The Difference Between Cool Roofs and Green Roofs

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Many homeowners know that cool and green roofs are energy-efficient systems designed to curb utility costs, while simultaneously being kind to our planet. Many homeowners, however, also make the mistake of thinking these roofs are one in the same – when they are not. And knowing the difference is important to choosing the right system for your home.

What is a cool roof?

A cool roof is designed to reflect heat back to the surroundings which, inversely, also means that it absorbs less heat. Heat-reflective paint, sheet coatings, tiles, or shingles, from which a cool roof is made, can help keep temperatures inside structures about 50 degrees Fahrenheit below average temperatures outdoors. For homes with no air conditioning, a cool roof helps make for a more tolerable indoor environment. Homes with air conditioning, on the other hand, will not have to overtax their equipment to keep those inside comfortable.

Difference Between Cool Roofs and Green Roofs1

Aside from the resultant utility savings, cool roofs can also extend the lifespan of your roof. Too much absorbed heat, after all, can prematurely weaken shingles and cause deterioration or structural failure.

The good news is, you can retrofit your existing roof into a cool roof: you just have to make sure the surface of the roof exposed to the sun is equipped to reflect and emit heat back. There are various cool roof requirements, though, depending on the Solar Reflectance Index (SRI) of the product, as well as the slope of the roof. For instance, the California Energy Commission requires SRIs of 64 and 16 for low and steep slope roofs, respectively. Note, too that cool roofs are not necessarily finished in white; colored coatings can be used on a cool roof as well.

Now, what is a green roof?

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A green roof is a vegetative roofing system:

  1. With three to five inches of overall vegetation depth, and no required irrigation. It is most often used as a living machine.
  2. Semi-intensive. Has five to seven inches of vegetation depth, with irrigation as required. Semi-intensive green roofs are used for diversity or as habitats.
  3. Has seven to 24-plus inches of vegetation, with automatic irrigation, and used as rooftop gardens or parks.

Most green roofs are found atop commercial properties, as they are best suited to shallow or flat roofs.
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But you can install one on your home, too. Most green roofs for homes come in plastic trays with a soilless medium and fully mature plants.

And once installed, a green roof can help you better insulate your home, as well as curb energy loads. The entire community stands to benefit, as well. Green roofs are known to mitigate the urban heat island effect by reducing the amount of heat absorbed within the city. The vegetation in these roofs also help filter the air.

The biggest drawback to a green roof is that it can be expensive to install. So we recommend consulting a professional and going over all the technicalities before making a final decision.

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Author Bio:

Tom Petrilli founded Lyons Contracting with the idea that the Northern Virginia residential roofing industry needed a new, more customer-centric approach to meeting homeowners roofing needs. Too many companies were not listening to homeowners and fully understanding their needs on roofing projects.  Tom and his team at Lyons Contracting leverage their deep expertise to meet the homeower’s vision for their new roof and deliver quality installations and repairs every time.

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