Air tightness testing, also known as air leakage testing or air permeability testing, establishes the rate at which air leaks out of a building. It has been a mandatory part of the Building Regulations for new build and refurbishment projects since Approved Document L was revised in 2006.

Air leakage occurs through any opening in the building envelope and can affect a buildings energy performance, this has been addresses by changes to the building regulations. Our Air Tightness Testing is UKAS accredited and certificates are then registered with ATTMA, a professional association dedicated to promoting technical excellence in all air tightness testing and air leakage measurement applications.

We are dedicated and accredited air leakage testing service providers in LOCATIONXXX and we are available to provide you testing services whenever required. You can also contact us for assessment and consultancy services.

In addition to air leakage testing we can provide SAP and SBEM calculations for Part L compliance, Energy Performance Certificates, Part G water calculations, and Part F Mechanical extract fan flow rate testing. As registered members of the Air Tightness Measurement Association you can rest assured that our air leakage test certificate will be accepted as evidence for Building Regulations sign-off. If you need experienced professionals in LOCATIONXXX who take the time to explain the testing process, and we are able to give informed advice on where problem areas may occur during testing how improvements can be made based on results of air pressure testing, we deliver professional value for money service to the highest standards

Prevent such and its resulting inconvenience and costs by getting air tightness testing from the professionals in LOCATIONXXX you can trust. Call us now on 020 3372 4430

What is Air Tightness Testing?

Air tightness testing is a method of measuring the extent to which air is lost through leaks in the building fabric. It is sometimes referred to as air leakage testing or air pressure testing. Air leakage is the uncontrolled flow of air through gaps and cracks in the fabric (often referred to as infiltration or draughts) and not ventilation, which is the controlled flow of air in and out of the building.

Air Tightness Testing is the recognised method used to measure the total air lost through leaks in the building fabric. This is often referred to as uncontrolled ventilation (draughts). Too much air leakage leads to unnecessary heat loss and discomfort for the occupants. As the Government strives to reduce CO2 emissions from new buildings, building regulations now place greater emphasis on reducing air leakage from the building envelope, therefore reducing fuel usage to maintain a comfortable environment.

Air tightness testing is important in establishing air leakage from a building’s the energy efficiency of a new building and can identify poor build quality within new developments. With the introduction of tougher regulations, building designs will often consider air tightness at the early stages of the construction process ensuring attention to detail during construction; to create an air tight envelope, understanding this at an early stage can make a build more cost and time effective, but also create a higher quality finished construction that is more energy efficient due to minimising uncontrolled air leakage, creating a more comfortable environment

If the property has an Air Permeability rating over 10m³/h/m² @ 50pa (7m³/h/m² at 50pa in Scotland) then the property will fail the test, due to significant uncontrolled air leakage.

What is air leakage?

Air leakage is where air enters and leaves a building uncontrollably through cracks and holes in the building fabric. It is also known as infiltration and is different to ventilation, which is air that enters a building in a controlled manner. As Air Leakage is uncontrolled, too much air may enter the house during cold or windy weather, leading to excessive heat loss and the uncomfortable feeling of cold draughts.

Air Leakage plays a major part in the energy efficiency of buildings, and testing is necessary as a means of demonstrating that the air tightness targets used in building energy calculations have been achieved.

What is the impact of air leakage?

When moist air hits a cooler surface within a wall structure, water vapor in the air can condense and collect inside these spaces. This moisture can then be absorbed in various building materials and cause a host of serious structural problems.

Wet wooden framing or sheathing can rot and break down, dramatically diminishing its strength. Steel structural members can become oxidized, rusting and gradually losing their integrity. Even masonry can be compromised by vapor diffusion, as moisture passing through the wall can rob salts from the mortar, causing efflorescence and slowly breaking down the joints between bricks or concrete blocks, until the wall loses its integrity. Over time, any of these conditions can cause structural damage to the building.

Over time, any of these conditions can cause structural damage to the building. Other impacts include:

  • unwanted heat loss
  • discomfort for occupants (cold homes)
  • increased heating bills (to counter the cold)
  • greater CO² emissions (as result of additional heating required)

The key to minimizing the damage potential of moisture is effectively managing the flow of air into and out of the building. A properly installed, continuous air barrier minimizes air leakage, which, in turn, minimizes the potential for water vapor to condense on vulnerable wall structures. Correct ventilation is important, whether it is passive or active, to remove water vapour and pollutants.


Why should we do an Air Tightness test?

 Airtightness is a key factor in building energy efficiency, and consequently is a feature of Government led initiatives to combat climate change through improvements in building energy performance. Heating buildings involves burning fossil fuels which contribute towards CO2 emissions and global warming.

Reducing air leakage, results in less heat loss, which in turn reduces the amount a heating system must be used. There are also health issues around buildings with a lot of uncontrolled air leakage– when a building has poor levels of controlled ventilation and high levels of uncontrolled air leakage this can cause excessive moisture and mould growth which can affect the occupier’s health. Best practice advice is “Build tight, ventilate right”.

