Explore I Blog I Architectural ceramic, long lasting, high impact

28 January 2022

If knowledge is power, then the art of the architect is to use that knowledge to reduce the power needed to make and use buildings.

Ceramic is an incredibly creative material to work with through the variation in colour, texture and profile that can be produced to create truly bespoke designs. However, it is carbon-intensive in its manufacture. As with other carbon-intensive materials such as brick, steel and glass, we first need to evaluate and understand the implications of the choice and how the environmental impact can be reduced. This comes through research and greater understanding of its production and use.

A fuller understanding of the embodied carbon in everyday building materials informs the decision-making process and allows us to make better decisions when designing buildings, as well as highlighting ways of reducing the impact of the material at each stage in its life. To help with these insights, we have developed  FCBS Carbon to bring forward early-stage evaluation of embodied energy in our designs which and to quickly examine the implications of decisions made.

Recently, we have designed ceramic facades on a number of our projects, including Circle Square, St Albans Place, University of Warwick Faculty of Arts and the University of Southampton’s Centenary Building. In doing so, we have looked closely at the journey the material makes, from ‘cradle to grave’ – from the quarrying of clay, manufacture and transport to site, to asking what might happen to the material at the end of the building’s life.

Ceramic and terracotta is a material that has been used for thousands of years and there is a rich history of its use around the world. It has seen a renaissance over recent years, particularly due to the increased use of rainscreen facades.

Each design process starts with the production of new dies, creating endless possibilities to manufacture ceramics of any profile, colour or texture. We have played with this variation and visual richness across a number of schemes and have collaborated with visual artists to create bespoke pieces- eg with Matthew Raw at the University of Warwick.

At Circle Square, we explored a range of finishes including natural, engobe (paint based matt finish), glazed (glass-based, generally gloss finish) and double glazed (high gloss finish). We settled on a single glazed tile of varying profiles and colour across the buildings, a modern interpretation of the local vernacular which includes the heavily glazed façade on the Grade II listed Lass O‘Gowrie pub and the Alfred Waterhouse designed Palace Hotel.

We worked closely with NBK, a specialist manufacturer of terracotta facades, to develop samples and profiles suitable for the project.

Clay is not an infinite resource. To obtain it, it must be quarried - which has an environmental impact on the immediate biosphere but also adds to the carbon footprint of the product. As with all materials, we have to be careful about how and where it is sourced.

At the factory, the clay is extruded through a steel die and then cut to size. Up until this point, it is possible to recycle the clay endlessly, by mashing it up and pushing it back through the die creating very little waste.

After shaping, the panels are dried and either left as a natural finish or a glazed / engobe coating applied before firing. At the end of that process the tiles are cut to size and stacked for shipping.

The greatest carbon impact of the ceramic industry comes from firing the clay, and this has been estimated to account for up to 55% of the total energy requirements to produce the product. Kilns have improved in recent years with the traditional box kiln being replaced with more efficient roller kilns, however, this does place limitations on the design.

In a box kiln, the ceramics are first loaded, then the kiln heated up to the requisite temperature and for the requisite period of time. Afterwards, the tiles are left inside to cool before unloading. The constant heating and cooling of space is inefficient both in terms of energy and time, and therefore a lot of production has moved to roller kilns. These can be hundreds of metres long. They have the capacity to be constantly fed tiles, which roll through a process of variable heats before coming out at the end, to be cut and packaged for distribution. These highly insulated units are rarely turned off, increasing the quantity of throughput, and energy efficiency.

The manufacture and transport of ceramics uses a lot of energy. If we are going to make the most of this long-lasting and beautiful material, then we must work hard to ensure we can minimise its impact.

We have built a close relationship with the manufacturers over a series of projects and gained an understanding of the opportunities and limitations of the material - the design and depth of the profiles along with the lengths and proportions of the tiles. Working within these boundaries ensures the design is buildable but also efficient and produces minimal waste.

We explored double glazing the tiles, as this produces a spectacular visual depth to the façade. However, this involves two trips through the kiln and significantly increases the embodied carbon of the material as the process is estimated to produce up to a staggering 55% more emissions than natural or single fired finishes (1).

Substructure is a major player in terms of the amount of carbon that is embodied in the façade and can account for over half of the embodied carbon in a ceramic façade. It is therefore important to make the most efficient layout of the tiles in terms of the lengths and spans and again, this comes back to working with the manufacturer, drawing on their specialist knowledge and experience, and asking the right questions to keep making improvements.

Ceramic façade panels are large, heavy and fragile, so transport and packaging are important factors. How can the elements be efficiently stacked? Simple decisions like this can minimise the number of shipments, again reducing costs and transport-based emissions.

Finally, there is close collaboration with the contractors. In a lot of specifications, no damage is acceptable on the tiles, so subcontractors commonly order additional tiles to account for damage, and this can be as much as 10% extra. On Circle Square, we have worked towards a shift of attitude across the project team. In the first instance, it is a process of understanding if damage to a tile is structural or aesthetic. If aesthetic, can the tile be repaired or placed in a high or difficult to view area? We reached an agreement with the contractor and client that whilst no repaired tiles would be used below level 10 or in window reveals, that we could repair rather than replace where possible which made a significant reduction in tile quantities required.

At the beginning of a building’s life, how its constituent parts will be dealt with at the end of its life isn’t always at the forefront of people’s minds. Historically, most of the ceramics used have ended up in landfill. We would like to move towards a circular economy approach but this brittle, fragile material poses difficulties. When a building comes to the end of its life, the ceramic might still have 50 plus years of life in it. The challenge is: how can we design for that? how can we plan for future reuse?

As we move away from using ceramics in a traditional bonded way, they are typically clipped onto the building using aluminium clips. This leaves plenty of opportunity for dismantling and reuse and there are examples of terracotta tiles being repurposed to create bris soleil and new façade treatments. How to repurpose and reuse remains an open question and one we will continue to explore.

Whilst there are obvious environmental impacts to using materials such as terracotta or brick which are energy-intensive to produce, it is clear that their durability, as well as context and planning requirements, will mean that they will continue to be used in the future. Through our greater understanding, careful specification, and engagement in the design and construction process, we can address the challenge of how to minimise the impact and offset the embodied carbon within these materials.

David Bates

David Bates is based in FCBStudios Manchester office, and has worked on the design and delivery of the residential buildings and Symphony Park at Manchester’s Circle Square development. He represented Ceramic at our Material Matters panel discussion as part of our Carbon Counts exhibition. You can re-watch the whole event, here . Carbon Counts is currently on show at Liverpool School of Architecture.

FCBS Carbon is a free early-stage carbon calculator developed by FCBStudios.



Images

Top: Samples showing the variety of shapes and finishes available in architectural ceramics.  (c) NBK

Middle
1. Faith in the Miraculous\, by Matthew Raw\, Ceramic mural at University of Warwick Faculty of Arts Building. (c) Matthew Raw

2. Circle Square in Manchester\, where ceramic rainscreen facades take inspiration from vernacular ceramic use\, and together unite the development

3. Burgundy\, single glazed ceramic facade on No 1 Circle Square\, Manchester

4. Bronze\, single glazed ceramic facade on St Albans Place\, Leeds (c) WIll Pryce

5. White\, single glazed fluted ceramic facade on Centenary Building\, University of Southampton

6. Terracotta\, single glazed ceramic facade on University of Warwick Faculty of Arts Building (c) Hufton and Crow

Bottom
1 & 2 Ceramic production at NBK

All photos c FCBStudios, unless otherwise stated.

References: https://ec.europa.eu/research-and-innovation/en/projects/success-stories/all/developing-better-producing-less-polluting-kiln