BREEAM Testing and inspecting building fabric

1 Background
2 Aim and benefits
3 When to consider
4 Step-by-step guidance
5 Tools and resources
6 Tips and best practice
7 Typical evidence
8 Applicable schemes
9 Related articles on Designing Buildings Wiki

[edit] Background

The requirements for air tightness testing and thermographic surveys stem from criterion 4 of Approved Document L2A – Conservation of Fuel and Power in New Buildings other than Dwellings. Criterion 4 falls under Section 3 which looks at the Quality of Construction and Commissioning, a key element of which is the building fabric.

The Approved Document states the following with regards to building fabric performance:

3.2 The building fabric should be constructed to a reasonable quality so that:

a. the insulation is reasonably continuous over the whole building envelope; and
b. the air permeability is within reasonable limits.

Compliance with the above can be demonstrated as follows:

Continuity of Insulation:

To use construction details that have been calculated by a person with suitable expertise and experience following guidance set out in BRE Report BR 497 (Conventions for Calculating Linear Thermal Transmittance and Temperature Factors) and following a process flow sequence that has been provided to the Building Control Body indicating the way in which the detail should be constructed. The calculated value can then be used in the Building CO2 Emission Rate (BER) calculation.
To use construction joints with no specific quantification of the thermal bridge values. In such cases, the generic linear thermal bridge values as given in IP 1/06 increased by 0.04 W/(m.K) or 50% (whichever is greater) must be used in the BER calculation.

Air Permeability and Pressure Testing:

Pressure testing should be undertaken in accordance with the approved procedure as set out in the ATTMA publication Measuring Air Permeability of Building Envelopes.
All buildings that are not dwellings must be subject to pressure testing, although there are some exceptions as set out in section 3.12 of the Approved Document.
One listed exception which an assessor may come across more often relates to large complex buildings where, due to the building size or complexity, it may be impractical to carry out pressure testing of the whole building. The ATTMA publication indicates situations where such considerations might apply. If this approach is adopted, a detailed justification should be provided and endorsed by a suitably qualified professional (such as a competent person approved for pressure testing). The suitably qualified professional should be appointed to undertake a detailed programme of design development, component testing and site supervision to give confidence that a continuous air barrier will be achieved.
The measured air permeability should not be worse than the limiting value of 10 m3/(hm2) at 50Pa.
Should satisfactory performance not be achieved, remedial measures should be carried out on the building and new tests carried out until the building achieves the design criteria.

BREEAM and Airtightness Testing / Thermographic Surveys

The requirements of this issue, as is common with BREEAM, go above and beyond the standard requirements to promote best practice through the industry through the use of airtightness testing (as set out in the Approved Document) and also thermographic surveys to quality-assure the integrity of the building fabric. This includes continuity of insulation, avoidance of thermal bridging and air leakage paths.

The credit also requires that the main contractor rectifies any defects identified in the thermographic survey prior to building handover.

[edit] Aim and benefits

BRE Report 176 (A Practical Guide to Infra-Red Thermography for Building Surveys) states that thermographic surveys can be used to demonstrate performance of a building and its components and services including:

Insulation defect detection.
Air leakage detection.
Heat loss through window frames.
Dampness detection.
Examination of heating systems (e.g. damage to insulation).
Preventative maintenance.
Electrical defect detection.

Many of the above are not applicable to the BREEAM scope so the key benefits are stated below:

The benefit of undertaking thermographic surveys to demonstrate the continuity of insulation is that it verifies that the construction details set out during the design of the building have been followed during construction of the building. This gives confidence to the building owner/occupier that the building and its associated systems will perform as designed to meet the thermal comfort requirements and reduces the building energy consumptions due to the reduced losses through the building fabric. As such this can avoid expensive unexpected costs and failure to comply with Part L.
A thermographic survey can be perceived as a good way of checking the standard / quality of work that cannot normally be seen.
A thermographic survey is the best non-destructive testing method and large areas can be surveyed in a short period of time and typically alongside the air-tightness test which will quantify the leaks identified on an air tightness test.
The survey can also act as a tool to determine areas of the building that could be made more energy efficient – reducing energy bills and improving the thermal comfort of the building. For example, on existing buildings, thermography can be used to assess the overall performance of the individual building fabric elements such that informed decisions can be made on improving energy efficiency. If required, in depth analysis can also be undertaken to estimate the potential cost and CO2 reductions if particular improvements are undertaken.

[edit] When to consider

An air tightness test and thermographic Survey will need to be written into the project programming and costing.
The integrity of the building envelope should be complete for the survey. Drawings (plans and sections) and specification details regarding the areas to be surveyed shall be supplied prior to the survey taking place.
Strict weather conditions make it advisable not to carry out surveys between mid June – mid September. The reason for this is that internal / external temperature difference on the entire building must be a minimum of 10°C for at least 12 hours prior to the survey. If not, you will not achieve compliance for BREEAM credit or BS EN 13187:1999

[edit] Step-by-step guidance

There are two approaches that can be adopted for carrying out thermographic inspections:

Qualitative approach: a straightforward approach that can be used to identify items such as missing or defective insulation without the need for measurement detail. The images generated from this type of survey require interpretation by a skilled operator through examination of the thermographic images and the building structure.
Quantitative approach: a more detailed and stringent survey that requires analysis by a software package and produces a more comprehensive analysis of the building performance.

The operator will use their expertise to assess the survey data to identify any defective areas that require remediation based on the building construction methods and specified design criteria.

The BREEAM criteria are not prescriptive on the approach that should be adopted and advice should be sought from the project team on which is appropriate given the nature and complexity of the building being assessed. The wording of the criteria suggests that a qualitative assessment would be sufficient to meet the credit requirements but there are benefits in undertaking a quantitative approach for more complex buildings that may justify the increased expenditure. It should be noted that, having completed a qualitative level survey, if a decision is subsequently made to follow the quantitative approach it is likely that the surveys would need to be redone as the level of detail required is increased.

[edit] Tools and resources

UK Thermography Association: http://www.bindt.org/institute-committees-and-groups/institute-groups/ukta/

[edit] Tips and best practice

For a BREEAM credit, 100% of the roof and elevations must be surveyed, unless it can be demonstrated to be unpractical.
Where an air test is not required for building regulations it can still provide a benefit to the Ene 01 credit score due to the need to not take the default data.

[edit] Typical evidence

A survey report from a Level 2 Thermographer in accordance with all necessary standards and current regulations

[edit] Applicable schemes

The guidelines collated in this ISD aim to support sustainable best practice in the topic described. This issue may apply in multiple BREEAM schemes covering different stages in the life of a building, different building types and different year versions. Some content may be generic but scheme nuances should also be taken into account. Refer to the comments below and related articles to this one to understand these nuances. See this document for further guidelines.