What is a Green Roof? (Types, Benefits, and How to Build)

Are you looking to make your home green and eco-friendly? Then you may want to consider installing a green roof!

In this article, we’ll explore what a green roof is, the different types of green roofs, the benefits of having a green roof, and how to build one. You’ll have all the information you need to start your green roof project!

Table of contents

What is a green roof?

A green roof is a type of roof that has plants and vegetation growing on top of it. It is also known as a living roof or eco-roof. Green roofs have a layer of soil or growing medium that supports plants, which helps to absorb rainwater, reduce heat in cities, and provide a habitat for wildlife.

There are different types of green roofs, such as intensive, semi-intensive, and extensive, which vary in the number of plants and maintenance they require.

Green roofs are becoming more popular because they are eco-friendly, help to reduce energy costs, and provide a green space in urban areas where there is less natural vegetation.

What is the purpose of vegetation on a rooftop?

The purpose of vegetation on a rooftop is to create a green space that provides several benefits to people and the environment.

When plants are growing on a rooftop, they help to absorb rainwater, which reduces the amount of runoff and prevents flooding. This is especially important in cities where there is a lot of pavement and buildings, which don’t allow water to soak into the ground.

Vegetation on a rooftop also helps to keep buildings cool in the summer by shading the roof surface and releasing moisture into the air. This reduces the amount of energy needed to cool the building, which saves money and reduces greenhouse gas emissions.

People are excited about green roofs because they provide a natural space in a city.

Green roofs can be used for gardens, outdoor spaces, and food. They provide a habitat for birds, insects, and other wildlife, which can help increase biodiversity in urban areas.

Benefits of having a green roof

Increased insulation and reduced energy costs

Green roofs help to insulate buildings by reducing the amount of heat lost through the roof in the winter and reducing the amount of heat absorbed through the roof in the summer.

This can lead to lower energy costs for heating and cooling the building, which can save money and reduce greenhouse gas emissions.

Improved air quality and reduced air pollution

Green roofs absorb pollutants and filter particulate matter from the air, which can lead to improved air quality and reduced air pollution.

This decreases greenhouse gas emissions and improves the health of people living in urban areas.

Improved stormwater management and reduced runoff

Green roofs absorb and store rainwater, which reduces the amount of stormwater runoff that can cause flooding and erosion.

This can help improve the health of local waterways and cut down on the need for expensive systems to manage stormwater.

Increased biodiversity and wildlife habitat

Green roofs provide a habitat for plants, insects, and other wildlife, which can help increase biodiversity in urban areas.

This can lead to a more balanced ecosystem and a healthier environment for people and wildlife.

Aesthetic improvements to the building and the surrounding area

Green roofs provide an attractive natural space that can improve the aesthetic appeal of the building and the surrounding area.

This will create a more pleasant living and working environment.

Improved drainage and drainage system performance

Green roofs can improve the performance of drainage systems by reducing the amount of stormwater runoff and increasing the amount of water absorbed by the soil.

It can prevent flooding and reduce the need for costly drainage systems.

Cost savings on gardening

Green roofs can provide a cost-effective alternative to traditional gardening methods by reducing the need for expensive soil amendments, fertilizers, and pesticides.

The benefit here is saving money on gardening and reducing the environmental impact of gardening practices.

Reduced strain on storm-water and sewer systems

Green roofs take in and store rainwater, which makes it easier for stormwater and sewer systems to do their jobs.

This will prevent flooding and reduce the need for costly stormwater and sewer systems.

Heat island mitigation and reducing heat

Green roofs can help to mitigate the urban heat island effect by reducing the amount of heat absorbed by the roof surface.

The results are cooler and more comfortable living and working environments.

Health benefits for building occupants and communities

Green roofs can provide health benefits for building occupants and communities by improving air quality, reducing noise pollution, and providing a natural space for recreation and relaxation.

This will provide a healthier and more enjoyable living and working environment.

Cons of having a green roof

High initial installation costs

One of the biggest cons of having a green roof is that the initial installation costs can be high. The cost of materials, labor, and design can add up quickly.

However, this cost can be offset by the long-term benefits of the green roof, such as energy savings and reduced stormwater runoff.

One solution to reduce the initial installation cost is to work with a qualified green roof professional who can provide cost-effective solutions and designs that fit within your budget.

Structural load and weight

Green roofs can be heavy, and not all buildings are designed to support the additional weight. If a building is not structurally sound, installing a green roof can be dangerous.

The weight of the green roof (which includes the plants, and water-absorbing soil) can cause damage to the roof structure or even lead to collapse if not properly installed.

Before putting in a green roof, you should have a structural engineer look at the building to see if it can handle the weight.

If the building is not structurally sound, then retrofitting or strengthening may be necessary before a green roof can be installed.


