Forthcoming Technical Guide: CIBSE TM57 Integrated School Design

Keywords: schools, design, TM57, technical guide, CIBSE

A team of around 30-40 academics, policy makers and industry experts have recently come together to significantly update CIBSE’s Technical Memorandum (TM) on school building design, known in shorthand as TM57. Since this document was first published in 2015, there have been significant terminological, technological and regulatory changes in the sector. Hence updates to chapters were deemed necessary to existing chapters such as heating, energy, control systems and overheating, as well as entirely new sections including indoor air quality, low carbon case study, inclusive and biophilic design.

The document begins with describing the overarching design process, illustrated in Figure 1. This provides the design team with a framework to integrate interlocking and often contradictory briefs on educational outcomes, technical and operational requirements and cost, with RIBA’s Plan of Work as a spine (RIBA, 2021). Fostering and empowering an “informed client” to act as a bridge between future educational/operational needs and the current design is also critical to this process. Performance-in-use metrics are summarised in this chapter to give professionals a means of optimising performance across a range of factors. Inclusive design is also highlighted as a requirement to make the reasonable adjustments for disabled students, guaranteed through the Equality Act (2010), and a list of standards are provided to ensure compatibility.

Figure 1. The impact of design solutions on teaching and learning in schools.

Individual aspects of Indoor Environment

Following a section demonstrating early engineering considerations to overcome interrelated conflicts, the rest of the document summarises the different requirements for various individual aspects of school buildings beginning with Indoor Environmental Quality aspects of acoustic, lighting, indoor air quality and thermal comfort.

Figure 2. Summary of factors influencing acoustic performance.

Critical factors relating to acoustic performance, as shown in Figure 2, are often considered too late in the design process to influence architectural layout and material selection, requiring remedial work. Hence the acoustic chapter in TM57 describes possible solutions to a number of design and operational requirements which can conflict with the provision of acoustic performance. These include heat pumps, which although necessary for planning of BREEAM credits, even when located outdoors can prevent effective use of ventilation or even indoor teaching spaces themselves. Similarly, with daylighting, methods to keep heat out of classrooms may unintentionally prevent the ingress of natural light; TM57 describes a number of daylight distribution systems, such as light wells and clerestory windows which maximise ingress while minimising glare.

Successful school ventilation strategies balance a complex set of interacting factors, including maintaining safety and security while minimising noise ingress. Thermal comfort, indoor air quality (IAQ) and heat loss are the most significant factors to be balanced with ventilation so the middle sections of TM57 considers these factors in consecutive chapters. Following the post-Covid mass installation of carbon dioxide (CO₂) sensors, the ventilation chapter describes advantages and disadvantages of the use of carbon dioxide as a popular proxy for ventilation quality. Differences are identified in how mechanical, natural and mixed mode ventilation systems can be used appropriately to ensure compliance with ventilation and heating guidelines such as Building Bulletin 101 (DfES, 2018). Although a comprehensive list of natural ventilation strategies are retained from 2015, a new section for 2025 covers corresponding mechanical ventilation strategies such as centralised vs localised systems and use of peak lop cooling using heat pumps.

Although overheating is the first of three ventilation-related impacts to be addressed, methods to manage overheating risks themselves should be implemented in the correct order, hence a cooling hierarchy has been described (see Figure 3), showing the correct order to enact various passive and reactive responses. Resilience of UK school buildings, as insulation and air tightness are increased to address climate change, as well as for future climate scenarios, is a key recent addition to overheating assessment. As well as a description on the practical operation of, and performance evaluation of ceiling fans, recent work on effectiveness of other passive methods such as nighttime ventilation and shading is presented. A brand new IAQ chapter summarises source, design, urban and meteorological factors which can exacerbate ingress or generation of pollutants indoors before providing a hierarchy of mitigation methods. Most relevant developments here include a comprehensive description of indoor sources from World Health Organisation reports (WHO, 2022), moisture control tools to prevent mould and case studies on how to ventilate airtight near zero carbon schools.

Figure 3. The cooling hierarchy.

Design, control and monitoring of heating and other building services.

The heating, cooling and hot water section provides a bridge from ventilation into controls, environmental and energy sections. Recent concepts which are introduced here include the more stringent Building Regulations Part L concerning construction while minimising energy and carbon consumption, as well as solutions such as thermal storage and Thermally Activated Building Structures (TABS). Heat scavenging is of articular relevance in 2020s schools, due to the increasing prevalence of server rooms and a case study of a Net Zero Carbon in Operation (NZCiO) school is provided to show how thermal performance has been improved in practice.

