The last few decades have seen copper and its alloys grow in popularity as modern architectural materials, but the sustainability and performance characteristics of copper should also not be forgotten. Graeme Bell of Aurubis explains more
Copper’s unique architectural qualities are defined by its naturally developing patina, determined by the local environment, which cannot be replicated successfully by other materials using applied coatings. Weathering over time gives a darkening surface colour to copper that can eventually result in the distinctive green or blue patinas seen on older roofs.
To provide – straightaway – the brown oxidisation or blue/green patination of copper surfaces, factory-applied surface treatments are popular, particularly for facades where rainwater ‘dwell-time’ is insufficient. These processes can enable designers to determine both the colour and intensity of patina for each project from the start. As well as a solid patina colour, other intensities can be created revealing some of the dark oxidised background material as ‘living’ surfaces. Some of the processes involved are very similar to those taking place in the environment and utilise copper mineral compounds, not alien chemical actions.
They bring forward the environmental changes without taking away the integrity of copper as a natural, living material. They form an integral part of the copper and are not coatings or paint, and on-going changes will continue over time depending on the local environment. Alloys of copper have also grown in popularity with architects. They include bronze, an alloy of copper and tin, which gradually changes to a dark chocolate brown, and brass, which can also be supplied pre-weathered. An innovative alloy of copper with aluminium and zinc, it enjoys a rich, golden through-colour, which remains very stable, just developing a matt surface – but no patination – over time. Most recently, these surfaces and alloys have been made available with a diversity of mechanically applied surface treatments, particularly suited to interior design applications. Apart from traditionally jointed, rolled material supported by a substrate, various other forms of copper are increasingly being explored by designers. For example, copper can be supplied in profiled sheets or extremely flat honeycomb panels, pressed to provide surface textures and modulation, or perforated, expanded or woven as mesh for transparency.
But there is more to architectural copper than meets the eye, particularly in terms of recyclability, sustainability and long-term performance. Copper architectural products are produced in modern plants with strictly monitored environmental performance and well-established recycling routes. They include high levels of recycled materials – typically 85 per cent or more with scope up to 100 per cent, saving on energy and greenhouse gases, and contributing to the circular economy.
As a lightweight and flexible covering in buildings, structural support demands are reduced, resulting in lower carbon and whole-life costs. At the end of a building’s life, copper retains a high scrap value, which drives recovery and recycling. Copper can be recycled again and again without any loss of performance or qualities. Copper’s exceptional longevity is due to the patination process, which ensures extreme durability without maintenance and resistance to corrosion in virtually any atmospheric conditions. The lifespan of copper roofing and cladding can therefore be regarded conservatively as 200 years, subject to substrate and structure, and this is endorsed by experience. Naturally, this longevity has a significant impact upon comparative whole-life cost assessments.
Natural and safe
Copper is a natural element within the earth’s crust, which has been incorporated into living organisms throughout the evolutionary process. It is an essential nutrient required by virtually all higher life forms and nature is well adapted to making best use of copper, protecting itself from any negative effects. Copper is safe to use and can be worked at any temperature, without becoming brittle in cold weather or deforming in hot weather. It requires no decoration, maintenance or cleaning, saving resources, cleaning chemicals and cost. Its interaction with the environment has been assessed under the European Reach chemical policy, and has no classification/restriction.
With a melting point of 1083˚C and ‘A1 (non-combustible material)’ fire classification to EN 13501-1, copper is also suitable for cladding tall buildings, using appropriate constructions. Low thermal movement makes it straightforward to use in any climates and locations. It is also non-toxic and safe to handle, as well as non-brittle and predictable to work. Copper’s inherent antimicrobial qualities make it ideal for touch surfaces internally as well.
Graeme Bell is sales and marketing manager at Aurubis