Sponsored: Greening our Heritage properties, a holistic approach to energy efficiency

In its sixth Carbon Budget, the Committee for Climate Change stated that buildings, including homes, are the 3rd largest carbon emissions producers in the UK – accounting for 13% of all the UK’s carbon emissions. We can’t drastically modify these heritage structures, and for more modern buildings it is neither feasible nor environmentally desirable to conduct a mass demolition and rebuilding programme, so we need to find practical ways to decarbonise our existing and historic building stock. The National Trust has already assessed its carbon outputs and has set ambitious targets to decarbonise by 2030 – but how can engineers balance issues of sustainability and energy efficiency against the need to preserve original structural features and fabrics?

It cannot be assumed that modern or ‘standard’ engineering and technologies will solve all these problems. Adapting heritage sites to meet modern usage and environmental demands requires an appreciation and understanding of the building’s structure, the environment in which it sits, and the solutions that sustained it in the past. For example, visitors to heritage attractions expect modern facilities which need to be incorporated sensitively. The historic building itself may have been designed as a family home originally, but now it will have back offices for staff, storage requiring precise humidity conditions for precious artifacts, and sometimes private accommodation for the incumbent owners. This means multiple requirements regarding heat, light and ventilation that need to be met sustainably and efficiently.

These conflicting demands do not just apply to stately homes, of course: many public buildings including hospitals, town halls, theatres and schools face similar challenges. In addition, large swathes of our basic housing stock comprise Victorian terraces, 1930s suburbs, post-war ‘homes for heroes’ and garden cities. As engineers, we need to find solutions that will not just deliver short-term energy bill savings, but that transform these aging buildings into sustainable living spaces.

Indigenous or vernacular design, which uses readily available material resources, hints at some solutions, as well as ‘lost’ building practices. Shutters can help keep heat in at night, natural flooring materials can retain heat but remain permeable, and reinstating ‘cold’ roofs allow the removal of humidity and reduces thermal losses from insulating at ceiling level. We can draw inspiration not only from the UK, but internationally. In Ghana, locally available wood and stone are variously used to combat atmospheric conditions ranging from dry heat to extreme humidity.  In north Africa and the Gulf peninsula wind towers provide a means of passive cooling using the prevailing wind direction. Malay houses are perfectly adapted to the high humidity with natural materials promoting ventilation and providing solar shading with overhanging roofs.

In the UK, we are relearning the benefits of some older materials. Concrete render applied in the mid-20^th century to reduce heat loss is now causing damp problems in properties originally constructed of porous materials that easily exchange moisture with the air. These concrete skins are now being replaced with traditional lime renders, which will work sympathetically with the building’s original structure. Sustainable, natural wool insulation is being reintroduced. Sash windows are common in heritage structures, and need regular maintenance due to their timber frames, but keeping on top of this can reduce cold draughts.. Repairing external walls can also reduce uncontrolled infiltration.

The potential to improve energy efficiency and decarbonise our housing stock is significant. Thousands of houses were built in the same period using similar construction techniques and materials, which means they are likely to face the same issues. But this also means that appropriate, sustainable solutions can be applied on a grand scale (if the industry can respond to demand).

It further offers the opportunity for householders to come together collaboratively and collectively. For example, it could give them better buying power to reduce the cost of investment, or the ability to pool their own skills to help each other achieve the necessary improvements. And in the end, being invested in the process is what will make the difference in achieving our carbon reduction targets, reversing climate change, and securing the long-term future of the planet.

Clearly, what is required is a holistic approach that considers the existing building fabric and design, the needs of the occupants over time and the longer-term impacts of any energy efficiency measures. It is simply ineffective and inefficient to disregard solutions that have been deployed in the past – especially if they were designed into the structure and use of the building. In taking this approach to regeneration, we can preserve our past whilst protecting our future. This is precisely the philosophy that underpins Engineers Without Borders UK and the principles of global responsibility that it promotes.

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