The air tightness of the building envelope is a requirement for achieving the latest energy techniques in new buildings as much as for retrofitting of existing buildings. Specifically targeting the removal of unwanted air leakage brings about the energy savings potential required to get a good BER result. Installing air tightness systems such as the SIGA air tightness also helps prevent moisture transfer into the building construction. Furthermore maximizing energy-efficient standards of heating systems or windows only develop their full potential if unwanted air leakages in your building envelope are eliminated.

Why is air tightness so important

Air tightness does not necessarily imply constructing a building totally airtight, but eliminating undesired leakages in the building envelope. This is really important, for the reason that warm air will pass outside via the joints, which in turn makes the heating system work harder and that means increased energy costs for the occupants.

Concurrently, the warm air carries moisture; It cools at the outside wall of the building and condenses. The now water could potentially cause considerable structural damage. Outside air going through the house through joints carries contaminants and dust particles in the air and into the house, which can result in ill effects for the inhabitants health. The diagram shows the location of the air barrier which should be placed on the warm side of the insulation layer and if attainable on the inside side of the supporting structure, thus preventing indoor air from penetrating the construction.

Goals and objectives of air tightness

• Saves energy
• Lowers energy costs
• Effective function of the ventilation systems
• Avoid convection-related building damage
• Safeguard against contaminants entering the home
• Comfortable draught free home

Testing the air tightness barrier

 The Blower Door pressure test makes it uncomplicated to test the air tightness of buildings, and assures the quality of the Air tightness membranes and tapes installed.

The test highlights any weakness in the completed barrier and all windows and doors that have been installed. The air tightness measurement must be carried out by an NSAI registered air tightness tester such as myself.

Construction-related leakages or permeability often occur at connections and penetrations. When planning an air barrier, these areas should be given careful consideration to avoid costly rework later.

Air leakages mainly occur in the area of

• Junctions and joint butts of building components
• Pipe and cable penetrations through the air barrier
• Floor junctions at doors and windows at floor level in converted attics
• Connections of different building materials
• Building extensions and bay windows
• Window sills and external door reveals
• Roof lights and dormers
• Trap doors

Air leakages caused by errors during the planning stage or a lack of data on the connections between the airtight layers of different building components are usually at this stage of the build not going to be completely eliminated. Leakages created by mistakes in the implementation can usually be eliminated by doing rework, if they are detected in time during an early blower door test.