Vegetated Roofing Systems: What You Need To Know

Climate-friendly construction continues to increase in popularity and user acceptance. Recent reports show that the Global Green Buildings market is growing at a massive compound annual growth rate (CAGR) of 14.3% between 2020 and 2027. Such rapid expansion signals a keen desire for green material use, efficient operations, and sustainable communities. Considering the impact commercial structures have on the environment, the shift into economically viable green architecture is a welcomed solution to urbanization.

While there are many ways to incorporate eco-friendly infrastructure, one of the most effective ways is by installing a vegetated roof. The roofing system uses ‘green’ materials and natural plants to manage solar reflection, heat retention, and water run-off, elements that are critical to the interior cooling and overall environmental footprint of your building. Considering that a roofing system can cover 50-70% of the exterior enclosure exposed to the weather, a vegetated roof is ideal for improving your building’s energy efficiency.

Let’s explore the benefits of vegetated roofs and explain how they are one of the most environmentally-conscious ways to achieve the advantages of sustainable architecture.

What Are Vegetated Roofing Systems?

Vegetated roofing systems are ‘green’ roofs that employ a plant layer upon flat or sloped roofs. The use of plant life distinguishes vegetated roofing systems from other ‘green’ roofs that also incorporate heat reduction elements.

More than a decorative recreational space focused on plant growth, a vegetative roof is a planned system with many parts that support the function of your roof (e.g., proper drainage and weather protection). The structural integrity of your building is maintained through layers of insulation, water membranes, and growing mediums—it is an active roof with many subsystems that support the efficient operation of your building. It is imperative to note that consideration of the weight of the system being installed must be analyzed as to whether the building can support the load.

Vegetated roofs also consist of unique plant solutions

Different climates require different native greenery that supports the local environment. Various soil types, moisture barriers, and growth medium materials have specific use cases that can help with UV reflection, water absorption, water holding capacity, and cooling effects. Your vegetated roof will be a tailored space that can improve building efficiency, roof integrity, and the strength of the local ecosystem.

What Are the Benefits of a Vegetated Roofing System?

Vegetated roofs offer a series of benefits to both building owners and the community:

Community benefits

  • Mitigated heat island effects: Cities experience higher temperatures than the surrounding areas because standard building materials absorb and reflect UV rays at a rate greater than natural landscapes. As a result, limited green areas create a heat island that causes several adverse effects, such as increased energy consumption, elevated emission of greenhouse gasses, respiratory and heat-related health issues, and water quality issues.

    Vegetative roofs are an equalizing solution to the urban heat island effects. Plants engage in evapotranspiration, releasing moisture into the air that reduces heat. Moreover, vegetated layers are helpful with solar reflection, with some green roofs reaching temperatures 30-40% less than conventional roofing systems.
  • Reduced air pollution: The benefits of plant life regarding air quality is common knowledge. But evapotranspiration also involves a filtering system that can capture pollutants. Recent studies show that concentrations of pollutants such as ground-level ozone, carbon monoxide, and sulfur dioxides experience a 5-8% decrease with the inclusion of green roofs. Green roofs also clean the air through prevention; renewable and green building options are far more eco-friendly than standard construction materials that can leach out after sun exposure or decay.
  • Better stormwater management: Many paved areas and roofs contribute to flooding and erosion. While city stormwater management aids runoffs, the holding capacity and water retention of a vegetated roof system can replicate the engineering features of stormwater basins. Many green roofs can even harvest rainfall for irrigation and non-potable use cases. Even water quality will increase as the biodiversity of aquatic life will suffer from the increased heat and the introduction of building materials. Up to 30% of nitrogen and phosphorus release is due to dust accumulation on rooftops—a vegetated layer can protect, clean, and manage water dispersion.

Owner benefits

  • Thermal efficiency: Vegetated roofing systems are devised to decrease heat flow, increase insulation, and provide shade that can limit the effects of sunlight and UV rays. Your selected roofing system can affect interior cooling capacity, and there are reports that the air conditioning load can decrease by 10 – 30% due to the installation of a green roof. Gain electricity usage and cost savings by choosing a vegetated roofing system.
  • Extended roofing system lifespan: Vegetated roofs and their included plant growth help protect roof membranes that lead to longer roof life spans. Greenery is a natural barrier to weather elements, mechanical damages, and other environmental stresses (some can even help limit fire damage). While conventional roofs can fall apart after 10 – 20 years, green roofs are expected to last 50 – 75 years and are relatively maintenance-free beyond standard plant care (you will need to weed two to three times a year).
  • Increased building value: A green roof adds aesthetic beauty and potential recreational space to increase property values. Buyers often look favorably upon the climate-proof construction, and the included utility cost decreases. The overall worth of your building will increase with the installation of an effective vegetated roof system, further aiding property appreciation and future return on investment.
  • User comfort: The natural air purification, cooling abilities, and heat reduction/reflection delivered by your vegetated roofing system will directly improve the interior air quality and overall comfort of your building. There is even a dampening effect to acoustic sounds, which could benefit large commercial properties that work with loud machinery. A well-devised vegetated roofing system will make it far more comfortable for the people who use the facilities.

Vegetated Roofing System Considerations

If you are interested in renovating and upgrading to a vegetated roof, there are several aspects you should consider before you go through the installation process. A green roof is an involved process, and without due care, you could run the risk of leaks, damages, and the weakening of your building’s structure.

For example, you will need to choose from three possible system types: Intensive, Semi-intensive, or Extensive. Intensive has a deeper growing medium, while extensive green roofs use shallow systems that are easy to install. Each system type has different maintenance requirements regarding irrigation, weeding, and professional landscaping. More importantly, each system requires specific structural materials and load-bearing components that ensure your safety.

You can also use different planting systems that offer other substrates and vegetation possibilities. Sedum mats are common pre-planted options, while potted plants and plugs will take on more installation expenses and require more customization.

It is critical to consider the type of roof system that is installed beneath the vegetation. Properly installed and durable membranes, water barriers, drainage mats are key components to ensuring a long-lasting and beautiful garden rood. Lastly, be sure to follow the code requirements of your state, as there may be specific building laws regarding ‘green’ roofs. Most building rules outline safety issues related to wind uplift risk, soil stability, and water repellency. A well-built green roof will help support the biodiversity of the local ecosystem and the safety of tenants rather than increase risk.

Opting for Sustainable Architecture

A vegetated roof is an excellent option for those who want to gain the economic benefits of a climate-conscious roofing system. If you want to invest in sustainable architecture, a green roof is an ideal method compared to other conventional systems.

But the installation process can grow intensive. There is a lot to consider when creating a vegetated roof, such as planning stormwater run-offs, selecting planting systems, and ensuring structural safety. Meeting with a roofing system expert can help make your commercial roofing system upgrade easy and cost-effective.

Want more information about vegetated roofing systems? Contact RoofSource for any consultation or guidance regarding sustainable roofing upgrades and renovations.