Balancing the need for a functional, forward-thinking design with an increasing demand to reach net zero is the unenviable task faced by architects and specifiers today.
With sustainability, every part of a building needs to be considered, and every stage of the building’s lifespan. Operational carbon, the emissions of a building in use and embodied carbon – the emissions produced during manufacture, demolition and end of life – are equally important considerations for architects.
Roofing systems are only one part of a wider plan for a project, but as 25% of the heat from a building escapes through the roof, the roof build-up has a huge influence on the energy efficiency and sustainability of the whole building. A sustainable roofing system is one that is able to effectively insulate and waterproof the building: an important consideration during specification. A roof has the potential to make or break a project’s sustainability credentials and greatly affect the sustainability assessments of a BREEAM or LEED rating.
On the legislative side, there are few concrete rules in place, but with net-zero targets set for 2050, and the drive towards UN Sustainable Development Goals, this is likely to change. At present, two of the most pertinent are Procurement Policy Note (PPN) 06/21, which decrees Government contracts over £5m will only go to businesses with a carbon reduction plan, and PPN 06/20 – taking account of social value in the award of central Government contracts. As Government policy typically sets the standard for others working in the industry, it is likely that others will follow suit in making more stringent, legally-enforced sustainability demands; many local authorities have surpassed this already and are demanding more from a social value perspective than the Government.
At this stage, however, the majority of sustainability efforts work to reduce emissions and essentially futureproof a building, ensuring it is compatible with legislation that doesn’t yet exist and aligns with net-zero targets.
Sustainable roofing systems
For sustainability in the construction industry, physical performance is as important as any other factor. In some ways, there is no sense in declaring a certain system as the most sustainable: if a roofing technology doesn’t suit the roof and quickly fails, it is ultimately no longer sustainable.
That being said, there are roofing systems with more sustainable potential than others that combine sustainability and physical performance exceptionally well. Provided they are carefully chosen to work well with any given project, any of these roofing systems could help you meet Environmental, Social and Governance (ESG) targets, adhere to potential sustainability legislation and futureproof a building.
Green roofs
In a discussion of sustainable roofing systems, green roofs usually sit top of the list. With their eco-credentials the focus of any discourse, green roofs have become almost synonymous with sustainability in the roofing industry.
Available in three types, biodiverse, extensive and intensive, these roofs have a vegetative layer that actively works to absorb carbon dioxide, insulates the building and controls stormwater levels. Green roofs are long lasting and work to reduce the urban heat island effect of cities; provided the roof is suitable, this roofing system is incredibly sustainable and could futureproof a building for decades to come.
Solar roofs
This roof type is generally less about the roof build-up and more about what sits above it. Renewable energy as the single source of our energy needs is the ultimate aim of net-zero targets and many sustainability policies: a solar roof puts any business one step closer.
A business can generate its own green energy during the day, lowering its reliance on the national grid and potentially saving thousands of pounds in energy costs. Solar roofs are becoming increasingly efficient at generating energy and are becoming a more popular option as energy costs rise.
Hot melt
Hot melt roof build-ups are a little different from the other roofing systems mentioned here. Rather than any obvious feature, it is their durability that contributes to their sustainability. Construction is a notoriously carbon-heavy industry, and a roof that needs regular maintenance or is replaced more frequently is going to amass all the additional carbon emissions associated with the work.
Hot melt roofs are known to last for several decades and, in many cases, can have a lifespan as long as the building itself. Sika’s hot melt structural waterproofing, for example, is BBA certified to provide durable roof waterproofing for the design life of the roof in which it is incorporated. Hot melt is also compatible with green roofs, acting as the waterproofing membrane in the build-up, so it can be part of a wider sustainable roofing system.
Single ply
In a similar manner to hot melt roofs, the durability and longevity of single-ply roofs help make them sustainable. Single-ply membranes have proven their performance as a roof waterproofing product, lasting for decades on a roof, and when installed correctly, will require minimal maintenance and are straightforward to replace when required.
Some single-ply membranes are more sustainable than others, however, as manufacturers strive to create a more sustainable roofing package. Leading roofing manufacturer Sika has created the Cradle to Cradle Silver-certified Sarnafil AT, a single-ply membrane with exceptional sustainability credentials.
Combining technologies
Perhaps the most sustainable roof of all is one that utilises multiple roofing technologies. If the project permits, combining multiple roofing technologies into one sustainable package can help you reap the benefits of all the systems. In a green roof system, the vegetative layer sits at the very top: in the build-up, the waterproofing membrane plays a vital role. Including a membrane with certified sustainability credentials like Sarnafil AT ensures the whole system is considered. Solar panels can also sit above a green roof, generating renewable energy for the building.
Third-party proof
To avoid greenwashing, you need a roofing system that has been assessed and certified by a third-party organisation. An Environmental Product Declaration (EPD) has long been the standard for sustainability certification, but that is exactly what it has become: standard. An EPD is expected at this stage, and all it does is list the impacts; it doesn’t rank them or consider other aspects, such as social value. Therefore, companies must do more to prove the sustainability of their products and themselves.
For the highest level of sustainability ratings, you should look for a certification from an independent, respected testing body with a rigorous assessment process. One such example is Cradle to Cradle, an organisation that evaluates a product’s ability to join the circular economy. To be certified, a product must excel in five separate sustainability categories: Material Health, Material Reutilisation, Renewable Energy Use, Water Stewardship and Social Fairness. Cradle to Cradle sets a high bar for manufacturers and is one of the most respected accreditations an architect or specifier can look for.
