Buntingford First School is an exemplar project for Hertfordshire County Council, and forms the Council’s first carbon neutral school building, for both operational energy and embodied carbon. Holmes Miller have derived a concise route map for the project, which ensures key performance and sustainability targets are met, and an agreed methodology and validation processed established from the outset. The school design has been developed through intensive consultation, where building functionality and client preferences are fused with an education in low carbon ecological design. Through clear, confident discussion, the client has been able to make informed decisions, around building form, orientation, materiality and internal adjacencies, all of which have been tested to ensure end user requirements are being met and exceeded, whilst monitoring design decisions against building energy performance.

The key ecological targets for Buntingford School relate to operational energy, with peak energy use capped below 60KWh.m2.pa [of which only 15KWh.m2.pa should be assigned for building heating], all of which will be generated on site through renewable technology. Both regulated and unregulated energy demands have been assessed through Passivhaus Planning Package (PhPP) analysis, which has been independently validated and certified during design stage, with target to achieve Passivhaus certification. The building also adheres to the London Environmental Transformation Initiative [LETI] guide, for embodied carbon use in construction, through modules A1-A5, capping carbon at below 600kg.CO2e.m2. This target was monitored throughout using One Click LCA (life cycle carbon analysis), with resultant embodied carbon verified and offset to Gold standard through approved partners. An early passive design analysis and fabric first approach was adopted to drive down energy demand and minimise reliance on active building services systems.

. Factors such as building form, massing, layout, orientation, enhanced fabric design, natural daylighting provision and ventilation strategies were considered, modelling optimised to effectively manage ambitious carbon reduction targets, whilst balancing a range of user comfort issues and ensuring occupant wellbeing was also prioritised. Detailed design and buildability issues were closely monitored, modelled and managed, eliminating any thermal bridging risk. Examples of savings include a 40% reduction in carbon from the substructure elements as a result of increasing the GGBS mix for cement (resulting in both cost and environmental savings) and almost a 10% reduction from MEP and internal finishes, favouring low VOC and low GWP product specifications and the use of natural products.

The design also favours a CLT structure, allowing for more than a 60% reduction in embodied carbon when compared with a steel alternative. A carbon monitoring and reduction strategy has been prepared to support the contractor during the construction phase, minimising waste and transport emissions where possible.

An early-stage Life Cycle Costing analysis was integrated with the Whole Life Carbon analysis, allowing whole life impacts to be considered for both cost and carbon. This exercise influenced design options appraisals and helps mitigate some of the operational and embodied carbon impacts of the building over its lifecycle. Detailed simulation models were developed in parallel with the PHPP analysis, fully integrating the building design and services strategy. Highly efficient services with intuitive and responsive control strategies further enhanced the operational efficiency of the school and reduced the whole life carbon impacts.  

A soft landings approach was adopted from the outset, ensuring end user needs were clearly captured and performance outcomes agreed prior to feasibility stage. Key actions were developed and activity closely monitored throughout the design development stages. A detailed commissioning, training and handover plan is place to support FM and end user needs and a detailed aftercare programme will support performance optimisation from a very early occupation stage. The agreed performance outcomes will be used during the delivery of a structured post occupancy evaluation programme, validating the carbon reduction and other environmental and social benefits during the in use stage.   

The project clearly demonstrates the application of sustainable design standards against the backdrop of the output specification, DfE accommodation matrix + associated Technical Annexes.