Lately, it seems all we can talk about is the weather, and with good reason. The Met Office recently announced that 2025 is on track to be one of the hottest UK summers on record. All season long, back-to-back heatwaves sent the country into a sweaty frenzy as we desperately searched for ways to stay cool. And while summer may be drawing to a close, many of us are already thinking ahead to how we can better cool our homes next year, as we adjust to this new high-temperature normal.
While fans and portable air conditioners are tried-and-tested cooling heroes, there may be a more permanent—and more surprising—solution: green roofs.
Never heard of them? I don’t blame you. Neither had I until I spoke to experts at CIBSE, an engineering organisation focused on best practices for future-proofing buildings against climate extremes. They told me this eco-friendly home upgrade could be the future of sustainable living. Big claims, I know—so I turned to Dr Zoe De Grussa, Research Manager at CIBSE, to find out what green roofs are, how they work, and whether they could be right for your home.
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What is a green roof?
“A green roof is a roof that is partially or completely covered with vegetation, planted over a waterproofing membrane.” explains Dr. De Grussa. Green roofs are made up of several layers that support plant growth while protecting the roof underneath. At the base is a root protection layer to stop roots from damaging the structure. Above that, a drainage layer regulates how much rainwater is retained or allowed to drain away. A filter layer keeps the drainage from getting clogged, and the top substrate layer acts as the growing medium. Think of it as a mini garden for your rooftop.
There are two main types: extensive and intensive. “Extensive green roofs feature a thin (30 – 100 mm), lightweight growing medium and are typically planted with low-maintenance species such as sedums.” says Dr. De Grussa. They are the more cost-effective option and require minimal maintenance. They often need no additional structural support, making them the ideal type for those with low-load-bearing rooftops.
Intensive green roofs however are a bit more heavy duty. Dr. De Grussa explains they, “use a much deeper soil profile (>150mm) capable of supporting larger vegetation, including shrubs and lawns and suitable for accessible rooftop spaces (e.g., roof top gardens/parks). These systems are heavier, more expensive, and demand regular maintenance such as irrigation and feeding.” The upside? They’re often more visually striking and allow for greater landscaping creativity.
How do green roofs cool down your home?
So, what does any of this have to do with the weather, I hear you cry? These sky-high gardens are surprisingly effective at regulating the temperature of the rooms beneath them, both in summer and winter.
“The soil and plants on a green roof provide an additional layer of insulation, helping to prevent heat from entering the building during warmer months and reducing heat loss in winter.” explains Dr. De Grussa. “Unlike typical roofs that absorb and transfer heat indoors, vegetation releases moisture into the air during hot weather, which evaporates and cools the surrounding environment.” So, unlike air conditioning, green roofs cool your home without pumping hot air back into the outdoors.
“This natural cooling effect lowers local outdoor and indoor temperatures, reducing reliance on mechanical cooling and improving comfort. The insulation also helps retain warmth in colder seasons, enhancing energy efficiency year-round.” In short: they boost your comfort and could ease the strain on your energy bills.
Other benefits of green roofs
If that's not enough to sell you on this clever green cooling machine Dr. De Grussa explains “Green roofs offer a range of environmental, social and health and well-being benefits.”
Boosts surrounding ecosystems
It should come as no surprise that more greenery means more opportunity for nature to thrive. As they grow in popularity, green roofs have the potential to bring more green space into urban environments, with all the benefits that come with it.
“They support urban biodiversity by attracting wildlife such as birds and insects, and depending on the vegetation used, can help improve air quality by filtering pollutants.” says Dr. De Grussa. Carbon dioxide emissions are one of the leading contributors to climate change, and LETI (London Energy Transformation Initiative) estimates that 49% of UK emissions come from buildings like homes and offices. By reducing the need for air conditioning in summer and heating in winter, green roofs can play a real role in shrinking this figure.
Flood and storm protection
We’ve already discussed how green roofs can help protect us from heatwaves and cold snaps, but they can also be massively beneficial when it comes to floods and storms. “One of their most valuable functions is managing stormwater - retaining and slowing rainfall runoff which eases pressure on drainage systems.” explains Dr. De Grussa. “With climate change increasing the frequency of intense rainfall following hot weather, this function is becoming even more valuable.”
They act as a Sustainable Drainage System (SuDS) by managing rainfall at the source, allowing it to evaporate naturally. This reduces the load on drainage systems and lowers the risk of flash flooding, particularly in urban areas.
Mental health
Dr. De Gussa was also passionate about the personal benefits a green roof can have on a human level. “Access to nature is also well known to enhance mental and physical wellbeing, making green roofs a key contributor to healthier, more liveable cities. Personally, I’d much rather look out onto a green rooftop than a bare asphalt one!” And honestly, same. The phrase “go out and touch some grass” feels relevant.
Drawbacks of green roofs
Like all home improvements, green roofs come with challenges, and it’s important to understand them before rushing to the garden centre.
Unsurprisingly, they aren’t cheap. Installation costs can be high, and ongoing maintenance, especially for intensive systems, requires time and investment. That said, it can pay off over time in the form of reduced energy bills and improved insulation.
It’s also essential to consult experts to assess whether your roof is suitable. “Technically, intensive systems might need structural reinforcement, and if waterproofing and drainage aren’t carefully designed, they can lead to problems.” says Dr. De Gussa. “Green roofs aren’t suitable for every building or climate. Structures with low load-bearing capacity may not support the added weight of intensive systems, and very steep roofs can make installation difficult and, in some cases, not viable.”
There’s also a small fire risk if vegetation becomes too dry in hot weather, so it's important to follow safety guidance, such as the FLL standards. This is why organisations like CIBSE are pushing for better awareness and education to help people adopt green roof systems safely and effectively.
CIBSE’s own Technical Director, Dr Anastasia Mylona—whom I previously interviewed about the risks of at-home air conditioning—has one installed on her own home. Despite some early hiccups, she told me it’s been a roaring success, especially during this year’s heatwaves.
How to maintain a green roof?
Having access is another important design constraint in order to be able to maintain the green roof effectively. Maintenance is required in the first 1 -2 years until the green roof is established, after that the roof is more stable.
“Green roofs require different levels of maintenance depending on their type,” explains Dr De Grussa. Extensive roofs planted with sedum typically need weeding three times a year and feeding once annually. Intensive roofs, however, need more regular attention, just like a traditional garden, based on the needs of the plants you choose.
“During hot or dry summers, watering becomes more important—especially for roofs with moisture-sensitive plants or those still establishing,” she adds. “Even drought-tolerant roofs may need extra attention during prolonged dry spells, so having access to a water source—and ideally rainwater harvesting—is key.” You’ll also need to keep an eye on drainage systems to ensure they remain clear and effective.
Dr De Grussa emphasises the importance of getting more people talking about these systems. “Ultimately, the long-term benefits—environmental, financial, and social—make green roofs a smart investment for future-ready buildings.”
