One Angel Square houses over three hundred and thousand square feet of flexible office space. The building architecture and its mechanical and electrical systems allow easy reorganization of indoors as and when requirements change without excessive refit expenditure. 

Angel Square is the highest scoring BREEAM ‘Outstanding’ building of the United Kingdom and has been designed to achieve a 50% reduction in energy usage compared to its current Manchester complex, and an 80% cut-down in harmful carbon emissions, thus setting a new benchmark for sustainable design of flexible commercial buildings.

The Planning Phase

One Angel Square’s distinctive form was conceived in a simple notebook sketch before it was refined and developed by 3DReid. The construction work began in July 2010 and Mike Hitchmough was the lead architect of the structure. The first task was installing over five hundred pile foundations, and each at a depth as deep as 18 meters. 

BAM Construction, was the main building contractor for this project, BAM worked together with Gardiner & Theobald, who provided the project and cost management services. Before the commencing and construction phases of the project, the building was digitally modeled by BAM to check for safety and prepare a construction schedule thus saving time and cost during the construction phase.

One Angel Square by 3DReid: Largest commercial office building in Manchester - Sheet1
The One Angel Square Complex ©

Architectural Design 

Shortly after it was unveiled to the public in May 2009, this structure got its nickname, “Sliced Egg” because of its double-skinned façade. The building’s interior primarily comprises huge open spaces that can accommodate over four-thousand people. One Angel Square’s green principles have been put into practice by setting up facilities that encourage cycling. 3DReid incorporated recycling systems for used water and rainwater harvesting systems to shrink water wastage. More than 4,000 workers from over 90 different companies came together for the building’s construction, making it the largest construction site outside South East England. 

The Sliced Egg and Its Significance 

The building’s double-skin facade has a cavity between its inner windows and the outer glass panel. During winter, the louvers atop this double-skin façade are closed to hold the warm air generated within the building. During summer, the opposite happens and these louvers open to expel the warm air, the rising air from the building to prevent overheating. Mecanoo and Manchester-based Royal Haskoning designed the picturesque landscape of the One Angel Square complex. The building’s form is often compared with The Ark and the iconic City Hall in London.

One Angel Square by 3DReid: Largest commercial office building in Manchester - Sheet2
The South Façade ©

Building Materials and Cost

Apart from aiding in heat and ventilation, the building’s double-skin facade serves both sustainability and aesthetic purposes. This peculiar looking outer skin accentuates the three curved corners of the building. To accentuate the form further and make the building shimmer in the sunlight, the client decided to drop the original plan of powder-coating the exterior aluminum surface (which holds the glass panels) and spent a whopping £120,000 on a bronze anodized finish. This lavish spending was justified as being cheaper over several years than using a powder-coated finish which would require expensive and frequent maintenance. 

In keeping with the building’s sustainability credentials, locally produced rapeseed from nearby farms has been used to produce the fuel for One Angel Square’s sustainable cogeneration power plant, the power plant is fueled by both bio-fuel and waste cooking oil. The remaining husks of the crop are used as animal feed. 

Underground concrete earth tubes provide heating and cooling for the incoming air, the concrete acts as a thermal sponge, passively absorbing heat and minimizing the amount of energy needed to cool the building. Concrete also helps control temperature fluctuations. Out of the total £100m costs, approximately £17m of construction materials has been locally sourced thus significantly reducing the structure’s embodied energy and minimizing the building’s environmental impact. 

One Angel Square by 3DReid: Largest commercial office building in Manchester - Sheet3
The Double Skin Facade ©


3DReid has addressed the issue of climate change and future-proofed the structure, the building’s fabric and environmental systems have been designed to cope with an expected 3-5 degree increase in temperature and approximately 30% more rainfall. The building also features computer systems that recycle waste heat

Excess energy is directed back to the grid, with waste energy being sent through an absorption chiller used to cool the air inside the building. Waste air is finally extracted over the balcony edge owing to the atrium’s natural stack effect thus negating the dependence on large space-consuming extract risers. 

The open atrium faces southwards to soak in the sun’s heat, an example of a passive solar building. Before being expelled at the topmost point of the roof, the air passes through a heat-exchanger that recycles the warm air to heat the office spaces below, As a result of its exceptional sustainability credentials, One Angel Square is among the largest in Europe to have a BREEAM-Outstanding distinction. In December 2011, One Angel Square scored the highest recorded BREEAM score, making it one of the most sustainable buildings in the world. 


Sowmya is an architectural journalist and writer. In this column, Sowmya takes you through stories on eco-architecture, biophilic design, and green buildings from across the globe.

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