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Green roof installations have shown a proven return on investment beyond the environmental benefits. Building owners, architects and city planners are turning to sustainable construction for more than just a carbon footprint reduction.

Here are seven reasons why building owners and developers should consider installing a green roof on their next construction project:

1. Improves stormwater management

In dense, urban environments, asphalt and concrete prevent the absorption of rainwater into the ground. The result? Sewer overflows, flooding, and even compromised water quality. Green roofs successfully address these concerns, retaining up to the first 20mm of rainfall, preventing it from becoming runoff (or in other cases, increasing the time that it takes for the water to runoff from the roof by up to three hours). Overall green roofs reduce runoff by nearly two-thirds.

2. Reduces energy consumption

Because green roofs absorb sunlight, provide shading, promote evapotranspiration, and deliver insulation benefits, they help maintain indoor temperatures. This helps lower the dependence on air conditioners and heating systems. Studies have shown that the annual energy consumption savings for total green roof systems averaged 601,502 kilowatt-hours, that’s equivalent to the carbon sequestered by 555 acres of forests in one year.

3. Extends roof’s lifespan

As green roofs help protect roofing materials from eternal elements, they can extend the lifespan of the roof, in some cases doubling the number of years before replacement is necessary. In fact, the average lifespan of a green roof is 40 years, compared to 17 years for a conventional roof.

4. Enhances wellbeing

By offering an aesthetically pleasing landscape, green roofs can reduce stress and increase worker productivity for both building residents and the occupants of nearby buildings. In some configurations, green roofs offer accessibility to building tenants, which provides a deeper, more intimate environment. And by producing a healthier atmosphere, worker absenteeism declines.

5. Reduces the urban heat island effect

Air temperatures are often higher in urban areas than in rural locations; the result of surfaces that absorb solar radiation and lead to increased energy consumption (the effect is known as urban heat islands or UHI). Green roofs and their plant coverings can reduce UHI and moderate those temperature spikes.

6. Improves air quality

Green roofs and their thick vegetation help filter the air by removing carbon dioxide and releasing oxygen, thereby significantly improving overall air quality. They also absorb air pollutants and particulates, serving as a purifier for both indoor and outdoor air.

7. Reduces ambient noise

Green roofs absorb sound, resulting in quieter spaces — both inside and outside. They are more efficient at reducing noise than traditional roofs, and even when used without ceiling insulation they can enhance noise reduction on the building’s upper levels. The effect is especially pronounced in densely populated areas where outside noise is greater.

The most important elements when it comes to developing a green roof are:

• High-quality waterproofing such as Hydrotech
• Root repellent barrier
• Drainage system
• Lightweight growing medium and of course, plants

Allco has a range of solutions to help architects design their next green roof projects. Our technical team can provide support from the design stage to completion to help designers create a unique green roof space.

Check our latest green roof case study: Auckland Central Library 

To start the green roof journey contact Allco’s technical team on tech@allco.co.nz