What are Green Roofs and What Benefits do they Provide?

Overview of city building green roof surrounded by skyscrapers


The conversation around conservation and sustainability is rapidly moving past concrete reduction and how many trees are being planted to offset carbon emissions. A more dynamic dialogue has started surrounding how to best utilize urban space and eliminate roof systems that mainly absorb heat and lead to increasing temperatures.

Green roofing has become a leading industry trend in various parts of the world, and it is becoming much more common now in North America. Green roofs offer a host of benefits that go beyond aesthetics and architectural interest.

What Are Green Roofs and Their Benefits?

A green roof is a carefully designed layer of vegetation installed and incorporated into a flat or slightly sloped rooftop. A green roof system also includes waterproofing and drainage layers, insulation and structural support layers and membranes designed to support the vegetation above. It is a complex system but one that offers several key benefits that have made green roofs more prevalent in modern design.

Temperatures in cities are often higher than their surrounding rural areas due to the urban heat island effect. Large amounts of structures and paved surfaces absorb and re-emit heat more than natural landscapes. These non porous surfaces also cause issues when it comes to stormwater management.

But creating natural green spaces reduces some of the effects of urbanization. Vegetation absorbs less heat which lowers temperatures. By covering a traditionally dark rooftop with plants, the temperature within the building stays more regulated and rooftop mechanical equipment runs more efficiently.

Green roofs are also one of the best stormwater management systems and can help prevent storm drains from overflowing.

Examples of Green Roofs

Green roof of California Academy of Sciences building in San Francisco


Green roofs can be found all over the world in a vast array of designs. Here are a few examples that highlight the value these systems bring to growing cities.

California Academy of Sciences, San Francisco

One great way to break up the urban landscape and bring the surrounding nature into big cities is through green roofs. Strategic plans, as seen with the California Academy of Sciences building, can incorporate native plants into the design revitalizing the space and helping to achieve LEED Certification.

Chicago City Hall

With growing concerns over the urban heat-island effect, the Chicago City Hall construction was a part of the initiative to find plausible solutions and improve the urban air quality.

The main feature of this initiative was the green roof project that includes more than 150 varieties of plants and a rainwater collection and storage system.

Toyota Headquarters

When Toyota set out to build their new headquarters in Texas, they wanted to stay committed to their goal of finding opportunities to have a positive impact on the environment.

One of the ways they achieved this is with their massive rain-capture system and rooftop vegetation that helps save and manage stormwater. The green roof landscaping also consists of native plants suitable for the local climate.

Stormwater Management

One of the biggest benefits of green roofing is the stormwater management solution it provides in cities.

Areas with a lot of concrete, asphalt and other impervious surfaces have issues with precipitation runoff that can overflow the storm drains and sewer system. When storm drains cannot handle heavy rainfall or melting snow, basement level and street flooding can occur, sometimes with contaminated water.

One way to prevent overwhelming storm drains is to implement green infrastructure practices, like green roofs, that retain rainwater. The plants and soil on a green roof act as a sponge and absorb the water then release it back into the environment naturally rather than letting it run off the building.

Some green roofs are even sloped to further assist in stormwater management. The sloped deck transports excess water to drains, preventing pools of sitting water and potential leakage. A sloped green roof can absorb up to 90% of stormwater year-round, depending upon the conditions and plant type.

How Does Atlas Help?

Prudential Plaza Green Roof

Atlas has the knowledge and experience to help design the perfect structural deck and insulation layer for any green roof project nationwide. Here are just a few key features that make Atlas Molded Products stand out:

Compression Resistance

Crew installing Atlas Geofoam for a green roof application in Chicago

Some may be concerned about the weight and durability of the materials needed to create a green roof. Many factors like high foot traffic, heavy planters and paving systems are important to consider when deciding on what foundational products will perform best.

When anticipating heavy loads, Atlas Geofoam is the perfect lightweight structural deck product with high compression resistance and predictable material behavior due to its dimensionally stable properties. It will not crush under the weight of soil or pavement.

Another Atlas product perfect for lighter loads is ThermalStar which comes in a range of 10-60 PSI and multiple standard thicknesses. It is still a high load bearing product but works better for smaller garden spaces with less foot traffic.

Choosing the right structural deck product depends on anticipated roof loads. Atlas has done several roofing projects that have dealt with a range of PSIs, and they can help anticipate exactly what the compressive strength needs are for any given structure.

Drainage Solutions

Crew members installing Atlas Geofoam for green roof application

While green roofs prevent stormwater from overflowing storm drains, the water still needs a place to go. The vegetation and soil can only absorb so much until it becomes oversaturated. Water also adds additional weight on the roof of the building, so there must be a solution for the excess.

The deck of the roof, when built properly, can serve as a drainage point. If the structural deck is tapered, it will allow water to flow to a drain or storage system instead of pooling.

The inverted taper system is challenging to create, but it is being used more and more to protect and prolong the roof of a building. The inverted tapered system creates a flat surface instead of a sloped one, but the drainage happens beneath the insulation layer.

Atlas has experience working with both traditionally tapered roofs as well as inverted tapered roof systems, so they can help find and create the right products for even the most challenging jobs.

Their EPS products also absorb very little water and will not increase significantly in weight if they get wet.

Easy Installation

Crew member carrying Geofoam block over his head for a green roof application in Chicago.

Atlas products are the best solution for pre-existing buildings. Other products need to be brought up to the roof by cranes, meaning extra time, extra labor costs and the possibility of damaging the structure.

But due to their lightweight nature, Atlas products can easily be carried by hand or brought up in an elevator. It only takes two crew members to move a 16ft long block by hand. The easily portable products significantly ease the process of installation.

Atlas products are also customizable and can be manufactured to specific dimensions or easily cut on-site to fit wherever they need to go.


An aerial view of two green roofs in a city.


Green roofing takes a typical and often unused space and turns it into a green park to benefit the local community and environment.

For help designing and installing green roofs to help the planet and meet LEED requirements, reach out to an Atlas representative today.