will vary based upon geography, materials and insulation, the U.S. Environmental Protection Agency estimates that reflective roofs can save up to 40 percent of a building’s cooling energy costs.

When utilizing the U.S. Department of Energy’s Cool Roof Peak Calculator, contractors will discover that the total value of energy savings offered by a cool roof averages more than $1,000 annually in most climate zones for a typical commercial building. Furthermore, this applies to both cool roofing installed over both existing roof insulation and new insulation.

Proven Strategy

As established by documented study and significant heat build-up reduction levels, cool roofs are a proven strategy for supporting longer lasting roofs, reducing both utility costs and decreasing a building’s environmental footprint as Steuben and Richter conclude, “cool roofs are one of the most effective ways to obtain energy savings and environmental rewards through building envelope design and re-roofing projects.”

Urban Heat Island, Part 2: How Cool Metal Roofs Benefit Building Owners

Posted on August 22, 2016 by Candy McNamee

In our prior blog post, Urban Heat Islands, Part 1: How Cool Metal Roofs Benefit the Community, we identified the existence of urban heat islands and their contribution to higher air temperatures that are found in urban areas compared to surrounding locations. We also identified a high Solar Reflectance Index (SRI), on a scale of 0-100, as the means to specify materials that can help reduce urban heat islands and benefit entire communities. In this post, let’s focus on the specific benefits to the building owner when cool metal roofs are used.

The Boundy Residence features a cool metal roof

Energy Savings for Cool Metal Roofs

In many commercial and industrial buildings, energy use is one of the largest ongoing operating expenses, meaning that building owners and operators are usually quite interested in lowering or controlling that expense. Cool metal roofs with a high SRI rating can help with that quest. For instance, since air conditioning is commonly a larger cost that heating for many such buildings, it is a natural place to target. Lowering the temperatures at the roof means there is less heat surrounding the building, reducing air conditioning load and directly impacting energy costs.

Comfort in Outdoor Areas

Some building types, such as restaurants, retail, and entertainment facilities, rely on outdoor seating or gathering areas to support their business. If urban heat islands make these spaces uncomfortable to spend time in, the business usually suffers too. Providing these buildings with high-SRI metal roofing can improve the situation.

Long-Term Durability

Building materials can degrade prematurely if they routinely exposed to high heat. The heat can cause them to dry out, become brittle, or simply decompose faster than expected. Using high-SRI roofing is not only good for the longevity of the roofing, it can be good for the durability of the materials directly under the roof as well. Roof sheathing and other substrate materials directly in contact with the roofing receive the same intense solar radiation that the roofing surface does.

Attic spaces below the roofing plane also receive the heat, making attic temperatures in excess of 130 degrees common, causing degradation of materials in those spaces, including mechanical and electrical equipment. That could mean more expansion and contraction of connections and joints or it could mean that air conditioning duct work is being heated, contrary to the efficient operation of the system. In any of these cases, a cool metal roof will help alleviate the negative impacts of solar heat and allow materials to achieve full life expectancy.

Supports LEED Certification

In the Sustainable Sites category of the LEED rating system, Heat Island Reduction can be selected as a credit to receive either one or two points toward certification. This credit relies on both roof and non-roof strategies and looks for calculations of solar reflectance (SR) and demonstrated Solar Reflectance Index (SRI) levels on specified products.

Favorable Payback

All of these benefits above can translate to financial benefits to the building owner or operator. Any cost premium incurred for selecting a high-SRI cool metal roof can likely be realized very quickly in energy cost savings, increased business, or maintenance and durability savings. In addition, the benefits of human comfort and achievement of LEED or other sustainability goals can be realized for the life of the building.

Urban Heat Islands, Part 1: How Cool Metal Roofs Benefit the Community

Posted on August 4, 2016 by Candy McNamee

Summer in the city usually means it’s hot – hotter than surrounding areas. Those who have investigated this phenomenon have identified the presence of “urban heat islands” – places that heat up disproportionately to those nearby.

One reason for this is the predominance of dark asphalt pavement and dark-colored roofing. The significance is that dark surfaces are known to absorb sunlight and re-radiate it back as heat. That’s how thermal solar panels work, but it is also dramatically apparent when walking across a black asphalt parking lot in the summer sun. The heat is coming not only from the sun above, but from the pavement below.

If nearby buildings have dark-colored roofs, the same is happening there. Studies have shown that this re-radiated heat can build up in urban areas and raise the surrounding air temperature by up to 5 degrees Fahrenheit on average. So while it might be a tolerable 85 degrees and pleasant a few miles away, the urban core could be sweltering in a self-induced 90 degrees – even higher on those dark roofs and parking lots.

Measuring Solar Heat

How do we know what materials help or hinder these urban heat islands? First, all materials will absorb and reflect varying amounts of solar radiation based primarily on the color and reflectance of a material. The way to measure that variation is based on ASTM test standards E903 and C1549. These tests are used to determine the solar reflectance (SR) of materials, which is expressed as the fraction of solar energy that is reflected on a scale of 0 to 1. Black paint, for example, has an SR of 0 and bright white titanium paint has an SR of 1 (highest reflectance).

Reducing Heat Islands with Cool Metal Roofs

Taking things one step further, the Solar Reflectance Index (SRI) has been developed as a measure of the ability of a constructed surface, particularly roofs, to stay cool in the sun. It relies on both an initial SR value as well as a thermal emittance value being determined for a material or product. Using ASTM E1980 and values from the Cool Roof Rating Council Standard (CRRC-1), an SRI of between 0 (common black surface) and 100 (common white reflective surface) can be determined. The higher the SRI, the higher the amount of solar radiation that is reflected and thermal radiation minimized, thus creating a comparatively cool surface.

Metal roofing is particularly well suited to achieve high SRI values, minimize heat build-up, and reduce urban heat islands. Recognizing this, many manufacturers test metal roofing products and publish the SRI results, allowing professionals and consumers to make informed decisions. Of course, other roofing materials are tested for SRI values too, but few test as effectively and economically as metal roofing.

(For specific information about the radiative properties of MBCI’s colors, consult our listings in the respective databases on the CRRC and ENERGY STAR websites.)

Benefits to the Community

Specifying and building with high-SRI metal roofs has benefits beyond just the immediate building—reducing urban heat islands keeps excess heat from building up in the surrounding community too. Higher summer temperatures can be detrimental to plants, trees, and people who are outside in urban areas. By using cool metal roofs that reduce the surrounding air temperature, plants don’t lose water as quickly, people are more comfortable, and trees are less stressed. Cooler air temperatures around a building also means air conditioning does not need to work as hard or as often. That translates into less energy use and fewer greenhouse gas emissions from electricity to run the air conditioning—both of which could significantly contribute to cleaner air in the community.

Results

By recognizing the existence of urban heat islands and their impact on people and the environment, those of us in the design and construction field can choose to do something about them. By specifying and installing high-SRI cool metal roofs, the environment benefits, people benefit and our buildings benefit.

Tag: cool metal roofs

Metal Roof Skylight Benefits

Types of Metal Roof System Skylights