Sustainability Report

Whole-building carbon assessment

• The redevelopment of Hertford Theatre was designed to increase the capacity of the existing theatre through a new extension, which accounts for the majority of the project’s upfront carbon. While the flytower was not extended, the main auditorium was remodelled with a new balcony to increase capacity to 550.
• The design sought to reduce embodied carbon and was the subject of a whole-building carbon assessment during the design stage. The assessment was undertaken by Cundall for the Net Zero Theatres Study in 2021, using RIBA Workstage 5 information and a RICS-aligned external calculation method. It was later adjusted to align with the UK NZCBS limit scope.
• The assessment relates to a 3,228-square-metre GIA culture/performance building, comprising 2,367 square metres of existing NIA and 861 square metres of new NIA.

Summary and comparison to UK NZCBS limit

• Upfront carbon: 602 kgCO2e/m² (A1–A5) excluding sequestration and including contingency
• Sequestered carbon: -165 kgCO2e/m² (A1–A3)
• UK NZCBS limit: 680 kgCO2e/m² (Year: 2025 Sector: Culture)

Reuse, retention, and lower-carbon structure

• Part of the existing building was reused, with elements of the old theatre retained within the redevelopment. The building also makes extensive use of mass timber in the superstructure, with prefabricated cross-laminated timber (CLT) panels forming the main walls and pitched roofs of the new cinemas and second theatre space.
• A flexible structural approach allowed more of the existing building fabric to be retained alongside new lower-carbon construction methods for the cinemas and studio. Reducing the embodied carbon of the structure was a key project driver from the beginning. Assessments at concept design stage helped the team limit higher embodied carbon concrete elements, adopting them only where other materials were not technically feasible, for example where the building bridges over the River Lea, a branch of which runs directly under the new cafe/bar.
• Elsewhere, lower-carbon materials included CLT, which had benefits across the design disciplines, including reducing the weight of the building over the river, increasing the speed of construction, and aiding acoustic separation.
• Where possible, materials and elements from the original theatre were reused or adapted. The flying system uses a combination of new and refurbished equipment, the lighting bridges over the auditorium are interwoven with the original steel trusses, and the orchestra pit lift frame has also been reused.
• Working with the existing auditorium structure required a different approach. The original 1970s engineer’s drawings were sought to understand how the structure had been designed. This understanding helped the team weave new lighting bridges into the roof trusses and carefully insert the new balcony structure.

• A significant part of the project aim was to decarbonise the building in operation. The gas boilers and gas connection were removed to make way for an electric-based heating system.
• The ventilation systems now employ heat and coolth recovery to support improved operational efficiency.