what are cool roofs
Energy Efficiency | June 22, 2018

What Are Cool Roofs?

If you have a small business, the wrong type of roofing can make the summer incredibly hot, forcing your HVAC system to work overtime and leaving your employees—and customers—overheated and uncomfortable. Cool roofs help combat rising temperatures in hot climates, offering small businesses opportunities to save on air-conditioning costs while providing a cool work environment.

So, What Are Cool Roofs?

Cool roofs are designed to reflect sunlight while absorbing less heat. Compared to traditional roofs, a reflective roof has a high albedo, or solar reflectance. A higher albedo means that a roof has a higher ability to reflect the sun’s rays, and thus reflects more sunlight than traditional roofs. Cool roofing systems also have high thermal emittance, which is the ability to radiate absorbed heat back into the air and away from your business.

Cool roofs reflect sunlight in order to absorb less heat and keep the inside of a building cool

What advantages do cool roofs bring to small businesses?

The primary advantage of a cool roofing system is that business owners can expect to use less energy to cool their small businesses. In hot climates, traditional roofs in the contiguous United States can reach temperatures of 150 to 185 degrees Fahrenheit. A cool reflective roof stays 50 to 60 degrees cooler when exposed to the same summer heat.

Generally speaking, the cost of installing cool roofing during construction is comparable to traditional roofing, as this energy-saving calculator demonstrates, so small business owners may save on energy costs in long-run by installing a cool roof.

Types of Cool Roofs

Small business owners have a wide selection of cool roofs to choose from, and the type of cool roof you install largely depends on the size and structure of your building, and the slope of your roof. In addition to energy-saving white reflective roofs, other cool roof solutions that small business owners can choose from include roof coatings, single-ply membranes and cool roof shingles.

Painting white roofs vs. black roofs

Traditional roofing is typically dark colored or black—colors that absorb heat faster than brighter colors. However, there are energy-saving benefits to painting your roof white–this increases your roof’s albedo causing more heat reflection, which keeps your small business cooler.

And if you think simply opting for a happy medium—such as gray, for instance—is the answer, consider that it’s not all about white roofs vs. black roofs. For instance, when you compare a white reflective roof with a gray roof, the white roof reflects 80 percent of incoming sunlight compared to the gray roof, which reflects only 20 percent.

The difference means the white roof will stay approximately 55 degrees Fahrenheit cooler than its gray counterpart. Ultimately, painting a roof white to save energy is a great idea, because it’s one of the simplest ways to increase its solar reflectance and thermal emittance properties.

While dark roofs reflect 20 percent of incoming sunlight, light roofs reflect 80 percent.

Flat or low-sloped cool roofs

While a flat roof has no gradation, a low-sloped roof is generally defined as a roof that rises at an angle of less than 18.5 degrees. If you have a small business, it is likely that you have a flat or low-sloped roof. To find out the slope of your roof, you can call a professional for accurate estimates and measurements.

Cool roof solutions for flat or low-sloped roofs often come in a variety of materials to reflect thermal heat, and provide flexible solutions for you and your small business.

Cool roof coatings

While there are benefits to painting your roof white to save energy, applying a roof coating provides even better results. These coatings, which resemble thick paint, protect the roof from ultraviolet damage while increasing reflectivity. Some also provide water protection. Cool coatings are the easiest cool roofing solutions available for low-slope roofs.

Single-ply membranes for cool roofs

Single-ply membranes are prefabricated sheets rolled into place on the roof and attached by mechanical means or chemical adhesives. Generally a more expensive cooling solution than coatings, single-ply membranes are sturdier and provide additional protection to the underlying roof. Single-ply membranes come in two categories:

  • Single-ply thermoset membranes are sealed together with tape or contact cement.
  • Single-ply thermoplastics form a seamless surface after the installer applies heat to the membrane’s edges.

Flat or low-sloped cool roofs can also be used with green roofing systems to help save even more energy. That’s why Constellation’s headquarters uses a flat cool roof, in combination with green roofing, to create an energy-efficient solution that decreases both energy use and greenhouse gas emissions.