Finally, high levels of air leakage can lead to moisture ingress into the building fabric, potentially resulting in very expensive repair costs and potential health problems to the occupants due to mould.

When Do I Need an Air Tightness Test?

An air tightness test is completed towards the end of the construction process, in order to meet Building Regulations/Standards. The results of the test are used within SAP and SBEM calculations, and can influence a new buildings overall energy rating.

Larger residential developments do not require testing to be completed on each individual property; instead testing is undertaken on the different dwelling types within the development. With selective testing there is a penalty of +2 m3/h/m2, therefore if the target score is 5 m3/h/m2 .

Where the dwelling has not been pressure tested, the assessed air permeability is the average test result obtained from other dwellings of the same dwelling type on the development, increased by +2.0 m3/h/m2 at 50 Pa

Selective testing is not advised as the testing does not get a realistic picture of how tight each individual building will be, one might be a lot tighter than the one not tested. But also because of the penalty that is implemented on the houses not being tested, as you will have to reach a much higher air permeability rate which is very difficult to achieve. All commercial properties with a floor area over 500m² will require an air pressure test in order to comply with the

Why Choose AF Acoustics For Your Air Tightness Testing?

Our air tightness testing expertise at AF Acoustics have aided several home and business owners in LOCATIONXXX. We come highly recommended by our clients because of the following guarantees of working with us

Helpful service and expert knowledge

Our diverse experience serving a variety of clients in LOCATIONXXX guarantees we have the expertise to satisfy your needs regardless your unique circumstances, or type or size of your property. Our accredited and qualified air testing experts are polite and competent. They are trained to provide the service you need without compromising your convenience.

If you need knowledgeable and trustworthy air leakage experts who can provide you solutions with exemplary results, AF Acoustics is the team you need in LOCATIONXXX.

Registered member of the Air Tightness Testing & Measurement Association (ATTMA)

We are registered members of the ATTMA. ATTMA is a professional association dedicated to promoting technical excellence in all air tightness testing and air leakage measurement applications. This means our expertise and quality of services is recognised by the leading air tightness testing body in the UK.

Responsive scheduling (Monday –Fri 8am to 6pm)

We want you to be able to access comprehensive air tightness testing in LOCATIONXXX whenever you need it. Thus, we offer responsive scheduling options through Monday to Friday, 8am to 6pm. You can schedule for air tightness testing at your convenience within this time frame. We guarantee no undue delays or complications regarding scheduling.

Same day turnaround on test certificate where possible

The sooner you get results from air tightness testing, the sooner you can take necessary actions to  LOCATIONXXX AF Acoustics offer a no fuss, professional and reliable service, we understand that our clients are keen to get their test results as quickly as possible, to facilitate this, we strive to deliver in all scenarios same day turnaround on test certificates.

Very competitive pricing

Some property owners in LOCATIONXXX delay getting air tightness testing because they consider it costly. At AF Acoustics, we offer some of the most competitive prices on LOCATIONXXX to ensure you have access to affordable air tightness testing as soon as you need it, we keep costs down being a small business with low overheads allowing us to be very competitive with our pricing, passing this saving onto the customer, whilst guaranteeing a highly professional and experienced service.

Request a call from our technical sales team
Or you can email us at info@af-acoustics.com

Air Tightness Testing for domestic & commercial buildings of all types and sizes in LOCATIONXXX

Regardless of the size, type, or complexity of your domestic or commercial building in LOCATIONXXX, we can provide you with air tightness testing, carried out by an experienced and professional air tightness tester and issue you with a certified ATTMA certificate. An air leakage test is used to determine the level of uncontrolled air flow through gaps or cracks in the fabric of a building. The result of the air leakage test is expressed as a quantity in the form of m3/h/m2 –  (m3 per hour) per square metre of building envelope.

Air leakage testing is a requirement of Approved Document L2A. Each building tested must achieve a maximum air permeability rate of 10m3/h/m2. In order to comply with the carbon emission target it may be necessary to achieve a lower air permeability rate. The required air permeability rate for each building can be found on the design-stage SAP assessment SBEM for that building.

Too much air leakage leads to unnecessary heat loss (and consequently, higher CO2 emissions) and can lead to discomfort to the occupants through cold draughts, but also create convective loops within the structure, this is often referred to as thermal bypassing and wind washing, creating energy loss. Exfiltration/infiltration of air can be caused by a stack effect, this is due to the pressure difference between inside and outside, rising warm air reduces the pressure in the base of the building and draws air in, wither through open doors, windows or other openings and leakage points.

