BUILDING PERFORMANCE 1 UNIVERSITY CASE STUDY
Gradual changes were made to Elizabeth Fry over a 15-year period, resulting in increasing occupancy levels and a proliferation of computer equipment. This is north façade of the building, facing on to Chancellor’s Drive, a bus route
The new control strategy was simple:
during occupancy hours, the AHUs endeavoured to maintain a supply air temperature of approx 21C by varying the amount of heat recovery. If slab temperatures in locations towards the room ceiling outlets fell below 20C, the heating was boosted to maximum, with recirculation at night. If the slab temperatures rose above 22C, the heat exchangers were bypassed and outside air cooling was extended overnight. Monitoring showed that the thermal inertia of the hollow core slabs made finer
control unnecessary: it simply increased energy use. The lecture room systems also included air quality control to boost air volumes for short periods if needed, bypassing the Termodeck.
Building features Elizabeth Fry in the 1990s It was the second building
Elizabeth Fry is a four- storey rectangular building with a gross internal area of 3,250 sq m and treated floor area (TFA) 3,130 sq m. Its principal elevations face almost north, on to the main distributor road, Chancellor’s Drive; and south, on to a courtyard. In the 1990s it had lecture
rooms on the lower ground floor, and seminar rooms and offices on the upper ground floor. On the first and second
floors were one-, two- and four-person teaching and administrative offices at the west end, seminar rooms and common rooms at the east end, and a catering kitchen.
32 CIBSE Journal March 2012
in the UK to use the Swedish Termodeck system of mechanically ventilated hollow core concrete floor and roof slabs with exposed soffits. It was very well insulated:
block walls with 200 mm mineral fibre cavity fill; triple- glazed (2+1) aluminium-clad timber windows with blinds between the inner and outer panes; a roof with 300 mm of insulation and a profiled metal sheet covering; and an insulated floor. The U-values of all these elements remain better than the limiting requirements in the 2010 edition of Approved Document L2A. Thermal inertia was further enhanced by blockwork internal
and external walls and good airtightness. With a design heat loss of only 15 W/sq m, two 24 kW domestic wall-hung condensing boilers could provide all the heat required, with a third in reserve. Heating and cooling is
entirely through the air. The four air-handling units incorporate heat recovery: the two AHUs serving the lecture rooms having conventional cross-flow systems; and the offices and seminar rooms the more efficient (nominally 85%) flow-reversing regenerators. Following initial monitoring,
six small (200W) electric heaters were added in six rooms to counter additional heat loss through overhangs and exposed corners.
1995 to 2011 During this 15-year period, changes to the building were gradual. PCs inevitably appeared on everyone’s desk, with computer projectors and audio-visual systems in the lecture rooms and some seminar rooms. Room occupancy increased generally, while staff and student common rooms on the first and second floors were converted into offices and meeting rooms. In 1997 the building contained 70 office workstations. In 2010 there were 120. Changes in operation of the catering
kitchen on the top floor significantly affected overall energy use. In the 1990s the kitchen was used for special events, typically one a week; and usually just for serving, not cooking. During 2004-06 the kitchen was in
regular daily use while the Sainsbury Centre was being refurbished. In 2008 the kitchen and dining area were converted into a densely-occupied, open-plan postgraduate administrative office with 25 workstations: a purpose to which it is not very well suited, because the kitchen only had three small windows and no views. Bigger changes happened in summer
2011. However, these alterations are too new to be evaluated reliably for energy use and occupant satisfaction, so this
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Roderic Bunn
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