Cool Roof at Exelon Headquarters Building

Constellation’s cool roofing system has even helped the building earn an overall LEED Gold designation, and the interior was awarded LEED Platinum status. The US Green Building Council awards LEED (Leadership in Energy and Environmental Design) certification to healthy, cost-efficient, sustainable buildings based on a strict set of criteria.

Exelon building with cool roof

High-sloped cool roofs

Unlike low-sloped cool roofs, high-sloped roofs generally have a gradation steeper than 18.5 degrees. Because of their slope, it can be difficult to apply most cool reflective roofs to their surfaces.

A professional will be able to determine the slope of your roof, and what cool roofing system will work best. Reflective coatings, for instance, are difficult to apply evenly. Some single-ply membranes may be installed on high-sloped roofs, but the most effective solutions for high-sloped roofs are cool roof shingles and tiles.

Cool roof shingles and tiles

Cool roof shingles, tiles and slate may be coated with special granules to give them better solar reflectance. The heavy mass of cool roof shingles and tiles can also provide some degree of thermal protection by absorbing and blocking heat during the day, and releasing heat throughout the night.

Reflective metal roofing may also cool high-slope roofs. For more information, check out Constellation’s post about energy-efficient roof shingles, tiles and metal roofing.

Cool Roofs: Pros and Cons

Cool roofs are excellent for keeping small businesses cool during peak summer months or year round in hot climates, but you may be wondering about possible disadvantages. Let’s examine the pros and cons of cool roofs.

Benefits of cool roofs

Cool roofs have many benefits, from lowering indoor temperatures and improving air quality to reducing cooling costs and greenhouse gas emissions.

The benefits of cool roofs include:

  • decreased indoor temperatures by reflecting sunlight and radiating heat outward, providing cooler indoor environments for non-air-conditioned spaces;
  • lowered cooling costs by allowing air-conditioners not to work as hard, reducing electrical costs and potentially increasing the life cycle of cooling equipment;
  • reduced greenhouse gas emissions by ensuring your business’s cooling systems consume less energy, your small business will help decrease carbon emissions;
  • improved air quality by reducing the formation of ground-level ozone as a result of lower urban air temperatures, which in turn reduces smog; and
  • extended roof life—reflecting ultraviolet rays lowers roof temperatures, thus decreasing roof weathering and potentially increasing your roof’s life span.

Disadvantages of cool roofs

Many disadvantages of cool roofs can be offset by your choice of cool roofing system, or by adapting other aspects of your building’s heating/cooling system, but it’s worthwhile to be aware of the possible cons.

The disadvantages of cool roofs include potential:

  • retrofitting costs, as converting an existing roof can become expensive—especially when you include repair work, recoating and cleaning costs;
  • algae or mold growth, which can occur when a cool roof is installed in warm, humid locations (even though chemical treatments can reduce such growth);
  • condensation in hot, humid climates, which in turn can cause water damage;
  • glare, as the lighter colors associated with cool roofing materials and coatings can disturb occupants of taller neighboring buildings; and
  • increased winter heating, as the same reflective and thermal emittance features that make cool roofs so good at controlling temperatures in the summer can lead to increased heating needs in the winter (for this reason, cool roofing is not well suited to cold climates).

 

3 Ways to Work with Your Cool Reflective Roof

Cooling your roof is only one way to improve your small business’s energy efficiency! You can try these other strategies to help you save on your energy use:

  1. Landscape shading: Careful location of shade landscaping will help keep your small business cool in the summer months.
  2. Weather-stripping: choosing the right types of weather-stripping for your small business will help prevent air leaks and drafts, preventing conditioned air from escaping outside.
  3. Insulating walls and attics: insulating walls helps maintain a consistent temperature in your workplace, and understanding your attic insulation R-value helps prevent the loss of conditioned air.

As a final note, keep in mind that making changes to your roof or taking steps to reduce your small business’s energy expenditures may qualify you for small business energy tax credits. These incentives allow you to recoup a portion of the expense associated with transitioning to an energy-efficient workplace.

Painting the roof white, or implementing any type of cool roof, is only one step small businesses can make to conserve energy, reduce their carbon footprint and provide a more comfortable workplace for employees and clients alike.

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