Anya Blanchfield is a sustainability engineer and net-zero consultant at property and construction consultancy McBains, and a BREEAM Assessor, working on decarbonisation assessments of existing buildings
The 500,000 buildings on the National Heritage List for England are a vital part of our nation’s cultural heritage. One of the most important things the construction industry can do is to conserve and adapt these buildings for future generations.
One of the UK’s largest property estates recently estimated that £35m could be generated in economic output annually by improving the energy efficiency of historic properties. This is partly because retrofitting helps to avoid future expenses associated with maintenance, repair and potential asset deterioration. Between 4.6 and 7.7 metric tonnes of carbon could be saved in operational carbon per year if fabric improvements were made to listed buildings and unlisted historic dwellings in conservation areas.
The previous government consulted on a new national development management policy specifically for historic buildings, which was expected to provide a welcome boost to the sector. Now that Labour has formed the new government, it is critical that this important consultation isn’t shelved. In fact, it would be desirable if the government put an even greater focus specifically on retrofitting for historic buildings, as well as providing support to the industry in getting the right people on board with retrofitting contracts.
“It would be desirable for the government to take a more holistic approach towards the conservation of historic buildings”
The policy that is currently on the table includes a series of commitments to drive energy efficiency and low-carbon heating improvements for listed buildings and buildings in conservation areas. It aims to provide clear guidance for historic-building owners, and to give greater certainty and consistency in relation to planning requirements.
Planning requirements can include carrying out a heritage survey, specifying insulation materials with a level of ‘breathability’, and employing specialists with the skills to install measures. A rigorous and lengthy planning-permission application process will be needed to, for example, install solar panels, air-source heat pumps and external wall insulation.
However, it is vital that we are able to retrofit our historic buildings in alignment with current environmental targets by considering resource conservation and embodied carbon. The policy that was proposed by the Conservative government fell short of adequately reforming the way in which energy-performance data is calculated. While useful, the current energy-performance assessment methods, primarily reliant on Energy Performance Certificates (EPCs), do not accurately reflect the sustainability of older buildings.
Improving accuracy
It would be desirable for the Labour government to take a more holistic approach towards the conservation of our historic buildings – one that considers not only operational energy, but also embodied energy in retrofitting materials and the resultant carbon savings.
A more accurate way of assessing a building’s performance level would be to compare its data prior to its retrofit, and the same data after, once measures have been installed. The type of modelling used in EPCs can be very valuable, but there can be performance gaps between what is simulated and what actually occurs due to assumptions in modelling, poor specification at design stage or below-average installation.
A more holistic approach would not simply look at the operational energy of a building, but would conduct an analysis that incorporated how much carbon was involved in the building works, including the embodied energy in the materials used in retrofitting, and the savings created by them.
Such an approach would ideally include whole-life, circular design principles, futureproofing strategies, and could seek certification from BREEAM or WELL. This approach could enhance the value of an asset but also mitigate its environmental impact and maintain a cultural reference.
While awaiting any such changes, current useful tools for overcoming the challenges involved in retrofitting listed buildings include the PAS 2038, which can be used in parallel with best practice guidance from Historic England. In addition, energy modelling and lifecycle assessments are useful when providing detailed evaluations of an entire building.
More generally, however, we need an industry-wide shift, with older buildings valued rather than knocked down. We have access to cutting-edge green technology and skilled contractors. The complexities of retrofitting historic buildings can be navigated and will result in a more sustainable future.
