An apartment complex in Manchester has been conceived on the basis of allowing extended escape corridor distances, in exchange for mechanical smoke extraction.
Normally, building regulations require that means of escape corridors have maximum lengths to enable occupants to escape safely and in good time. In residential buildings where there is a dead end corridor, the travel distance from the dwelling door to the staircase is limited to 7.5m. In addition, a smoke shaft system or Automated Opening Vent (AOV) should be installed.
The designers of the Angel Meadow apartment complex in Manchester have come up with an alternative approach, using an extended corridor application. The 108-apartment building consists of six residential floors and two levels of underground parking. Each of the first four floors has an area of approximately 1600m2 – this reduces to 1550m2 and 1475m2 respectively on the two top floors, which are stepped back to provide continuous perimeter balconies and terraces.
At Angel Meadow, the designers were presented with the challenge of designing a smoke extraction system for a far longer corridor measuring 18m. In order to comply with building regulations, they would need to demonstrate that this approach would provide equal or superior performance to the conventional one.
Floorspace
The architects, BRH of Liverpool, selected Colt’s Extended Corridor System to dispense with the need for a third staircase in the building, and therefore maximise the floorspace devoted to the apartments. The Extended Corridor works by installing a mechanical extraction system at one end of the corridor, and a dedicated air inlet system at the other. This inlet air prevents the corridor from becoming excessively depressurised, which could make it difficult for escaping occupants or firefighters to open doors, as well as potentially causing extract fans to stall, resulting in total system failure. In addition, a mechanical extraction system has the advantage that it is unaffected by positive wind pressure, whereas the performance of a conventional AOV can be reduced by adverse wind conditions.
Other fire safety measures at Angel Meadow include smoke and heat detectors in each apartment. The large, open terrace areas are equipped with sounders and beacons, and the car park detection and alarm system is interconnected with that of the apartment block.
Colt carried out Computational Fluid Dynamics modelling in both escape and fire fighting modes to compare the performance of the External Corridor Solution with a natural Automated Opening Vent system. The modelling shows that in the early stages of the fire, the two systems perform satisfactorily – both the AOV and the mechanical system keep conditions clear for evacuation, although a ceiling smoke layer hangs around with the AOV. Ten minutes later, when an apartment door is opened, large volumes of smoke spill out, filling the corridor. The AOV system is overwhelmed, but once the apartment door is closed, the mechanical system can clear the corridor within 60 seconds.
Shaft work
Colt’s engineers first conceived the Extended Corridor Solution’s mechanical ventilation system when developing and testing the Colt Shaft – a ventilating firefighting shaft that can reduce spatial requirements by 80%, compared to other systems. As with the Colt Shaft, the Extended Corridor Solution enables developers of apartments, hotels and office buildings to increase saleable space while maximising safety, potentially saving lives.
With the conventional scheme, it would have been necessary to introduce a third staircase into the building, which would have taken up around 13m2 of each floor plate at the expense of apartment area. If it had been needed, it would not necessarily have meant reducing the number of apartments in the building, but more likely reduced a two-bed apartment to a one-bed on each floor.
Other projects either completed or in progress which have the Extended Corridor System include Mill Harbour (to be Europe’s tallest residential building), Brabazon House, and Paynes & Borthwick Wharf – all in London, and Plymouth Grove apartments in Liverpool.
