The Government recently announced updated guidelines (Building Bulletin 101) for improving indoor air quality, thermal comfort and ventilation in education settings. Laura Mansel-Thomas, Partner at property and construction consultancy Ingleton Wood, who was part of the advisory board, looks at some of the challenges faced by schools and colleges in order to meet the new recommended performance levels:
The new guidelines mean that designers working for Principals, College estates and facilities managers will now have to look much more closely at the ventilation strategies for new buildings and refurbishment projects. The document presents a number of new recommendations and requirements to improve air quality and reduce levels of CO2.
What are the changes?
The key differences between BB101 2006 and BB101 2018 include a requirement that the average fresh air rate must be at least 5 litres per second per person.
The purge fresh air rate also needs to be 8 litres per second per person for all new build teaching spaces. For natural ventilation systems, CO2 levels should average below 1,500 parts per million (ppm) and for mechanical ventilation systems, CO2 levels should average below 1,000ppm. The guidelines state that for either system, CO2 levels cannot exceed 1,500ppm for greater than 20 minutes.
The guidelines also set out a major change for refurbished teaching spaces, which now have to achieve an average CO2 level of below 1,750ppm.
Any future classroom refurbishment will therefore now have to include a review of the existing ventilation system to ensure maximum CO2 levels are not exceeded.
Naturally ventilated classrooms
It will be much more difficult – but not impossible – for naturally ventilated classrooms to comply with BB101.
Colleges will need to assess the cold draught implications of their solution as well as the summer and winter thermal comfort and CO2 levels.
A ‘push button’ mechanical solution is the easy way to prove compliance.
However, the new guidelines advise that where mechanical ventilation is used, it should not be the sole means of summertime ventilation in occupied spaces. Windows or vents should be provided to ensure an ‘effective opening area’ equivalent to approximately 3-5% of the floor space.
The real solutions will be site – and even room – specific, as has always been the case. Increasing worries about air quality will mean that mechanical ventilation – with high levels of filtration to remove pollutants – will continue to be the best solution for urban properties close to busy roads.
However, rural locations, with high air quality and fewer external noise issues, should continue with a ‘natural ventilation first’ approach.
Eliminating cold draughts
The need to eliminate cold draughts has also been introduced. These may appear to be of minor importance, but it has been a major problem, particularly in naturally ventilated rooms with teachers closing windows to reduce draughts. This results in much higher CO2 levels which are known to cause drowsiness and lack of attention in students.
There is now a new focus to minimise cold draughts in teaching spaces which will likely mean that low level openings as the main method of ventilation will no longer be appropriate without using additional heating.
Natural ventilation could be achieved provided that the building’s design allows for the incoming air to enter at a suitable height to allow the air to mix adequately before reaching the occupants.
BB101 also introduces hybrid systems and it could well be that some form of natural/mechanical hybrid will be the solution for most buildings.
Hybrid refers to systems that are generally passive, driven only by air pressure, wind or temperature difference. Fans are only used where external environmental conditions mean temperature or CO2 cannot be adequately controlled via natural means.
The average cost of adoption of hybrid ventilation systems within new builds is approximately £4,000 per classroom, with an estimated annual increase in maintenance of around £200, which may vary based on the complexity and type of solution used.
Dedicated plant rooms
Additional consideration should also be given to the siting of the central mechanical ventilation equipment. Where a piece of apparatus on a classroom roof was once adequate, colleges may now need to allow for a proper plant room, which will need to be addressed early on within any project design.
Understand your choices
The new guidelines – which also require window openings to be provided as supplementary purge ventilation – will likely mean increased costs as colleges take the necessary measures to become compliant.
This is particularly true for those that have traditionally been naturally ventilated through the use of openable windows.
The key is to ensure, as with any building, that you understand the choices you are making and the implications for running costs and maintenance in the years to come.
Laura Mansel-Thomas, Partner, Ingleton Wood
About Ingleton Wood: Property and construction consultancy Ingleton Wood specialises in projects for the education sector. Laura Mansel-Thomas, was part of the advisory board for BB101 2018, which replace those of 2006.