Air tightness testing is highly recommended for domestic buildings to ensure energy efficiency and comfort within the home environment. It is also a legal requirement that all new builds have an air tightness test carried out to meet energy efficiency standards before it can get signed off by building control in LOCATIONXXX

For your commercial building, air tightness testing will ensure your workers and visiting clients are in a comfortable environment. It will also help you reduce the cost of maintaining heating or cooling in your commercial building, a comfortable environment is a more productive environment.

Part L Test

Air tightness testing has been a mandatory part of the Building Regulations for new build and refurbishment projects since Approved Document L was revised in 2006.

The air-tightness of a building is known as its ‘air permeability’ or leakage rate. Air leakage can occur through gaps, holes and cracks in the fabric of the building envelope (service penetrations, wall/roof junctions etc), which are not always visible.

Part L of the Buildings Regulations requires that all non-domestic buildings which have a gross floor area greater than 500m2, be subject to mandatory air permeability tests. For domestic dwellings a representative sample of houses (in a development) must be tested.

Part F Test

We can provide you with a single point of contact to serve all your Part L and Part F requirements. In addition to conducting your air pressure test, we can provide SAP calculations, Energy Performance Certificates, water calculations and extract fan flow rate testing

Approved Document F of the Building Regulations requires that all mechanical extract fans in new dwellings must be subjected to a flow rate test. Evidence of this test must be passed to the Building Control Body (BCB) as part of their sign-off procedure.

There are three alternative methods which can be followed to test, record and report the testing of extractor fans. Using a Vane Anemometer, our testing procedure follows Method 3 – The minimum benchmark method.


Types of Air tightness testing services we offer

 There are different levels of air tightness testing established from the size and complexity of a building. An overview of each is provided below:

  • Level 1: Air Pressure Testing for single dwellings and other smaller non-dwellings up to 4000 m³ gross envelope volume, typically tested with a single blower door fan.
  • Level 2: Air Pressure Testing for simple and complex buildings larger than 4000 m³ gross envelope volume. This does not include large and complex, high rise (LCHR) buildings, and phased handover/zonal buildings.
  • Level 3: Air Pressure Testing for LCHR buildings, phased and zonal handover buildings.

Air tightness testing of houses and flats to meet Approved Document L1

An air leakage test is a test to determine the level of uncontrolled air flow through gaps or cracks in the fabric of a building. The result of the air leakage test is expressed as a quantity of air leakage (m3 per hour) per square metre of building envelope.

Air leakage testing is a requirement of Approved Document L1A. Each dwelling tested must achieve a maximum air permeability rate of 10m3/h/m2. In order to comply with the carbon emission target it may be necessary to achieve a lower air permeability rate. The required air permeability rate for each dwelling can be found on the design-stage SAP report for that dwelling.

Too much air leakage leads to unnecessary heat loss (and consequently, higher CO2 emissions) and can lead to discomfort to the occupants through cold draughts and higher energy bills.

Air tightness testing of commercial buildings to meet Approved Document L2 requirements

An air leakage test is a test to determine the level of uncontrolled air flow through gaps or cracks in the fabric of a building. The result of the air leakage test is expressed as a quantity of air leakage (m3 per hour) per square metre of building envelope.

Air leakage testing is a requirement of Approved Document L2A. Each building tested must achieve a maximum air permeability rate of 10m3/h/m2. In order to comply with the carbon emission target it may be necessary to achieve a lower air permeability rate. The required air permeability rate for each building can be found on the design-stage SBEM report for that building.

Too much air leakage leads to unnecessary heat loss (and consequently, higher CO2 emissions) and can lead to discomfort to the occupants through cold draughts.

Air permeability testing of smoke shafts (for automatic opening vents)

We undertake smoke shaft integrity testing to confirm that the shaft is sufficiently air tight to allow the automatic opening ventilation to perform as required when it is fitted and commissioned.

The automatic-opening vents are a key part of the fire strategy for multi-storey buildings to extract smoke in the case of a fire. For the fans and vents to perform as required the shaft itself must be sufficiently air tight that they can create the pressure difference to draw smoke out of the building and protect the occupants and/or emergency services.

We work to air permeability targets set by the automatic-opening ventilation manufacturers that allows their equipment to operate effectively.

An air pressure test is conducted using a fan installed into the shaft. The intended openings of the shaft (i.e. extract point and openings for ventilation grilles on each floor) are sealed off for the test so that the integrity of the shaft itself can be determined. The test takes place in advance of the automatic-opening ventilation equipment being installed and commissioned.

Air flow measurement of domestic ventilation (extraction fan testing)

The requirement to build more highly insulated and air tight buildings means that it is increasingly more important to ensure buildings are not only adequately ventilated but the ventilation system is suitable, balanced & commissioned correctly to ensure it’s effective and efficient operation.

We are able to test extraction rates . This is not only a Building Regulations requirement but is also important to ensure the ventilation strategy is working as effectively as possible, this helps remove pollutants from the air incllucding odours, but also to control excess humidity, particularly in rooms such as bathrooms and kitchens.

