Clean Energy Solution Providers

What is Building Air Tightness Testing?

Building air tightness testing is a simple tool used to measure the air tightness of buildings and to help locate leakages. The procedure is straightforward and applied to new and existing dwellings. Building air tightness measurements are used for a variety of purposes, including:

Identifying unintentional air paths into a building.
Documenting the construction air tightness of buildings.
Estimating natural infiltration rates in buildings.
Measuring and documenting the effectiveness of sealing activities.
Providing the air tightness metric for the Building Energy Ratings.
Reducing the costs of heating a building by taking Preventative measures against unintentional air infiltration.
Reducing a house’s carbon footprint.

What is an Air Leakage?

Air leakage is the infiltration and exfiltration of air through a building envelope or component due to imperfections in its construction. It takes place, for example, through:

Cracks around doors, windows, panels and cladding material.
Gaps where the structure penetrates the construction envelope.
Services entries, pipes, ducts, flues.
Measuring and documenting the effectiveness of sealing activities.
Porous construction, bricks, blocks, mortar joints.
Joist connections within intermediate floors.

Air leakage can also detract from the thermal performance of a construction, by providing a ventilation path within the constructions for heat loss, therefore ‘short-circuiting’ the thermal insulation, and reducing the u-value of the construction.

For air leakage to occur, there must be both a hole/crack and a pressure difference to push the air through the hole. The most common pressure differentials which operate in buildings are:

1. Stack Effect

The stack effect is the tendency for warm air to rise and leak out of the middle of the building and be replaced by colder outside air entering the bottom of the building. In winter, the stack effect creates a small positive pressure at the middle of the building and small negative pressure at the bottom of the building.

2. Wind Pressure

Wind blowing on a building will cause outside air to enter on the windward side of the building and leave on the leeward side. Wind causes negative pressure in the building on the windward side and positive pressure on the leeward side.

3. Point Source Exhaust or Supply Devices.

Chimneys for combustion appliances and exhaust fans (i.e. kitchen extractors, and bath fans) push air out of the building when they are operating. Air leaving the building from these devices causes a negative pressure in the building, which draws outside air in through the holes and cracks in the building envelope.

Under Floor ventilator grills.
Gaps in and around suspended timber floors.
Leaky windows or doors.
Pathway through floor/ceiling voids into cavity walls and then to outside.
Gaps around windows.
Gaps at the ceiling-to wall joints at the eaves.
Open Chimney.
Gaps around attic hatches.
Service penetrations in ceilings.
Vents penetrating the ceiling/roof.
Bathroom wall vent or extract fan.
Gaps around the bathroom waste pipes.
Kitchen wall vent or extractor fan.
Gaps around kitchen waste pipes.
Gaps around wall-to-floor joints (especially with timber frame).

Test Procedure:

Clean Energy Ireland uses the BS EN 13829 test procedure using a Minneapolis Blower Door kit (calibrated to National Standards requirements) to perform the measurement.
In advance of the test, the ground area and building volume is calculated, (excluding unheated areas). Preparation for the test will normally include the closure of all adjustable ventilation openings in the building envelope, sealing any extract fans and chimneys and ensuring the plumbing traps are filled with water.
Turning off all gas, oil and solid flue appliances for the duration of the test is mandatory.
All exterior doors and windows should remain shut and internal doors left open to allow free air movement.

The test fixture is set up on an exterior door and the test commences, measuring the air flow rate through the fan between 60 Pascals and 30 Pascals in decrements of 5 Pascals.
A summary report is generated when the test is completed; this includes the Air Changes per Hour (ACH) at 50 Pascal and a graphical representation of the test results. See figure 2.0.
There is an opportunity to identify area of infiltration/exfiltration, remedial action is taken to improve the air-tightness performance and the test could be repeated.

The Air Permeability Summary outlines the air permeability differences between concrete build and timber frame construction.

Further information can be obtained by contacting us.