Case study The Entopia Building

© Max Fordham

This world first for a deep retrofitted sustainable office building sets new standards for low energy use, carbon emissions and impact on natural resources, as well as user experience and wellbeing measured against multiple benchmarks.

The Entopia Building is on course to achieve multiple sustainable building certifications, including BREEAM 'Outstanding', the Passivhaus ‘Enerphit’ standard, WELL 'Gold' certification, alongside the application of circular economy principles to minimise the volume and impact of natural and human-made resources used in the building.

The former 1930s Telephone Exchange at 1 Regent Street, Cambridge, has been transformed into an ultra-low carbon sustainability hub and new home for the University of Cambridge Institute for Sustainability Leadership (CISL). The building houses CISL’s Cambridge-based staff, currently spread across five buildings, and provides a dynamic virtual hub for its offices in Brussels and Cape Town, and partner organisations in China, Australia and the UAE, providing a space to engage with its global corporate partners, donors, alumni, Fellows, and Senior Associates, researchers and visiting academics. It's also home to Canopy, a workspace and community for sustainability-focused start-ups, and small and medium-sized enterprises.

Significant moisture modelling and thermal bridging analysis was needed to help deliver a low-risk, low embodied energy, high thermal and airtightness performance envelope.

The building fabric was comprehensively upgraded – including internal wall insulation – to reduce heat loss and achieve the EnerPHit airtightness targets. The wall build-up has been carefully designed to balance the benefits of increasing the thermal performance with the use of bio-based materials and the moisture risks inherent in building against a solid masonry wall. Existing windows were replaced with high-performance triple-glazed units. Thermal bridging was carefully managed, particularly where the internal structure cuts through the internal insulation line. These measures delivered 75% lower heating demand in comparison to an average office building, and airtightness at more than five times that required by building regulations.

The approach to building services was to tread lightly, minimising the amount of equipment required, and reusing existing items where possible. Whole-building mechanical ventilation with heat recovery was provided from a single central unit. The ventilation unit has an integral heat pump, which is used to provide efficient background heating.

The summer comfort strategy combines natural ventilation with tempering of the incoming air. Secure night purge ventilation is also provided mechanically by a system which, coupled with the exposed thermal mass, limits the active cooling requirements and helps control temperatures when the building is occupied.

The deep green retrofit has resulted in an 80% saving in whole life carbon emissions (over 10,000kg CO₂e/m²) compared to a standard office refurbishment.

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