The Centre for Medicine at University of Leicester is an impressive building that brings together the department for Medical Education, Health Sciences and Psychology along with a mixture of lecture rooms, social spaces, offices and lab facilities. The realization of this building, with a gross internal floor area of approximately 13,000 m2, has been motivated by a huge demand for new doctors as well as demand for research in the field.
One of the most urgent request of the University of Leicester was the reduction by 80% of the annual energy bills, which for building of this size represented a pretty big sum. The decision to go for the demanding Passivhaus standard was then very logical, although it posed a number of challenges due to the scope and size of the development.
First considerations were made in regards to the building envelope which needed to be of high thermal performance in order to compensate for exposed surface and complex design. The building shape is, in fact, relatively far from the very compact form suggested by the Passivhaus principles. This was due to the project brief of having 3 departments with equality of office accommodation, resulting in 3 towers blocks connected by the ground floor spaces.
The curtain walling was chosen as external wall solution for its light weight and speed in building it up as it is a quite well known construction approach. However, it turned to be challenging to build up as additional insulation ( 250 mm rock wool insulation plus 2 layers of plasterboard) was required and it needed to be well airtight to meet the airtightness standard.
Also the glazing type and orientation cannot be considered a common practice solution for Passivhaus buildings, since floor-to-ceiling windows were chosen and oriented equally onto the 4 facades, despite of the Passivhaus ‘rule’ of South exposed glazing for enhanced heat gains. The UK based architectural practice Associated Architects, who carried out the design of this Centre for Medicine, suggested that the windows solution was totally necessary and ‘it was adding something to the character of the exterior and to the feeling of a room’. The facade is actually a very interesting result and something never seen in a commercial Passivhaus building of this size.
Additionally, a smart shading system was implemented to protect the rooms from excessive solar gain ‘the blinds are controlled through an astronomical time clock to track solar path and linked to internal temperature monitoring’ says Lee Davis of the M&E consultancy Couch Perry Wikes. Even though it is an automatic system, it can be overridden by users when they feel that the internal conditions are not optimal, so there is still control on what has been designed.
In terms of heating system the campus is connected to the city district heating system featuring a CHP plant for electricity and space heating. An underfloor system and radiators are provided throught the building with individual controls for the latter ones. Whereas for hot water provision, since the demand is low in the centre, electric point of use heaters are installed, which reduce the length of pipes int he building bringing down heat losses and at the same time minimising the risk of overheating.
The Cooling strategy is applied via circulation of chilled water through the concrete frame along with the use of a ground-to-air heat exchange system. The latter system involves a labyrinth of underground pipes buried down to 6 meters in the soil, that allows to pre-warm incoming air in the winter and pre-cool air in the summer maximising the efficiency of the system.
Another challenge was posed by the Mechanical ventilation system, which according to the Passivhaus standards should be a certified component in order to guarantee quality and efficiency. However, there was no available component to fit the size and performance required, therefore air handling units (AHUs) were suggested as an alternative solution for the provision of fresh air. In this way a penalty was applied by the PHHP software which again needed to be compensated by an improvement in the fabric efficiency.
Ultimately, an extensive and rich green wall has been designed with more than 18 indigenous species providing a cooling solution for the warmest months of the year along with a interesting exterior facade which gives character to the Centre for Medicine.
This project, now the current largest single building to achieve the Passivhaus standard in the UK, is a milestone in the Passivhaus approach for the design and implementation of sustainable strategies. The process of realization of this cutting-edge development has proved that, despite the Passivhaus standard is demanding and challenging to achieve, particularly when going outside the comfort zone of ‘the compact shape’, there are not limitations to possible interesting architectural design. Moreover, well engaged and ‘educated’ to the Passivhaus standard contractors and sub contractors are determinant in meeting the target and making sure the build up is carefully followed throughout the process.