What is an Air Tightness Test?
An air tightness test is a test used to detect air leakage or air infiltration through gaps and cracks in a building’s fabric and around service pipes, windows, door etc.
What is air leakage / air infiltration?
Air leakage or air infiltration is the uncontrolled flow of air through gaps and cracks in the fabric of dwellings (sometimes referred to as infiltration or draughts). This is not to be confused with ventilation i.e. the controlled flow of air into and out of the dwelling through purpose-built ventilators which are required for the comfort and safety of the occupants. Too much air leakage leads to unnecessary heat loss and discomfort as a result of cold draughts. With more stringent building regulations requiring better energy efficiency, air tightness is an increasingly important issue. The aim should be to ‘build tight – ventilate right’.
Buildings cannot be too airtight; it is, however, essential to ensure appropriate ventilation. Air leakage is quantified as air permeability. This is the rate of leakage (m³/h/m²) into or out of the dwelling. It is measured at a reference pressure difference of 50Pa between the inside and outside of the dwelling. A building’s design and the quality of its construction will have a major effect on the amount of air leakage.
Other factors include building exposure and the buoyancy effect i.e. warm air rises and creates a drawing effect, pulling cold air in through gaps in the walls, ground floor and ceiling (infiltration). In some cases, infiltration can cool the surfaces of elements in the structure, leading to condensation. Similarly where cold air can gain access to the interior of the dwelling, heat produced internally can escape at these breaks in the external envelope.
What are the most common areas of air leakage or infiltration in a building?
Under floor ventilator grilles
Gaps in and around suspended timber floors
Leaky windows, doors & gaps around frames
Pathways through floor/ceiling voids into cavity walls and then to the outside
Gaps underneath and behind window boards
Gaps at the ceiling-to-wall joint at the eaves & eave vents
Gaps around loft hatches
Service penetrations through ceilings
Ventilation through ceilings
Bathroom wall & extractor fans
Gaps around bathroom waste pipes
Kitchen extractor fans
Gaps around kitchen waste pipes
Gaps around floor-to-wall joints (particularly with timber frame)
Why get an air tightness test?
It is an easy way of locating cracks or gaps in a building that cause drafts and heat loss in the building. These drafts and excess heat loss mean that you will be running your heating system for longer and therefore you will be spending more on your annual heating bill. By getting an air tightness test carried out, these problem areas can be identified and rectified or improved, thus reducing your annual heating bill.
When is an air tightness test required?
Technical Guidance Document (TGD) Part L 2011 states in sections:
22.214.171.124 Subject to the guidance in paragraph 126.96.36.199,air pressure testing should be carried out on a proportion of dwellings on all development sites including single dwelling developments, as outlined in paragraphs 188.8.131.52 to 184.108.40.206 to show attainment of backstop value of 7 m3/hr/m2.
The tests should be carried out by a person certified by an independent third party to carry out this work, e.g. National Standards Authority of Ireland certified or equivalent. The test report should contain at least the information specified in Section 7 of I.S. EN 13829. 220.127.116.11 On each development, an air pressure test should be carried out on at least one unit of each dwelling type. One dwelling from the first four units of each dwelling type planned for completion should be tested.
The basic number of tests for each dwelling type is presented in Table 4. The total number tested is related to the number of units of that type in the development and to the results achieved in any earlier tests carried out. Where a number of apartment blocks are constructed on the same site, each block should be treated as a separate development irrespective of the number of blocks on the site.
18.104.22.168 For small developments comprising no more than three dwelling units, specific pressure testing of these dwellings would not be necessary if it can be demonstrated with air pressure test reports that, during the preceding 12 month period, a dwelling of the same dwelling type constructed by the same builder had been pressure tested according to the procedures given in this sub-section and had satisfied the criterion set in paragraph 22.214.171.124. However, if the assumed air change rate in the calculation of the EPC and CPC using the DEAP methodology is less than the criterion set in paragraph 126.96.36.199, a pressure test to verify this assumed value should be carried out. The guidance given in this sub-section would apply in this situation.
How is the test carried out?
A tester will come and get the house ready for the test by closing any windows, doors, trickle vents and sealing any permanent openings such as open fires and extractor fans. They will then assemble the fan and frame into an external door and prepare to run the test. The fan is run and the test carried out.
How long does an Air-tightness Test Take?
The time a test will take to run depends on the size of the building, but it will generally take about 3 hours.