What is a green roof and should you install one?

Green roofed structures date back thousands of years, even before the concept of housing as it is known today was birthed. The earliest green roofs came in the form of sod roofs above caves. Plants were used on top of the caves for ceremonial and agricultural purposes. Over time, sod roofs lost their value due to natural disasters and borrowing by animals. 

The most famous green roof of all time was the Hanging Gardens of Babylon. The gardens were documented as one of the seven wonders of the world at the time. Although similar to what a green roof looks like today, the engineering was quite different. The gardens were built over arched stones overlaid with waterproof reeds with thick tar.

Related: Green roofs cover this sustainable school in Prague

As modernity kicked in, most people switched to iron sheets, shingles and roofing tiles, among other options. With these options available, a few considered the idea of green roofing. As industrialization kicked in, more roofing options made the Hanging Gardens of Babylon seem like an ancient idea. 

Years of environmental degradation, thanks to the agricultural and industrial revolution, followed. Eventually, the effects of environmental degradation started showing up. The world soon realized that preserving green spaces was key to human survival. As a result, most people started paying attention to nature, leading to the revival of green roofs.

Modern green roofing technology took shape around the 1960s. It all started when Germany invented technology against roof ingress. The new technology was heavily marketed, and most people in Germany started adopting green roofs. Since then, many technologies have come up that have advanced green roofs. Today, green roofs are growing in popularity across the world, and America is leading the race. Research shows that the global green roofs market will grow by 17.7% in 2023 from $1.53 billion in 2022 to 1.80 billion. The market is expected to hit $3.31 billion by 2027. 

In simple terms, a green roof is any roof that features green living matter. Such roofs are designed in such a way that they can hold water and grow vegetation throughout the year. The U.S. General Service Administration (GSA) estimates that green roofs reduce storm runoff speed from roofs by 65%. 

In most cases, the vegetation grown on green roofs does not require plenty of water and hence often doesn’t have irrigation. However, installing a green roof is not a straightforward affair.

Before installing a green roof, you must consider the drainage system, the cost implications of creating several layers on your roof, and the maintenance aspects. 

Green roofs explained

There is more to green roofing than meets the eye. What most people crave is the green outer vegetation, but what they do not know is the details beneath. Classically, there are two types of green roofs: intensive and extensive.

The extensive roof design has a thin depth of soil with few layers, while the intensive one has multiple deep layers of soil with widely varied plant life. The main difference between intensive and extensive is the nature of the soil profile and the types of plants available. Intensive green roofs have a varied plant life, while extensive ones have few plant options.

Extensive roofs are also easy to set up and maintain compared to intensive ones. It is up to the homeowner to choose which option works.

In the design of a green roof, there are key factors that count. In the example of an extensive roof, the green section is placed like a rug over an area where people do not walk often. However, installation involves several steps. 

The first part to be installed over the roof is a special membrane used to protect the roof from water damage and root penetration. The protective membrane could be hot-applied rubberized asphalt or a synthetic layer of rubber. Root-repellent materials are also used in this stage of green roof installation to prevent plant roots from damaging the roof.

Once the protective membrane is installed, a drainage layer is put in place. The drainage is made up of pebbles or a special geocomposite drainage mat. Most people prefer having a filter cloth just above the drainage. On top of the filter, the layer of growing matter is well spread. This layer is made up of a growing medium of choice. 

Several types of plants do well on green roofs, including sedum, chives and delosperma, among others. These plants have shallow roots and are ideal for anyone trying to put up a green roof. Further, they are not thirsty for water, a key factor to consider when choosing green roof plants. 

Benefits of green roofs

Green roofs offer design, environmental and ecological benefits. On the design aspect, a green roof is one of the main ways to integrate nature into your home. It brings the beauty of the wild right into your home. They offer spectacular views from above and below where applicable. The roof is worth every penny when it comes to the aesthetic value it adds to a home.

Environmentally, a green roof is one of the best ways to create a microclimate in your home. They provide a cool, serene microclimate for your home. Even if you live in a hot area, a green roof will bring a cooling effect to your surroundings. Green roofs reduce the heat flux from your roof by up to 72% on hot days. You do not have to undergo expensive cooling costs if you install a green roof.

The other vital factor is the role that the roof plays in providing habitat for wildlife. Wild insects and birds may find your roof to be a good habitation just because you have installed a green roof. At the end of the day, it is a win-win for you and the ecosystem.

Disadvantages of green roofs

Green roofs are expensive, and this is one factor that most people don’t fully consider. You must first consider how much you are willing to spend before going for a green roof. According to Rand Engineers, it costs approximately $25 to $30 to install one square foot of a green roof. Note that this is exclusive of the cost needed to repair or install the normal roof underneath. If you are installing a normal roof that costs $30 per square foot, that means installing a green roof doubles your roofing cost.

Some extra weight piles up on the house when a green roof is used. If you intend to use a green roof, you must make sure you have a stable foundation and walls. As a result, you might have to spend a little more on your foundation and walls than you would without a green roof.

Green roof materials

The most important aspect of creating a green roof is picking the right material. Green roof materials can range from grass to bamboo and even solar panels. The most important aspect is to ensure that the material you choose has truly been verified to be green. Among the best green roof materials in the market include biodegradable canvas, Mexican Amazulu Grass, and Solar Panel roofs.

Is a green roof good for you?

A green roof is a win for the environment in many aspects. However, this does not mean it is good for you. Its environmental benefits are only applicable in situations where you intend to keep it for long. If you intend to replace yours in a few years, stick to a normal roof. Green roofs use so many materials underneath that they could be harmful to the environment. 

You should probably also consider your location and the cost of setting it up. Based on location, a green roof might be a bit problematic if you experience very cold weather. Green roofs bring a cooling effect. In cold regions, they may lead to extra heating costs. In hot or warm regions, green roofs are a perfect solution to bring in a cooling effect. In terms of cost, make sure you get the full picture of the cost requirements before you start installing the green roof. 

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