Introduction

Air-tightness testing of buildings is also known as “Blower-Door Testing” or “Air-Permeability Testing”. The terms “Air Tightness”, “Air Leakage” and “Air Permeability” all relate to the extent to which air can move from inside to outside the building, or visa-versa, as a result of gaps, openings, porosity, etc, in the buildings fabric. The more ‘leaky’ the building is, the more ‘air infiltration’ will occur.

Cold draughts and unpredictably high energy costs can often be traced directly to air leakage into and out of your building. Uncontrolled air loss from a building can have a significant impact on comfort, heating/cooling costs and maintenance. Typically, unwanted air leakage can account for as much as 25% or more of building heat loss.

Under the most recent amendments to the 2008 Building Regulations Document Part L, it is now required that standards of air tightness in new buildings are both achieved and proven by means of Air Tightness Testing.
This requirement for Air Tightness Testing to be carried out will lead to improved standards of energy efficiency in buildings. Air Tightness Tests using the Blower-Door enable the builder/owner to assess the “tightness” of a building, eliminating guesswork regarding unwanted leakage, draughts and energy losses.

The test methodology is widely accepted and is used as one of the predictors for “energy efficiency” in homes. It has been used by energy retrofitters for years to measure the success of their air sealing efforts.

The European Standard for Air Tightness testing of buildings is EN 13829. Under this standard, a test pressure of 50 Pascals is applied to the building with the use of a calibrated variable speed fan. The flow rate of air required to maintain a test pressure of 50 Pacals with in the building gives the Air Change Rate for the building. Under the 2008 building regulations all new dwellings must be proven, by means of a blower door test, to have an Air Change Rate of 10 or less.
Builders who carry out repeated blower door testing on finished houses learn to anticipate where and how air leakage problems are likely to occur and are able to find ways of avoiding them during the construction process. By avoiding air leakage problems in the first place, builders can avoid costly call-backs and increase customer satisfaction with their product.

The Blower Door system

The system consists of a powerful, variable speed fan with a speed controller mounted in an adjustable panel/frame that is temporarily fit into an open exterior doorway. A set of manometers or differential pressure gages are used to measure pressure differences generated by the fan. Airflow across a calibrated opening in the fan housing is also measured.

When operating, the Blower Door fan acts as an exhaust fan and vents indoor air to the outside. This sucking action causes the air pressure in the house to drop below the pressure of the air outside. The direction of air flow is then reversed and instead of depressurising the building a positive air pressure is applied to the inside of the building.

Detecting air leakage is a simple matter of feeling for leaks around openings such as window trim, doors, or sockets, to name just a few of the possible sources of air leaks. Alternatively, a smoke pencil or smoke box can be used to make leakage paths visible. A thermal imaging camera is a very precise and effective tool for finding and visually representing air leakage paths in buildings.
The results produced by blower door tests can be useful for buildings that are too tight as well as those that are leaky. Buildings that are very airtight may need supplemental ventilation.

BioPower Energy Savings can pressure test your building, in compliance with EN 13829, to identify leaks/draughts and then advise you on how to remedy any problems to increase the comfort and efficiency of your home. We will issue you with detailed report of our assessment using the specifically designed blower door software.

How to Achieve A Good Level Of Air-Tightness

Careful design, specification, quality control and performance testing during and/or after construction will achieve an airtight building envelope.

Design 
The building form, position and types of opening, interaction of the structure and airtight layer all affect the air leakage performance of the building. An appropriate air-tightness specification must be selected. The line of the airtight barrier should be identified as soon as possible allowing examination of details at openings and junctions in the envelope.

Specification
The components and systems that make up the external envelope such as external walling, windows, floor joints, roof joints, cladding, etc. must achieve at least the specified level of air-tightness set for the building. Responsibilities for dealing with continuity of the air tight barrier at junctions and openings should be clearly spelled out.

Draught entering at the joint between ceiling and wall

Construction
All supervisory staff and subcontractors should be adequately briefed on the importance of maintaining the airtight barrier, quality control and reproduction of the designers details.
The blower door test pressure is sufficient to expose any air infiltration points in the building under test. With the assistance of an infrared camera, the infiltration points are recorded and printed into a report. When remedial work is completed, the test can be re run to provide documented proof that the building has achieved a good level of air tightness.  

Testing the building when the external envelope is complete will confirm the air tightness performance of the building. Achieving a good level of air tightness will add to the overall thermal efficiency of the building and will positively influence its building energy rating (BER).