The net zero challenges of retrofitting our historic buildings

The Savills Blog

The net zero challenges of retrofitting our historic buildings

The UK’s wealth of historic and traditionally constructed buildings presents a challenge for the government’s net zero aspirations. 

It is hoped that the consultation which was announced in December 2024 will pave the way for improving the energy performance of a wider range of building types as it is widely accepted that the current Energy Performance Certificate regime lacks the nuance needed to provide sound advice for improving the energy performance of older properties.

When well-intended interventions backfire

Solutions encouraged by government retrofit grant schemes, such as wall insulation and double glazing, are often unsuitable for older buildings. Taking a one-size-fits-all approach can result in unintended negative consequences. Much of the recent reporting on mould in rental properties neglects the part that inappropriate retrofitting has played in the problem.

Modern buildings employ an ‘anorak’ principle, keeping moisture out using waterproof materials such as concrete and cement. Traditional buildings are more like a tweed jacket, using water-permeable materials such as timber and lime mortar that absorb moisture deep into the fabric and dry out slowly while keeping occupants warm.

Careless or poorly specified retrofit measures can cause irreversible damage by disturbing the delicate balance of a building’s performance, leading to issues like condensation, mould, cracked ceilings, and timber shrinkage. 

A wet wall is always going to insulate less well than a dry one, and an insulated wall which is still wet because of water being trapped by use of inappropriate materials may well be colder and more prone to mould than an uninsulated dry wall. Many people involved in the retrofit industry are unaware of these risks, or that Building Regulations exemptions exist for traditionally constructed buildings.

The need for a holistic approach

Historic England’s advice note on retrofitting, published in July, is viewed by many as a controversial but bold step in reconciling the tension between preserving historic buildings and meeting modern comfort and sustainability needs. It recognises that far from static relics of the past, these buildings must continue to evolve to meet the challenges of the future. The key takeaway is the importance of considering the potential interactions of retrofitting interventions as a ‘whole house’ system.

Solutions should be designed on a case-by-case basis as each building will present its own unique challenges and opportunities. For listed buildings, the first step must be to assess the heritage significance and the impact differing interventions might have.

Finding the right fit

Not all options will be suitable. The sensitive repair of timber windows and the installation of secondary glazing often provides better acoustic and thermal performance than double glazing, for example. Likewise, technologies such as solar power and air source heat pumps offer rapidly evolving opportunities for enhanced energy efficiency – but only if appropriate.

Only by taking a holistic approach can we ensure our historic buildings retain their beauty and cultural significance while remaining relevant, resilient and energy-efficient.

Further information

Contact Claire Brown

 

Recommended articles