Low-Rise Social Housing Retrofit, Coventry

Project Overview

Background

Citizen Housing has been operating for over 50 years and currently provides around 30,000 social homes across the West Midlands. These span numerous urban and rural neighbourhoods and feature a variety of designs. Some of them were built many decades ago and, like many older archetypes, no longer meet modern standards for thermal insulation. Citizen has therefore made strenuous efforts to improve them.

This £19 million project, which launched in 2023, formed part of that effort, focusing on decarbonisation retrofit measures to more than 650 solid-walled homes.

Brief

The project would be funded by Wave 2.1 of the Social Housing Decarbonisation Fund (SHDF). All works and designs would therefore have to be delivered in accordance with the PAS standards. The required measures would include external wall insulation (EWI), loft insulation, and the installation of replacement doors and windows.

The properties at the heart of the project would be of various archetypes, so an important first step would be to carry out detailed retrofit assessments and structural surveys. These would help to determine which EWI systems should be used and, crucially, assess whether the intended systems could safely be affixed to the walls without damaging them.

The client also required that the appearance of the chosen systems must be sympathetic to the character of the original buildings and their surrounding neighbourhoods.

A key target for the scheme was that every property should ultimately achieve an Energy Performance Certificate (EPC) rating of at least band C.

Design and Specification:

Permarock technical staff assisted in all these vital planning and testing stages, and conducted pull-out tests to gauge the robustness of the concrete infill panels, masonry and other substrates. In all, they conducted substrate tests on approximately 10% of the properties. On the basis of these investigations and client meetings, the team developed an action plan. It included the completion of structural repairs wherever necessary, and the installation of systems based on Permarock EPS Premium insulation, together with various Permarock finishes in a number of different colours.

System Characteristics

The chosen system comprised Permarock EPS Premium insulation, together with Permarock Brick Effect Render and Dry Dash Finish.

Permarock EPS Premium is a lightweight, high-performance insulation system that combines expanded polystyrene with microscopic graphite particles that improve the material’s thermal performance. It can be applied in thicknesses up to 300 mm and is well suited for schemes that seek to achieve low U-values.

Permarock Brick Effect Render is a two-coat, cement-based render that can be used to simulate the appearance of traditional brickwork. It incorporates a silicone-based water repellent that helps to keep the surface clean, and it can be used in combination with other decorative finishes. In this case, it was used in conjunction with Permarock Dry Dash Finish, which produces a tough, cost-effective finish that helps to minimise maintenance demands.

The Permarock system for the main walls was complemented with a Permarock Plinth system below the level of the DPC. The system – which comprised Permarock EPS insulation panels (200 mm) and a bituminous waterproof coating – ensured compliance with the demands of PAS 2035 by minimising the risks of cold-bridging at this point. It also produced a neat, contrasting finish at the base of the external facade. The plinth system provides at least 75% of the thermal resistance of the main wall EWI system.

Installation

We provided project-specific training for 10 installer operatives and site management. Work began as planned in September 2023 and progressed smoothly. Having played an important part in the planning, surveying and testing stages, we were able to provide relevant drawings and detailing. This facilitated a rapid pace of completions by the main contractor, Sustainable Building Services. Moreover, our technical services team continued to provide remote and on-site support for the duration of the scheme, and conducted weekly site visits to monitor progress.

The EWI systems and other decarbonisation measures were all installed in accordance with the demands of the PAS 2030/2035 standards.

Result:

The scheme delivered valuable improvements to Citizen’s housing stock, and by raising the homes to an EPC rating of C or better, helped to improve living conditions for more than 1500 residents.

U-value calculations indicate that the EWI systems played an important role in improving the properties’ energy efficiency. The client has estimated that the total calculated energy savings amounted to over 4,375,000 kwh/year. This, in turn, has meant valuable savings for residents and helped to reduce overall carbon emissions by almost 1.2 million kg each year.

Client
Citizen Housing
Specifier
Sustainable Building Services (UK) Ltd
Substrate
Various (solid wall)
System
Permarock EPS Premium External Wall Insulation Systems
Finish 1
Permarock Brick Effect Render
Finish 2
Permarock Dry Dash