Building Bulletin 101 (2016): Everything you need to Know

Building Bulletin 101 - 2016 - Guidelines on Ventilation, Thermal Comfort and Indoor Air Quality in SchoolsBuilding Bulletin 101 (BB 101) has been a staple guide in the design of school buildings for the last ten years. The original guide released in July 2006 titled ‘Ventilation of School Buildings’ set the ventilation standards that schools needed to meet and offered useful guidance on implementing various natural ventilation techniques.

As well as natural ventilation regulations the BB 101 guide also set the standards for the avoidance of overheating. You can find out more about the original BB 101 guide here, but for now let’s talk about the recent 2016 update.

Although it is still going through its final consultation period until the 25th August, the 2016 update to BB 101 will be called ‘Guidelines on Ventilation, Thermal Comfort and Indoor Air Quality in Schools’.

The new guide will draw inspiration from the last 10 years of school design as well as other regulatory guides such as the Priority for Schools Building Programme, CIBSE TM 52 and Part L of the Building Regulations to deliver a greater emphasis on energy efficiency and indoor comfort.

Natural Ventilation

Natural Ventilation within schools can be somewhat of a double-edged sword. On the one hand you should be able to effectively ventilate a school without the use of energy, however on the other you are at the mercy of the stack effect or wind speed to deliver sufficient air, there is also the problem of draughts that need to be accounted for.

Under the old BB 101 regulations a maximum litres per second per person of fresh air that needed to be supplied to a teaching space at any occupied time was 8 l/s/p, a daily average of 5 l/s/p and at no time could the ventilation rate drop below 3 l/s/p.

The same rates applied if mechanical ventilation was to be used. This was to ensure that carbon dioxide within the teaching space does not exceed 1500 ppm.

The new 2016 BB 101 guide has a similar standard to the old one, also asking for a naturally ventilated teaching space to receive an average daily ventilation rate of 5 l/s/p in order to achieve a concentration of carbon dioxide of less than 1500 ppm.

A mechanically ventilated teaching space will now need to achieve a daily average carbon dioxide concentration of less than 1000 ppm. This is typically achieved by supplying around 8 – 9 l/s/p of fresh air.

Although a school will either be primarily naturally or mechanically ventilated there are a wide variety of hybrid systems in between that may prove to be a more effective way of ventilating a classroom and meeting the regulations.

BB 101 2016 Hybrid Ventilation Systems

Avoidance of Overheating

It is no secret within the industry that the old version of BB 101 had a relatively easy to pass set of criteria in order to demonstrate that a classroom would not suffer from overheating. The three criteria can be found below, as well as this the CIBSE TRY (Test Reference Year) weather data instead of the much hotter DSY (Design Summer Year) weather data could be used for the simulation.

a) There should be no more than 120 hours when the air temperature in the classroom rises above 28°C

b) The average internal to external temperature difference should not exceed 5°C (i.e. the internal air temperature should be no more than 5°C above the external air temperature on average)

c) The internal air temperature when the space is occupied should not exceed 32°C.

In order to show that the proposed school would not suffer from overheating two of these three criteria needed to be met.

Under the 2016 version of BB 101 in order to demonstrate that teaching and learning spaces will not suffer from overheating, they should comply with the recommendations of CIBSE TM 52. The three criteria of CIBSE TM 52 are:

Criterion 1 – Hours of Exceedance (He):

For schools, the number of hours (He) that DT is greater than or equal to one degree (K) during the period 1st May to 30th September for the defined hours shall not be more than 40 hours.

Criterion 2 – Daily Weighted Exceedance (We):

To allow for the severity of overheating the weighted exceedance (We) shall be less than or equal to 6 in any one day.

Criterion 3 – Upper Limit Temperature (Tupp):

To set an absolute maximum value for the indoor operative temperature the value of DT shall not exceed 4K.

Two of the three criteria must be met in order for a teaching space to satisfy the regulations.

As well as the more stringent overheating criteria set by CIBSE TM 52 the fact that the DSY weather data also needs to be used makes the new overheating regulations in BB 101 2016 much more difficult to pass than the old BB 101. This however is a good thing, as it calls for greater care to be taken in the initial design of the school and ensures that any teaching spaces will be future proofed against climate change induced temperature increases.

How we can Help

Does your new school design need to show compliance with the new BB 101 2016 regulations in order to meet its planning conditions. Email us today at to find out how our dynamic simulation modelling services can help.

If you have any questions regarding the new BB 101 regulations or would just like to discuss it please leave a comment below.

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