What is air tightness testing?

Air tightness testing is a method of quantifying actual amount of air changes which occur in a building as opposed to the number of air changes for which the building actually requires or in other words testing a building for uninvited air.

What buildings require air tightness testing?

1. All developments/ one off dwellings which apply for planning from the 1st of July 2008 will be required to carry out an air tightness test on a proportion of the dwellings the following table from TGD Part L 2007 gives the requires testing regime.
   
   

   NUMBER OF PRESSURE TEST	PER DWELLING TYPES
   Number of Units	Number of Test
   4 or less	One Test
   Greater than 4, but equal or less than 40	Two Tests
   Greater than 40, but equal or less than 100	At least 5% of the dwelling type
   More than 100: (a) where the first five tests achieve the design air permeability (b) Where one or more of first five tests do not achieve the design air permeability	At least 2% (for dwellings in excess of first 100 units) At least 5% of units, until 5 successful consecutive tests are achieved, 2% thereafter

   
   
   
2. Any dwelling which wishes to use test results in DEAP for the calculation of Building Energy Ratings
3. Any dwelling which is fitted with mechanical ventilation which does not have an air tightness test carried out on it will be penalised on the BER thereby removing the benefits of the mechanical ventilation with heat recovery on the dwelling.

How does Air tightness effect a Building energy rating?

The DEAP Software for calculating BER contains a default value for air permeability depending on the structure type e.g Timber/ steel frame or masonry. Where a building receives a better result than this default value it improves the BER of the building. Example a typical 3 bedroom semi - detached house could improve its ratings by around 9kW/m²/yr with a good air tightness test as opposed to the default values. This is equivalent to the addition of about 2m² of solar panels at a lower cost.

How can I ensure air tightness on my dwelling?

1. Air tightness can be improved by following the guidelines for reduced thermal bridging for your building system. During our consultancy process we will advise you on how to limit the amount of thermal bridging resulting in better air tightness.
2. A good attention to detail on building construction ensuring any penetrations of the building fabric are sealed properly.