Part F Building Regulations also requires standard intermittent extractor fans in new buildings (such as bathroom and kitchen extractors) to have their air flow rates measured on site and the results submitted to the building control body prior to completion.

Specific Test and Building Preparation Procedure

An air tightness test measures the extent of air leakage in a building. Improving air tightness of a building not only increases the comfort of the occupants, but can also enhance the building’s energy efficiency.

Gaps and cracks in the building that cause air leakage are often difficult to detect. They may be obscured by internal building finishes or external cladding. Thus the only satisfactory way to show that a building fabric is reasonably airtight is to detect and measure leakage paths within the building fabric.

Air tightness testing is central to the revised 2010 building regulations Scotland (section 6). Under the new regulations developers must test a min 20% of the dwellings on a site but this also depends on the amount of differing house types to ensure that a consistent sample is taken throughout the construction of the development. We would recommend all dwellings to be tested as there is a penalty for developments that are not tested

Pre Test Requirements

 The client needs to send our test engineers the drawings of the development and the design air permeability requirements;. An Air tightness testing can normally be undertaken in 30 – 60min. s. Wind speed should not exceed 6m/s;

Test engineers need to know the size of building envelope and requirements prior to coming to the site. Preparing the site to create an air-tight environment will involve:

  • Open and secure all internal doors;
  • Close all windows;
  • Switch off all mechanical ventilation systems;
  • Seal ventilation grids;
  • Close smoke vents;
  • Fill all drainage traps;
  • Switch off all range cookers/stoves 24 hours before testing (if applicable)

Building Envelope Calculations

We normally undertake the building envelope calculations before we arrive on site. The calculations are taken from the drawings, The building Envelope is the surface area of the thermal boundary of the building. This is then fed into our calculations when we are air testing the property.

Technically, it is everything that separates and protects indoors from out, which may include exterior walls and siding, roofing, foundations, windows and doors. These elements are exposed and need proper maintenance, materials, and construction to continue to function effectively. As these systems age it is normal to have problems such as roof leaks or cracked siding.

Air Permeability Envelope Area (m2)

It is defined as air leakage rate per hour per square metre of envelope area at the test reference pressure differential of 50 pascals (50 N/m2). The envelope area, or measured part of the building, is the total area of all floors, walls and ceilings bordering the internal volume that is the subject of the pressure test. This includes walls and floors below external ground level.

Overall internal dimensions are used to calculate this envelope area and no subtractions are made for the area of the junctions of internal walls, floors and ceilings with exterior walls, floors and ceilings.’

Air Change Rate Volume (m3)

Air change rates are often used as rules of thumb in ventilation design. However, they are seldom used as the actual basis of design or calculation. Residential ventilation rates are calculated based on area of the residence and number of occupants.

Cold Roof Construction Envelope Area Calculation

This is essential to calculate if the roof area is same as the ground floor area
A cold roof has the insulation at the horizontal ceiling level and usually a large void or space between the insulation and the pitched roof rafters.

Warm Roof Construction Envelope Area Calculation

The Envelope Area is defined as the boundary or barrier containing the overall internal ‘conditioned space’, and separating it from the external environment (or non-conditioned spaces and adjacent buildings), and is located on the warm side of the insulation.

A warm roof has the insulation running along the pitched roof rafters with an air barrier normally running parallel along the inside face of the insulation.

Building Preparation

  • Open and secure all internal doors;
  • Close all windows;
  • Switch off all mechanical ventilation systems;
  • Seal ventilation grids;
  • Close smoke vents;
  • Fill all drainage traps; check weather conditions (wind speed, temperature, barometric pressure);
  • Connect a fan (or fans) to an aperture in the building envelope (e.g. door);

Site Test Procedure

  • check weather conditions (wind speed, temperature, barometric pressure);
  • Connect a fan (or fans) to an aperture in the building envelope (e.g. door);
  • Set up testing equipment;
  • Record the air volume flow through the fan (this equals the air leaking through the building envelope);
  • Gradually increase the fan speed from 20-25 Pa to maximum of 55-60Pa;
  • Record pressure differences across the building at each fan speed;

Measuring air leakage

We will thereafter analyse the recorded air tightness test data and present the results to the client in a technical report. In the event of test failure we will make every effort to advise the client on site on appropriate mitigation measures. Our expert knowledge will help in pin pointing the areas of air leakage.

Measuring air leakage

 We will thereafter analyse the recorded air tightness test data and present the results to the client in a technical report. In the event of test failure we will make every effort to advise the client on site on appropriate mitigation measures. Our expert knowledge will help in pin pointing the areas of air leakage.

