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Haggerston school benefited from a comprehensive acoustic overhaul (see case study)

Sound advice

Nicholas Jones looks at the acoustic implications of the newly updated standards for the design and construction of schools

Posted by Dave Higgitt | March 02, 2015 | Facilities & buildings

December 2014 saw the much-anticipated release of the updated Building Bulletin 93 (BB93), providing criteria and advice for those involved in the design and construction of schools. The original BB93 (‘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. Unfortunately, many of the acoustic criteria were at loggerheads with the sustainability aspirations (and cost limitations) of new schools. So to cut costs, many contractors relied heavily on the use of ‘alternative performance standards’, whereby the BB93 standards could be significantly relaxed. As a result, many schools were not able to benefit from the acoustically impeccable standards that BB93 set out.

The new document seeks to rectify this. Still enforced by the Building Regulations, 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; 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 BB93 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.

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. For example: serving hatches between kitchens and multi-purpose halls used to mean that the BB93 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. There was little allowance for these in the previous BB93, 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.

The strict reverberation requirements for large halls, particularly gymnasia and sports halls in the old BB93 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, but less so than previously and they now vary according to room size.

All in all, the new standards appear to represent a positive step, promoting and maintaining good acoustic standards in schools without compromising wider aspirations. In relation to school design, we are all older and wiser than when the original BB93 was released in 2003, so only time (and implementation) will tell if lessons have been learnt and the new document achieves its goals.

Case study: Haggerston School 

As part of the building schools for the future programme, grade II-listed Haggerston School in Hackney underwent significant regeneration work, including a new teaching block and refurbishment work on the original buildings. Hilson Moran’s acoustic engineering team provided consultancy on the acoustic aspects of the new and refurbished areas, including designing new external façades to reduce road traffic and aircraft noise to acceptable internal levels; analysing existing rooms and advising on acoustic upgrades so that the refurbished rooms achieve BB93 standards; internal structure design to maximise privacy between teaching areas; and the incorporation of visually and acoustically suitable room finishes in teaching areas with exposed soffits. 

Nicholas Jones is head of acoustics at Hilson Moran W: www.hilsonmoran.com

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