ARCHITECTURE & DESIGN
Finalising OBC n Final selection of selected MMC options. n Keep a number of options viable within the approved outline planning massing envelope until contractor involvement.
The Whipps Cross Hospital redevelopment is ‘a significant mid-rise new-build hospital’, and part of Cohort 3 of the NHP.
Mitigating the risk of supply chain delivery issues When decisions were made, they were tested against which MMC options and associated opportunities might be ruled out, iteratively evaluating the impact of decisions made to optimise our solution. This mitigated the risk of subsequent supply chain delivery issues until further testing can be completed alongside a main contractor’s supply chain. Crucially, floor to floor heights, and the planning envelope for the hospital, were determined to allow for a range of structural solutions when design moves into the Full Business Case (FBC) stage.
Poised to capitalise Our approach was not to close down to a single preferred option at the end of the OBC process. This approach has ensured that the Whipps Cross Hospital redevelopment is poised to capitalise on the growing capacity and expertise of the
MMC industry into the FBC stage. Our approach to ensuring that flexibility for MMC is built into the design throughout OBC stages, without early contractor engagement, has been:
Early OBC n Analysis of initial typologies, including suitability to maximise MMC opportunities.
n Assessment of all MMC options against key, specific criteria, and selection of the most appropriate options to proceed.
During OBC n Refine the typology assessment to a selection.
n Development of a flexible framework based on a standardised platform approach.
n Test all decisions against the framework of MMC options to keep as many open as possible for as long as possible.
National Rehabilitation Centre – Retrofitting an MMC approach After being brought into the NHP as a Cohort 2 project, the National Rehabilitation Centre (NRC) near Loughborough has a target to achieve 65% PMV (Pre-Manufactured Value). The challenge on this project is that the design concept and principles pre-date adoption into the NHP, and MMC was not a key driver in the development of the original design. The design team has therefore reviewed where the most appropriate locations are to achieve these values. In order to maximise the use of MMC, and in particular offsite construction, a regular façade module has been developed that aligns with the proposed 8.2 m structural grid. The upper floors have a 4.1 m wide façade module with consistent window placement. A range of external façade typologies
were considered and evaluated against criteria including cost, percentage of MMC, embodied carbon content, reaction to fire, airtightness, and speed of construction. The initial approach for the external facade was based on a SFS infill frame with insulation between members, cement particle board, further insulation, and rainscreen cladding. This façade system, however, had an embodied carbon
global warming potential of 196 kg CO2 equivalent per m2
GIA. Through further
analysis, an alternative proposition utilising non-combustible Structurally Insulated Panels (SIPS), manufactured off site, was developed, which offers enhanced MMC advantages, and has a global warming potential of 125 kg CO2
equivalent per m2 GIA.
After being brought into the NHP as a Cohort 2 project, the National Rehabilitation Centre near Loughborough has a target to achieve 65% Pre-Manufactured Value.
64 Health Estate Journal February 2023
Expertise in construction logistics Integrated Health Projects (IHP), an alliance between Sir Robert McAlpine and Vinci Construction UK, was appointed at the beginning of detailed design, bringing access to supply chain, and expertise in construction logistics, which were fundamental in developing the MMC strategy. A series of detailed design sprints at the outset quickly integrated the IHP team into the project, and enabled the effective input of the supply chain. With this input the use of non-combustible SIPs panels was developed, positioning the panels outside of the post-tensioned concrete frame to allow a faster construction programme than a more traditional construction technique. This enables the building to be weathertight earlier for concurrent works to commence. In addition to applying MMC principles
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