An airtight building has several positive impacts when combined with an appropriate ventilation system (whether natural, mechanical, or hybrid):

  • Lower heating bills due to less heat loss, with potentially smaller requirements for heating and cooling equipment capacities
  • Better performing ventilation system
  • Reduced chance of mold and rot because moisture is less likely to enter and become trapped in cavities
  • Fewer draughts and thus increased thermal comfort
  • From a single dwelling to the largest commercial development, we offer stress-free compliance to Part L Building Regulations and Scottish Building Standards.

We provide airtightness testing, consultancy, design reviews and support services on all buildings, both dwellings and non-dwellings in LOCATIONXXX.  Our engineers are based in LOCATIONXXX to provide a cost-effective, local service that complies with all relevant Building Standards.

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Good and Best Practice Standards

Standard good practice for air tightness testing in the UK is a maximum of 7 m3/hr/m2 and best practice is 3 m3/hr/m2 of air loss. Section 6 of The Scottish Building Regulation requires a maximum of 7 m3/hr/m2 of air loss at a pressure of 50 Pa. The Scottish regulations will be fully enforced for all dwellings by 1st October 2011 and this test is mandatory.

The Building Regulations approved document Part L1A 2010 now specify that any new dwellings are built airtight. The regulation is focused upon conservation of fuel and power usage. Part L1A states that any new dwellings are tested for air tightness in accordance with existing regulations.

Measuring Air Permeability on Building Envelopes (Dwellings) – To meet Building Regulations Technical Standard L1

the Air Tightness Testing & Measurement Association (ATTMA), provides the technical standard to be followed for the testing of dwellings in the UK as set out in Building Regulations and specifying documents around the world.

This Technical Standard sets out to provide detailed guidance and clarification of BS EN 13829:2001: “Thermal Performance of Buildings. Determination of air permeability of buildings. Fan pressurisation method” and ISO 9972:2015: “Thermal performance of buildings – Determination of permeability of buildings – Fan pressurization method”, in order to ensure consistency by testing companies.

Contact us today for more information about our Air Tightness Testing services or to book a no obligation quote, free of charge.

Building Regulation Requirements Part L 2010 (England and Wales)

If you are constructing a dwelling then Approved Document L1A states that, with few exceptions, you must perform an air pressure test. For developments of two or more dwellings an air leakage test should be carried out on the lower of: Three units of each dwelling type; or 50% of all instances of that dwelling type.

For developments where no more than two dwellings are constructed, it may be possible to avoid the need for any pressure testing by using an assumed value of 15m3/h/m2 within the DER/TER calculations. Your SAP assessor will be able to confirm if this is the case for your dwelling.

Measuring Air Permeability on Building Envelopes (Non-Dwellings) – To meet Building Regulations Technical Standard L2

The method for testing required by the building regulations is set out in ATTMA TSL1 (for dwellings) and ATTMA TSL2 (for non-dwellings).

Testing is required on all residential developments (this may be a sample of units) and non-dwellings. buildings with a useful floor area less than 500 m2 MAY be exempt. Where testing is not carried out, an assessed air permeability of 15 m3/h.m2 must be used in calculations.

Building Regulation Requirements Part L (England and Wales)

In January 2015, the ATTMA Scheme for Competent Air Tightness Testing Firms and their Testers (The ATTMA Scheme) was launched. It is an industry competence scheme authorised by the DCLG and specified in Approved Document L1 & L2 of the Building Regulations. It is based on the performance criteria and knowledge requirements set out in the suite of National Occupation Standards (NOS) and under the requirements of the Minimum Technical Competence (MTC) document.

There are three levels of tester:

  • Level 1: Testers can test dwellings and non-dwellings up to 4000m3 gross envelope volume when tested as a single entity, with a single fan
  • Level 2: Testers can test all buildings except large, complex and or high-rise buildings and or phased handover or zonal buildings unless part of a team managed by a Level 3 tester.
  • Level 3: Air tightness experts who can cover large, complex and or high-rise buildings and or phased handover or zonal compartmentalisation.

Part F2 (Northern Ireland)

F2 (Conservation of fuel and power in buildings other than dwellings) refers to all new buildings except dwellings.  All new buildings with a usable floor area of 500 m2 and over must be tested.

The maximum acceptable air permeability is 10 m3/ (h.m2).  There is also a requirement to demonstrate, via the SBEM (or equivalent) for non dwellings, that the BER for the proposed  building is less than or equal to the TER.

In many cases, building designers choose to achieve the required energy efficiency by reducing the air permeability. As a rule of thumb, reducing air permeability from 15 m3/(h.m2) to  5 m3/(h.m2) will reduce the BER by 30% in a naturally ventilated building.

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Section 6 of the Non-domestic Handbook (Scotland)

The Government has required changes to the Building Regulations, in relation to the Conservation of Fuel and Power. Four new Approved Documents have been produced for England and Wales, while a separate document, Section 6 relates to Scotland.

it is the intention of Section 6 of the Act, to ensure that effective measures for the conservation of fuel and power are incorporated in a building and contains energy conservation provisions for the building fabric and the building services.

