Buildings Will Fail Tougher Air Tightness Test

Chiltern warns that buildings will fail tougher air tightness test if government plans to enhance building performance by reducing air permeability levels go through for the 2005 revision.

Commercial buildings will struggle to pass the air tightness test required by Part L of the Building Regulations if government plans to enhance building performance by reducing air permeability levels go through for the 2005 revision, Chiltern Dynamics has warned.

In the past 12 months only around half of the commercial buildings that have undergone the company's air leakage testing service have passed the current air permeability level (10m3/h/m2).

As Richard Bate of Chiltern Dynamics commented, 'In fact, until 30th September of this year buildings were allowed some leeway and might have passed by achieving only 11.5m3/h/m2.

Of the buildings we have tested in the past year, barely 10% would have been able to achieve 5m3/h/m2 or less.

Going by the results we have seen, developers are struggling to meet current levels, so have some way to go to improve their performance.' Simple, modular buildings such as warehouses seem more likely to pass than more complex designs, he added.

'If careful thought is given to air permeability in every aspect of a design the structure will perform well.

In more complex buildings, with more design detailing, greater care will be needed.' And Mr Bate stressed that good design and close attention to detailing would be more critical than ever if the dramatic changes to Approved Document L - suggested in a leaked draft document - come into force.

'Attention to eaves detail, seals around windows and doors and gaps around services are all areas that demand attention.' Remedial work to buildings which fail their air leakage test, will be costly and re-tests or smoke tests to identify possible air leakage paths are additional costs that contractors will wish to avoid, Mr Bate warned.

He recommended that, to ensure a pass, air tightness be policed during the construction phase and not just prior to handover.

'A design might work well on paper but that has to be translated onto site.

Good site practice and tighter building control will help developers achieve the performance the building is designed to have.' The Chiltern Dynamics test can take from two hours to a full day depending on the size and complexity of the site.

'We can typically test two buildings on the same site in a day,' said Mr Bate.

'Smoke generators can be used during testing to detect leaks and to help clients better understand the performance of the building.'.

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