Vegetative Roof Systems – Types, Benefits & Challenges!

The use of vegetative roof systems is becoming an increasing trend for many commercial and residential buildings. Whether for aesthetic or sustainable purposes, having a vegetative roofing system will definitely enhance any property. If you’re not familiar with what vegetative roof systems are, here is a brief overview of what you need to know about this roofing feature.

What Are Vegetative Roof Systems?

Also known as living roofs, a vegetative roof system refers to a roofing design wherein living plants are utilized to create green spaces on top of a building. While some people refer to them as “green roofs”, the term “vegetative roof system” is more accurate to refer to roofs with living vegetation because there are different roofing materials that can also be considered green or environmentally friendly without necessarily having plants installed on them.

A properly designed and well-constructed vegetative roof system would typically consist of the following elements:

Drainage – The design of the drainage of a vegetative roof must be able to manage heavy rainfall with no damage because of ponding or erosion.

Support for the vegetation – The system be able to maintain ideal growing conditions for the vegetation and support plant growth.

Waterproofing systems and protection – The vegetative roof system must have a waterproofing feature that will protect the structure from the intrusion of water. This waterproofing system must also have a protection from potential damage that may be caused by solar degradation, natural phenomenon, and human actions such as maintenance.

Insulation – This is critical for conserving energy.

Types of Vegetative Roofing Systems

There are two categories of vegetative roofing systems. You may use either of these systems depending on the size, purpose, and design of the structure.

#1 Extensive Vegetative Roof Systems

This type of vegetative roof is typically six inches or shallower, which means shorter types of plants and vegetation are utilized. Because these roofs normally use only two to four inches of soil, plants must also have shallow root systems to make it more practical to maintain. Extensive vegetative roof system can absorb rainwater and are used to provide insulation for the roof. Herbs, small, grasses, and flowering plants that require little maintenance are often used for these types of vegetative roofs.

#2 Intensive Vegetative Roof Systems

An intensive vegetative roof system is more similar to a roof garden. These roof systems require a minimum of six to twelve inches of soil, which means that they can hold a wider variety of vegetation, larger perennial plants, and even trees.

Large commercial buildings who want to use their roof area as an additional living space often use this type of vegetative roof system. Many intensive vegetative roof systems mimic a park-like environment with paths, walkways, benches, fountains, and other architectural features where people can interact. Because intensive vegetative roofing systems are larger, they also require more maintenance.

The Benefits Of Vegetative Roof Systems

Many property owners are now recognizing the advantages of sustainable architecture not only on how it impacts the environment, but also on how it provides economic, social, and wellness gains. For commercial buildings located in urban settings, installing a vegetative roof system is a popular option in achieving sustainability goals. Aside from being sustainable, vegetative roof systems also deliver the following benefits.

Vegetative roof systems can control water run-off

When heavy rainwater runs off roofs and sloped areas, this contributes to erosion, destruction of habitat, flooding, and other damage. A vegetative roof can help prevent the rapid flow of water as well as retain rainwater.

When the volume of water run-off is reduced, this can also help improve the water quality in the area. This is because heavy water run-off can dilute sanitary wastewater in combined storm and wastewater sewer systems, which can cause treatment to be less efficient.

Improved air quality

Having more plants in the environment delivers more oxygen. This will obviously improve the air quality in the area, which can also result in improved health and wellness for the people in the community. Many new hospital buildings are integrating vegetative roof systems in their buildings to benefit their patients.

Add aesthetic value

A roof that is with greenery and flowering plants certainly looks better than a plain slab of concrete or metal. Similar to living walls, having a vegetative roof system is a sustainability feature that adds a visual impact to any property. These roof systems are more pleasing to look at and they can serve as communal areas where people can unwind and relax.

Save energy

Vegetative roof systems can act as insulation, which can help regulate the temperature in the structure. This can potentially provide energy savings both during winter and summer seasons. What this means is that it can possibly lower your utility bills, saving you money in the long run.

Mitigate Urban Heat Island Effect in Urban Environments

Urban areas typically have higher temperatures than rural environments. This is because there are lesser natural elements and due to the heat produced from the high level of energy usage in cities. This issue is often referred to as the UHI effect or the Urban Heat Island Effect. Utilizing vegetative roof systems can help lessen or at least equalize the UHI effect by reducing the temperature above the roofs.

Provide sound insulation

Another benefit of vegetative roof systems is that they can serve as sound insulators by absorbing a portion of the sound that would otherwise bounce off other roofing materials. This benefit may be useful for people living in environments with lots of noise.

Extends the service life of the roof

Having a vegetative roof system means that your roofing materials will have extra multiple layers of protection from mechanical damage, ultraviolet radiation, dust, heavy rainfall, winds, debris, animals, and other elements. This can help prolong the lifespan of your roof.

Challenges of Vegetative Roofing Systems

Having a vegetative roof can be a beneficial addition to many different types of buildings and structures. However, you must also be aware of the different challenges in installing a vegetative roof system.

Added cost

One of the main factors that you would need to consider is the added cost of having a vegetative roof system. Depending on the size or type of your property, you may find that putting up a vegetative roof will cost you significantly more than just a typical roofing system. Aside from the materials and construction cost, you also have to take into account the cost of ongoing maintenance.

Specialized maintenance

Even if budget is not an issue, you would still have to make sure that your vegetative roof system if properly maintained. You have to hire professionals to ensure that all the vegetation are growing properly and that your roof is free from any damage. If you have to perform maintenance on the roof material itself, you need someone with experience to work on it without damaging the vegetation.

Having a living roof also means you will attract other living things including weeds, wildlife, insects, pests, and birds. While there may be no harm with a few birds hanging out on your roof, you may have to employ a pest control expert if there are harmful pests like ants, wasps, spiders, or bees.

Weight Considerations

Having a vegetative roof system means extra weight that the structure needs to bear including the weight of the waterproof roof system, the vegetation or plants, the soil, and the retained water. If you’re planning to have an intensive vegetative roof system, you should also account for the added weight of the landscape features like walkways, fountains, and even the people who will be using the space. You have to ensure that the structural strength of your building is robust enough to hold the extra weight.

Are vegetative roof systems worth it?

While vegetative roof systems may pose added cost, time, and effort to the property owner, the benefits of having this green feature in your structure often outweigh the challenges. With a vegetative roof system, you are not only making your property more visually pleasing and sustainable, but you are also contributing to the environment and to community wellness.