Air Tightness Test Report

Air tightness reports are issued by accredited firms that carry out air permeability tests on buildings of different sizes or complexities. Temporary sealing of purpose built extraction will be done by the tester and noted, all test results will be noted and a shortened form report will be written which will include the findings of the test.

The report will be produced in accordance with company procedures, the relevant standards and the requirements of all relevant governing bodies

Test Results

We will interpret and evaluate test data results checking for accuracy of entries and correct number apply to any correction to data using standard equations and correction methodologies AF Acoustics will ensure the test result is expressed in accordance with the test standard requirements, identify any deviations from the relevant standards within the report and check air tightness against target value ensure report correctly identifies tester, the customer, the building and its address. Where applicable, we will identify pass or failure of your building and provide recommendations for any remedial action or improvement to the building if any further testing is required

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Air Tightness Checklist – Dwelling

 Before we arrive on site please ensure you have sent us the design air permeability figure and been through the checklist below, this will greatly increase your chances of passing first time.

Air Leakage Pathway Checklist – Check will be done for visible leaks in the following places:

  • Windows: Check the seal beneath the sills and around the frames.
  • Doors: Check the seal around all external door surrounds (especially French doors).
  • Drainage traps: Check they are filled with water .
  • Skirting and coving: Check above and below all skirting and coving, sealing where necessary.
  • Meter Boxes: Check all external supplies are sealed appropriately.
  • Light Fittings: Check the seal around all light fittings and switches.
  • Radiators / Fans / Heaters: Check the seal around all pipes and wires.
  • Boilers: Check the seal around the boiler supply and flue.
  • Extractor Fans: Check around the edge of the extracts, only the front of the grill can be sealed.
  • Cooker Hoods: Check the seals around all penetrations.
  • Soil pipes: Check the seal around all soil pipes and sink waste pipes especially those boxed in or behind kitchen cabinets.
  • Bath Panels: Check all pipes behind bath panels are sealed properly.
  • Hot water tank: Check the seal around all supply pipes.
  • MVHR: Check seal around all terminals.
  • Chimneys: Open fireplaces must be sealed prior to our arrival.
  • Air Bricks: Does the dwelling have air bricks these should be sealed for the test.
  • Tumble drier extracts: Check the seal around the extract.

Please note only the controllable airflow pathways listed below can be temporarily sealed during the test, all the non-controllable leakage pathways above must be permanently sealed.

We Provide Temporary Sealing – the following should be temporarily sealed during the test:

  • Trickle Vents: Should be closed.
  • Extractor Fans / MVHR terminals: All extracts should be temporarily sealed (Please ensure these are off before sealing).
  • Cooker Hoods: Should be sealed from the outside or inside.
  • Chimneys Flues and Air Bricks: Should be temporarily sealed.

Our Clients


Air Tightness Testing FAQ’s

At AF Acoustics, we will endeavour to help you identify air leakage/infiltration paths.

There are a number of methods we employ to do this, including:

  • Smoke pens– smoke can be used to identify where air is moving when the building is being tested
  • Depressurise the building –By depressurising the building air is drawn in and can be felt at the air leakage points, our experience will be able to pin point these locations easily, whist the building is being depressurised, we will be able to show you around and will point you to the areas that have air leakage. You will usually be able to feel the air blowing on your skin when you are close to leakage areas, using the smoke pens these leakage points can be seen as the smoke changes from a steady flow to a turbulent flow.
  • Smoke testing – if the air paths are less direct it may be necessary to use smoke puffers and/or fill the building with smoke and pressurise/depressurise again. Points of air ingress and egress should be identifiable.
  • Thermography – if it is still not apparent where air is escaping, infra-red cameras can be used to identify hot spots and cold spots on the internal and external surfaces of the building. This requires a temperature difference between the inside and outside.

In the vast majority of cases the first two methods are sufficient to identify the most significant air leakage paths along with our expertise we will be able to point our the problem areas should they arise. The air leakage areas will have to permanently sealed and the test repeated to reduce the air permeability of the building. Where problems are larger and sealing cannot be addressed on the day, the building may need to be re-tested at a later date.

A test certificate from The Air Tightness Testing and Measurement Association (ATTMA)

Testing procedure is to be carried out to comply with TSL1 for domestic or TSL2 for commercial, The test certificate should include sufficient information to describe the building tested e.g. location, type and size (the envelope area is an important component in calculating the air permeability and must be accurate) plus the design air permeability as well as the actual result. In addition, if the result has been achieved with temporary sealing outside that allowed in ATTMA Technical Standards, TSL1 for domestic TSL2 for comercial, this should be detailed in the certificate. Testing procedure should be representative of the actual building performance.