Green roofs require regular maintenance, such as watering, weeding, and fertilizing. If the roof is not properly maintained, it can lead to plant die-off, soil erosion, and other problems.

The cost and time required to maintain a green roof can be a challenge for some building owners.

Have a maintenance plan in place that includes regular inspections and upkeep.

Building owners can also work with a professional green roof maintenance company to ensure that their green roof is properly cared for.

Fire risk

Green roofs can create a fire hazard, as vegetation can act as fuel for a fire. This risk can be especially high in areas with dry or hot climates.

The vegetation on a green roof can create a fire hazard that can put the building and occupants at risk.

Building owners can reduce the risk of fire by selecting fire-resistant plants, maintaining a well-watered roof, and installing fire-resistant barriers around the roof’s perimeter. Invest in fire extinguishers and smoke detectors.

How to install a green roof on a roof

  1. Lay down primer and put a waterproof elastomeric membrane as the main waterproofing portion of the system.
  2. Build a rim around the exterior, cover it with the same membrane, and then cover it all with a second layer of asphalt roll roofing so that the first membrane would never be exposed to UV rays.
  3. Install a root barrier membrane which is a 15 mil polyethylene, and then install Delta floor acts, which is a heavy roll plastic system that cups water but lets water overflow onto the membrane below.
  4. Install Delta bio top, which is a geotextile that allows water to pass through it without letting soil clog up the cups.
  5. Add dirt and plant plants that will be adapted to the conditions.

How much does a green roof cost?

As a general rule of thumb, green roofs can cost anywhere from $10 to $25 per square foot for a standard installation, but more elaborate designs can cost significantly more. You may be looking at $10 per square foot of extensive roofing and up to $25 per square foot of intensive roofing.

Roof Size (sqft)Extensive Roof CostIntensive Roof Cost
This table represents the different sizes of roofs based on square footage and their extensive and intensive roof costs

The cost of a green roof can vary depending on a number of factors, such as the size of the roof, the type of plants or vegetation used, the climate in the region, and the installation and maintenance requirements.

Keep in mind that while a green roof may have a higher initial cost than a traditional roof, it can provide long-term benefits such as energy savings, reduced stormwater runoff, and increased roof longevity.

Can all roofs have green roofs?

  • Traditional roofs: Traditional roofs, also known as sloped roofs or gable roofs, have a steep pitch and are not well-suited for green roofs. The angle of the roof makes it difficult for soil and vegetation to stay in place.
  • Flat roofs: Flat roofs are the most common type of roof used for green roofs. They are generally easier to work with and can support more weight than traditional roofs. Flat roofs are commonly found on commercial buildings and are a popular choice for green roofs.
  • Pitched roofs: Pitched roofs are sloped roofs that are not as steep as traditional roofs. These types of roofs can be suitable for green roofs but require additional structural support to prevent soil and vegetation from sliding off the roof.
  • Mansard roofs: Mansard roofs are similar to pitched roofs but have a much steeper slope. While they can technically support green roofs, they require significant structural reinforcement to support the additional weight.
  • Commercial buildings: Commercial buildings are a great fit for green roofs because they often have flat roofs that are well-suited for vegetative cover. Additionally, green roofs can help commercial buildings meet sustainability and green building requirements.
  • Vegetated rooftops: Vegetated rooftops are designed specifically for green roofs and can be installed on a variety of roof types. They are modular systems that can be customized for different buildings and roof types.
  • Parking structures: Parking structures can support green roofs, but they require additional structural support to handle the weight of the soil and vegetation. Green roofs on parking structures can provide a range of benefits, including improved stormwater management and reduced urban heat island effects.

What is the importance of a drainage layer in a green roof installation?

Imagine you’re making a cake, and you put a layer of frosting on top of it. But, instead of putting the frosting on a plate or tray, you put it straight onto the counter. What do you think will happen? The frosting will spread out and make a big mess!

Now, let’s think about a green roof. When you put soil and plants on top of a roof, you need to make sure that the water from rain or watering doesn’t just sit on the roof and make a mess, like the frosting on the counter.

That’s where the drainage layer comes in. It’s like a tray or plate that sits under the soil and plants and helps water move away from the roof.

So, just like the plate helps keep the frosting in one place and not make a mess, the drainage layer helps keep the water in one place and not make a mess on the roof.

Do you need a waterproof membrane on a green roof?

Yes, you need a waterproof membrane on a green roof! This is because a green roof has soil and plants on top of it, and if water leaks through the roof, it could damage the building underneath and the plants on the roof.

The waterproof membrane acts as a barrier to prevent any water from seeping through the roof and into the building.

It’s kind of like wearing a raincoat to keep you dry on a rainy day – the waterproof membrane keeps the building dry and protected from any water that might get through the soil and plant layers on the roof.

How can a green roof help reduce stormwater runoff?

