Cool roofs provide protection from solar heat in warm climates or on hot 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 – high or low
- Other heat conducting factors i.e. inadequate or poor ventilation
- 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 improve the level of comfort in non-air-conditioned rooms like garages or attics that can be uncomfortably hot during the summertime.
Benefits Beyond the Home
There are additional benefits of cool roofs that go beyond the home. Solar gain can cause something called the “urban heat inland affect.” 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 inland effect.
Electrical grid failures are quite common during the summertime because of increased usage of AC in concentrated areas. If multiple homes in the same area had cool roofing, the strain on the grid would be much lower. The lower demand could also mean lower levels of local air pollution being released into the air – a good side-effect of cool roofing.
Cool roofing reduces heat by releasing the 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 minor existing leaks and cracks on certain roofing materials and it can make the roof appear newer.
Roofs with gentle slopes can also be covered with single-sheet membranes that have reflective. 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.
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, but if your home tends to rely heavily on AC, then a cool roofing system would be a good investment.
By Cris Hernandez, President, HRC Roofing