Tom Gregory, head of Chiltern Dynamics’ Energy Services Department, answers the most frequently asked questions about air tightness and sound insulation testing as required under Approved Documents L & E.
Air Tightness
Air testing has been a requirement of Approved Document L (ADL) for more than four years. The 2010 revision, which has been published but which will not take effect until October, is set to raise the complexity of test regimes and the number of tests needed. The following questions are based on the 2010 edition. For current requirements see our Air Tightness Testing FAQs page.
L1) Which projects need to be tested?
• New dwellings
• New buildings other than dwellings
• Extensions to buildings other than dwellings
Under the revised regulations it is unlikely that smaller developments will be excepted from testing, because they will not be able achieve the overall Target Emission Rate (TER) for ADL compliance by using the poorer assumed air permeability of 15 in energy calculations.
L2) What do buildings need to achieve?
With a 25% improvement in the TER. under the 2010 revisions, it is unlikely that buildings will be able to achieve the overall targets for energy improvement without significantly improving air tightness. Although ADL refers to tested buildings achieving 10m3/(h.m2) at a pressure difference of 50Pa as a ‘reasonable level’ of air permeability, the actual requirement will often be significantly lower to achieve the overall TER.
This will mean lower results and greater variation in test requirements between units on the same development, as well as between different sites.
In addition for dwellings, if air test results are to be used in SAP calculations for untested plots of the same dwelling type, 2m3/(h.m2) must be added to the result for the 'assessed' air permeability of any untested plots. In other words, if the target air permeability for the dwelling type in SAP is 6, the tested plot would need to achieve 4, for the result to be assumed for untested plots.
L3) How many units need to be tested?
All ‘non dwellings’ must be tested.
Dwellings are subject to a sampling regime. Under the 2010 revision, three tests or 50% of each dwelling type must be tested. The definition of types has changed and there are likely to be more types and therefore more tests on any development. In addition to variations in position (eg end terrace house or top floor flat), construction details and size (now defined as 10% difference in envelope area), other variables defining type will include: design air permeability, number of significant penetrations (doors, windows, flues, soil vent pipes, etc), storey height and adjacency to unheated spaces (eg garages, stairwells). The process of deciding on test regimes and tracking results will become more complicated.
L4) Who selects the sample to be tested?
Building Control, in consultation with the tester. The emphasis is still on testing early: half of the scheduled plots should be among the first 25% of completed types.
L5) What sealing should take place in advance of testing?
Certain temporarily sealing is required (eg ventilation, now including trickle vents) but other parts of the building may have to be sealed up too.
Often this is sensible (eg missing trickle vent, broken window pane) but whole rooms or sections of the building may be included for less obvious reasons.
The test certificate is likely to highlight where additional sealing has taken place – which in combination with a narrow pass might raise concerns about the final performance of this and other units on the same site.
L6) Who is competent to conduct the test under ADL?
Building Control is authorised to accept evidence from a BINDT-registered tester.
BINDT registration can be achieved in two ways:
- BINDT L1 registration for an individual wishing to just test dwellings can be achieved by attending an approved training course and having calibrated equipment.
- BINDT L1 & L2 registration is only through company membership of the Air Tightness Testing and Measurement Association (ATTMA). This entails UKAS accreditation to vet procedures, equipment, procedures, training, on-site testing, etc, as well as technical review by ATTMA.
Building Control is responsible for checking that the tester has the appropriate training and is registered for the specific class of building.
L7) What are the most common air leakage/infiltration paths?
Achieving the required air permeability relies on identifying, creating and maintaining a continuous air barrier. For dwellings this may just mean achieving a good internal finish. In more complex designs, the air barrier may be less obvious but it typically comprises external or party walls, ceilings and floors plus elements bordering ‘unconditioned areas’ (eg plant rooms, garages and cold roof spaces). Extensions can create particular difficulties.
It is common for air leakage paths to be ‘out of sight’ behind dry-linings, above suspended ceilings, behind bath panels, kitchen units, etc. Timely inspection of these areas as well as communication of the location of the ‘air barrier’ helps to reduce the risk of problems.
Sound Insulation
E1) Which projects need to be tested under Approved Document E (ADE)?
Flats, houses and rooms for residential purposes (eg care homes, student accommodation, hotels) either new build or formed by material change of use.
Builders can either test to the regime set out in ADE, or pay to use Robust Details, a set of specific design details for walls and floors that have been previously tested. Testing provides more flexibility by allowing out of the ordinary designs. NB: Rooms in other buildings may also need to be tested for specific or client requirements eg classrooms (BB93) or consulting rooms in hospitals/surgeries.
E2) What do buildings need to achieve?
Party walls and floors need to achieve an airborne sound insulation of greater than 45dB (43dB for change of use). Party floors need to achieve an impact sound insulation of less than 62dB (64dB for change of use).
E3) How many units need to be tested under ADE?
It states that one set of tests is required for every 10 units in a group or sub-group, defined as a significant change in design or use and broken down in detail in ADE.
- For new build houses – one set of two tests on the walls.
- For new build flats - one set of six tests on separating walls & floors (two airborne wall tests, two airborne floor tests and two impact floor tests).
- Rooms for residential purposes (student accommodation, hotel rooms, care homes etc) – one set of three tests: one airborne wall test, one airborne floor test and one impact floor test.
- For change of use (eg conversion of houses to flats or non-dwellings to dwellings) all of the above rules also apply.
E4) How are units selected for test?
Typically this is left to the discretion of the test engineer. However the local authority building control officer, warranty provider or other concerned parties may wish to test in specific areas. Tests are always conducted between pairs of rooms.
E5) Who is competent to conduct the testing under ADE?
The testing body should be UKAS-accredited, or a member of the Association of Noise Consultants (ANC).
E6) What are the common problem areas?
Many aspects of the build can affect the acoustic performance of the separating walls or floors. One of the single largest factors influencing performance is, predictably, workmanship. Sealing of air paths, clearing of cavities and good detailing are all key aspects in maximising on site performance. Generally, good workmanship for acoustic performance also leads to a better air leakage performance and we strongly advocate this to clients. Sound testing needs to be taken into account very early in the construction stage, to make sure a correct combination of building materials is used to achieve the performances required.
PDF: Air tightness & sound insulation: Building Control's questions answered
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