Green roofs can help reduce stormwater runoff by absorbing and retaining rainwater. When it rains, the plants and growing medium on the green roof soak up the water, and some of it is used for photosynthesis and growth.

The remaining water is retained in the growing medium or substrate, where it is slowly released back into the atmosphere through evapotranspiration, or into the drainage system at a slower rate.

This process can help reduce the amount of stormwater runoff that would otherwise flow off the roof and into streets and other surfaces, potentially causing flooding and pollution in bodies of water.

By reducing the amount of runoff, green roofs can help alleviate strain on stormwater management infrastructure, and improve water quality in urban areas.

What is the difference between a stormwater runoff system and an irrigation system?

A stormwater runoff system and an irrigation system are two different systems designed for different purposes.

A stormwater runoff system is designed to manage excess water runoff from rain, storms, or melting snow.

The system is designed to capture the excess water and direct it away from buildings and other structures to prevent flooding and damage.

This system typically includes gutters, downspouts, and a network of pipes and drainage ditches that collect and transport water to a designated discharge point.

On the other hand, an irrigation system is designed to provide water to plants and grass in a controlled manner.

The system distributes water through a network of pipes and sprinklers to ensure that plants receive adequate water to grow and thrive.

This system typically includes a timer or controller to ensure that water is distributed at the appropriate times and in the appropriate amounts.

The recommended substrate depth for a green roof installation depends on the type of green roof being installed.

For an extensive green roof, which typically features shallow-rooted plants like sedum, the recommended substrate depth is around 2 to 6 inches (5 to 15 cm).

For an intensive green roof, which can support deeper-rooted plants and even trees, the recommended substrate depth is around 6 to 24 inches (15 to 60 cm) or more.

What is the role of insulation in a green roof installation?

Insulation is an important component in a green roof installation as it helps to regulate the temperature of the building below.

It acts as a barrier to reduce the transfer of heat between the interior and exterior of the building, helping to keep the interior cool in the summer and warm in the winter.

In a green roof installation, insulation is typically placed on top of the waterproof membrane and below the growing medium and vegetation layers.

This helps to protect the waterproof membrane from temperature fluctuations and potential damage caused by the roots of the vegetation.

By reducing the energy needed to regulate the temperature of the building, insulation in a green roof installation can also help to lower energy costs and reduce the overall carbon footprint of the building.

What type of wildlife can be found on a green roof?

  • Insects such as bees, butterflies, and ladybugs
  • Birds such as sparrows and swallows
  • Small mammals such as mice, squirrels, and voles
  • Reptiles and amphibians such as lizards and frogs
  • Plant life such as grasses, herbs, and wildflowers

What type of maintenance is required for a green roof?


Depending on the climate and weather conditions, a green roof may need to be watered to prevent the plants from drying out. Typically, the plants will need to be watered during the first few weeks after installation and then on an as-needed basis.


Just like any garden, a green roof will need to be weeded to prevent invasive species from taking over and competing with the desired plants.


Depending on the soil and plant types, fertilization may be required to ensure healthy growth.

Pruning and trimming

Overgrown vegetation can shade out other plants and create a breeding ground for pests, so regular pruning and trimming may be necessary.

Inspecting the drainage system

The drainage system should be inspected regularly to ensure that water is flowing properly and that there are no blockages.

Inspecting the waterproofing system

Also, the waterproofing system should be checked often to make sure there are no leaks or other problems that could damage the roof.

Inspecting for pests

Insects and animals may be attracted to the green roof, so regular inspections are needed to catch any problems before they become severe.

How can I purchase a green roof system for my home or building?

  1. Determine your needs and goals: Consider the green roof’s purpose, the roof’s size, and the specific features and benefits you are looking for.
  2. Research green roof suppliers and installers: Look for experienced and reputable companies that have a track record of successful installations.
  3. Obtain quotes and proposals: Get detailed proposals from several suppliers or installers, including costs, materials, and project timelines.
  4. Check permits and regulations: Check local permits and regulations for green roofs in your area.
  5. Plan the installation: Work with your chosen supplier or installer to create a detailed plan for the installation, including design, materials, and logistics.
  6. Arrange for maintenance: Make sure to arrange for regular maintenance to ensure the longevity and optimal performance of your green roof system.

What kind of professionals should I seek for green roofs?

Green roof consultants

These specialists can provide guidance on the best type of green roof system for your specific needs, as well as assist with planning, design, and maintenance.

Landscape architects

These professionals can help design the green roof and ensure that it complements the surrounding landscape and meets local zoning and building codes.

Structural engineers

These specialists can ensure that the building’s structure can support the weight of the green roof system and provide input on drainage and irrigation systems.

Roofing contractors

These experts can install the green roof system and make sure it is waterproofed and sealed properly. Vet them to make sure they understand this specialized type of roof.

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Author: Logan

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