The Updated Building Bulletin 93 - Lessons Learnt?
December 2014 saw the much-anticipated release of the updated Building Bulletin 93 (BB 93) giving updated 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 gave various acoustic performance criteria for new school buildings. Critically, the document brought new school buildings under The Building Regulations, giving weight and importance to the acoustic standards.
Unfortunately, many of the acoustic criteria were at loggerheads with the sustainability aspirations (and cost limitations) of the new wave of schools. In addition, to cut costs, many contractors relied heavily on the use of ‘Alternative Performance Standards’, whereby the BB 93 standards could be significantly relaxed. This resulted in many schools derogating from the standards and the BB 93 vision for acoustically impeccable schools being diluted somewhat.
The updated document seeks to rectify this. Still enforced by the Building Regulations (and supporting the 2012 School Premises Regulations 2013 Independent School Standards), a set of relaxed standards have been included to apply to refurbished buildings. In addition, clearer guidance on the use of the standards for nurseries, higher and further education institutions, and universities, has been given, summarised below.
Alternative Performance Standards are still present in the updated document, but much better guidance is given on what relaxation, if any, can be proposed – 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) – more often than not, an urban or suburban school site anywhere near a road was just too noisy. This raised many a curious eyebrow, especially at times when it was highlighted that current school buildings on a site have openable windows and exam results are just fine!
"The updated document gives 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 – walls, floors, doors, etc. – but there is clarification for some of the trickier scenarios which come up on most school sites but which weren’t 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 new 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 playing havoc with room acoustics! The revised standards are still onerous for this type of space, but less so than the previous version and now vary according to room size.
All in all, the updated standards appear to represent a good 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 the updated document achieves its goals.
Contact auricl today for a lesson in school acoustics....