Overview

Air permeability is a term that is used to define how well controlled the movement of air into and out of a building is. Obviously if air is uncontrolled, then heat which you have generated is being lost. This costs you more money through excess energy usage and results in higher CO₂ emissions.

Insulate right & build air-tight are two terms that consumers and builders alike are going to hear more often. Significantly improved construction standards to allow for the better fitment of higher-quality & more efficient insulation coupled with closer attention to detail to close gaps in construction are being actively encouraged.

Many houses are being tested for their air leakage and as of 1st July 2009, all new houses when being built must have an air-leakage report showing the air permeability of the house. The result of this report is inputted into the BER calculation. A good result will have a significant positive effect on a BER.

The machine used to undertake an air permeability test is commonly known as a blower door machine. It is built tightly into a window or doorframe and performs a number of operations according to EN-13829 to under and over pressurise a building.

The test machine determines two results of particular interest.  The n50 and the q50.

The n50 is how the air permeability rate is expressed in air changes per hour (ac/h).  It is the relationship between the total volume of air in m³ and how often leaks in the building envelope allow the air to exchange at 50 Pascals air pressure.

Best practise in domestic dwellings calls for an ac/h rate of not more than:

1.      3.0 ac/h         –          natural ventilation (with wall vents)

2.      1.5 ac/h         –          with mechanical ventilation

3.      0.6 ac/h         –          Passive House Standard

 

The q50 is an expression of the amount of air leaked from the dwelling in relation to the total exposed area per house and is expressed as m³/h/ m².  The maximum upper limit allowed according to the Irish Building Regulations Technical Guidance Documents Part (L) is 10 m³/h/m².

 

During the test, whilst the specialised software is generating a result and a report, leaks can be identified in the building fabric during a walk around with the client using a number of methods including smoke tests & thermal imaging.

When a house is being built ideally two tests will be done - once during construction so that faults can be identified and cost effectively repaired and once at the end of construction to get the final result for BER certification.

Click here to see an air permeability test being undertaken in a house that has been built airtight to ensure it is compliant with the client/architect’s specification.

In order to completely make a house air tight in accordance with the best practise European standards, it has to be planned to achieve a very low level of air changes per hour and will require input from specialist contactors and possibly the installation of a mechanical ventilation system.

2eva.ie can provide air leakage tests on new or existing dwellings as well as advice to clients how to most cost effectively achieve a specific result.