Impact case study database

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Lowering household fuel bills

Following LBU research, party wall heat loss was incorporated into the 2010 Part L of the UK Building Regulations (5.1). This has led to substantial impact in this REF cycle, specifically all new homes built after 2014 have fuel lower bills. Removing the party wall bypass in existing dwellings may reduce whole house heat loss by up to 8% (3.6), when a party cavity wall is not capped. This may be used as a proxy to quantify the impact of the regulatory changes for new build homes. The average annual gas bill in England and Wales in 2019 was £588 (5.2), and of this around 2/3rds may be used for space heating. Thus, removing the party wall heat loss mechanism could equate to a maximum of £31 per home, per year. 53.5% of homes are terraced or semi-detached properties (5.3) and therefore, contain at least one-party wall, and there have been just over 1 million homes built 2013 and 2019 (5.4). Assuming the same proportion (53.5%) of these have a cavity party wall, this equates to cumulative maximum savings of £66 million during this period alone, assuming these party walls would have otherwise been poorly performing. Even if only a fraction these party walls would have been poorly performing this still equates to millions of pounds of fuel bill savings.

In addition, data suggests that 1,724 existing homes have had party cavity wall insulation (PCWI) retrofits funded via the Energy Company Obligation (ECO) during this period (5.5), resulting in a further maximum saving of £53,000 per annum collectively for these homes. It is important to recognise that these savings will be achieved every year as long as the insulation remains installed in the homes, which could be many decades. These savings are based on heat loss reduction measured from the retrofit of a single party wall. However, even if the national average savings indicated here were only half this per house (i.e. some party walls were better performing), this still represents a huge financial saving of millions of pounds to UK households every year.

New markets for domestic construction businesses

Incorporation of the party wall bypass for new build homes has increased the sales of insulation substantially. Cavity wall insulation can cost £10 per m² (5.6) and party walls may be 25m² representing a new build market of up to £250 million for the million new homes built during the 2014 to 2020 REF period. This will grow year on year as new homes are added to the housing stock. The party wall bypass is also now being addressed through retrofitting existing homes. There are estimated to be 7.3 million existing homes in the UK with cavity party walls with potential to be insulated, though the extent of the party wall bypass in these homes is not known (5.7). Assuming only half of these homes could have a cavity party wall retrofit and considering that the average cost of a retrofit is £350 per home (5.6), LBU findings have unlocked a market worth up to £1.2 billion. Following LBU research, party cavity wall retrofits were adopted into the Energy Company Obligations (ECO) policy in 2013, a government energy efficiency scheme to help reduce carbon emissions, with the impact that these now make up 0.7% of all ECO funded retrofits taking place (5.5).

Reducing Fuel Consumption for low-income households

In this REF period, the Government’s fuel poverty policy (ECO), has funded 1,724 party cavity wall insulation retrofits. People in fuel poverty are more at risk of health problems resulting from cold homes, party wall retrofits can improve thermal comfort and make homes easier to heat. The discovery of the bypass by LBU has therefore contributed to health and wellbeing of thousands of occupants in these retrofitted homes.

Preventing Carbon Emissions

The impact of party cavity wall insulation in new build and existing homes also means fewer carbon emissions. The maximum estimated national fuel bill savings, previously mentioned of £66 million, means that, assuming gas sells at 4p per kWh, up to 2.6 GWh of gas use may have been avoided in this REF period. At the Government’s conversion rate of 1.83 kgCO₂eq per kWh of gas, we can estimate up to 120,000 tonnes of CO₂eq for the qualifying period was avoided by insulating party cavity walls, assuming they would have otherwise been poorly performing. The significance of this saving is further enhanced in that these savings will continue to be achieved each year, and every new home built in the UK in the future will also benefit.

Leading policy reform around domestic construction performance gap

Bell was chair and lead author for several Zero Carbon Hub repots, a public private partnership, set up to review industry practice, academic research, and state of the art of UK construction, including the highly acclaimed End of Term Route Map for achieving zero carbon homes in this REF period (5.8).

This led to LBU research being recognized in national press for establishing and quantifying the building fabric thermal “performance gap” and contributing to a U-turn in the acceptance of UK housebuilders to this phenomenon (5.9).

The LBU co-heating protocol has been promoted by the IEA and is in the process of being developed into an international standard by the European Committee for Standardization (CEN). The protocol has also been adopted by the UK Government in multiple research projects worth over £10 million during this REF period and is recognised as the ‘ best currently available and proven measurement option for calculating the heat transfer coefficient of homes” (5.10).