Advantages and disadvantages of green roofs

From an aerial perspective, the UK’s towns and cities aren’t appealing, with a sea of black and grey as far as the eye can see. This doesn’t have to be the case though and in recent years a growing trend has made its way to British shores from our European friends.

Looking great, energy efficient and environmentally friendly too, green roofs better utilise an often neglected area. Green roofs are covered with plants and vegetation, bringing a number of excellent benefits to every building.

As with anything though there are a few negatives and this post will aim to highlight both the advantages and drawbacks of implementing a green roof.

The benefits of green roofs

Improve the drainage system

Sustainable drainage is an important component of any building, as a way to counter flooding in the event of excess rainfall. Traditionally, a network of pipes connected to the sewage system has helped control water. However, as a result of increasing urban development, as much as 75% of water is running off into urban areas.

Global warming isn’t helping the cause either and the risk of flooding is heightened throughout the UK. To counter this threat, green roofs are a terrific option. Water is stored in plants and substrate, before being released back into the environment naturally.

Increase the lifespan of the roof

A rooftop is continually under attack from the elements and has plenty to cope with throughout the year. Not only will a roof need to sufficiently deal with wind and rain, but ultraviolet light and fluctuating temperatures too. As such, it’s common for both homeowners and businesses to consider an alternative option for the roof.

Green roofs offer this opportunity and have proved to double or even triple the life expectancy of your rooftop. The barrier of greenery helps protect the waterproof membrane underneath and ensure your rooftop’s life expectancy lasts well for decades.

Boosting thermal performance

Without doubt, one of a green roof’s most beneficial advantages is thermal performance and it’s staggering just how much of a difference this can make. One of the biggest problems facing a typical roof is poor insulation, leading to substantial heat loss in winter and sweltering conditions over the summer months.

This all changes with the aid of a green roof. By implementing a green roof you can ensure to improve energy efficiency and limit the usage of air conditioning too. Plants absorb the sun’s energy and therefore reduce the temperature of the roof in summer, whilst aiding thermal efficiency in the colder winter by locking heat inside.

Helping out the environment

The release of carbon dioxide is one of the key contributing factors to global warming and as such, the government has been charged with meeting stringent EU targets by 2020. Green roofs are ideal for doing exactly this. According to the UKQBC, 44% of total CO2 emissions are released from buildings.

In a similar vein to the point above, green roofs reduce the need for air conditioning, whilst also ensuring less heat is required for the winter. Both air con and the generation of heat create CO2.

Supporting wildlife habitats

Green roofs also help support wildlife and in turn, can create a healthy habitat. Whilst they won’t directly replace ground environments, they’re perfect for attracting birds and other wildlife to create a thriving eco-friendly habitat.

Each green roof will support varying habitats, dependent largely on the type of vegetation included. According to a survey in Switzerland, the study of 11 green rooftops found there to be an incredible 172 separate species.

Aiding air quality

Air pollution remains an important issue in the UK and staggeringly there are some 24,000 who die from this every year. As you would expect, air pollution is a greater problem in urban areas, especially the larger cities such as London and Birmingham.

A green roof helps to improve the overall air quality. According to a study, green roofs help reduce up to:

  • 37% of sulfer dioxide
  • 21% of nitrous acid
  • 0.2kg of dust particles / square metre each year.

Disadvantages of green roofs

Now, that’s a large number of superb advantages to consider a green roof. For those very reasons it’s surprising there aren’t more green roofs around the UK, as you would find in the European countries of Germany and Switzerland, for instance. The government is keen to encourage the uptake of green roofs for all the benefits outlined above though, especially for larger British cities including London.

But whilst the advantages speak for themselves, there are a few drawbacks you should consider before making an investment too.

A greater expense than traditional roofs

Unfortunately for green roofs, they do tend to be slightly more expensive than the traditional option. One of the significant reasons for this being the extra support required to handle the increased load.

However, despite the greater initial setback, over time these green roofs more than make up for the outlay. When you consider the range of incredible benefits highlighted earlier, there should be no reason to allow cost to play a determining role in your decision.

An increase in weight load

There’s no doubt about it, green roofs are heavier and as such, require more structural support to be implemented. Typically, the addition of a green roof will add between 50 and 200kg/metre squared to an existing rooftop. Although some rooftops will need to be retrofitted to cope with the increase in load, fortunately flat roofs are often able to handle this capacity.

Require extra maintenance

There seems to be much debate as to the full extent of maintenance required for a green roof, however what’s clear is you’ll need to do some work to ensure it remains a thriving atmosphere. You should treat your green roof as a garden and as such, it will require watering, feeding and weeding. You could undertake this yourself or even employ someone to take care of the space. Either way, it’s great to keep on top of this brilliant green area.

As you can see, with a green roof there are by far greater benefits for implementing one and as such, you should give the matter serious consideration. There’s a reason green roofs are a common sight around other European countries, so now’s the time to take action and enjoy this beautiful environment.

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