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rendering of office building featuring a green roof with trees and grass areas

Are You Considering a Green Roof? Here’s What You Need to Know

Craig Gardei, AIA, LEED AP
The idea of a roof covered with thriving vegetation has a way of firing the imagination. It’s easy to envision the beauty of an entire city’s infrastructure covered not in asphalt and modified bitumen, but in grass and flowers, like something out of a fantasy movie.

While the vision may seem far-fetched right now, green roofs are becoming more popular. As green roof technology continues to improve, we expect them to become considerably more common.

If you’re considering a green roof for your next project, here are the pros and cons that you need to know before planning one for yourself.

Advantages of a Green Roof System

There is no doubt that a green roof has a certain “wow” factor. Nobody will ever forget your building, especially if you are locating it in the U.S., where green roofs are still uncommon. Here are some additional advantages to consider.

  • Energy efficiency
  • LEED points
  • Air quality
  • Wildlife

Energy Efficiency. Green roofs provide substantial thermal performance over most traditional roofs. The soil, vegetation, and moisture provides insulation, while the plants and their respiration have a cooling effect by absorbing the energy of the sun.

LEED Points. A well-designed green roof can offer between 2 (for covering only 50% of the building) and a whopping 9 LEED points. At the high end, that is nearly 20% of the total points necessary for USGBC LEED Certification.

Improves City Air Quality. Plants naturally purify the air around them by absorbing CO2 and releasing oxygen. They also reduce sulfur dioxide, nitrous acid, and dust particles in the air, all while shading and cooling the surrounding areas to reduce summer city temperatures.

Great for Wildlife. A well-designed and maintained green roof will attract a wide variety of aerial wildlife, including butterflies, bees, and birds, and provide a crucial habitat for feeding and breeding. This makes these roofs both environmentally friendly and socially conscious.

office building green roof with roof equipment made to look like plants
office building green roof with grassy areas and seating

Disadvantages of a Green Roof System

If green roofs were as easy and cheap to install and maintain as other roofing systems, we might soon see entire city-scapes of green, and all enjoy cooler, fresher air in the city.

Unfortunately, there remain some challenges that must be addressed before green roofs become the only and best choice for commercial buildings. Here are the disadvantages to consider.

Expensive to Install. Despite advances in green roof technology, they are still substantially more expensive to install than conventional methods, in both materials and labor.

Prone to Leaks. Green roofs have come a long way in functionality from the 1970s, when they were an environmentalist’s oddity. Nevertheless, when you place dirt and plants on your roof and then water them, you naturally invite leaks. Furthermore, it can be hard to locate leaks when they do occur, due to the fact that surface of the roof is covered in organic material.

Heavy. All of that dirt and vegetation produces a hefty weight load, that requires careful engineering and in the case of a re-roof, where a traditional roof is being replaced with a green roof, significant and costly structural enhancements are often necessary. It can also be a hazard in hurricane conditions, when high winds can move all of that weight around.

Difficult to Maintain. Plants are living things that require care. Even a well-designed and carefully planted roof will require irrigation and attention to the health of the plants. Additionally, monitoring the integrity of the sub-materials and substructure is challenging and the roots of poorly chosen vegetation can, over time, dig through the waterproof membrane and cause leaks.

Despite their disadvantages, green roofs are beautiful, environmentally friendly, and much more practical than they were even a few years ago. If you are considering installing one, take the time to learn about how green roofs are constructed, here.

You can also learn more about the pros and cons of other commercial roof types here, or contact us today to talk about your roofing system design.

Previous post 5 Ways to Reduce Your Hurricane Season Risk Next post What You Need to Know to Choose the Right Commercial Roof Type

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What You Need to Know to Choose the Right Commercial Roof Type

aerial top view of commercial roof
Craig Gardei, AIA, LEED AP Director of Building Assessment & Construction Consulting Services As GLE’s Director of Building Assessment and Construction Consulting Services at GLE, Craig Gardei leads a team of construction inspectors and administrators who oversee construction projects with respect to both costs and quality of construction, to evaluate the condition of existing buildings, and to perform forensic evaluations to identify building issues that are affecting the health and comfort of building occupants. His experience includes inspection and evaluation of existing real estate portfolios, extensive experience in providing forensic architectural services, roof consulting services, construction oversight and management services for large-scale projects, and multi-building construction programs. Contact

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