An indicative result is available at the time of testing. Certificates can usually be issued within a day of testing.
If needed you can request all calculations including pre and post environmental measurements, individual static pressures, envelope area breakdown, flow readings and calibration certificates can be provided at no extra charge

Air permeability is essentially a function of the pressure difference between the inside and outside of the building and air flow rate through the fan(s) to produce that pressure difference. This is averaged out over the envelope area. The result takes account of environmental conditions.

The final air permeability at 50 Pa is based on a logarithmic graph of pressure difference and flow rate, the graph should:

  • Have at least 7 points (ideally 10 or more)
  • The highest figure should be at least 35 Pa but preferably would be in excess of 50 Pa and ideally higher than 60 Pa
  • The lowest figure should be at least 10 Pa or 5 times the ‘static pressure’ (the pressure difference between inside and outside without the fans) – which in itself MUST be less than 5 Pa to limit uncertainty
  • The readings should be no more than 10 Pa apart
  • The correlation of the graph should be at least 99%
  • The gradient of the graph (n) should be between 0.5 and 1.0

These are aspects that the BCB should be checking carefully if choosing to accept air permeability results from non-accredited testing bodies

Most air tests to domestic units and simple commercial units are carried out in 30 – 60 minutes which may be extended if the test fails and leakage paths are investigated with smoke. Re-tests can be carried out at no extra charge if completed within the allowed time.

On larger commercial  units, which require 1 large air test fan, air tests usually take 1 hour if all temporary sealing has been completed prior to starting the air test.

If complicated or very large buildings are being air tested with multiple fan units, allow up to 4 hours for the test and longer if smoke investigations are required.

The envelope area is the total internal surface area of the conditioned areas of the building ie the sum of floor area, wall areas and ceiling area (of the thermal barrier within the building).

This should be calculated or verified by the air tightness test body as the accuracy of the envelope area has a significant impact on the final air permeability result.

The building inspector should check this is being done correctly and/or approximately verify the area.

Generally, this involves mounting a door profile, incorporating one or more electrical fans, into an external door opening(s). Depending on their orientation, the fans can be used to pressurise or depressurise the building. The resulting difference between the external and internal pressure can be used to calculate the permeability of the building envelope (given that the envelope area is known).

This permeability is an indicator of how well sealed the building is, and whether there are openings in the envelope. Generally, 10 differential pressure points are taken at different fan flows to establish an accurate result for the building. Our certified specialised software is used to establish an accurate Air Tightness Test result.

Our experts at AF Acoustics will provide a simple checklist for building preparation, which includes the following:

  • The building should be ‘completed’
  • All external doors and windows closed
  • All internal doors wedged open
  • All fire dampers, ventilation louvres and trickle vents closed but not sealed
  • Mechanical ventilation turned off with inlet/outlet grilles sealed
  • All combustion appliances switched off
  • Drainage traps must contain water

This needs to go to site. The preparation would ideally be undertaken by the contractor in advance of the test body arriving on site to maximise the testing time in a day.

For dwellings it may also be necessary to agree the test programme with the building inspector before arriving on site.

Where possible, it is helpful to accurately calculate the envelope area and confirm the fan installation arrangements based on architectural drawings before coming to site

How many plots being tested, Location, Plans and elevation drawings, cross sections if possible. Air permeability target, and a brief description of the property e.g does it have fireplace or a loft space

For dwellings, sufficient information is required to identify the different dwelling types and the number of each eg General Arrangement/Site Plan and Schedule (including other important details such as variation in storey height or construction method).

For buildings other than dwellings, the approximate envelope area is the key factor for quoting. It is required to establish the necessary fan arrangement. This affects the time on site and potentially the number of people. This can be calculated from drawings – floor plans AND elevations.

The testing body may also need to identify the potential aperture(s) into which test equipment is to be installed, in some circumstances this may require additional time on site, extra people or bespoke templates to be made.

Approved Document L states that Building Control can accept evidence from BINDT or ATTMA Registered testers. However, the BINDT scheme was closed down at the end of 2014, subsequent to the last revision of Approved Document L. So the ATTMA scheme is the only valid registration scheme referred to in Approved Document L.

The ATTMA scheme is based on the performance criteria and knowledge requirements set out in the suite of National Occupation Standards (NOS) and under the requirements of the Minimum Technical Competence (MTC) document.

There are three Levels of tester:

Level 1: Testers can test dwellings and non-dwellings up to 4000m3 gross envelope volume when tested as a single entity with a single fan.

Level 2: Testers can test all buildings except large, complex of high-rise buildings and or phased handover or zonal buildings unless part of a team managed by a Level 3 tester.

Level 3: Air tightness experts who can cover large, complex and or high-rise buildings and or phased handover or zonal compartmentalisation.

