When completed, A3 New Bailey in Manchester will be one of Europe’s greenest buildings.
Not only has it been designed to achieve the toughest sustainability ratings, it will also feature Europe’s largest living wall. But as with any innovative project, it presented some major challenges when it came to the specification of the rainscreen façade system.
Lester Cladding NW Ltd were responsible for the design and build of the façade. A rock mineral wool product with a thermal conductivity of 0.035 W/mK had been specified. But when conducting the calculations, they instantly ran into a problem. An insulation depth of 240mm was required to achieve the U-value of 0.15W/m2K.
Jamie Simm, Operations Director at Lester Cladding NW Ltd explained: “There was a strict external and internal boundary, so we needed to keep the façade wall build-up within those measurements. But the amount of insulation needed to meet the target U-value increased the depth of the wall, pushing it over the boundary line.”
When looking for an alternative solution, the company approached Knauf Insulation’s Project Specification Team to discuss the brief. As well as meeting the thermal performance requirement, the insulation needed to comply with building regulations that ban the use of combustible materials in the external walls of certain buildings over 18m tall. It also needed to help reduce noise and meet the project’s sustainability targets.
After running 3D U-value calculations, Knauf Insulation’s Technical Support Team recommended 170mm Rocksilk RainScreen Slab for the ventilated façade, a rock mineral wool insulation which has a thermal conductivity of 0.034 W/mK. For the Steel Frame System (SFS), they recommended 150mm OmniFit Slab 35, a glass mineral wool insulation with a thermal conductivity of 0.035 W/mK.
This combination reduced the thickness of the wall build-up by a significant 70mm, ensuring the U-value could be met within the required parameter for the wall build-up.
Simms said: “Not only did Rocksilk RainScreen Slab offer superior U-value performance for a slimmer profile, it reduced costs across the whole build. As well as reducing the quantity of insulation required, we could use smaller helping hand brackets and thinner fire barriers for example. It was the product that steered the job through.”
In addition to achieving the required thermal performance, both products are non-combustible with a Euroclass A1 reaction to fire classification. This means they will not add to the development or spread of fire, so comply with the building regulations. Rocksilk RainScreen Slab is also British Board of Agrément (BBA) certified for use in buildings of any height and for the broadest range of thicknesses and build-ups of any rainscreen solution on the market.
Mineral wool also has an open fibre matrix, which means it has sound absorbent properties. The insulation will help to reduce noise from the busy city centre location and from disturbing residents.
The choice of insulation was not the only challenge for the build. There is no template for supporting Europe’s biggest living wall. So, Lester Cladding NW Ltd needed to draw on their own extensive knowledge and expertise, as well as that of the whole supply chain to create a bespoke solution from the ground up.
One problem with this approach, was that every potential solution impacted another aspect of the façade build-up. To overcome this, Lester Cladding NW Ltd took the unusual step of arranging a meeting between representatives from eight different design and manufacturing partners. Together they discussed the whole system ‘screw by screw’.
“Getting everyone sitting around the table meant that all our manufacturing and design partners were completely engaged. They understood what we were trying to achieve, and all worked together to find the best solution.”
There was one particular factor that could affect the insulation – water. While a living wall utilises planting schemes that thrive in drier conditions, a 4,000m2 living façade still requires a lot of watering – something that could introduce lots of extra moisture into the system.
Knauf Insulation’s Rocksilk RainScreen Slab has a water-repellent additive that promotes water run-off and ensures the slab will maintain its integrity. A traditional façade system prevents the insulation from getting saturated by rainwater, while the ventilation reduces the build-up of condensation and allows the insulation to dry out if it does get wet.
However, the water-repellent additive does not make the insulation waterproof, so it needed protection from the constant flow of water from the irrigation system. As a result, an additional breather membrane was installed to prevent moisture from penetrating the façade system and affecting the insulation.
A3 New Bailey has been designed to UKGBC’s Net Zero Carbon Framework and WELL Building Standard principles, as well as to achieve BREEAM Outstanding and Wired Score Platinum ratings. This meant the sustainability of the construction materials themselves was also important.
Here Knauf Insulation’s products ticked all the boxes too. Its glass and rock mineral wool insulation are made from materials that come from either naturally abundant sources or are recycled. For example, its glass mineral wool is made with upto 80% recycled glass from locally collected and processed household bottles and jars.
Glass mineral wool has the lowest levels of embodied carbon of any mainstream insulation material. So, combining the use of both Knauf Insulation glass and rock mineral wool meant that the insulation solution for A3 New Bailey had less embodied carbon than a traditional all-rock insulation solution.
Both products are also manufactured with ECOSE Technology, Knauf Insulation's unique bio-based binder that contains no added formaldehyde or phenol. ECOSE Technology is made from natural raw materials that are rapidly renewable and is 70% less energy-intensive to manufacture than a traditional binder.
They also generate low levels of dust and VOCs and have been awarded the Eurofins Gold Certificate for Indoor Air Comfort. This contributes to the health of both installers and residents. Its entire glass mineral wool product range is also Declare Red List Free, which means that it does not contain any harmful chemicals on the ‘Red List’.
Thanks to Knauf Insulation’s advice, technical support and high-performance insulation solutions, Lester Cladding NW Ltd was able to deliver the rainscreen façade for A3 New Bailey – and with it, Europe’s largest living wall.