Cool Greenroof Summer: How Greenroofs Can Help Keep Temperatures Down

As cities continue to grow and concrete landscapes increase, the urban heat island effect is an ever-looming presence in city life. In the summer, cities can be several degrees hotter than surrounding rural areas, largely due to the heat-absorbing nature of their building materials. Enter greenroofs. Also known as living roofs, greenroofs are more than just an aesthetic addition to buildings. They offer substantial environmental and economic benefits, particularly in cooling urban areas during the most sweltering months of the year.

First, a refresher: greenroofs are rooftops that are either partially or entirely covered in vegetation and planted over a waterproof membrane. Sometimes they also feature extra layers, including root barriers, drainage systems, and irrigation systems. Greenroofs come in two main types: extensive and intensive. Extensive greenroofs have a shallow soil layer, typically supporting hardy, low-maintenance plants like sedums and grasses. Intensive greenroofs, on the other hand, have deeper soil layers that can support a wider variety of plants, including shrubs and small trees, requiring more maintenance and structural support.

Cooling Effects of Greenroofs

Thermal Insulation

Greenroofs act as an insulating layer reducing the amount of heat transferred through a building’s roof. During the summer, this means less heat penetrates into the building, reducing the need for air conditioning. The soil and plants absorb and retain heat during the day, which is then released slowly, maintaining a more consistent and cool temperature throughout the building.

Evapotranspiration

Plants on green roofs undergo a process known as evapotranspiration, where water is absorbed by the roots and then released into the atmosphere via the leaves. This process heat, which is extracted from the surrounding air, leading to a cooling effect. As plants "sweat" via this process they help to cool the air around them.

Albedo Effect

Traditional roofing materials like asphalt and concrete have low albedo, meaning they absorb significant levels of solar radiation and transform it into heat. Greenroofs, in contrast, have a higher albedo because the plants reflect more sunlight and absorb less heat. This reduces the overall temperature of the roof surface and, by extension, the surrounding air.

Greenroof Benefits Beyond Cooling

Cool air is just the beginning. Greenroofs offer many other summer perks that extend beyond temperature.

Energy Efficiency

By reducing the need for AC, greenroofs translate to decrease energy bills for property owners and can help reduce the strain on your local electrical grid during peak summer months.

Better Air Quality

Like all plants, the plants on greenroofs help pollutants and carbon dioxide out of the air. The vegetation captures particulate matter and absorbs gasses to help create a healthier and cleaner environment.

Stormwater Management

During summer thunderstorms, green roofs can absorb and retain significant amounts of rainwater, reducing runoff and alleviating the burden on urban drainage systems. This doesn't just help prevent flooding -- it also improves water quality by filtering pollutants before they hit waterways.

Biodiversity and Habitat Creation

Greenroofs provide habitats for various species of plants, insects, and birds, promoting urban biodiversity. In cities where green spaces are limited, these rooftops offer crucial refuges for wildlife and help to connect fragmented habitats.

Noise Reduction

The soil and plants on greenroofs can even act as sound barriers, absorbing and deflecting noise. This is pariculatly beneficial in noisy urban areas, where peace and quiet is a rare to come by.

As the climate continues to change, greenroofs serve as an excellent cooling tool. Contact us today to get started on building your greenroof with Fujita Company’s FTM bags. They’re durable, portable, easy to use, and crafted with care and intention to meet all your greenroofing design needs.