Green Roof Statistics in the UK
The UK green roof market continues to grow year on year, with London leading the way.
We’re all aware of the multiple benefits awarded to us by green roofs – insulation, pollution and noise reduction, urban cooling – the list goes on.
But green roofs in the UK are still relatively expensive because the market is comparatively immature. For us to reap the rewards, improved awareness and understanding is key.
Living Roof Market Size
Whilst the UK green roof market is growing by 17% annually (according to the most recent data from 2017), it’s very London centric. 42% of all green roof installations occur in London.
But whilst there’s growth, the UK market lags significantly behind other European nations. Particularly Germany.
- The German green roof market is arguably the most advanced in the world and covers somewhere between 100 – 150 million square metres.
- The UK probably only has between 5 – 7 million square meters of green roof coverage.
- 2 – 3 million of those square meters are in London
Intensive vs Extensive
Extensive vs Intensive Roofs in the UK
Extensive roofs are so much more popular in the UK primarily due to the cost and ease of installation.
This isn’t the same in every country, but we don’t anticipate this changing anytime unless there’s a significant uptake in commercial projects.
In the German market where there have been significant grants and subsidies the ratio of extensive to intensive (85 – 15%) is roughly the same.
However Hungary is the total opposite, with 65% of all green roofs installed being intensive. For the UK to move towards this sort of ratio we’d need to promote commercial projects and reduce the overall cost of installation.
How much will a Green Roof Cost?
The cost of a green roof project varies significantly. Commercial projects can cost hundreds of thousands of pounds – if not more – based on the type of green roof, it’s accessibility, the materials used and the machinery and labour required.
But in reality, for a traditional, domestic green roof project you’re probably looking at somewhere between £4,000 – £15,000.
Of course a DIY living roof project is going to save on costs significantly. But you’ll need to be confident in your ability to gauge the structural stability, installation and ongoing maintenance.
How much Will I Save with a Green Roof?
The above report included three different roof sizes (5,10 and 50,000 square feet – American, sorry) and came to some incredibly promising conclusions.
A 5.2% IRR – defines the annual growth rate – means you would make your money back in under 20 years.
A 224% ROI means that once you have paid the initial costs (and general maintenance fees), you will make around 124% profit.
- So if you purchased a £7,000 green roof
- Annually you would make £364 a year
- Recouping your outlay in 19.2 years
- And lifetime profit of £8,680
So if you’re got the capital (and time) to spare, green roofs can be an excellent financial investment.
Living Roofs and Pollution Statistics
Studies in the USA showed that the aboveground section of the plant collected 84g of carbon / m2 .Whilst the roots accumulated 53g of carbon / m2 in one vegetation season.
And research in Singapore showed that the substrate and vegetation could capture up to 37% of S02 from the air.
The plants also lower the ambient temperature, which slows down the photochemical reactions and leads to the reduction of secondary air pollutants such as ozone. Making green roofs an excellent option to mitigate climate change.
Of course this is difficult to extrapolate because weather conditions are different everywhere. But, based off of this it could be assumed that a 70m2 green roof in a 90 day growing season would offset:
Living Roof Lifespan in Numbers
By protecting the roof’s membrane from the elements and improving a roof’s structural integrity, a green roof can extend your roof’s lifespan by up to 300%.
Of course it depends on:
- The type of green roof you install
- The type of plants you use
- Your building’s structural integrity
Typical estimates are around 40 – 50 years with some claiming an extensive green roof with PVC products can last for up to 90 years.
Generally this is around a 20 – 40 year increase from conventional roof longevity.
Green Roof Statistics on Heating & Cooling
Green roofs provide excellent insulation for buildings, consistently reducing the average daily heat flow, particularly in the summer.
A living roof’s thermal effectiveness can reduce air conditioning useage by as much as 75%. They’ve even been proven to reduce the urban heat island effect by over 2.5°c.
And whilst they’re certainly more effective in hotter months, their ability to retain heat in the winter make them a year round winner.
Green Roof Heat Gain - Summertime
Heat gain – the increase in building temperature due to solar radiation and high outdoor temperatures – is significantly lower on green roofs than black roofs.
The 84% disparity in heat gain provide exceptional energy savings throughout all seasons.
Green Roof Heat Loss - Winter
Whilst a living roof’s innate ability to retain heat in the cold make it a great winter insulator, they’re more effective in summer months.
Which, considering air conditioning sales across Europe are rising rapidly, is a very useful trait to have.
Living Roof Energy Saving Statistics
Well based on the above, an average home could save:
- The £1,750 on the air con unit for starters – if the reduction in heat flow is efficient enough this is a huge upfront cost gone
- And at 8p an hour, if you use the air con unit for 1500 hours a year, an 84% reduction would save over £100 a year.
Drainage and Green Roofs Statistics
Green Roofs Reduce the Rate of Runoof
And they can add 3 hours to the time it takes for the rain to runoff the roof. Some studies showed an average of 93% slowdown and runoff reduction in the summer months. All attributed to green roofs.
Typically extensive roofs intercept and retain the 1st 0.5 – 0.75 inch of rainfall. The thicker, hardier (and generally more intensive the roof), the more rainfall they can intercept.
The types of plants you use has an effect too. Succulents like sedums contribute to around 40% of the runoff reduction. The remaining 60% is attributed to evaporation from the growth medium.
Green Roofs and Noise Pollution Statistics
Noise levels penetrating the interior of the building through both green and conventional roofs, the noise level was reduced by 20dB for both intensive and extensive green roofs.
That’s roughly the difference between a washing machine (70dB) and an underground train (90dB).