The controls section outlines best practice for service controls incorporating heating, ventilation, environmental and lighting systems, as well as what is required in building regulations. However much of the focus lies on key considerations of building users with different capabilities and considerations, from facilities managers to pupils themselves. As well as describing different modes for heating, lighting and ventilation control systems to address these differences, implications for documentation, complexity of controls and graphical user interfaces (including alarms) have also been considered. As with the design considerations above, references are made to the different stages within the RIBA Plan of Work, focussing on the handover in Stages 3 and 4.

A new chapter on Biophilic design describes the rationale as well as examples of key features such as green walls, green roofs and rain gardens which can be incorporated into school building design to provide connection between building user and the natural environment. The concept of the Flourish Model (Clements-Croome, 2021) is introduced which has been associated with stimulation of relaxation alpha brain waves and lowering of stress beta waves (Figure 4).

Figure 4. The Flourish Wheel. (Clements-Croome 2021)

As well as updating metrics for Energy Use from the 2015 version based on technological and operational changes, the Energy chapter describes how to include ‘Zero’ Carbon into operational design, based on repurposing the existing estate. A major conflict here is that often condition and improved energy performance funding are available separately, however a dual approach to improve both simultaneously should be sought. A five-step carbon hierarchy, involving engagement with building users, reduction in demand and wastage and decarbonising and neutralising supply, is provided to ensure all issues relating to energy efficiency are dealt with first before tackling carbon emissions. A description of Post Occupancy Evaluation (POE), as a means of systematically investigating a school’s operation before making performance improvements is therefore a logical follow-on from energy. This chapter encourages designers to go beyond what is specified in the DfE’s Output Specifications Technical Annex 2K (DfE, 2021).

The best-practice part of the document concludes with the facilities management chapter, relating to the documentation and training required to effectively handover the building to a site manager for the operations phase. The major challenges of this phase are that there is no one-size-fits-all definition of the site manager role, and quite often there is no single person responsible for delivering the teaching environment, with teachers and even students also involved in learning environment control. Zoning, extended occupancy outside of school hours, and use of monitoring equipment are also covered in some detail.

Use of case studies in TM57

TM57 utilises case studies in three main ways:

1.    Examples of best practice specific to a certain aspect of school building design (e.g. acoustic performance) presented within a specific chapter

2.    Two integrated case studies, presented in standalone chapters representing a Modern school (retained from 2015) and a newly added Passivhaus school, showing how design can incorporate the range of aspects presented in each chapter.

3.    An addendum of case studies bridging both individual aspects and integrated design and not limited to best practice will be provided separately to the main document, which will be updated and added to as time goes on. These are best categorised as lessons learned examples.

It is hoped the mixture of best practice, integration of a number of aspects and lessons learned provide a realistic view of school design in practice which complements the main document and can be updated more frequently so that readers are not left waiting for another decade to understand the most up to date design specifications.

References

[1]     RIBA (2021). Plan for Use Guide. (available at: www.architecture.com/-/media/GatherContent/Plan-for-Use-guide/Additional-documents/Plan-for-Use-Guide-2021.pdf)(accessed 8 April 2025).

[2]     DfES (2018) Building Bulletin 101: Ventilation of school buildings (London: The Stationary Office) (available at https://www.gov.uk/government/publications/building-bulletin-101-ventilation-for-school-buildings) (accessed 8 April 2025).

[3]     WHO (2022)‎. Measures to reduce risks for children’s health from combined exposure to multiple chemicals in indoor air in public settings for children with a focus on schools, kindergartens and day-care centres: supplementary publication to the screening tool for assessment of health risks from combined exposure to multiple chemicals in indoor air in public settings for children. World Health Organization. Regional Office for Europe. (available at: https://apps.who.int/iris/handle/10665/354225) (accessed 8 April 2025).

[4]     Clements-Croome, D. and Al-Dmour, Y. (2021). Using the Flourish Model for Environmental Design.

[5]     DfE (2021) School Output Specification - Technical Annex 2K: Building Performance Evaluation Methodology. (available at: https://www.gov.uk/government/publications/employers-requirements-part-a-general-conditions) (accessed 8 April 2025).