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Biosolar roofs are a biodiversity encouraging, energy bill reducing solution to our ever-growing city limits in the UK.

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What is a Biosolar Roof?

Essentially a biosolar roof is a green roof that is integrated with a solar panel – or PV – system. Or, in Layman’s terms, solar panels on a green roof. The combination of the two increases biodiversity, renewable energy production and reduces your energy usage. 

If you’re looking for a sustainable, eco-friendly way to mitigate your impact on the planet (whilst producing your own renewable energy), biosolar roofs – when implemented correctly – could be the solution for you.

Biosolar roof

And What is a Green Roof I Hear You Ask?

A green roof is a vegetative layer grown on the roof of a home, commercial building or even sheds in DIY cases – designed to maximise energy efficiency, improve air quality and raise biodiversity.

This green layer provides numerous environmental and economic benefits, including:

  • Provide improved insulation (both heat and sound)
  • Reduce energy consumption
  • Create habitats for wildlife

Biosolar Roofs in the UK

With space – particularly in cities – becoming more of a premium. Biosolar roofs present a green, urban opportunity to minimise energy efficiency and promote biodiversity. Even helping reduce climate change.

Bauder – the UK flat roofing company – first introduced biosolar technology into the UK market in the mid-1980s. Unfortunately it hasn’t taken off as we had hoped it would.

Whilst the practice of combining the two technologies is a relatively recent phenomenon that’s growing in popularity amongst Europe’s green-roof elite. Primarily Germany, Switzerland and Austria. As ever in these situations, the UK is somewhat lagging behind.

Biosolar Roof Performance

Whilst solar power and living roofs are often thought of as two entirely separate disciplines, the two can work rather well together. As a green roof minimises heating and cooling cycles, energy expenditure and the urban heat island effect – amongst a host of other benefits – they can be help make solar panels 3.6% more efficient on average.

Crucially, when it comes to biosolar roof performance, integrating solar mounts with green roof layers is key. And there are multiple elements that will impact biosolar roof performance, including:

  • Waterproof layer: If the solar mounts penetrate the roof’s waterproof membrane, the structural integrity of the roof is ruined and the building is put at risk
  • Substrate: The depth of the living roof’s growing medium must be enough to support the solar arrays
  • Roof Stability: The roof in question must be secure enough to support the weight of the green roof + the solar panels
  • Light and rainfall: The vegetation will need light and water, primarily for photosynthesis. Ensuring that both can penetrate beneath the solar panels is essential.
Solar PV on a flat roof with flowers

How Much Does a Biosolar Roof Cost?

There are a number of variables to take into account here:

  • The size of your roof
  • The type of green roof you want to build
  • The plants you use
  • The type and quantity of solar panels you use

Typically, a green roof in the UK will cost around £50 – 200 / m2. And a single solar panel will cost somewhere around £350 – 500.

Where to go all-in and (professionally) build a green roof on your home – the average UK roof is between 65 – 75m2  – and add a traditional 4kwh solar panel system, it would likely set you back around £13 – 15,000.

Yikes. Even if that would cover all of your energy needs!

Fortunately this isn’t the only option. Extensive green roofs are significantly cheaper than intensive roofs. Even more so if you build the green roof yourself. DIY green roof projects can cost as little as £500.

And you can buy singular solar panels for a few hundred pounds, install them yourself and get a system up and running for under £1000.

However. To make the most of solar energy you will need a solar battery so you can store electricity and use it in the darker months. And batteries can cost upwards of £5,000.

Biosolar Roof Maintenance

Whilst an extensive green roof is almost maintenance free, solar panels and green PV roofs will require some maintenance.

Larger, intensive green roofs may require some generic landscaping:

  • Watering
  • Deadheading
  • Weeding
  • Fertilsing

But are still fairly minimal. Solar panels do require some additional maintenance. Particularly cleaning a few times per year. You can do this yourself, or pay someone who knows what they’re doing somewhere around £100 – 200.

Benefits of Biosolar Green Roofs

  • Green roofs reduce a building’s temperature in the summer and solar panels are more effective at lower temperatures. 

Solar panels are ‘power tested‘ at 25 degrees Celsius and on hotter days they can become 10% more inefficient.

  • Panels create shade, (further cooling the building) and even increase biodiversity as animals are drawn to shade, shelter and areas of moisture

Animals using solar systems as habitats is fairly well documented. Particularly when combined with green roofs, such is the abundance of insect life – or food in this case – for either resident or migratory birds.

  • Significantly reduced energy bills

a 4KW solar array will provide enough power for a family home in the UKproviding you also use a solar battery. But even a 1KW system will dramatically reduce your energy bills. Particularly when coupled with a green roof.

  • Reduced reliance on energy companies, carbon emissions and rising energy bills – an expected rise of 30% in 2022

The insulation benefits of a living roof alone are worth it. Even though energy from Britain’s grid is very green – in the last 7 years carbon emissions from the electricity system have decreased by 66% – there are still substantial savings to be had. 

  • Reduced floodwater runoff

With the inevitably of climate change, using green sources to tackle it is, or at least should, undeniable. Towns across the UK are being told to adapt or die‘ when it comes to flooding. And a biosolar roof – with it’s intensive vegetative layer(s) – can retain up to 0.75″ of rainfall and slowdown runoff by 93%.

  • Increased roof life expectancy

A green roof can increase your roof’s lifespan by 300%they’ve been known to last for 90 years.

  • Improved air quality

They have been proven to capture 37% of sulphur dioxide and a green roof on an average UK home would absorb around 50,000g of C0² a year

Biosolar Roof FAQs

For solar panels to be supported on a green roof, the panels must be:

  • Fitted on specialist mounts
  • These mounts raise the panels higher above the roof than normal
  • And create a steeper angle for the panels – typically around 15 degrees compared to 10 on a conventional roof – so the vegetation can accrue enough sunlight and grow

These mounts are fitted into the growing medium that can balance the mount effectively. Installing the two together makes this process much, much easier.

Yes. Combining the two is what is known as a biosolar roof and is commonplace throughout mainland Europe. 

As long as the substrate depth of the green roof – and the roof itself – can support a solar array, then the two can work very well together.

DIY extensive green roofs will be to shallow and not structurally sound enough to support solar panels. Unless you purchase very small, lightweight solar panels.

If you purchase a full solar PV system, a sturdy, intensive roof  is essential. You need enough substrate to support the solar array. 

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