A cool roof is an environmentally conscious option for roofing that reflects sunlight and thus, in theory, keeps the building cooler. Just as our skin feels cooler in the sun when we wear clothing that reflects its light, a cool roof is also an excellent reflector. This article will define what cool roofing is and whether cool roof shingles are effective or not. Also, we will discuss the advantages and disadvantages of this type of roof. Last but not least, you will find considerations of what to look for when you are ready to purchase and install it.
What Is a Cool Roof?
A cool roof consists of two major characteristics that rate how effective the roof will be at reflecting sunlight. The scale to rate this is from a 0 to 1. One can determine the rating by the cool roof rating council. Moreover, you can evaluate it post-construction and three years after the roof’s installation.
The reason this roof works is that it has a reflective white or colored metal on its top layer. If it is effective, it should reduce heating and cooling costs by increasing reflection and ventilation. People concerned about the environment and greenhouse gasses find these roofs appealing. This happens because they immediately reflect solar energy before absorption of the energy can take place.
While white roofs are more common than regular ones, there is a dark colored cool roof coating that also meets energy star requirements. You can reduce energy cost by 10 to 12 percent. If there is a threshold of roofs installed in urban areas, then the impact of urban heat islands can decrease in a significant way. Urban areas experience warmer temperatures, anywhere from 2 to 8 degrees Fahrenheit than surrounding rural areas. Traditional black roofs are a large reason that cities are normally warmer.
Pros and Cons of a Cool Roof
Advantages of a Cool Roof
The original reasons for installing one of these roofs such as reducing energy costs create other advantages as well. The bulleted list below details some of these benefits.
- The roof can withstand hurricane-type winds. This is particularly important in warmer areas that have severe storm risks.
- Increased comfort in the summer, particularly in houses without air conditioning. You will find more pronounced areas of reduced temperatures around or very close to the roof.
- Has a longer roof life than traditional roofs. This means that it reduces maintenance costs when it comes time to repair or replace the roof.
- Reduced air pollution from air conditioners occurs when installation occurs. The air conditioner has to run less for the same temperature.
- There are possible utility rebates or subsidies to lessen the initial cost of installing a cool roof. The CRRC maintains this list, but additional local utility rebates may also exist.
- Through critical threshold use, one can significantly reduce the impact of manmade global warming.
- These roofs indirectly reduce the level of smog in a city. Smog occurs when pollutants undergo photochemical reactions. The rate of reaction is much higher when the temperature increases. If people will accomplish their dream to reduce the overall heat in cities, then the amount of smog will also follow the same trend.
Disadvantages of a Cool Roof
While there are several benefits of a cool roof, there are also negative impacts. Some of these are known ahead of time while others emerge as unintended consequences.
- Reduce rainfall caused by the immediate reflection of the sun, which interrupts the water cycle of water leaving the ground and entering the atmosphere. This can be potentially dangerous in areas like Phoenix where rainfall is already sparse.
- Increase heating costs in the winter in cold climates. The general recommendation is that if you live in latitudes above Chicago, the decreases in cooling costs in the summer are offset by the increase in heating costs in the winter.
- If there is not an extremely tight seal under the roof, there is the potential for increased condensation under the roof. This is a potentially devastating consequence that can cause ice to form under the roof and increase the chance of mold.
- The original science that led to much of the belief that these roofs help reduce global warming has been refuted by more recent studies, including a study by Stanford University.
Guidelines and Standards for a Cool Roof
There are many decisions that you need to make when deciding to install a cool roof. A company that installs these roofs should be able to make you aware of and explain how these decisions will impact the installation of the final product. The following section discusses what you need to consider before installing a cool roof.
There are numerous tools online that provide calculations for the quality of different cool roofs. Two of these tools are the Department of Energy calculator and the Environmental Protection Agency calculator. Use these tools to compare any quotes you have been given on the level of reflection with actual results.
There are three major factors to consider before installing a cool roof. These are slope, climate, and projected energy savings. Experts recommend different products for differing slope levels. A quality roofing contractor should be able to tell you exactly what materials or recommended for these slopes.
As seen in the disadvantages section above, there are some climates where a cool roof could actually cost money through increased heating in the winter. Finally, an energy company or roofing contractor should be able to give you an estimate on the monetary amount of savings you would see by installing a cool roof. If they didn’t do this, you would be wise to think about working with a different roofing contractor.
To review, cool roofs use a very simple phenomenon in which they immediately reflect the light back to space and thus minimize the amount absorbed into the atmosphere. They will be a conversation starter in any neighborhood. You now have the necessary information to talk to your neighbor about installing this roof and what the expected benefits are.
This creates a vast amount of advantages such as reduced urban island temperature, reduced use of air conditioners, and substantial energy savings. However, unintended negative consequences such as reduced rainfall and potential condensation under the roof can also occur.