INCA Case Study: Bristol City Leap – Pilot Retrofits Scheme


 

Bristol City Leap – Pilot


Project Type: Refurbishment

Building Type: Low Rise, Residential

Architect: N/A

System Designer: Mapei UK Ltd

Installer: ESW Construction Services Ltd

System & Finish: Mapetherm Mineral Wool External Wall Insulation

U-Value Before: 2.06W/m²K

U-Value After: 0.22W/m²K

ESW achieves “massive’ improvement in heat retention, comfort & aesthetic at BCL pilot with a Mapei Mapetherm EWI System

The Mapetherm Mineral Wool External Wall Insulation (EWI) system from Mapei, has been installed as part of a Bristol City Leap (BCL) pilot retrofits scheme.  The scheme, in the City’s Brentry district, comprised the upgrade of 16 Easiform homes to achieve energy efficiency and carbon reduction.  The EWI system was installed by Bristol-based ESW Construction Services Ltd.  Following installation of a cavity fill system combined with the Mapetherm EWI, a u-value of 0.22 W/m2K was achieved, compared with a pre-retrofit rating of 2.06 W/m2K, demonstrating greatly improved heat retention and comfort.

An innovative partnership between Bristol City Council and Ameresco Ltd, Bristol City Leap aims to accelerate green energy investment in Bristol and help towards decarbonising the whole city.  Over the next five years, it will invest at least £424 million into low carbon energy infrastructure including solar, wind, heat networks, heat pumps and energy efficiency measures in order to help the city meet its carbon reduction target of becoming carbon neutral by 2030.

Each of the 16 Easiform homes in Brentry features a non-standard concrete cast-in-situ construction.  The scope of renovation works included replacement of roofing elements, renovation of chimney stacks, insulation of cold roof space, internal ventilation works, cavity wall extraction, fenestration installation, cavity wall fill and a wide range of enabling works.  As part of the energy efficiency improvements, Mapetherm Mineral Wool – BBA 13/4977 certified high-density rock wool insulating panels for thermal insulations systems – were installed throughout the properties external walls, totalling over 1400 m2. 

Specific design & technical challenges

Throughout the project, ESW Construction Services observed and implemented best practice to resolve a number of challenges:

  • Externally, several issues arose where occupants had incorporated patio or decking areas which breached DPC requirements of 150mm, resulting in the removal of concrete and slabs, etc.
  • Soil, vent and rainwater pipes were imperial cast iron and, in the majority of cases, required replacement with a plastic metric system. This presented a particular issue where works were terraced onto private properties, with no option to remove the cast stacks.  The team worked closely around these areas to minimise thermal bridging.
  • Due to the existing use of imperial systems from WC/bathrooms to exit penetrations, there was a requirement to provide a continual pipe section from internal to external areas and replace pipework to the rear of toilet pans or under baths; this required careful management, to minimise internal disruption to tenants and meet rectification as quickly as possible whilst managing expectations.
  • Early 2024 proved one of the worst on record for rainfall; installing EWI over this period was challenging.
  • A number of properties along the terrace were not aligned; in some cases, the line from soffit end to under croft stepped across circa 450mm.  Careful consideration was required, to ensure that EWI was kept within the demise of the property being retrofitted and to avoid breaching onto neighbouring properties.
  • Originally, the team planned to leave adequate spacing behind soffits to dress the EWI insulation up to, providing continuity of the envelope insulation.  However, this proved difficult and resulted in the inclusion of a UPVC filler to close deviations between EWI and soffits. As a pilot, this has enabled an improved system for all future retrofit projects where the replacement of facia and soffits will include the insulation within this area – to be completed by the roofing contractor and checked prior to closing off with facia.

Carlo Bonomini, ESW’s Commercial Manager:

“The Mapetherm system has been tried and tested on many of our projects. Mapei’s products are high quality, easy to use and the final results speak for themselves. The service we get from Mapei’s sales and technical team has always been first class and the support they offer on site is second to none,” commented

Jay Shuttleworth, Construction Manager at Bristol City Leap:

“ESW has been instrumental in the success of the pilot project; having accumulated experience and knowledge of the Mapetherm Mineral Wool EWI system over several years proved essential in overcoming the initial teething problems of the pilot. Diligence and thoroughness prior, during and after works paved the way for high standards, outstanding results and a happy client, as well as improving the lives of those residing in the properties,”

Jay Shuttleworth added:

“Tenant comments have been positive following the completion of their properties, with a remarkable difference and satisfaction of the results experienced, an improved exterior with a massive improvement to internal heat retention and comfort. Many tenants also appreciate the reduced CO2 footprint resulting from the works,” .

The Mapetherm system has been tried and tested on many of our projects. Mapei’s products are high quality, easy to use and the final results speak for themselves

Carlo Bonomini

Commercial Manager, ESW

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