Using improper techniques and materials to enhance energy efficiency can have adverse effects on the structural integrity of older buildings. For example, blocking the ventilation features that allow air to flow to prevent moisture build-up can cause long-term damage. Traditionally solid walls can equally create difficulties in installing insulation without compromising on their aesthetic appeal.

With less standardized approaches to construction and less available data to draw on, historic buildings also call for more tailored retrofit assessments.

“There’s more need to analyze what the asset offers, what the building fabric is capable of and what building regulations allow,” says Draper.

Depending on the building’s structural integrity or scale of the project, interventions may need to be phased.

New York’s Empire State building undertook eight energy efficiency projects to cut its carbon footprint. This included retrofitting all 6,514 windows along with installing 67 elevators that generate electricity instead of heat when braking. It consequently surpassed its original target to reduce energy use by 38% and delivered annual energy savings of $4.4 million.

Specialist skills can also be required. Fit-out teams experienced with historic buildings can streamline many construction complexities yet finding the right skilled workforce can be an issue. About 100,000 people work on historical buildings in the UK, according to Capital Economics – around half of what’s needed.