New air quality guidelines for schools mean that designers working for headteachers, school estates and facilities managers will have to look much more closely at ventilation strategies for new buildings and refurbishment projects, it has been warned.
The Government recently announced updated Building Bulletin 101 (BB101) recommendations which aim to improve indoor air quality, thermal comfort and ventilation in schools.
Laura Mansel-Thomas, Partner at property and construction consultancy Ingleton Wood, which specialises in projects for the education sector, was part of the advisory board consulted on the changes. She said that much closer attention will now have to be paid to ventilation strategies if schools are to meet recommended performance levels.
“The new guidelines will likely mean increased costs as schools take the necessary measures to become compliant. This will be particularly true for those schools that have traditionally been naturally ventilated through the use of openable windows.
“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 three to five per cent of the floor space.”
BB101 also introduces hybrid ventilation systems – driven only by air pressure, wind or temperature difference instead of fans.
Mansel-Thomas added: “This could well be an effective solution for most schools – but the average cost of adopting such a system is around £4,000 per classroom in new school buildings, along with an estimated increase of £200 a year on maintenance costs, although this will vary depending on the complexity and type of solution used.
“The key is to ensure, as with any building, that headteachers and facilities managers understand the choices they are making along with the implications for running costs and maintenance in the years to come.”
The guidelines also state that additional consideration should be given to the siting of central mechanical ventilation equipment. Where a piece of apparatus on a classroom roof was once adequate, schools may now need to allow for a proper plant room.
The elimination of cold draughts is also a major part of the new recommendations.
Chris Brown, Building Services Engineer at Ingleton Wood, who was also part of the advisory board, said: “Cold draughts can be seen as something of minor importance, but it has been a major problem, particularly in naturally ventilated schools 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.
“The new focus will likely mean that low level openings as the main method of ventilation will no longer be appropriate without using additional heating.”
BB101 2018 updates guidelines first published in 2006. The average fresh air rate within schools must now be at least five litres per second per person. The purge fresh air rate also needs to be eight 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.
They 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.