City West Housing Trust

City West Housing Trust


The boundary between adjoining properties has always been assumed to be an area of neutral heat loss. However, research undertaken by Leeds Metropolitan University, MIMA (the Mineral Wool Insulation Manufacturers’ Trade Association), BRE (Building Research Establishment) and Knauf Insulation has revealed that a significant amount of heat is actually lost through uninsulated cavity party walls.

It is estimated that there are 7.4million existing party walls that have been built with a cavity across the UK.

Although these walls provide fire and acoustic separation to meet the requirements of relevant building regulations, the thermal performance of a party wall had not previously been considered.

Knauf Insulation has provided solid evidence that its Supafil® Party Wall glass mineral wool blowing insulation is a reliable way of eliminating party wall bypass and so City West Housing Trust, a Salford based housing association, has installed the product as part of a pilot scheme to a number of its properties.

Working alongside Bridgewater Surveyors and others, City West wanted to improve the energy efficiency of their tenants properties and are continually looking for other ways to reduce energy costs and consumption. Knowing that by insulating the cavity party walls of properties could lower energy bills for their tenants they embarked on the trial project – with the aim of a possible roll out across other areas in the North West.

After approaching Knauf Insulation for advice, City West and Bridgewater Surveyors settled on a reliable solution: Knauf Insulation’s Supafil® Party Wall insulation.


Supafil® Party Wall prevents heat loss through party separating cavity walls by fully filling the cavity. Supafil® Party Wall is an in-situ formed unbonded, non-combustible glass mineral wool. Knauf Insulation have now completed an extensive research programme to develop a proven methodology for installation into existing homes to add to the product’s use in new build applications.

As well as being an excellent thermal insulant, Supafil® Party Wall insulation also has good sound absorption characteristics which help to ensure that when a party wall is upgraded, it complies with the requirements of Approved Document Part E of the Building Regulations - which is designed to protect occupants from noise in adjoining rooms or buildings.

As part of the Salford project, houses were tested before and after the installation took place. The reduction in the heat loss was equivalent to an improvement in the effective U-value of the party wall of at least 0.5 W/m2K. This shows there is a significant beneficial impact for tenants in fully filling cavity party walls with Supafil® Party Wall Insulation.

Supafil® Party Wall insulation fitted into City West’s obligation to maintain a greener environment as the product conserves energy and reduces the emissions of the major greenhouse gas, CO2. The energy and CO2 emission saved by the product in use vastly outweighs those generated in its manufacture. Supafil® Party Wall has a generic BRE Green Guide Rating of A+ and has zero Ozone Depletion Potential and zero Global Warming Potential.

When completed, the trials will measure the extent of customers’ energy bill savings – estimated to be up to £90 a year – as well as the amount of carbon emissions that could be reduced.

We are committed to ensuring our properties are as energy efficient as possible and along with Supafil Party Wall insulation we have installed cavity and loft insulation to our portfolio of properties.
Gary Vaughan – Head of Sustainability & Supply Chain, City West
Products used
Client City West Housing Trust
PROJECT: Salford, Greater Manchester
MAIN CONTRACTOR: Ecogee Energy Solutions