Project Overview 

KJ Tait were appointed to provide MEPH and sustainability design services to enable The Cawthorn Building at Tonbridge School, Kent to be converted into Staff Facilities to support 100 members of staff. 

Tonbridge School is a public boarding and day school founded in 1553 by Sir Andrew Judde. It is a member of the Eton Group and has close links with the Worshipful Company of Skinners, one of the oldest London livery companies. 

The Cawthorn Building has previously been a chapel, museum and most recently a teaching and lecture theatre. The building is Grade II listed as the “School Museum (The Old Chapel)”.  

Challenge 

The challenge on this project was to balance the desire for a robust modern energy efficient building whilst maintaining the character and helping to enhance the original features. 

The progressed architectural solution called for a single large double height space with a small Mezzanine below which sit low height support spaces for WCs, plant and storage. Finding an appropriate and sympathetic solution for both these space types was key. 

Our Solution 

Displacement ventilation is provided in the main space via floor grilles (low level wall grilles on Mezzanine level) and the air is tempered to provide background heating and cooling via an AHU air source heat pump. This approach offers the following benefits: 

• Ventilation is provided at occupant level improving indoor air quality 

• Low velocity/noise distribution (associated reduction in energy use) 

• Better balanced thermal comfort 

• Ductwork was minimised and, where required, mostly hidden in existing building fabric (floor void). 

Radiators are provided for boost heating in cooler months and also future proofed for site wide, low carbon heating solutions. 

Slender halo lights were suspended from the vaulted ceiling to both provide task lighting at floor level and up light to enhance the original ceiling features. The fittings both allow the User to “look through them” ensuring the features are not obscured and help set a notional plan to reduce the scale of the space. 

The School has aspirations for the School Campus to be Net Zero but this is to be tackled on a site wide basis rather than building by building.  New and refurbished buildings should be low energy and heat pump ready. 

To ‘best ready’ The Cawthorn building for future carbon reduction schemes the following were included: 

• Improved fabric efficiency 

• Secondary glazing 

• Background heating and cooling via air handling unit heat pump 

• Heat pump ready radiators 

• Use of electric heaters for hot water provision 

• Entrance lobbies on main pedestrian doors 

• Low energy LED lighting 

• CO2 demand controlled ventilation to suit fluctuating occupancy.