Advances in technology are enabling a panoply of approaches to facade design and construction. Tudor Pop, associate director in CBRE’s Facade Consultancy team, highlights the five trends we might expect to see more of on UK construction sites.
From timber to tiles that flutter in the wind to curved glass and complex composites, modern facade technology means that architects looking for statement designs are simply spoilt for choice.
The move away from glass and aluminium curtain walling as the automatic choice for any self-respecting modern office block has been driven by three developments: new technology has brought alternative materials into reach financially; tighter energy regulations have prompted a move away from standard glass; and a desire to make buildings stand out from the crowd – or, for that matter, blend into their surroundings – has sparked demand.
The adoption of new facades is happening all across Europe, paving the way for the exchange of new ideas.
Here are the five big talking points:
1. Kinetic facades
Kinetic facades, as the name would suggest, are dynamic facades which change, rather than being static. Elements can be programmed to respond to climatic factors, to improve energy efficiency or reduce solar heat, or for aesthetic reasons such as an art installation.
Buildings that fall into this category include the Al Bahr Towers in Abu Dhabi in the United Arab Emirates which has computer-controlled facade made of umbrella-like panels which open and close in response to the sun’s movement through the day, to achieve optimal shading and light entering the building.
A more recent phenomenon is the appearance of new type of rainscreen cladding mainly used to overclad existing buildings, but also used on a smaller scale on new buildings. In this arrangement, thousands of aluminium tiles are hung off a framework in a way that allows them to move in the wind and create a fluid facade.
Debenhams, Oxford Street
The first major use of a kinetic facade in the UK is on Debenhams in London’s Oxford Street. The new rainscreen was part of a £40m store makeover that also included an atrium, canopy, signage, extended shop windows and a complete internal refurbishment.
Designed by Archial Architects in conjunction with US-based environmental artist Ned Kahn, the cladding screen has been conceived as a kinetic facade comprised of 185,000 suspended aluminium shingles that will ripple gently in the wind.
Specialist contractor Dane Architectural Metalwork Division worked with contractor Wates to create the facade, which has been designed so that the shingles can all move independently of each other to provide a visual pattern of air movement across the facade.
The shingles are suspended within a steel structural cladding frame, which has been projected 840mm from the face of the precast reinforced Reema concrete panels that form the building’s existing facade.
Although the cladding system will not require routine maintenance, the 840mm gap will allow maintenance access if required.
The technique has been pioneered by US artist Ned Kahn, who has collaborated with architects around the world to install the rainscreen cladding on a number of buildings, including a car park at Brisbane Airport. In the UK this type of facade made its debut with the 2014 refurbishment of the Debenhams store on London’s Oxford Street.
These kinetic facades represent a wider range of aesthetic opportunities without providing a major improvement in thermal performance, although these facades do provide some protection against rain.
Take-up potential: This is a great idea for creating impact and iconic status – and novelty value, particularly on an existing building. It’s perfect for a retail store, like Debenhams, which wants to create interest.
We can certainly expect to see greater take-up in the UK, though because the system is bespoke costs will be at the high end. Because the system has not been used on a large scale we still know little about long-term performance – though because the tiles are anodised aluminium one would expect them to perform quite well.
2. Curved glass
If you walk around London, one of the most notable trends, in both commercial and high-end residential buildings, is the growing use of curved glass. New CAD technology and advanced manufacturing techniques have brought down costs, making this possible on a larger scale.
The glass comes with a number of finishes and can be modified using dichroic glasses. These display two or more colours in certain lighting conditions or viewing angles. These characteristics are achieved by using a special interlayer in laminated glass or applying a window film – so the iterations are almost endless.
61 Oxford Street
This curved glass facade in London’s West End takes inspiration from the classic vase designed in the 1930s by architect Alvar Aalto.
Architect Allford Hall Monaghan Morris (AHMM), worked closely with Westminster Council and contractor Wates to create an iconic focal point that sets the bar for the ongoing redevelopment of the area.
The building’s distinctive wave design tapers up to a bespoke glass lantern at the top, accentuating the corner location and providing a modern successor to the original Victorian masonry of this building type.
Curved glass is also being used in double-skin facades – where the inner layer is monolithic glass or another material – which opens up the possibility of different suppliers on the inside and outside.
