KENT COLLEGE | EARTH LABYRINTH VENTILATION CHAMBER MUSIC To help maintain comfort conditions in Kent Colleges Great Hall, air is cooled using five giant, subterranean concrete chambers. Andy Pearson speaks to engineer Brinson Staniland Partnership about how the labyrinth ventilation system works W hen James Staniland read about the use of an earth labyrinth at the University of Warwicks Digital Laboratory, in the April 2012 edition of CIBSE Journal (bit.ly/CJApr12lab), he recognised the potential of the system to pre-cool large quantities of outside air without the need for mechanical cooling. Eight years on, the practice of which he is a partner, Brinson Staniland Partnership (BSP), is using an earth labyrinth-type natural ventilation solution to help maintain comfort conditions in the Great Hall, at Kent College, Canterbury. The Great Hall has been designed by architect HMY, working with BSP, to provide the college with a professional-quality performance space for musical and theatrical performances, and a facility for college assemblies. The 11m-high hall can accommodate up to 600 people seated in the stalls and first-floor circle. The two big driving factors that make this assembly space conducive to natural ventilation with labyrinth cooling are its considerable height and the high internal heat gains from the audience and from stage lighting and dimmer racks, which totals about 63.5kW, says Staniland. Externally, the Great Halls brick walls and pitched, grey, standingseam roof give it an understated appearance. Its a theme that continues inside, with a relatively robust but aesthetic look derived from the exposed brick and timber finishes of the performance space. The hall is oriented on a north-south axis, with the stage to the south. Because it is a multi-purpose space, the envelope incorporates a significant glazed area, although the fenestration is concentrated mostly on the north and east elevations, where solar heat gains are less of an issue. Earth ducts The earth ducts are fundamental to the performance of the natural ventilation system to keep the hall comfortable in summer. Outside air enters the building from the south, through five giant, subterranean concrete chambers, each measuring up to 3.5m wide and 2m deep. The ducts cross-sectional area has been designed large enough to allow the air to pass practically unimpeded. With a natural ventilation system, you generally only have a maximum pressure of about 0.5Pa to play with, Staniland says. In summer, the relatively constant temperature of the ground, at about 12C, will ensure the chambers walls are maintained at a temperature close to that of the ground, to help cool the outdoor air entering the building. Dividing the intake into five separate ducts helps increase the area of duct in contact with the air, to maximise heat transfer, and helps with zoning the supply air. Each duct also incorporates a modulating 24 July 2020 www.cibsejournal.com CIBSE July 2020 p24-27 Kent college.indd 24 19/06/2020 15:53