Building Bulletin (BB) 101 - Ventilation for school buildings

BB101 explained

Initially released in 2006, Building Bulletin (BB) 101 (BB101) sets out relevant regulations, standards and provides guidance on ventilation, thermal comfort and indoor air quality in school buildings. BB101 includes the following topics:

BB101 is the main reference document when it comes to ventilation in schools, it is referred to within Building Regulations parts F and L.

BB101 includes the following topics

  • An introduction and description of what to consider when designing the indoor environment of schools.
  • Talks about the regulatory framework for schools and the recommended performance standards from the Department of Education (DfE) for compliance with UK regulations.
  • Goes into further detail on how to design schools in a wat that achieves the required ventilation, indoor air quality and thermal comfort levels.

It has been over 12 years since BB101 was initially released, during which time ventilation technology has advanced; insulation in schools have improved and new insights into ventilation strategies have been developed.

Drawing from this experience, the Education and Skills Funding Agency has published a revised edition of BB101 at the end of 2018.

The Priority Schools Building Programme (PSBP) has piloted the new guidelines, set out in the revised BB101 (2018) and shows direct benefits to schools in lowering capital costs, improved comfort conditions and reduced energy costs.

Better design standards for school ventilation
School ventilation standards

BB101 changes

Building from experience gained over the past few years, there are two key areas where BB101 will change:

  • Indoor Air Quality (IAQ): carbon dioxide CO2 levels
  • Thermal Comfort

BB101 (2006) previously recommended the use of a natural ventilation strategy within classrooms (e.g. openable windows as the sole source of ventilation). However, this setup has been shown to result in higher energy usages than expected and less resilience to varying external conditions.

BB101 (2018) has now placed tougher demands on ventilation strategies. Greater focus during the initial design of the school, ensures that any teaching spaces will be more comfortable for learners and more robust against possible future temperature increases due to climate change.

This has led the document to introduce a new category for ventilation: Hybrid Ventilation – systems which combine aspects of both natural ventilation and mechanical ventilation.

Hybrid Ventilation is now the suggested method to meet BB101’s (2018) more stringent temperature and carbon (CO2) requirements.

BB101 changes at a glance

  • Mechanical systems – which use a fan to drive in airflow – must adhere to a daily average of 1,000ppm CO2. Natural ventilation systems cannot exceed a daily average of 1,500ppm CO2.
  • The degree of excursions has been restricted, too. CO2 levels can reach 2,000ppm for no more than 20 consecutive minutes in a given day.
  • The guide has also introduced the concept of adaptive thermal comfort, in line with CIBSE TM52 The Limits of Thermal Comfort: Avoiding Overheating in European Buildings – so the temperature threshold can change daily, depending on external conditions.
  • Criterion one, which must be met, BB101 states that the number of hours the predicted operative temperature exceeds the maximum acceptable operative temperature by 1K or more, must not exceed 40 occupied hours during the period 1st May to 30th September.
Different methods of ventilation
Simulate indoor airflow
Thermal models for hybrid ventilation systems in buildings
CO2 level BB101 limits for a naturally ventilated system

To get a better and more detailed understanding of what is changing in BB101, please see our BB101 technical guide on the subject.

Consulting on better ways to gain indoor air in schools
BB101 technical guide