U-value research on older buildings to improve EPCs conference hears

New research on the U-values of historic building materials is expected to soon offer project teams a more accurate view of energy performance in historic stock, delegates at the CIOB’s Retrofit Conference in Cambridge heard yesterday.

Keynote speaker Neil May, who represents the Sustainable Traditional Building Alliance and is also managing director of consultant and supplier Natural Building Technologies, outlined progress on current research projects run by the STBA and BRE for the Department of Energy and Climate Change. 

The projects are examining to what extent current calculations on solid walls, which are based on contemporary bricks and insulation materials, underestimate the insulation performance of historic materials.

May told CM: “When we did the Responsible Retrofit of Traditional Buildings report in 2012, a group analysis of retrofit on traditional buildings, we found there were huge gaps in our understanding, and a lack of data and solid research. There was a lack of understanding about how different elements of the fabric work together.

New Court at Trinity College, Cambridge, is being retrofitted to achieve energy efficiency improvements of 83%

“We also saw there were sometimes conflicting values – heritage value, economic value, energy efficiency and health – and they needed to be considered together.”

May said that the ongoing work would result in the STBA publishing a “decision-making tool” on historic retrofit, together with new guidance and risk assessment documents. Topics to be examined include moisture, which May says is not adequately covered in existing guidance, as well as internal insulation and thermal bridging. 

Meanwhile, the BRE is leading on the research into the U-values of solid walls in historic buildings, under contract to DECC.

Rory Cullen FCIOB, head of buildings at the National Trust and chair of the CIOB’s Conservation, Maintenance and Refurbishment group, said that the BRE research could be particularly interesting for the National Trust’s estate.

“In 2018, government legislation is changing, and traditional houses and buildings can only be sold or rented if they have at least an E grade Energy Performance Certificate. We have a stock of around 5,000 properties, and only 49% would be at level E. To bring the rest up to an E would involve expenditure of £4.8m to £20m – that’s a real issue for us.

“But if the assessments are done using more accurate information, it could mean that 65% would meet level E.”

Other speakers at the conference included Jeremy Sanders, pro-vice chancellor in charge of the University of Cambridge estate, who discussed future proofing considerations on historic retrofit projects, and Roger Curtis, technical research manager at Historic Scotland, who examined insulation work carried out on traditional properties in Scotland.

Delegates also visited New Court, Trinity College, a grade I-listed building that is being retrofitted to the highest standards. The interventions – including a form of double glazing,  mechanical ventilation using the existing chimneys, LED lighting and underfloor heating – are expected to result in an 83% improvement in energy efficiency.