Take-up potential: Costs for curved glass are three times more than flat glass – so we’re still talking high-end curtain walling for buildings that want to show off a little. This approach could store up expensive service charges for residents – as certain elements need replacing every 25 years.
Something else to bear in mind is that few manufacturers can supply in large quantities. This can put a strain on the construction programme: glass will need to be ordered well in advance, meaning everything needs to be designed that will impact the facade. There is also the tricky issue of how to get hold of replacement curved panels should one of them break.
St Botolph Building
The St Botolph Building on Houndsditch in the City of London was designed by Grimshaw. Its distinctive facade, featuring some curved glass, is entirely bespoke.
Using multiple layers of glass, the unique blue-tinted glass spandrels elegantly sail past the windows below to act as solar shading.
The blue panels have a dual role: acting as shading devices and having an aesthetic role as well.
The glass is laminated and has been fritted in order to achieve the colour specified by the architect.
3. Fibre-reinforced materials
Advances in manufacturing techniques have increased the choice of materials, with new fibre-reinforced materials increasingly used in rainscreen systems. Glass fibre reinforced plastic (GFRP) and glass fibre reinforced concrete (GFRC) are now being used in various forms that have been made possible by new technologies.
Curved GFRP panels or extruded GFRC standard profiles are also used to increase sustainability credentials – the energy used in manufacturing is much lower than that in aluminium or glass production. Recent research found that fibre-reinforced materials may be used in innovative designs which carry improved thermal performance. But the longevity of the material and finishes require further testing.
Heydar Aliyev Center, Baku
The Heydar Aliyev Center is a 57,500 sq m building complex in Baku, Azerbaijan, designed by Iraqi-British architect Zaha Hadid and noted for its distinctive architecture and flowing, curved style that eschews sharp angles.
Glass fibre reinforced concrete (GFRC) and glass fibre reinforced polyester (GFRP) were chosen as ideal cladding materials, as they allow for the powerful plasticity of the building’s design while responding to very different functional demands.
Extruded GFRP profiles have been used in Thin Environmental Cladding (TEC) panels, which aim to achieve a similar structural performance as aluminium, at a fraction of the cost.
Take-up potential: This technology is not used as widely yet in the UK as in Europe, the United States or Middle East. This is mainly because of cultural reasons and traditional construction methods.
4. Weathered steel
Weathering steel, best known under the trademark COR-TEN steel , is a group of steel alloys which were developed to eliminate the need for painting, and form a stable rust-like appearance if exposed to the weather for several years.
The beauty of the material is that because it is already weathered and “rusted”, even in 200 years it will still perform to 99.8%. There are very low maintenance costs and no requirement for a protective paint system or extended service life.
Broadcasting Tower, Leeds
Broadcasting Tower is a university building in Broadcasting Place in Leeds, housing Leeds Beckett University’s Faculty of Arts, Environment and Technology, with student flats in the main tower.
Designed by Stirling Prize-winning architects Feilden Clegg Bradley Studios, the tower is distinctive, with comfortable and contemporary interiors and stylish decor. The exterior is clad in COR-TEN weathering steel, which gives it the rust-like appearance for which it is known.
Weathered steel is not suitable in marine or coastal environments. Its use requires careful design of interface details as run-off water may have a detrimental effect on other materials, especially in the first years after installation.
Take-up potential: This material is increasingly used in diverse contexts. Its main appeal for architects is the finish, for developers the low maintenance costs and for contractors the ease of installation and lack of a requirement for painting.
A number of buildings have used weathered steel with materials like glass and terracotta. But these have not been without problems. CBRE has been involved in instances where the run-off from wet rusted steel has stained the glass badly.
5. Procurement routes
Brexit and the fall of the pound is bound to make the issue of where to source cladding largely manufactured in Europe, even more an item for discussion.
Chinese cladding has been used on flagship schemes across London since 2013, including curtain walling for a 37-storey tower at the Elephant and Castle as well as British Land’s Cheesegrater in the City and the St George Wharf tower in Vauxhall.
Chinese facade contractors are looking to increase their share of the UK market. It is large, well established and has potential for growth. There are good chances of making a profit and no requirement for a large UK base as almost everything can be manufactured outside the UK.
Their focus will not just be London, but in other cities like Leeds, Manchester and Liverpool where there are other large high-rise schemes in the pipeline. There can be differences in “expectation of quality” and anyone going down this route would do well to inspect in the factory.
