Caterham School

When Caterham School in Surrey announced an extension to its facilities as part of the new Performing Arts Centre of Excellence (PACE) project, the concept of an experimental ‘Black Box’ Theatre formed the cornerstone of the proposal. 

The unusual theatre consists of a simple performance space – usually a large square room with black walls and a flat floor. It provides a modern and experimental performance area for the students as well as an additional rehearsal room.



The school expressed a need for comfort cooling especially given that at times numbers in the room could reach up to 120 people. However, the expansive space would also need to be efficiently heated in time of low occupancy such as during rehearsals or lessons.

The difficulty of designing a system which would not only deliver cooling on busy show nights, but also provide heating when necessary, was made even more problematic given the heat created and retained by the bright lights and heavy drapery in use. The requirement of the space also meant that when the theatre was in ‘black out’ mode, with the curtains and blinds down, the use of natural ventilation was heavily restricted.


To help combat the problem, building services and control specialists, Kestrel Mechanical, enlisted the help of ventilation specialists, Elta Fans Ltd. who suggested that ventilation could be supplied by allowing hot and cool air to mechanically flow into the building via an Air Design integral heat pump air handling unit (AHU), and a Komfovent Verso-RHP-20 was installed. This would help to deliver volume flow rates per person set out in Building Bulletin 101: ventilation for school buildings, while complying with CIBSE guidelines and exceeding the government’s revised heat exchange efficiencies through the use of an integral thermal wheel.

As a retrofit to an existing flat roof which already housed an old AHU, the installation had clear space limitations. The Verso’s integral compressors eliminated the need for external heat pumps, external fridge pipework and electrical supplies making it the ideal solution for the project. Guy Hammer, Senior Technical Specification Manager from Elta Fans worked closely with Kestrel to ensure the siting of the unit on the roof allowed the external and internal ducting to fit with the existing structure.

The time pressures of working at a busy school site also meant ease of installation was key. The unit came supplied with everything pre-wired, only requiring connection to the mains electrical supply in order to be ready for use.


Since the installation, the school has been enjoying the multiple benefits of the system which boasts an 81% efficient heat exchanger and heat pump, which runs at 60% efficiency.


Phil Radley, Mechanical Design and Build Project Engineer at Kestrel Mechanical Services Ltd commented, “By working closely with Guy we ensured the unit was handled correctly and the design criteria set out was achieved post construction so the school could achieve the best results both in terms of efficiency and payback period. One example of this is the ‘night time purge’ or ‘free cooling’ mode which benefits the school by helping to reduce and limit the need to run the unit in cooling mode, helping us to save energy.

“The unit has been well received from everyone involved, including my director. The full commissioning service was a real benefit to this project as limiting downtime was key and it was great to see Elta Fans getting involved onsite.”

Guy Hammer: “This project is an excellent example of how necessary and versatile good ventilation is. Schools often have issues with air flow and it is vital to ensure the correct airflow into a space in order for students to achieve optimum productivity.

“This project went very smoothly and we are delighted to have been involved. Following the success of this project we are looking forward to working with Kestrel Mechanicals in the future.”

The project was finished and commissioned in August 2016, with the film and theatre actor and director Simon Callow CBE officially opening the Performing Arts Caterham School’s new Centre for Performing Arts in October.