Written evidence submitted by the Air Tightness Testing & Measurement Association Limited (“ATTMA”) [BLD 008]

1. Executive Summary

• ATTMA submits this initial information and comment to the Committee in its capacity as a DCLG Authorised Competence Scheme Operator for the air tightness testing industry and a Trade Association supporting scientific, technical and operational improvement for the benefit of the industry.

• ATTMA Registered Testers carry out 85% of all building tests in the UK and each test is recorded in our Lodgement database, whether a pass, a fail or a retest. Since September 2015, we have produced 130,000 final certificates – about 500 per day – and we hold a great deal of data about the tests, their exact locations, the target and actual results, therefore the consistency of outcomes.

• ATTMA’s scheme members perform one of the few (often the only) physical tests on a dwelling before it is handed over to its first occupant. They measure buildings’ air leakage scientifically and accurately, so as to enable the result to be fed back into the SAP (energy) calculation, to calculate the as-built energy rating compared to the design target and hence give the Building Control Body (BCB) the accurate verified information for assessing compliance with Part L of The Building Regulations.

• The results of these tests can be seen as one indication of the quality of the build compared to the design criteria and the expected outcome – and as we record the initial tests as well as the final tests, we can see the initial failure rate and by how much the target was missed before any remedial works are carried out.

• Remedial works to improve energy performance and air quality may not be as robust as built-in quality of construction and the longevity of these fixes is unknown, hence the as-built performance may not be sustained through the life of the dwelling.

• Our own concern is not necessarily about the quantity of homes being built, but the quality of the build compared to the design criteria and how this might be adversely affected should the production volume be increased – i.e.: a training and consistency issue and how to measure it.

• ATTMA can help to promote the concept of “build right” and can give guidance on how to achieve the desired airtightness of buildings.

2. About ATTMA and its Registered Testers Scheme

• The Air Tightness Testing and Measurement Association (ATTMA) is a professional association dedicated to promoting technical excellence and commercial effectiveness in all air tightness testing and air leakage measurement applications. It was formed in 2002 to give recognition to competent air tightness testers, to promote the testing and measurement industry and it supports its members by extending market awareness of the technology and the members’ services.

• Now, ATTMA is a Government (DCLG) Authorised Competent Persons Scheme Operator whose scheme represents 85% of all testing carried out in the UK. It is also responsible for writing and publishing the “approved test method” and guidance, ATTMA TSL1 for dwellings and TSL2 for non-dwelling buildings. These Standards are adopted and/or referenced in ~60 countries and called up in UK Building Regulations.

• All testing members of ATTMA are trained, independently audited and certified, with a scope covering air tightness testing to the ATTMA Technical Standards (TSL1 &/or TSL2) and BS EN:13829 (2001), demonstrating knowledge and understanding, which enables them to test both commercial and domestic developments in accordance with relevant building regulations.

• ATTMA is a Company Limited by Guarantee and does not distribute profits. It uses surplus funds to support its members with technical and operational guidance and is involved in a number of technical research projects in partnership with Universities and other bodies to promote and improve the industry and its science.

3. The importance of air tightness and its relationship with ventilation

• Unintentional air leakage or infiltration is potentially the largest single factor in energy losses in buildings.

• Clearly, in dwellings as in all buildings, the adage “build tight, ventilate right” applies, but the actual air tightness target is generally set as part of the SAP calculation where design and cost are part of the trade-off to achieve the required outcome, therefore the targets set for the builder.

• However, dwellings with low air leakage values may need an additional ventilation strategy included in the design to ensure suitable air quality and reduce the potential for condensation, potentially leading to mould growth and other health related issues.

• Approved Document F covers the requirements for ventilation, but the related needs of Part L and Part F do not seem to be satisfactorily considered in the building process – e.g.: we have been in discussion with a building warranty insurer about a house which had an airtightness target of 5m3/(h.m2) (no additional mechanical ventilation required) which achieved 12.4 on its first test (extremely poor) then after remedial sealing achieved 1.8 (extremely tight). This dwelling is complete, but having achieved this air tightness value now requires a mechanical ventilation system. It is therefore not a compliant dwelling and should not be signed off or handed over.

• The lack of joined-up planning and communication in this design and build process needs addressing and more so if the volume of home building increases.

4. Observations on achievement of targets

To keep this initial submission simple and to prompt further questioning later, we have copied below, two sets of data on charts:

• First: Total tests per month (top line) and number of failures (blue area below), demonstrating the rate at which these tests do not pass the requirement at the first attempt, therefore requiring remedial fixes and retests;
• Second: The percentage of failures at different specified air tightness values.

This demonstrates the inconsistency in achieving targets and a lack of understanding of how to achieve particular air tightness targets, generally set as part of the SAP calculation.

5. Conclusion

• What ATTMA believes is that the designer/SAP Consultant/specifier/builder/ inspector/Regulator interface needs to become a more cohesive, communicative chain so that all stages are aware of the sensible approaches to take which do not create knock-on effects down the line, resulting in unsuitable outcomes at the end, the point at which it is the most inconvenient and expensive to correct.

• Certainly, our members do come under pressure on site to take actions which are not correct or allowable and there is evidence that they have been sent away from site in favour of less scrupulous testers, who will accept the unacceptable test conditions imposed and hence let noncompliant dwellings be signed off and be handed over to unwitting new occupants.

• ATTMA is keen to help this supply chain to have a smoother ride with more predictable and cost effective outcomes, as it is our members who are the last in line and come under the most pressure.

• So, remove the uncertainty by improving awareness, training and understanding which will enable them to “do it better with what they have already got”.

September 2016