Floor plenum airtightness

In July 2016, BSRIA published BG65/2016 Floor Plenum Airtightness – Guidance and Testing Methodology. This replaced BG 12/2010 Floor Void Airtightness – Air Leakage Specification,

Since the introduction of airtightness testing as part of the Building Regulations, the air leakage of buildings has steadily reduced as construction teams have become more familiar with the requirements. By introducing lower specifications for floor plenums, it is hoped that the effect will be similar.

A floor plenum is a void between a building’s floor structure and a raised access floor, used for distributing conditioned air to the spaces above.

It is important that conditioned air in a floor plenum flows into the occupied zone and does not leak into cavities, risers, stairwells, heating trenches or other adjacent zones. A properly sealed floor plenum will allow the diffusers and grilles to fulfill their primary role of delivering air at the correct flow rate. As a result, the airtightness of floor plenums can be a serious energy efficiency issue.

BSRIA’s new guide addresses these issues and places upper limits on the air leakage of floor plenums. Distinctions are made between air leakage to adjacent spaces (normally referred to as plenum leakage), and uncontrolled air leakage into conditioned zones (normally referred to as raised access floor leakage). A testing methodology for both plenum leakage and raised access floor leakage is given, and guidance on achieving both is provided.