The Project

In December 2007, RCT Homes Ltd became Wales’s largest social landlord after taking over the ownership and management of nearly 11,000 homes from Rhondda Cynon Taf County Borough Council. A not-for-profit organisation, RCT Homes provides high quality housing and manages housing services for more than 60 housing estates and 27 sheltered housing schemes.

RCT Homes Ltd’s latest refurbishment project is based in Cwmbach, Wales, refurbishing 60 properties of which 30 are Cornish Unit Homes. Work commenced in mid-September 2015 with a completion date set for the first quarter of 2016. RCT Homes worked directly with Hirwaun-based building contractor, Thomas Holdings, to oversee this project.


The Challenge

The 30 Cornish style homes required insulation to overcome various prevailing thermal issues. Synonymous with the housing regeneration post World War Two, Cornish Units have become an iconic addition to British neighbourhoods. As a temporary solution to the post-war housing crisis, many Cornish houses are now over half a century old and no longer meet modern day regulations and the minimum standard of social housing decency that RCT Homes Ltd has to abide by.

Despite their age and non-permanent intentions, many Cornish Units still stand today and are being renovated rather than demolished. Although iconic in British building history, the external aesthetics of the building posed several challenges for RCT Homes Ltd. Cornish Units are very recognisable, due to their contrasting ground floor and first floor structure and protruding windows and mansard roof. RCT Homes Ltd was therefore required to provide very different approaches to the whole house structure.


The ROCKWOOL Solution

Despite the UK housing around 30,000 Cornish Units, many are not aware of how best to manage and refurbish the properties. Unique to this project, ROCKWOOL provided a tailored solution that is being trialled for the first time in Cwmbach, before being offered to the wider market.

With Cornish Units being very different to typical housing assembly, ROCKWOOL Architectural Design Consultant, Lewis Ham, designed a unique technical approach to insulate the buildings. With the help of Lewis, ROCKWOOL was able to provide this design support in-house by combining its REDArt® External Wall Insulation System (EWI) on the ground floor with ROCKWOOL FLEXI® on the first floor. ROCKWOOL eradicated the prevailing thermal issues without comprising on the look and style of the iconic building.

Made from stone wool insulation, REDArt® is renowned for its thermal and fire protection properties. In addition to reducing fuel poverty, REDArt® has been developed to be installed on a wide range of substrates and wall construction types. This enabled Thomas Holdings to fix the insulation to the ground floor quickly and with minimal disruption to the occupants who were present during renovation.

ROCKWOOL FLEXI® is a multi-use, dual purpose thermal and acoustic insulation solution which was chosen for this project specifically due to its unique flexible edge. This patented feature ensures the insulation is fixed and maintained perfectly between the product and its supporting framework for both easy installation and optimum effectiveness. This was vital due to the building’s challenging design and timber frame structure. ROCKWOOL FLEXI® also provides Euroclass A1 fire properties, wrapping the timber framed property safely in non-combustible insulation.

Used in tandem, ROCKWOOL REDArt® and ROCKWOOL FLEXI® provided a tailored solution specifically designed for Cornish Units that achieved the required whole house approach rectifying all thermal issues. The acoustic qualities of ROCKWOOL also reduce sound disturbance for all refurbished buildings.


Qualified Competent Workforce

On this project, ROCKWOOL worked in partnership with Thomas Holdings, an experienced solid wall insulation company specialising in hard-to-treat non-traditional properties, to develop a technical and practical methodology to retrofit the Cornish property type. Also working with Thomas Holdings sister company, Smarter Training Group, the whole team ensured that all operatives were trained, qualified and competent to meet PAS 2030 standards, enabling the company to deliver a quality project and helping them to achieve a Construction Excellence Award in 2015.



Demonstrated through this unique refurbishment project, ROCKWOOL can be applied to any wall type, frame or block, and can be used to refurbish an existing property or a new build project. Providing a solution where there was no previous solution available, ROCKWOOL supplied RCT Homes Ltd with high-quality insulation that immediately reduces the buildings heat loss, minimises internal and external sound disruption and provides a fire resisting barrier, without disrupting the iconic design of the Cornish Unit buildings.

Project Location

Cornish Units

Bryn Awelon

ROCKWOOL performed above and beyond our expectations on this project. Working with a renowned difficult housing design, and with no previous or similar insulation refurbishment plan available, ROCKWOOL provided us with a brand new technical approach to insulate the houses, whilst adhering to the buildings unique style and structure. ROCKWOOL’s optimal thermal and fire resistance combined with its outstanding environmental credentials and easy installation made ROCKWOOL REDArt® EWI and ROCKWOOL FLEXI® the ideal products for this project

Mike Kelly

Thomas Holdings
Company Director
Cornish Unit Homes
Cornish Unit Homes
Cornish Units
Cornish Unit Homes
Cornish Units

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