In this article, Redland’s Technical Manager, Dr Kevin Ley discusses the issue of embodied energy in roof tiles.
Having been a supplier to the UK building industry for over 90 years, Redland has always looked to understand the preferences of its buyers and to pre-empt their demands by developing products slightly ahead of the curve; what we see coming up is a greatly increased focus on the embodied energy and carbon emissions of building materials.
In the UK, approximately 50% of all energy is used in buildings – with 90% of that energy relating to energy-in-use (for example heating, lighting, ventilation and running appliances) and the remaining 10% being embodied energy, or the energy used in the manufacture of the building materials.
Part L of the Building Regulations has focused squarely on the energy in use element and the Code for Sustainable Homes (whose objective is to deliver Zero Carbon new homes by 2016) has also been interpreted in this way. However, it is now widely acknowledged that this approach is not sufficient, and consultation on the future development of the Code is specifically asking if, and how, embodied energy and carbon should be a more significant part of the calculation.
For this reason Redland, historically manufacturers of both clay and concrete tiles, commissioned engineering consultants Ove Arup and Partners Ltd to analyse the carbon dioxide emissions of its operations.
The study, which was peer reviewed by the Carbon Trust and the University of Bath, takes as its baseline calculation the sum of all the carbon emissions involved in the manufacture of Redland tiles from cradle to factory gate, including raw materials extraction/production, transport to the plant, manufacture in the plant of the finished product and delivery to the factory gate ready for onward distribution. The report calculations conform to PAS 2050, the method developed by BSI, Carbon Trust and Defra to calculate the embodied carbon of goods and services.
The results, in terms of carbon emissions, confound the school of thinking that automatically assumes natural products such as clay are necessarily more environmentally friendly than concrete.
When looking at the manufacturing process, the key factor is the firing process: clay tiles must be fired at very high temperatures (around 1,000oC) – an energy intensive process. In contrast, just adding water and curing at less than 100oC achieves the necessary strength for concrete tiles. And while the cement used in concrete tiles has high embodied energy, it represents less than 20% of the tile by weight, the remainder being mostly natural materials such as sand and limestone.
The figures in the Arup report show that the embodied energy of concrete tiles at 91-146MJ/m2 is half that of equivalent clay tiles at 240-478MJ/m2, which broadly concur with previously published independent data.
Redland, as a manufacturer of both clay and concrete tiles, clearly has an interest in understanding the future demand for different material types, and is convinced that reducing the embodied energy and carbon of building materials will be the next major challenge for the sector.
Our Heathland range is a good example of this thinking in practice. Introduced 17 years ago, the Heathland tile recognised the demand (particularly in the South of England) for a product with the appearance of a hand-made clay tile. Redland made the choice to manufacture Heathland out of concrete (using a process that faithfully reproduced the attractive aesthetic and random irregularities in the size and surface texture that are expected with a hand-made product).
In marketing these products Redland is obviously drawing attention to the cost advantages of the concrete over the hand-made clay equivalent, but we regard the environmental message as equally significant. In doing so, we may be ahead of the game but are sure that specification decisions will be moving in this direction sooner rather than later.
Much of the information contained in this piece appears in Roofing, Cladding and Insulation magazine, April issue.
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