Chris Croly – Building Services Engineering Director – BDP
The new Student Centre for University College London offers an interesting example of a next generation low energy building, particularly due to the inclusion of a hybrid ventilation scheme combined with open loop ground water cooling within a city environment.
London has a warmer climate than that found in Irish cities and the use of hybrid ventilation in London shows the solution has significant potential for Irish buildings.
The climate in Ireland is ideal for the application of hybrid cooling as the external air is almost always at a lower temperature than that required inside our buildings. A fully sealed, air conditioned building denies one of the most natural forms of renewable energy available in Ireland – free cooling.
Hybrid ventilation combines the best of natural ventilation (User control, enhanced air quality, energy free cooling) with the best of active ventilation (heat recovery, draught free ventilation, filtration, humidity control and guaranteed cooling in warmer weather).
This 6,000m2 flexible learning space which is similar to modern office accommodation, can run in natural or mechanical mode or a combination of both and automatically adjusts its mode to respond to the conditions.
The mechanical ventilation is provided through displacement ventilation which minimises the volumes required for air quality control and maximises the cooling potential of the air during warmer weather. (Although it does limit free cooling potential in cooler weather).
The thermal mass of the soffit is exposed and its cooling potential is increased by pipes embedded in the slab that are fed from an open loop bore hole which provides close to zero carbon cooling.
The bore hole draws water from an aquifer that is 120m below the site and the water is then re-injected into a second borehole located some distance from the extract well. Open loop bore holes provide significantly higher rates of cooling (and heating) than closed loops at significantly lower costs but are often avoided due to perceived risks. The potential risks include consistency of water flow, short circuiting of water below ground and difficulties with re-injection of water where an aquifer may be under pressure. Councils who are unfamiliar with the system can also object to the re-injection of water in some cases. Hopefully the successful demonstration in this case will inspire further confidence in this form of free cooling.
The building is also provided with building integrated PV to provide on-site renewable energy.
A BREEAM score of Outstanding was achieved for the building and a formal soft landings approach was implemented.
Architects Nicholas Hare Architects
For further information on the buildings architecture visit: http://www.architecturetoday.co.uk/stepping-up-3/