Project Overview:
Background:
Park Hill Flats were built in 1961 by Sheffield City Council to provide accommodation for local people. The building’s design, in the brutalist style, won considerable acclaim at the time but its concrete frame was also a source of significant problems with poor heat retention. As a result, the building’s appeal and occupancy both went into gradual decline and it was only saved from demolition when it was accorded Grade 2 Listed status in 1998. This safeguarded the property and, coincidentally, made it Europe’s largest listed development.
However, the problems with cold and damp remained so the owners decided to upgrade the property in phases. Outline planning consent for the regeneration of the whole estate was granted in 2006 and work on Phase 1 took place between 2007 and 2016.
Approval for Phase 2 was granted in 2017 and the project was then scheduled to run until March 2022. This second phase was led by a joint venture between Places for People and Urban Splash. Its intention was to revitalise the property, including its characteristic ‘streets in the sky,’ and to make them fit for modern, energy-conscious residents. An early step in this process was to bring in the multi-award-winning architectural practice, Mikhail Riches.
The Brief:
The scheme as a whole entailed making many changes to the structure, including removing small, problematic bedsits and creating larger apartments with impressive double balconies. The design called for the creation of 195 flats in all, including 41 with one bedroom, a further 135 with two bedrooms, and 19 larger units with three bedrooms.
To improve heat retention and, in particular, to eliminate problems associated with thermal bridging, the architect developed plan that included insulating both sides of the concrete in each room, including the floors and ceilings. It explained its goals in a submission to the 2023 Housing Design Awards, stating that the building’s status meant that:
“Over-cladding the concrete, which acts as a massive cold bridge, (was) not an option; we needed to insulate both sides of the concrete in each room. Thermal imaging of the Phase 1 façade showed that the concrete frame on the balcony cheeks was the most thermally leaky element. This informed our response to insulate the exterior reveals of the building, expressed as coloured render panels.”
Design and Specification:
To create these insulated render panels, Mikhail Riches chose a system comprising:
- PermaRock Mineral Fibre External Wall Insulation System with 160 mm insulation adhesively bonded and mechanically fixed to the substrate;
- A reinforced basecoat with additional mechanical ‘fire safety’ fixings through to the substrate;
- PermaRock Brick Slips in ice white, one of 12 standard colours available in the range, and using Sand White adhesive and pointing compound.
Performance: Reaction to fire
The PermaRock Mineral Fibre EWI system with its Brick Slip finish has an A2-s1,d0 reaction to fire classification (EN 13501-1:2007 + A1:2009), which means that it can be used on buildings of any height and within proximity to any boundary. Being directly bonded and fixed, without a cavity, the system is optimised both for fire performance and thermal performance – there is no heat loss due to thermal bypass via a drained cavity. Moreover, no fire stopping, cavity fire barriers or fire breaks are required within the PermaRock Mineral Fibre System.
The PermaRock external wall insulation system also incorporates additional stainless-steel fixings through the reinforced basecoat layer. This provides additional support to the system in the event of a fire.
Performance: U-Values
The refurbishment was completed in March 2022, and in addition to the external wall insulation, it included a variety of energy efficiency improvements. Amongst others, these included new glazing, solar shading, and connection to a local energy-from-waste facility that provides domestic hot water and space heating.
The architect noted that as a result of these and other measures, “the increased fabric efficiency has enabled electric heating to be economically feasible, which allows the development to benefit from green energy as the grid continues to decarbonise…
“The predicted annual operational emissions for the existing pre-retrofit building are 151 kgCO2/m2 and for the post-retrofit building they are 20 kgCO2/m2, an 87% improvement. The principal improvements arise from the significant fabric upgrades to mitigate the thermal bridging present in the original building.”
The award submission also notes that by refurbishing rather than re-building, the scheme delivered appreciable carbon savings. It notes:
“The whole life embodied carbon for the post retrofit build is predicted as 360 kgCO2e/m2, compared to a new build equivalent of 800 kgCO2e/m2, representing a 55% improvement in whole life embodied carbon compared to a good practice new build.”
Result:
The scheme applied many examples of industry best practice and won numerous awards. In April 2023, it was named the winner of two categories in the ‘AJ Retrofit of the Year’ Awards - 'Housing' and the 'Listed Building £5 million and Over' categories. Judges noted that the two wins are "a measure of the success of this scheme, which balances the sensitive upgrade of a 1960s housing estate’s Brutalist fabric with its transformation back into a decent place to live."
In October of the same year, it was named the overall winner of the Housing Design Awards 2023 and, in the following December, it won the prestigious overall award in the Sustainability category of the Dezeen Awards.
Note:
This scheme formed the basis for an excellent ongoing relationship between PermaRock Products and Mikhail Riches. Indeed, even before this scheme was complete, the two companies were already working together on another scheme at Duncombe Barracks in York, and at the time of writing, they were on-track to begin Park Hill Flats Phase 4. They also expect to collaborate on Mikhail Riches’ City of York schemes at Ordnance Road and Burnholme.