Build it and they will come!
OK well that’s not entirely true unless you’re talking about invertebrates and fauana. But whether you’re looking to reduce the costs of your energy bills, improve a building’s aesthetics or your roof’s physical properties a green roof may well be the answer.
By substantially reducing the amount of heat loss and gain, improving structural integrity and increasing property value, a green roof can be financially significant – in the long-term of course. Green roofs are valuable weapon in the fight against climate change.
But for us living roof benefits go far beyond financial motivation. Providing much needed urban green spaces they encourage biodiversity and reduce pollution. A must when you consider roof surfaces of buildings tend to comprise 20 – 25% of the total urban surfaces.
And it’s important you’re aware of all the pros associated with living roofs before you decide on the type of roof you’re after.
Top 7 Green Roof Benefits
From the financials to the heating and cooling cycles, here are what we believe to be the top x benefits of installing a green roof on your property…
1. Reduction in Pollution
An in-built layer of rooftop vegetation improves the building’s heating and cooling cycle – essentially the building loses less heat in the winter through improved insulation and retains less heat in the summer.
- Reduced air pollution: External GHG emissions are taken in by plants and the need to heat and cool your own property is mitigated
- Reduced noise pollution: A living room’s insulation properties aren’t just thermic.
- Green roofs improve the soundproofing of a building AND reduce sound reflection by increasing absorption.
- Particularly effective when combined with green walls.
- Urban heat island effect: Urban areas are warmer than rural zones.
- The increased energy demands are a very real worry and rising temperatures are certainly focused around cities.
- A simulation in NYC found that the average roof temperature can be reduced by 0.8°c if 50% of the roof is living
During the day, heat from the sun is absorbed by city surfaces and radiated back during the night, creating a hotter city microclimate. This ever increasing rise in urban temperatures increases the energy demands to cool city buildings at night.
A conventional roof absorbs heat and increases the demand on HVAC equipment. Whereas a green roof reduces the roof temperature whilst it’s extra layers serve as insulation, decreasing the amount of heat passing into the building and reducing cooling loads.
In turn this reduces the need to use mechanical equipment like HVAC systems as much, improving their efficiency and reducing GHG emissions. This reduction in fossil fuel combustion works in tandem with the living medium’s ability to photosynthesis – taking in carbon dioxide and emitting oxygen.
2. Energy Bill Savings
And environmental benefits are not the only major plus point when it comes to reducing the load on heating and air conditioning. Through the use of:
- Increase in thermal mass
- Reduction of heat loss via radiation
Green roofs have significantly improved temperature regulation when compared to conventional roofs – and this pays dividends throughout the year, reducing the need to heat your property in the winter and cool it in the summer.
NB. Soil is not as effective an insulant in wet conditions, so this will be weather dependent.
Whilst the heat gain and loss figures above are from colder climates with a greater temperature fluctuations (Ottawa), you can see just how much of an impact the insulating properties of vegetation can have.
And the University of Michigan predicted $200,000 cost-savings when compared to a conventional roof through multiple mediums – including reduced energy consumption.
3. Increased Roof Life Expectancy
Introducing a green roof to your property protects the roof membrane from exposure to extreme weather conditions (such as freeze-thaw action), ageing caused by thermal expansion and contraction and UV radiation.
It is generally accepted that a greened roof will double, if not triple your roof’s material lifespan.
The typical lifespan of a green roof has been estimated at 40 – 55 years. Considering a conventional roof (comprised of asphalt shingle) usually lasts for 15 – 25 years you can see how substantial the improvements are.
The installation of a green roof can conceivably be seen as replacing your existing roof. An incredible feat when you consider how much less invasive the project is likely to be.
4. Improved Biodiversity
Cities are in dire need of green spaces and habitats for fauna and flora. The ever-rising population demands lead to high rise blocks of flats with limited green space available.
So designing roofs to provide habitats for nesting birds, plants and invertebrates is essential for a balanced ecosystem.
A study by Grant and Lane (2006) focusing on London found that green roofs can provide valuable wildlife habitats and that their construction is a potentially viable solution to mitigate the ever-increasing loss of habitat.
A green roof can be designed to suit individual species of plant or animal, so it’s vital to consider what you’re trying to attract. For example, the Black Redstart – an endangered bird that typically favours industrial sites – began to return to green roof sites in Sheffield. Primarily because the roof’s were kept ‘wild and natural.’
5. Increased Property Value
Green roofs are an expensive outlay initially – check our green roof costs page for more detail. But an average semi-detached home in the UK could be looking at £5,000 – £15,000+ depending on the type of living roof installed.
So whilst energy efficiency benefits and increased life expectancy are great, but what if you don’t live in this property for the rest of your life?
Fortunately we have even more good news. There have been multiple (global) studies undertaken to look at how green roofs affect a property’s value.
In fantastic news for landlords, one NYC study found that the cooling affects, stormwater control and amenity values contributed to a 16% increase in rental prices for property’s with green roofs in the Battery Park City area.
A large scale Australian study found that residential property values increase by 6 – 15% when green roofs and / or walls are fitted.
6. Improved Drainage
A typical extensive green roof will fully intercept between 50 – 75% of rainwater – retaining it for up to two months. And it will delay all surface runoff, typically retaining between 70 – 80% of it.
As 80% of people are expected to live in urban areas by 2050, the need to control and manage stormwater and runoff is clear. More and more impermeable surfaces are constructed at the expense of permeable, green surfaces.
In times of heavy rainfall, existing drainage systems are less equipped than ever to cope with the large volumes of water.
By reducing the amounts of stormwater runoff and attenuating peak flow rates, rooftop vegetation can be an incredibly effective method at reducing the risk of flooding.
One absolutely essential consideration is the structural integrity of the roof. A large scale intensive green roof already places significant stress on the property. Add to that the weight from rainwater absorption and the potential issue becomes clear.
7. Health and Wellbeing
(Intensive) Green roofs provide essential outdoor recreational areas on otherwise unusable spaces. It provides numerous wellbeing benefits, including:
- The use of open, green space was positively associated with employee wellbeing and self-reported satisfaction levels
- Several trials have revealed the beneficial effects on mood and mental health of simply observing nature, or even images of natural scenes
- The reduction in stress, blood pressure, muscle tensions and improved mental state are all clearly associated with green space(s) and improved air quality