When it comes to ensuring proper ventilation, thermal comfort, and indoor air quality in school buildings, the UK government has established Building Bulletin (BB) 101 as the primary reference document. Initially released in 2006, BB101 provides regulations, standards, and guidance for designing the indoor environment of schools. This blog post will delve into the critical aspects of BB101 and explore the recent changes introduced in the revised edition of 2018.

What is BB101 and its Importance?

BB101 serves as a comprehensive guide for ventilation in schools, with references within Building Regulations parts F and L. Its primary objectives include:

  • Describing the considerations for designing the indoor environment of schools.
  • Establishing the regulatory framework for schools and recommended performance standards by the Department of Education (DfE).
  • Providing detailed guidance on achieving the required levels of ventilation, indoor air quality, and thermal comfort
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The Evolution of BB101: Over 12 years since its initial release, BB101 has evolved to keep up with advancements in ventilation technology, improvements in school insulation, and new insights into effective ventilation strategies. In 2018, the Education and Skills Funding Agency published a revised edition of BB101, incorporating valuable experience gained during this period.

1.0 Better Design Standards for School Ventilation: One of the notable changes in BB101 (2018) revolves around two key areas: Indoor Air Quality (IAQ) and Thermal Comfort.

3.1 Indoor Air Quality (IAQ): The previous edition of BB101 recommended using natural ventilation, primarily relying on openable windows for air exchange. However, this approach exhibited higher energy usage and limited resilience to external conditions. Consequently, BB101 (2018) now emphasises the need for more effective ventilation strategies during the initial design phase. To meet the revised standards, a new category called Hybrid Ventilation has been introduced, which combines aspects of both natural and mechanical ventilation systems.


To gain a better understanding of the updated standards in BB101 (2018), let’s highlight the fundamental changes:

4.1 Indoor Air Quality (IAQ):

  • Mechanical ventilation systems using fans must maintain a daily average of 1,000 ppm CO2.
  • Natural ventilation systems cannot exceed a daily average of 1,500 ppm CO2.
  • Excursions beyond the defined limits are limited to a maximum of 20 consecutive minutes per day, with CO2 levels not exceeding 2,000 ppm.

4.2 Thermal Comfort:

  • The concept of adaptive thermal comfort was introduced, allowing the temperature threshold to vary daily based on external conditions.
  • BB101 (2018) aligns with CIBSE TM52, which focuses on avoiding overheating in European buildings.
  • Criterion one requires that the predicted operative temperature should not exceed the maximum acceptable operative temperature by 1K or more for more than 40 occupied hours between 1st May and 30th September.


Understanding and complying with the UK government’s Building Bulletin 101 (BB101) is crucial when refurbishing ventilation systems in school buildings. The revised edition of BB101 (2018) introduces significant changes to improve indoor air quality, thermal comfort, and energy efficiency. By adopting hybrid ventilation strategies and adhering to the updated CO2 and temperature requirements, schools can provide a comfortable and healthy environment for their students. Stay informed, stay compliant, and ensure the well-being of future generations through effective ventilation refurbishment.