Can a historic building be a green building?

by Francesca

Comment for Refurb & Renovation News by Richard Harris, Partner, Carter Jonas (Oxford)

With the climate crisis increasingly dominating the headlines, our industry is quite rightly focussed on creating properties which provide the greatest energy efficiency and the lowest emissions.

40% of the UK’s carbon footprint emanates from the built environment, and, worryingly, the property sector is one of the few in which emissions reductions have stalled, it is important to consider not only how to develop energy efficient new homes but how to use existing homes more efficiently, and not to overlook historic buildings.

Research published in March by Historic England revealed that carefully retrofitting historic homes could save up to 84% in carbon emissions. England has one of the oldest building stocks in Europe, with a fifth of all homes being over a century old and so the opportunity to reduce carbon emissions could have considerable benefit.

Admittedly this is a complex process. Success rests on taking a holistic approach, starting with a building survey to ensure that measures are suitable and can be well integrated and managed. Understanding the building and its limitations are key.

Water efficiency for historic properties can match that of new build projects, if the same measures – metering and leakage detection, low water appliances and sanitary supply shut off valves – are deployed.

In terms of embodied energy, historic buildings are ultimately sustainable as their construction created less carbon than modern construction material manufacturing. Often they were constructed using local materials with the associated benefits of low energy and carbon transport costs. They tend to perform well in terms of breathability although are generally less well insulated, requiring a careful and bespoke balance. Window upgrades to reduce draughts and secondary glazing to improve thermal performance may be possible, and likewise upgrading of heating systems, modern efficient boilers and radiators, and zonal heating controls can produce big gains. The installation of energy efficient external and internal lighting is relatively simple to achieve, and very effective.

There are many characteristics of historic buildings which are less energy efficient than many modern buildings – levels of insulation, ceiling heights and room volumes, single glazing and thermal retention. Importantly, any intervention should be planned and managed to avoid unintended consequences – from reduced indoor air quality, condensation or damp as a result of additional insulation, to aesthetic damage and irreversible impact on the historic integrity of the building. Interventions require statutory consent if the building is listed or is in a conservation area, and irrespective of whether the building is listed, modifications may also require planning consent if the external appearance is likely to be affected.

Renewable energy is often seen as a potential answer to the long term sustainability of the UK’s heritage stock and while there are many potential solutions, they are not yet a panacea. Technologies such as photovoltaics and wind turbines can have a substantial negative visual impact on heritage assets. Ground and air source heat pumps are worth further consideration but there are questions over their performance in old buildings which are not built to the same air-tight standards of modern housing.

Ground source heat pumps also require a considerable land-holding and the capital costs are high. Biomass boilers perhaps have more promise in terms of their use in heritage buildings and the size of some boilers are suitable for smaller domestic dwellings.

The performance of renewable energy sources in heritage buildings requires further research to establish which is the most suitable, but a greener, more affordable electricity grid with electric boilers, water heaters and radiators is the most likely route to a more sustainable future to our heritage building stock.

At a time when the country is emerging from a health crisis and increasingly concerned about an environmental crisis, historic buildings provide considerable value, both culturally and psychologically: they provide a reassuring link to the past and their sustainable future has never been more important.

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