Nicholas Jones, Head of Acoustics, discusses the recent update to Building Bulletin 93, Acoustics in Schools.
December 2014 saw the much-anticipated release of the updated Building Bulletin 93 (BB 93), providing criteria and advice for those involved in the design and construction of schools.
The original BB 93 (“Acoustic Design of Schools”) was published in 2003 and presented various acoustic performance criteria for new school buildings. Critically, the document brought new school buildings under the Building Regulations, providing weight and importance to the new standards. Unfortunately, many of the acoustic criteria were at loggerheads with the sustainability aspirations (and cost limitations) of the new wave of schools. So to cut costs, many contractors relied heavily on the use of ‘Alternative Performance Standards’, whereby the BB 93 standards could be significantly relaxed. As a result, many schools were not able to benefit from the acoustically impeccable standards that BB 93 set out.
The new document seeks to rectify this. Still enforced by the Building Regulations (and supporting the 2012 School Premises Regulations, 2013 Independent School Standards), a new set of relaxed standards have been included, which also apply to refurbished buildings. Additionally, clearer guidance on the use of the standards for nurseries, higher and further education institutions, and universities, has been given.
Alternative Performance Standards are still present in the new document; however, clearer guidance is given on the ‘relaxation’, ensuring that any justifiable alternative can be no worse than the new ‘refurbished buildings’ standards. And ‘justifiable’ means a full and proper case needs to be put forward by a qualified acoustic consultant, based on a specific educational, environmental or health and safety requirement.
A common difficulty with the original BB 93 was achieving the indoor ambient noise level limits where natural ventilation was proposed – usually openable windows – as more often than not, an urban or suburban school site anywhere near a road was just too noisy. The new document therefore provides expanded, pragmatic advice for various natural, mechanical and mixed mode ventilation options with definitions for each.
There isn’t much change to the internal sound insulation criteria for walls, floors and doors; however, there is clarification for some of the trickier scenarios that arise on most school sites that were not really catered for by BB 93. – For example:
- Serving hatches between kitchens and multi-purpose halls used to mean that the BB 93 criteria couldn’t be achieved and derogation needed to be agreed. There is now more pragmatic guidance for these scenarios.
- Interconnecting doors and moveable partitions are common elements of modern schools, providing flexibility and connectivity between spaces. There was little allowance for these in the previous BB 93, meaning that, again, the sound insulation criteria couldn’t be achieved and derogation needed to be sought. Detailed guidance is now given in relation to these elements.
A particularly difficult element of the old BB 93 was the strict reverberation requirements in large halls, particularly gymnasia and sports halls. The requirements for the latter were virtually impossible to achieve – the Sport England requirements for two sets of painted, parallel blockwork walls played havoc with room acoustics! The revised standards are still onerous for this type of space, but less than the previous version and now they vary according to room size.
All in all, the new standards appear to represent a positive step in the right direction, promoting and maintaining good acoustic standards in schools without compromising wider aspirations. In relation to school design, we are all older and wiser now than when the original BB 93 was released in 2003, so only time (and implementation) will tell if lessons have been learnt and the new document achieves its goals.
For further information, please contact Nicholas Jones, firstname.lastname@example.org