Landscape shot of a building using green roofing as a cool roof

Cool roofing isn’t an entirely new concept. Scientists have assessed materials that can lower thermal emittance and solar reflectance for countless years. In fact, the very first “cool roof” material was introduced in California more than two decades ago!

This article will explore some of the most efficient materials available on the market from which cool roofs are made.  

Over the past couple of years, the number of cool roofing materials and options have increased significantly—and new ones are continuously being developed.

Recently, Australian scientists have discovered a new roofing material boasting some incredible numbers. The coated polymer stack is known to keep roofs nearly 12°F cooler than even the best white roofs available on the market.

According to reports, if plenty of commercial buildings in an area install this innovative material, the heat radiating from the buildings can be lowered by several degrees, possibly reducing the urban heat island effect significantly.

The technology that goes into the production of coated polymer stack is still not widely available. Until then, we need to opt for some of the cool roofing materials already available. 

Most Efficient Cool Roof Materials

Fortunately, such materials are pretty efficient, and there is nothing “conventional” about them. Each of these materials has a unique look and set of features that might be more suited for a particular climate. Some materials are more effective in cooler climates, whereas others combat the heat of sunny and dry climates.

Below is a list of the top cool roofing materials that keep homes cool all over the US. So, without further ado, let’s get started!

Asphalt Shingles

Asphalt shingles are made of a fiberglass web coated with filled asphalt or filled modified asphalt that has been surfaced with colored ceramic-coated rock.

Even though these are common roofing materials, they generally aren’t the first thing people think of when searching for cool roof materials. This is because asphalt’s thermal emittance is still relatively low—even white asphalt is only about 30 percent reflective. 

All in all, asphalt is an excellent budget-friendly roofing material. However, there are much better options that will keep your home cooler. 

Cool Metal Roofing 

Cool metal roofing is an excellent cool roofing material that can offer double the solar reflectance of asphalt roofing—nearly 70 percent when coupled with a colored reflective coating. This reduction is a considerable difference compared with the 30 percent solar reflectance of asphalt shingles. 

The top of a home with cool metal roofing is shown along with a chimney stack

According to certain accounts, you can save over 20 percent of your air conditioning cost in the summers just by installing cool metal roofing. 

Moreover, cool metal roofing is very durable. It is made from zinc or aluminum-coated steel, and it is quite sturdy and lightweight.

Additionally, this cool roof material is mold, mildew, and weather-resistance. A good metal roof will last anywhere between 3 to 5 decades, given that it is adequately maintained. 

The cost of installing a cool metal roof lies between $5 to $14 per square foot, which is more costly than other cool roofing materials. Nevertheless, the investment you make right now can pay off several times over by reducing air conditioning needs and decreasing energy bills. 

Lastly, cool metal roofing is completely recyclable, thus offering great environmental benefits. 

Reflective Roof Coating 

Several kinds of reflective roof coating are available to keep your home cooler. Let’s take a look at some of these. 

White Reflective Coating 

White reflective coating is one of the best and most efficient cool roofing materials you can get because white is incredibly reflective. 

Workers retrofitting a home with white reflective cool roof coating in the desert

White reflective coating is opaque, generally made from polymers or other similar materials, mixed with a particular type of white paint or pigment.

It is incredibly effective—a white reflective coating can reflect almost 80 percent of sunlight! This figure is even higher than cool metal roofing resulting in a significant difference in your home’s indoor temperature. 

Pigmented Roof Coatings

Pigmented roof coatings are available in various colors apart from white. However, they aren’t as effective or reflective as white cool roof coatings. For example, darker colors such as black, red, or green may only reflect 20 to 30 percent of sunlight. On the other hand, lighter colors such as pale yellow or beige can be highly reflective—up to nearly 80 percent. 

These pigmented roof coatings are widely used by residential homeowners who want to enhance their homes’ visual appeal and appearance. However, they aren’t a great pick for cool roofs. 

Aluminum Roof Coatings

Pigmented and white roof coatings are generally made from some kind of polymer material. In contrast, aluminum roof coatings use a resin containing aluminum flakes. These flakes produce a “leafed” effect covering a large part of the roofing and creating a solid top layer that effectively reflects sunlight. 

Aluminum roof coatings can generally reflect 50 percent of sunlight. However, some high-end, premium models can even reflect 70 percent. If used correctly, they can cool your home’s indoor temperature by over 10 degrees which is a MAJOR difference!

The downside of this material is that aluminum also radiates and absorbs heat that is not reflected. Thus, it will become hotter than a composite material with the same “flaked” coating otherwise would.

Roofing Membranes

Roofing materials are composite materials made from sturdy, flexible, typically waterproof materials. These generally include a blend of polyester, fiberglass, or combined with asphalt, polymer, or synthetic rubber to connect and attach them. To maximize reflectivity, a reflective pigment or coating is typically applied to the top. 

PVC or single-ply EPDM are the most popular roofing membranes. Their reflectivity depends on the pigment used. A PVC or white EPDM can reflect nearly 70 percent of sunlight. Certain high-end, cool roofing manufacturing companies, such as Sika-Trocal or Ecology, manufacture roofing that reflects more than 80 percent of sunlight. 

Other advantages of roofing membrane are durability, flexibility, low cost, easy maintenance, and installation. Thanks to all these reasons, roofing membranes are the most popular commercial roofing. 

Tiles

Tiles are another tremendous cool roofing material. They are most commonly used in sunny and warm climates, such as Arizona, where they mesh with the earthen appearance of houses.

Clay tiles being installed to create a cool roof

They are generally made with ceramic because clay has higher reflective properties than cement. However, tiles can be made with cement too. Nevertheless, the reflectance of tile depends largely on its color. For example, red clay may reflect 20 percent of solar energy, whereas white clay tiles can reflect nearly 70 percent of sunlight. 

Other benefits of clay tiles include recyclability and durability. The best-quality tiles made with natural materials can be recycled entirely once you use them. 

Clay tiles are also non-combustible, making them an excellent pick where safety is essential. 

Disadvantages of tile as a cool roofing material include weight and cost. Cement and clay weigh considerably more than most metal roofing and asphalt shingles. They take much longer to install and are therefore more costly. 

Green Roofs

If none of the options above appeal to you, you can consider opting for a green roof. This term refers to growing vegetation instead of installing particular cool roofing material.

Green roofs are perfect for urban buildings with shallow-pit or low-sloped roofs and include anything from basic plant cover to a garden or even small trees. The fundamental reason for using this kind of roof includes managing stormwater and creating an enjoyable and attractive rooftop open space. 

An eco-friendly home with a green cool roof

Green roofs are “inverted” roofs, meaning the waterproofing membrane is located underneath the plants and most of the roof components. The membrane is effectively protected from the sun’s degrading UV radiation in that location. However, leaks are much more challenging to locate and repair. 

Green roofs are significantly heavier and more costly to build and maintain than non-vegetated roofs. This is because the building frame must bear the extra weight, and the plant cover usually requires some maintenance.

You need to inspect your home meticulously, weigh local climate conditions and building structure, and speak to experts before deciding to get a green roof. 

Green roofs are primarily cooled through the evaporation of water by plant surfaces rather than through the reflection of sunlight. The soil layer also offers extra insulation along with the thermal mass.

Last Few Words

With new products continuously being introduced and improvements to existing efficient, cool roofing options, homeowners need to research their options when building a new structure or replacing an existing one. 

Carefully evaluating your needs and looking for ENERGY STAR® roofing materials will help you get the perfect roof for your house.

By getting to know the efficient, cool roofing materials available and how different benefits each type can offer, you can positively impact the environment.

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