55 Gee Street, London

Munkenbeck and Partners’ 55 Gee Street in Clerkenwell, London is an eight-storey mixed-use building with six apartments perched on top. Squeezed into a tight urban site, the £6.3m building’s playful appearance belies a coherent sense and understanding of function. Nowhere is this more effectively demonstrated than the facade, which consists of a jumble of extruded piers of perforated terracotta airbricks. This serves two purposes: it breaks up the horizontal mass of the long, thin building, whilst the perforations allow a degree of natural ventilation without having to open the storey-height glazing, which is recessed and fully shaded from the sun.

Fresh air is drawn from roof level via a vertical shaft supplying an underfloor mechanical ventilation system. A second shaft forms part of the extract system, carrying air back to roof level where dampers regulate the flow, enabling it to be either exhausted to the outside or recirculated to save energy during the heating season (up to 90% recirculation). During the summer, the system can be run at night to cool the building’s thermal mass (provided by the exposed concrete soffits). Overall, the air-mixing arrangement aims to ensure that the interior does not require cooling or heating when the external temperature is between 0 and 28°C.

In the office space, the exposed concrete soffit contains recesses for locating the light fittings. These are connected via conduits cast in the slab, thereby avoiding the need to surface-mount or impinge on the floors above. The concrete slabs are posttensioned and incorporate 50% ground granulated blast-furnace slag (GGBS) cement replacement, reducing the embodied CO₂ of the structure. The building was awarded a BREEAM rating of ‘Very Good’, and proves that natural ventilation can work in high-quality offi ce space located in London. It also demonstrates that a rigorous low-energy agenda is not the enemy of playful architecture, and that there is no reason why speculative builds should not have their own architectural verve.