Air pressure testing is mandatory under the building regulations for new homes since the 1st of July 2008.

The procedure is used to improve the energy efficiency of the building. The test will pinpoint areas of heat loss (i.e. doors, windows, etc). Heat loss through a building's fabric demands more energy consumption thus costing more to maintain.

Air leakage testing plays a vital role in the building of an A rated home.

The Procedure

• Install a fan into the doorway of the main entrance of the house (No fixing applied in the process).
• Seal all the vents, flues and fans.
• The air flow rate required to maintain an excess pressure of 50 Pascal's (Pa) above outdoor is achieved.
• The air permeability is this way q50, expressed in cubic meters per hour per square meter of the envelope area, is divided by 20 to give an estimate of air charges at typical pressure difference under real conditions.

Air Tightness Terminology

Building envelope: External elements of the building, walls, windows, front and rear doors, floors and ceilings.

Air tightness: Defined as the resistance of the building envelope to inward or outward air leakage. Excessive air leakage results in increased energy consumption and reduced comfort levels.

Air leakage: Defined as the amount of air gaps or cracks in the building envelope, driven by pressure differences between inside and outside. Areas of air leakage, cold bridges i.e. around doors, windows and between floor levels.

Air permeability: Expressed as the amount of air leakage in cubic meters per hour per square meter of the building envelope at a pressure differential of 50Pascals between inside and outside the building envelope, maximum permitted level is 7  m3/hr.m2@50Pascals, This is measured by the instillation of the blower-door fan into the main entrance of the dwelling.

Air changes per hour: Measures the ventilation in the building. This can be controlled by mechanical ventilation heat recovery or opening windows and doors.

Building Regulations 2011 Technical Guidance Document L

Conservation of Fuel and Energy - Dwellings

1.5.4 Air permeability pressure tests
1.5.4.1
Air permeability can be measured by means of pressure testing of a building prior to completion. The procedure for testing is specified in I.S. EN 13829: 2000 "Thermal performance of buildings: determination of air permeability of buildings: fan pressurization method".

Additional guidance on testing procedure is given in Sections 2 to 4 of the BSRIA Guide "Airtightness testing for new dwellings" and CIBSE Technical Manual TM 23 "Testing Buildings for Air leakage" and the ATTMA publication "Measuring airpermeability of Building Envelopes". The preferred test method is that controllable ventilator grills should be temporarily sealed rather  than just closed. Permeability is calculated by dividing the air leakage rate in m3/hr by the envelope area in m2. The performance is assessed at 50 Pascals pressure difference.

It has been empirically determined that for dwellings generally the permeability at 50 Pascals pressure difference is approximately 20 times the air change rate at normal conditions. Guidance on appropriate extent of testing is given in paragraph 1.5.4.3.

Download the full Technical Guidance Document L