Airtightness is now an important issue for the construction industry. On 1st April 2002, Part L2 of the Building Regulations came into force that mean new buildings with excessive air leakage will no longer be acceptable.

This website explains in a nutshell what needs to be done. It describes:
BRE's airtightness testing service
the implications of the new Regulations
why airtightness is important
how it can be achieved.

Under the new Regulations...

designers are responsible for:
designing tight buildings.

contractors are responsible for:
building tight
commissioning an air tightness test when construction is completed
carrying out any necessary remedial work and arranging a re-test.

BRE is accredited to carry out airtightness tests on buildings in accordance with CIBSE TM23.

Help and guidance at hand

To help designers and contractors meet the new standards, BRE provides:
design advice
best practice guidance for construction detailing and workmanship
pre-completion audits to highlight potential problems prior to testing
airtightness tests
remedial advice.