7 Advantages & Disadvantages of Cool Roofs

By Ygrene on June 2, 2017

Cool roofs provide protection from solar heat gain in warm climates or on sizzling summer days. This innovative roofing is designed to reflect the sunlight from a building rather than absorb the heat and allow it to permeate the structure below. In the past, homeowners relied on white roofing for reflecting the sun’s rays.

While lighter colors are much better for reflection, new technology and modern design allow for more richly-colored roofing materials with the same reflective properties. This means that homeowners can now enjoy the benefits of cool roofs without having to sacrifice aesthetics.

Certain reflective shingles or tiles can provide these cooling properties, as can paint-like thermal coatings and sheet-like coverings. The best type of material for your rooftop depends on:

  • The degree of reflectivity desired
  • Other heat conducting factors
  • Overall project budget

Below are some tips to help you take advantage of cool roofs.

A Closer look at the Benefits of Cool Roofing

How much cooler is a cool roof? According to the Department of Energy, the surface of standard roofs (those without any special reflecting or heat conducting features) can surpass 150 degrees Fahrenheit in the summertime. The average cool roof’s surface can be as much as 50 degrees lower. A lower surface temperature means less heat is passing through the roof into the home, which translates into lower air conditioning costs.

Cool roofs can also vastly improve the level of comfort in non-air-conditioned rooms like garages or furnished attics – both known for being uncomfortably hot during the summertime. Furthermore, since the roof itself is not reaching such extreme daily temperatures, it may last longer and require less maintenance during its lifespan.

Benefits Beyond the Home

The benefits of these roofs go beyond the home itself. Solar gain can cause something called the “urban heat island effect.” If all the houses in a city or suburban area are absorbing 150-degree temperatures, they can cause the local ambient temperature to rise. Since cool roofing reflects the sunlight and heat back upwards, it can lessen the heat island effect.

Additionally, electrical grid failures are quite common during the summertime when everyone in a concentrated area is operating air conditioners simultaneously. If homes in the specified area had cool roofing, the grid strain would be much lower. Depending on how the electricity is produced, the lower demand could also mean lower levels of local air pollution – an appealing side-effect of cool roofing.

What Principles are at Work in Cool Roofing?

Cool roofing reduces heat in two different ways. Its most important quality is “solar reflectance,” meaning sunlight is reflected instead of being converted into heat. This leads to the other important principle, “thermal emittance,” which takes place when the roof releases heat from the sun back into the air rather than absorbing it. Therefore, not only is cool roofing characterized by reflecting the light, but it also pushes heat away from the house.

Options for Cool Roofing

One option for cool roofing is to add a light color of paint-like coating. Applied with a roller, brush, or paint sprayer, this thermal coating creates a reflective layer above the roof. It can provide additional benefits as well, such as covering existing leaks and cracks and making the roof appear newer without installing a new structure.

Roofs with gentle slopes can also be covered with single-sheet membranes that have reflective and emittance properties. Tile roofs, which are often used in tropical climates, can be glazed so that they do a better job of reflecting sunlight rather than absorbing it.

For homes that need a total roof replacement, new reflective shingles are the best option. Typically, the roof toppers are made from chipped marble or gray slag, which are spread into an asphalt base. These shingles can reflect solar energy much better than traditional models. Other reflective shingles use other types of specially-coated granules to provide similar benefits; some of these granule compounds can repel solar energy even when the shingles are darker colors.

What about metal roofs? Metal roofs are good at reflecting sunlight, but they do not have the other necessary quality of cool roofing: thermal emittance. The solar energy that is not reflected passes easily into the structure, causing it to become hotter. A layer of thermal coating on the top of a metal roof can increase both reflectivity and, more importantly, thermal emittance.

How Much Can I Save?

Savings vary depending on things like location and available natural shade. However, studies suggest that cool roofs can lead to a 40 percent reduction in cooling costs compared to standard “dark” roofing. These savings mean that a new roof or coating could pay for itself in six years or less.

How much does cool roofing cost? According to the EPA, reflective shingles may be the same price as premium standard shingles and between $0.10 and $0.20 more per square foot than regular mid-priced shingles. The paint-on, reflective thermal coatings cost about $0.75 to $1.50 per square foot, while cool roof membrane coverings range between $1.50 and $3.00 per square foot. The EPA also cited a study in California that estimated cool roofing saved an average of $0.50 per square foot per year. With these savings, even the most expensive cool roof membrane option will pay for itself in six years.

Drawbacks to Consider

The ability to absorb solar energy can be a positive trait in certain situations. In colder climates, solar gain can sometimes reduce heating costs during the winter. However, in more northerly climates where this could be the case, daylight hours are limited during the winter – and the roof may be covered with snow, which will block the sunlight anyway.

In cooler climates, it is a good idea to weigh the potential savings on cooling costs before installing a cool roof or applying a membrane or coating. If your home does not rely on air conditioning much during the summer, a cool roof might not be a good investment, especially since it could raise heating costs during the winter.

How to Pay For Your Cool Roof

Cool roofing may qualify for a property assessed clean energy (PACE) financing program. These programs are specially designed for homeowners who want to make improvements that will lead to energy savings. PACE programs allow homeowners to start the project without any upfront costs, so they can begin enjoying the energy savings without delay.

Because PACE is a special tax, homeowners then repay the amount financed over time as part of their annual property tax bill. Any money saved on cooling costs can then be put towards paying off the improvement over time.

Find out if PACE is available in your area – contact Ygrene at (855) 901-3999 or check your eligibility online.