The revised BB101 provides a valuable resource for architects with much needed clarity on how best to account for staff and student comfort when designing school buildings

BB101 provides a list of recommended operative temperatures for different spaces within a school during the heating season. Outside of this period, it uses an adaptive approach, changing the maximum indoor temperature from day to day based on external temperatures.


It is simpler and more cost effective to maintain internal temperatures if the build- ing is well insulated

Building Bulletin 101 (BB101) guidelines on ventilation, thermal comfort and indoor air quality in schools. The document offers a clear overview of the relevant regulations and standards for managing conditions within the classroom environment along with supplementary advice on best practice.

One of the most significant changes in the new version of BB101 is a more adaptive approach to how thermal comfort is measured and addressed.

Thermal comfort

In BS EN ISO 7730:2005 – Ergonomics of the thermal environment, thermal comfort is loosely defined as being a personal condition which “expresses satisfaction with the thermal environment.” Put more simply, it is the measure of whether a person feels neither too hot nor too cold. This can be affected by a wide range of personal and environmental factors, from our health and the types of clothes we wear, to our position in the room and the air temperature. Measures of thermal comfort attempt to consider all these factors and determine whether occupants are likely to feel too hot, too cold, or just right.

This definition is inherently problematic for architects, as the personal nature of many of the factors means that, within any given space, there can be a wide divergence in opinion on whether it is too hot or cold. To estimate the thermal comfort of all students and staff, BB101 uses a version of the adaptive thermal comfort standards within BS EN ISO 7730:2005, which has been specifically modified for school environments.

BB101 guidance

The modified standard within BB101 uses two indices to estimate thermal comfort: predicted mean vote (PMV) and percentage of people dissatisfied (PPD).

PMV considers a number of personal and environmental factors to generate a score on a seven-point comfort scale – from hot (+3) to cold (-3). The PPD is then calculated from this score with the percentage of people dissatisfied exponentially increasing, as PMV moves away from the central comfort scale score (neutral – 0).

A wide range of measures is available to control thermal comfort with the most suitable solution varying depending on the specifics of each project. One way to develop a solution is through dynamic thermal modelling where a 3D simulation model is created. Through this approach designers and engineers can: • predict internal comfort conditions • identify the likelihood of overheating during summer months • establish likely heating demands • maximise available natural light via daylight calculations. BB101 also suggests the use of night purge strategies, where air is introduced through windows and vents during the night, helping to efficiently cool the building.

Building insulation Whatever approach is taken, the building fabric will play an important role in allowing internal temperatures to be maintained at a constant level. With section 4.15 of BB101 highlighting the need to future-proof spaces, it makes sense to look beyond the standard U-value requirements outlined in the Approved Documents to the Building Regulations 2013 (in England), 2014 (in Wales), and Section 6 (Energy) 2015 of the Building Standards in Scotland. With a wide range of insulation options available, it’s important to carefully consider which solution is most suitable for any given project. The latest generation of phenolic insulation products have a thermal conductivity of just 0.018 W/m·K, the lowest of any commonly used insulation product. This can allow desired U-values to be met with slimmer floor, wall or pitched roof constructions. Vacuum insulation panels (VIPs) are also proving increasingly popular for refurbishment applications. The panels have an insulating performance up to five times better than commonly used insulation materials, making them ideally suited for applications where the construction depth must be kept to an absolute minimum – such as above an existing solid floor.

Quality focus

The revised BB101 provides a valuable resource for architects with much needed clarity on how best to account for staff and student comfort when designing school buildings. By applying its guidance, and making use of the latest insulation materials, designers can ensure schools achieve a high level of energy efficiency and thermal comfort.

Adrian Pargeter is head of technical and product development at Kingspan Insulation


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