INCA Case Study: Cheltenham Social Housing Decarbonisation

webertherm XM installed as part of Social Housing Decarbonisation Fund improvements

In the drive towards reaching net zero carbon emissions, one of the greatest challenges facing local authorities and housing associations is how they are going to retrofit social housing. This comes at a cost, and many are leaning on schemes such as the government’s Social Housing Decarbonisation Fund (SHDF) to help upgrade housing stock currently below Energy Performance Certificate (EPC) C.

Cheltenham Borough Council (CBC) is one of the local authorities allocated financial support via the SHDF and, in partnership with Cheltenham Borough Homes (CBH), which manages the homes on behalf of CBC, has been making various energy efficiency improvements to its properties.

In October 2022, under Wave 1 of the SHDF, CBH contracted the Joyner Group to retrofit 34 properties on four streets – Hawthorn Road, Orchard Avenue, Lee Close, and Kingsmead Road – in Cheltenham. These consisted of eight blocks of four maisonettes, and two single houses – one terrace and one semi-detached property (non-traditional construction) – that were originally built in the 1950s.

A fabric-first approach

 Each home was retrofitted in the same way, and the team from the Joyner Group worked closely with CBH to facilitate the work.

The contractor has worked with CBH on a partnership/framework arrangement for the last five years, during which time it has made improvements to a large number of properties.

The retrofit programme of works to update the fabric of the properties within this project commenced with the replacement of roofs, where required, and the installation of loft insulation. To further improve thermal efficiency, an external wall insulation (EWI) system was fitted on each property. For this, the retrofit team – consisting of CBH as the client, the Joyner Group as the installer, plus a retrofit coordinator and retrofit designer – specified Saint-Gobain Weber’s webertherm XM system.

Luke Joyner, managing director of the Joyner Group:

“Not only is the team familiar with Weber products, but we also liked the fact that, by using weberend LAC rapid as the render coat, we wouldn’t need to use a primer,” 

“This helped to reduce installation time, and the rapid setting allowed us to apply the finishing coat much faster than if we were to use a standard setting alternative.”

The webertherm MFD insulation was mechanically fixed to the wall by the Joyner Group team at a thickness of 110mm. After this, they applied one coat of weberend LAC rapid in two passes, between which they placed meshcoat reinforcement.

This formed the base coat upon which webersil TF – a silicone thin coat render – in a variety of colours was applied. Earth was specified for each ground floor, while Ocre Rose, Oyster Shell, Iced Water, and Cool Mint were chosen for the first floors.

Providing a highly weather resistant finish, webersil TF provides a reliable, long-wearing render solution – particularly for harsh or exposed conditions. The 1.5mm aggregate content provides an even, textured finish, available in over 100 colours to achieve a modern look.   

Subsequently, the U-values of the homes were improved from 1.79 W/m²K to 0.28 W/m²K.

Support from Weber      

Prior to the EWI system being installed, Phill Powell, applications manager at Weber, conducted pull out tests to ensure the correct system was specified and that anything fixed to the buildings would remain safely secured under duress. In the case of EWI, the correct length, type and material of fixing are all relevant to ensuring the insulation is reliably fastened to the substrate.

Colleagues from Weber were contactable throughout the project to support and advise the experienced team from the Joyner Group.

Luke added:

“Working on a collaborative basis with Weber, we installed its EWI system in accordance with PAS 2035 requirements. Weber worked with us to deliver the project by providing comprehensive technical support and ensuring delivery dates were met, thereby enabling us to complete the works in accordance with our programme and our client’s expectations.”

Phill also visited the site at each stage to conduct progress reports as part of Weber’s commitment to maintaining its BBA certification.

A 25-year guarantee from the Solid Wall Insulation Guarantee Agency (SWIGA) was secured, which is a requirement of PAS 2035 – the standard with which all projects funded by the SHDF must comply.

Benefits of EWI for residents

Domestic homes typically lose around 35% of heating through their walls, which not only impacts people physically but also mentally. From feeling cold in your own home through to the mental strain caused by worrying about rising fuel costs, living in an energy-inefficient home can severely impact health and well-being.

As well as physical discomfort, poorly insulated homes can lead to problems forming in the building itself which can cause serious longer-term health problems such as asthma.

EWI is one of the key elements of retrofitting to not only make homes more energy efficient – thus reducing energy bills – but also more comfortable to live in.

It can significantly reduce heat loss from a building, help to mitigate damp and mould, and play a big role in keeping out external pollutants and therefore improving air quality.

Luke concluded:

“The work done on this project has resulted in significant improvements to the energy performance of the properties and, most importantly, improved residents’ quality of life.

“Joyners has recently been appointed to CBC/CBH’s new five-year contract, which is a testament to the service we provide and our partnership approach towards our client and supply chain – all key factors in our ability to deliver.”

The retrofit work on these properties was completed in June 2023, allowing residents to enjoy the cooling benefits throughout summer and warming benefits during winter.