Holy Trinity Primary School

Shortlisted for the Constructing Excellence Project of the Year Award for London & the South East, 2011

The Holy Trinity School was awarded BREEM Excellent rating.

The new buildings are designed using the principles of Passivhaus design; the buildings are externally insulated, adopt a lightweight cross-laminated timber construction with low embodied carbon; achieve an excellent air tightness, and adopt a full Mechanical Ventilation Heat Recovery (MVHR) system.

The form and orientation of the new buildings was carefully modelled and analysed to maximise daylight and thermal gains during the winter months while avoiding overheating during the summer.

The school is located under the Heathrow flight path and so acoustics were of utmost importance – our air tight, triple glazed solution with MVHR avoids reliance on opening windows for summer cooling.

Open cell insulation combines with the mass of the green roofs to act as an acoustic absorber protecting against high levels of aircraft noise. An earth tube system provides pre-cooling of incoming air in summer and preheating in winter, and Ground Source Heat Pumps are installed.

Extensive green roofs increase biodiversity and reduce water run-off. Photovoltaic panels are installed on the school’s existing roof.

Our aim was to use and express a range of natural materials; reduce plastics and composites in construction; and incorporate as many pre-fabricated elements as possible, including surface mounted pin boards, and distinct furniture packages.

Low maintenance costs are achieved through the wide use of robust, ‘self finished’ materials including the CLT.
Deep overhangs around the building ensure that walls and the expressive timber soffits are protected – this also has a big impact on maintenance costs. In circulation areas, paints are chosen for their high durability specification. Our design integrates a series of super eco cross-laminated timber wings with green roofs that connect lightly to the existing structure to maximize future flexibility, and create a signature visual form for the new school.

These ‘green wings’ enhance the free flowing character of the school, providing direct connections to the outside, and a series of delightful courtyard spaces run between. Our environmental ethos runs throughout, and natural, expressive materials are crucial to give the school a warm, rich, tactile environment, that feels natural to the touch and is a great backdrop to the children’s activities and artwork.

The construction system for the new buildings is a Cross Laminated Timber modular system, which was fabricated off-site and then transported to be rapidly built on-site onto foundation sub-structures.

The cross-laminated timber (CLT) has very low embodied carbon, and creates a lovely warm textured interior.
The new wings are airtight with high performance triple glazed windows and mechanical heat recovery.