New CIBSE publication on Integrated School Design

CIBSE have recently published TM57 Integrated School Design. This document covers various design aspects for schools such as thermal comfort, acoustics, daylighting, air quality and ventilation.

It states:

“Teaching and learning spaces pose a great challenge to designers and engineers as the environmental needs are more complex than with most rooms. The challenge is not just to deal with high heat gains, due to operating at full or nearly full capacity most of the time with high internal heat gains from equipment, but also the intermittent occupancy as pupils move between spaces.”

We at Inkling have worked on many school designs and take a keen interest in new publications and guidance relevant to schools. TM57 provides useful guidance for all those involved in school design, including building users themselves. The document links to the relevant specific design guidance documents rather than covering any specific aspect in detail. The main frustration is that the revised BB101 is due out very soon and is expected to change the performance specification for schools in terms of ventilation and thermal comfort, and yet this document can now only refer to the existing, but soon to be superseded (2006) version.

Since we’ve read it, we thought we’d offer a ‘digested read’ picking out the aspects that seemed interesting to us:

At early design stages guidance is offered on site evaluation and layout including consideration of noise, pollution, microclimate, sunpath and access requirements. Guidance is offered on balancing the competing needs of daylight, ventilation and thermal comfort, and the necessary integrated design process needed to achieve this. It is emphasised that this is an iterative process rather than a linear one.

The emphasis is on holistic design, covering all aspects rather than considering any one aspect in isolation, so the see the following less as a list and more as a network of the interlocking considerations of school design:

Acoustics   A good acoustic environment is required for successful learning and this requirement needs to be considered early on in the project to avoid expensive remedial works. Pupils with special hearing requirements are particularly vulnerable, and are affected disproportionately by poor acoustics.

Lighting    Natural daylight is the best source of illumination, and there is evidence to suggest that it results in improved academic achievement, therefore it should be the principal source of illumination for all teaching spaces. However care must be taken to avoid glare and excessive solar heat gains by considering glazing extent and solar shading. Orientation is key here with south facing high altitude south sun angles being more easily shaded than lower altitude afternoon sun from the west. The two principle methods of establishing daylight performance are discussed, namely Daylight Factors (DF) and Climate Based Daylight Modelling (CBDM) and its metric Useful Daylight Index (UDI).

Ventilation   Poor indoor air quality affects the health and comfort of pupils, and prevents effective  learning. In winter ventilation must meet air quality requirements, while minimising ventilation heat loss, In the summer ventilation must reduce the risk of overheating. There is a strong overlap with acoustics issues when considering ventilation as windows have the potential to allow noise ingress into the classroom and mechanical ventilation has the potential to be a source of unacceptable noise if not suitably designed and sized.

Overheating   Simple passive measures are recommended to reduce overheating risk. Effective ventilation is key in order to remove heat from internal and solar gains from the classroom. Night cooling coupled with exposed thermal mass is recommended as an  effective way of reducing overheating risk. As schools built or refurbished today will be operated for many years in the future, it is recommended that designs are tested with UKCP09 future weather files to examine the risk of overheating in order to prevent cooling being required in the future as the climate warms.

Thermal Performance   Various issues affect the design of school heating systems therefore this needs to be considered alongside other aspects of the design. Classrooms are generally subject to high internal gains and rapid fluctuations in internal gains at the start and end of lessons. Ventilation for the high number of occupants must also be provided without uncomfortable draughts in winter and there may also be high thermal mass as a measure to reduce  summertime overheating.

Controls   The control of ventilation (including daytime ventilation and night-cooling), heating, lighting and solar shading needs to be considered. Controls need to be as simple as possible, well labelled, intuitive and take account of the different types of users.

There is a good summary of the document by Dejan Mumovic in the April 2015 CIBSE Journal.