Insulating solid walled homes can save on energy bills

Testing carried out by Energy House Labs at the University of Salford along with the Leeds Sustainability Institute (LSI) at Leeds Beckett University and Loughborough University found that, although solid wall insulation is expensive and can be tricky to install safely and effectively, it can bring many benefits to homes. And it is essential if the UK is to meet its energy reduction targets.

Benefits of insulation include: lower energy bills, feeling warmer in winter and cooler in summer, improved air quality, and less chance of condensation occurring.

The Energy House 1 test facility at the University of Salford was used to assess the potential benefits of a whole house approach to retrofit against traditional piecemeal retrofit practice. Energy House is a full sized Victorian terraced house in an environmental chamber that can replicate the outside temperature experienced in any part of the UK at any time of the heating season. It enables the impact of retrofit to be measured more accurately and in less time than is possible in the field.

The Energy House provided a detailed case study investigating solid wall fabric retrofit thermal performance and its interaction with space heating systems.

Research found that both the whole house approach and piecemeal retrofits reduced the fabric heat loss and space heating energy bills of the Energy House by around 50%.

However, the whole house approach resulted in significantly less risk of surface condensation and mould growth at junctions. It was also found that the fabric retrofit resulted in the original gas central heating system becoming oversized, which reduced its efficiency. However, the Energy House Labs research team were able to find low-cost solutions to solve this problem.

Dave Farmer, Research Fellow at the University of Salford, said: “The research is the most in-depth case study to date into how retrofitting insulation can affect the heat loss from a solid wall house and the performance of its heating system. The findings demonstrate that current retrofit standards and practices can significantly reduce space heating energy use and CO2 emissions while also providing a healthier internal environment for occupants.”

Professor David Glew, Director of the LSI at Leeds Beckett University, said: “Solid walled homes are among the least energy efficient – occupants are more likely to be in fuel poverty, and condensation, damp and mould problems can be common.

“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. It was by far the single most effective retrofit measure for solid walled homes - other types of retrofit couldn’t achieve the required improvement – and so this will be essential for tackling fuel poverty.”

The £3 million Demonstration of Energy Efficiency Potential (DEEP) project was commissioned by the Government’s Department for Energy Security and Net Zero. Investigating the retrofit (making energy improvements in homes) of solid walled homes, it is one of the largest research studies of its kind to have ever been attempted in the UK.

This new research measured how much the energy efficiency of the homes was improved by adding insulation and compared this with the predictions made by the homes’ EPC. The study found that substantial improvements could be achieved - though in most instances, the savings were lower than they were predicted to be by the EPCs.

The project compared different methods of retrofitting solid walled homes in England – installing a range of insulation and energy efficiency measures in addition to solid wall insulation, including: loft insulation, floor insulation, draughtproofing, and installing new windows and doors.

The researchers recommend using a ‘whole-house approach’ to retrofitting – rather than installing individual ‘piecemeal’ measures at different times.

Predictions based on the project’s case study homes suggest fuel bill savings of between 11 and 29% for solid wall insulation alone - depending on the condition of the wall and how much external wall is insulated. When combined with other retrofit improvements, savings were modelled to be as high as 33% off annual bills.