Taking the heat out
Through skilful planning, Feilden Clegg Bradley has created a BREEAM ‘Excellent’ Modernist block that avoids the pitfalls of its type
From a glance at the plan, Manchester Metropolitan University’s new business school and student hub looks like a conventional deep-plan Modernist building, if you ignore its cut corners.
Three 12 metre-wide bands of accommodation are divided by two 12 metre atria, all laid out on a six metre grid with regular service cores. The familiar advantages of standardisation therefore apply, with a regular structure, limited number of repeated room types and a tight, universal vocabulary of construction details. Such ruthless rationality could produce boredom and a sense of placelessness, but that threat is alleviated by two key moves.
The first is the tapered section, four storeys on one side and eight on the other, which points the sloping roof towards the sun and differentiates the two top-lit atria. The second is the cutting of the corners, which answer very different edge conditions. To the north-west lies a roundabout disgorging traffic from Mancunian Way, Manchester’s elevated inner ring-road. Here, the building had to be hard, sheer, and sound-proof. On the opposite corner, facing south-east, the building acts as the pedestrian termination to the university’s main square, welcoming students and visitors.
Although the building’s upper floors cut back on the diagonal, the ground floor fills the gap with a single-storey portico and foyer, daylit from above. This triangular threshold fronts a smaller local square opposite and links up with the adjacent library and law school, visually and spatially extending both atria. The two atria at ground floor level constitute the so-called student hub, public and independent of the business school: foyer-like spaces intended to encourage meeting, casual study, refreshment, and gathering between sessions. As a result of this clear planning, the building’s organisation is commendably simple. The upper floors allow glimpses into the atria for orientation, and daylight or sunlight are nearly always visible, along with views of the outside world.
You can therefore forget that you’re standing in a deep-plan building 54 metres-wide and wholly dependent on mechanical ventilation. Noise and pollution from the ring-road militated against opening windows and, with so many layers, cross-ventilation would in any case have been hard to control. Hence the whole building is sealed with a continuous glass skin and revolving doors, the atria serving as stacks for returning air, which is heat-exchanged and exhausted at roof level, with heating and cooling by ground-source heat pumps and 90m boreholes. Fresh air arrives through floor voids via multiple vents, slow-moving to reduce noise and fan energy.
As the building is intended, at least in part, for 24-hour use, the strategy is to anchor the temperature with high thermal mass, which is managed both with a concrete primary structure and 75mm-thick secondary precast floor slabs left as naked soffits throughout. Such extensive use of concrete did not promise well for the building’s embodied energy, but the incorporation of ground and granulated blast furnace slag in the aggregate reduced the cement content by 35 per cent, as well as giving the concrete a more creamy finish.
The skin is everywhere of glass, and parts of the sloping roof not transmitting light are solar panels, for once nicely integrated. The architects made much of the building’s jewel-like quality, enhanced by its rhomboid shape, which helped sell the idea of the building as an icon. While it might impress passing air travellers, the effect on the ground is of glazed vertical facades. These are clever, though, and
a welcome reminder of how far we have come from simple curtain walls.
Each six-metre module has two transparent vision panels, which make up 45 per cent of the facade. The other 55 per cent is opaque and also highly insulated, with fritted glass in front, each slice angled outwards from the facade plane by about 35 degrees, both to reflect solar radiation and to shade the adjacent open panel. The direction of these small triangular bays changes with orientation, and external fritted lines are added to the transparent panels where needed to further reduce solar gain.
Externally, this use of reflective glass in differently angled planes greatly increases the visual liveliness, and a final touch is added by projecting fins tipped with dichroic film. These produce rainbow colours, both by reflection and transmission, causing brilliant stripes on the facades, which change with sun and angle of view, a good advertisement for the university, at least until coloured fins catch on and everybody does it.
From within, the glazed panels appear to be edged with glowing lines, which continue in the rooflights with an effect like stained glass, casting blue or purple stripes on the floor and adding a touch of colour to an otherwise austere interior.
It was bold to place so much concrete on display, but the lack of secondary finishes, necessary to exploit the heat exchange capability of the concrete, has the added advantage of showing the substance of the building, a welcome relief at a time when too many architects deploy materials as if they were wallpaper. The solid concrete ground floor slab performs thermally as a heat sink and is ground off like terrazzo.
The exposed surfaces must have required great discipline in an industry where it is normal to do rough work then cover it up. Not only did quality of production have to be raised in order to keep the surfaces smooth and consistent, but inclusion of services had to be flawlessly planned, with no later adjustments. It is difficult to know at a glance whether elements are in-situ, precast, or formed with stepping hydraulic moulds.
That this is a green building attaining ‘Excellent’ on BREEAM standards is not self-evident, for the boreholes and solar collectors remain unseen, and measures to conserve heat and control solar gain do not shout.
The well-insulated envelope means that little heating is required. Instead, cooling is necessary, much of it due to ever-proliferating IT equipment. This makes a reversible heat pump system essential, but also allows exhaust heat to be turned into hot water. Even so, the technical systems remain mercifully in the background, with neither discernible draughts nor fan noises and even in the lecture halls ambient noise is low, helped by simple but effective acoustic damping.
Most importantly, daylight and view are almost everywhere, and you easily find your way around. Many of the conditions that turned Modernist buildings into air-conditioned nightmares – deep-plan, sealed envelope, mechanical ventilation – have been mitigated by skilful and thoughtful planning accompanied by effective technical solutions.
Peter Blundell Jones is professor of architecture at the University of Sheffield