Project Overview:
Background:
Drawing on funding from Wave 1 of the Social Housing Decarbonisation Fund (SHDF), Shropshire Towns & Rural Housing (STAR) commissioned a scheme to improve the appearance and energy efficiency of 26 Cornish Unit Type 1, pre-cast concrete houses. The works, featuring properties at West Place and Hammonds Place in the village of Gobowen, would represent the first phase of a larger SHDF Wave 1-funded project.
The Brief:
The project plan entailed the installation of multiple decarbonisation measures. These included external wall insulation to improve the walls’ thermal performance, complete re-roofing and insulation to the Mansard roof structure, and replacement doors and windows. Together, these measures would deliver a complete upgrade to the thermal performance of the building envelope. The target was to raise the energy rating of all of the properties to EPC bands B or C.
In addition to the thermal upgrade requirements, another key requirement was that the EWI system should be supplied with an attractive render that would resist the effects of weather and the build-up of dirt, mould and algae.
Careful design and detailing work would be essential for ensuring the effective performance of the external envelope, with attention given to removing thermal bridges at junctions between different façade and roof elements. In short, the scheme would demand expert technical support from the system designer, and from an early stage.
Design and Specification:
The client and main contractor sponsored a structural engineer’s survey of the houses to establish their structural integrity and suitability to receive the proposed improvements. They engaged with PermaRock’s technical team prior to commencement in order to ensure its early input into the design phase of the works. Properties were surveyed and assessed individually, and PermaRock then worked in conjunction with the project’s Retrofit Designer to develop the necessary details for the external wall insulation system. This early collaboration ensured rapid mobilisation and a clear, shared understanding of all relevant technical requirements.
The chosen EWI comprised:
PermaRock SiliconeUltra K Finish is a textured, through-coloured render that is lightweight, water-repellent and highly vapour permeable. It resists the accumulation of dirt and contains a preservative that helps to prevent algae and mould from marring its surface finish. It is similarly resistant to attack by aggressive airborne pollutants.
It is available in three textures – grain sizes of 1.5 mm, 2.0 mm and 3.0 mm – and in this case, the 1.5mm option was specified. It is also available in a very extensive range of colours. The range includes SiliconeUltra shades with the highest colour brilliance and excellent colour stability.
Performance: Sustainability and U-Values
PermaRock Mineral Fibre External Wall Insulation systems have low embodied energy and are BIM Level 2 compliant. They exhibit thermal conductivity of 0.036 W/mK, and have an Ecopoints score of 0.10 (m2) – an ‘excellent’ rating.
PermaRock Mineral Fibre Insulation is manufactured to EN 13162 and is CFC and HCFC free. It has zero Ozone Depletion Potential and zero Global Warming Potential.
Result:
The scheme was completed in September 2023. In the same month, Councillor Ian Nellins, Portfolio Holder for Climate Change, Environment and Transport addressed Shropshire Council during member questions, noting that as a result of the works, carbon emissions would fall by approximately 29 tonnes per year. The work, he said, would also “enhance the properties’ appearance and the visual amenity of the area.”
In a subsequent news item, the Council described the scheme as ‘impressive.’ It wrote that residents had given very positive feedback, reporting that the internal comfort of their homes had been “immediately improved”.
Harpreet Rayet, STAR’s managing director, said: “This project has been a great success, delivering significant benefits to the residents through improved energy efficiency and quality of life. We are proud to have contributed to raising the EPC values of these homes, making a positive impact on the local community and the environment. We look forward to continuing our work with our partners to make a real difference in the lives of those we serve.”
Councillor Dean Carroll, Shropshire Council’s portfolio holder for housing and assets, added: “This an excellent programme that not only upgrades the housing stock, but brings a real benefit to the tenants in terms of warmer more energy-efficient homes and savings on their bills.”