New research led by the Leeds Sustainability Institute (LSI) at Leeds Beckett University, with the University of Salford and Loughborough University, has found that insulating the UK's eight million solid walled homes has the potential to cut energy bills by up to 30 per cent1. The findings come from the Demonstration of Energy Efficiency Potential (DEEP) project, a £3 million study commissioned by the Department for Energy Security and Net Zero1.
The project investigated the retrofit of solid walled homes and is described as one of the largest research studies of its kind attempted in the UK, involving hundreds of tests, samples, surveys and modelling scenarios across England1. The Energy House test facility at the University of Salford was used to compare a whole house approach to retrofit against traditional piecemeal practice1. The aim was to consider the entire dwelling rather than the performance of individual measures, taking account of the interactions between fabric, ventilation and the occupant1.
Professor David Glew, Director of the LSI, said solid wall insulation was by far the single most effective retrofit measure for these homes, and that other types of retrofit could not achieve the required improvement1. The researchers noted that solid wall insulation may be expensive and complicated to install safely and effectively, but that it can make homes cheaper to run, warmer in winter and cooler in summer, with better air quality and less chance of condensation1.
"Our research found that insulating the solid walls of a home could save up to 30 per cent per year for some homes on their energy bills."
Dave Farmer, Research Fellow at the University of Salford, said the work was the most in-depth case study to date into how retrofitting insulation can affect heat loss from a solid wall house and the performance of its heating system, and that current retrofit standards and practices can significantly reduce space heating energy use and CO2 emissions while providing a healthier internal environment1.
The sources do not report a breakdown of savings by property type, region or insulation method, nor a cost per home for the work. No installation figures, funding routes or dates for any follow-up programme are given1.
Why it matters for households
Solid walled homes are among the least energy efficient, and their occupants are more likely to be in fuel poverty, with condensation, damp and mould problems common1. For a household in one of these properties, the finding that solid wall insulation could cut bills by up to 30 per cent for some homes points to a larger reduction than other single measures studied, which bears directly on how much energy a home must buy in and how exposed it is to price changes. The research also links insulation to a healthier internal environment and to lower space heating energy use and CO2 emissions1. The same research notes that the work can be expensive and complicated to install safely and effectively, a practical constraint on what any one household can achieve1. The choice between internal and external wall insulation affects floor area, appearance and where the work can be done, and the wider case for treating insulation as a route to energy independence rests on the size of the saving relative to the cost. Households weighing figures can compare typical outcomes in how much insulation saves on energy bills and insulation savings and payback.
What happens next
The DEEP reports have been published by the Department for Energy Security and Net Zero, including a synthesis report1. No further stages, funding decisions or implementation dates are reported in the sources.