Client: The Co-operative Group
Arc: AEW Architects Group
Completed: 2020
Carbon Reduction: Client confidential

We recently delivered the Building & Energy modelling, overheating analysis, climate change adaptation & mitigation reports and M&E design briefs for the low-carbon store design for The Co-operative Group. We were assigned to this project, along with AEW Architects, Ramboll (Structural Consultants) and Hilson Moran (Embedded Carbon) to define how a local Co-op retail outlook is designed, constructed and operated with learnings with can be used in future builds to help achieve Co-op’s ambitions to achieve net-zero for its direct and indirect carbon emissions by 2040.

We utilised a baseline store for the design to be compared against, after continuous analysis of the baseline we developed a servicing strategy. S I Sealy partnered with Clade engineering, who developed a bespoke Transcritical CO2 Booster system solution. The design comprised of an external condenser rack coupled with a dry cooler that serves all internal display and walk-in refrigeration units, capturing rejected heat into a buffer vessel. This arrangement allowed 100% of the Green Store’s heating and hot water demand to be served by waste heat, slashing over 5 tonnes in annual operational CO2 emissions. Rejected heat is now redirected into heating coils of hybrid ventilation (HV) units.

The baseline store was already equipped with good lighting specifications utilising low-energy LED and daylight sensors. Working with the Architects utilising daylight and we turned the lighting strategy on its head and made daylight take centre stage. Daylight now comes into the building not only through the side windows but also an array of 23 light tubes dotting the roof above the shop floor and BoH. This reduced annual lighting energy use by a third and saved over a tonne of annual operational carbon emissions.

The building orientation on-site was optimised around solar incidence; the footprint was elongated to optimise material use; the roof was replaced with mono-pitch saving materials, reducing complexity and providing a base for solar PV integration. The entrance is equipped with a draught lobby significantly reducing infiltration losses and the back of the house is partitioned off from the main shop floor.

To serve the Store’s active systems, a solar PV array is introduced to the optimised mono-pitch roof. The array is composed of 124 thin-film CdTe panels adding up to a total of 224m2 or 24kWp. The thin-film PV type provides several advantages over more traditional mono-crystalline panels, their weight allows for a less bulky roof structure reducing embodied carbon; CdTe panels operate better in cloudy conditions common in the UK; applied with adhesive strip, these panels are extremely easy to install. Overall, the proposed array has been modelled to generate 24MWh of electricity annually, 93% of which is used directly on-site. The PV array reduced the Store’s annual carbon emissions by 5 tonnes.