Common leakage sites are:

Around all pipe works within kitchen and bathrooms

  • Junction lower floor / vertical wall
  • Junction window sill / vertical wall
  • Junction window lintel / vertical wall
  • Junction window reveal / vertical wall (horizontal view)
  • Vertical wall (Cross section)
  • Perforation vertical wall
  • Junction top floor / vertical wall
  • Penetration of top floor
  • Junction French window / vertical wall
  • Junction inclined roof / vertical wall
  • Penetration inclined roof
  • Junction inclined roof / roof ridge
  • Junction inclined roof / window
  • Junction rolling blind / vertical wall
  • Junction intermediate floor / vertical wall
  • Junction exterior door lintel / vertical wall
  • Junction exterior door sill / sill
  • Penetration lower floor / crawlspace or basement
  • Junction service shaft / access door
  • Junction internal wall / intermediate floor
  • Holes in the walls
  • Radiator pipework penetrations in floors and walls

Sanitary pipes penetrating walls and floors

Our team of experts can support you through the following

  • Tender Stage – Estimate pricing structures and general advice
  • Design Stage – Desktop or site-based design team meetings
  • During Construction – Ongoing audits of the building, Building Control liaison, sample testing of completed areas of ‘comfort testing’ prior to final testing
  • Upon completion – preparation advice, shortly prior to the air testing, final testing and leakage diagnosis

Additional AF Acoustics services – Including acoustic testing, sound insulation testing services and building control

Employing the services of a reputable and accredited Air Tightness Testing Consultant, such as AF Acoustics, can help to identify and remedy potential problem details in a building design prior to, and during, construction.

Air Tightness Testing and Measurement Association (ATTMA) is approved by DCLG and are listed in the Building Regulations as an authorised Competent Persons Scheme for air tightness testing.

As an ATTMA registered company, AF Acoustics is independently certified by ATTMA with a scope covering air tightness testing to the ATTMA Technical Standards (TSL1 & TSL2) and BS EN: 13829 (2001), demonstrating knowledge and understanding, which enables us to test both commercial and domestic developments in accordance with relevant building regulations.

Part L sets the energy efficiency standards required by the Building Regulations. It controls:

  • The insulation values of building elements
  • The allowable area of windows, doors and other openings
  • Air permeability of the structure
  • The heating efficiency of boilers
  • The insulation and controls for heating appliances and systems together with hot water storage and lighting efficiency

It also sets out the requirements for SAP (Standard Assessment Procedure) Calculations and Carbon Emission Targets for dwellings. In addition to insulation requirements and limitations of openings of the building fabric, Part L also considers:

  • Solar heating and heat gains to structures
  • Heating, mechanical ventilation and air conditioning systems
  • Lighting efficiency
  • Space heating controls
  • Air permeability
  • Solar emission
  • The certification, testing and commissioning of heating and ventilation systems
  • Requirements for energy meters

Building Regulations are administered separately in England, Scotland and Wales.

The objective is to measure the volume of conditioned air escaping through the building envelope via uncontrolled ventilation at an induced pressure difference of 50 Pa.

The following basic steps are typical:

  • Check site preparation / Prepare site – including temporary sealing
  • Calculate the envelope area if not done previously
  • Explain the process to relevant staff and sub-contractors working on or near the building
  • Take environmental condition measurements – wind speed, temperatures, barometric pressures
  • Install template(s) into suitable aperture(s)
  • Install fan(s) into template(s)
  • Connect monitoring equipment
  • Check the static pressure
  • Take multiple pressure difference readings and record fan flow rate(s) – allowing sufficient time for the pressure readings to stabilise
  • Check the static pressure
  • Process the readings through appropriate software – check that readings fulfil the requirements of the standard
  • If the building fails, attempt to identify/quantify air leakage/infiltration paths
  • Disconnect measurement equipment
  • Remove the fan(s)
  • Remove the template(s)

Yes for buildings other than dwellings (ie industrial units, warehouses, schools, hospitals, residential care homes, hotels, offices, retail units, etc)

But for dwellings (flats and houses), there isn’t really a need for testing.

For buildings other than dwellings developments, where testing is required, each individual building unit will need to be tested i.e. if the ‘unit’ is not connected to adjoining units and intended to be occupied/operated separately.

For dwellings a sampling rate applies depending on:

  • Dwelling types
  • Adoption of ‘Accredited Construction Details’

All new buildings, dwellings and ‘large’. But there are some exceptions where buildings may be able to assume a poorer air permeability rather than undertake a test. The exceptions are explained below:

  • Small developments (1 or 2 houses) may avoid the need to test by accepting an assumed poor value for air permeability of 15m³/(h.m²) @ 50 Pa but this may add costs to other aspects of the building specification in order that the building meets overall targets for emissions. Alternatively it may be possible to re-use existing test evidence where building designs have been repeated within 12 months of conducting the original test.
  • ‘Small’ commercial buildings (with a floor area less than 500m2) may avoid the need to test by accepting an assumed poor value for air permeability (15m³/(h.m²) @ 50 Pa) but this may add costs to other aspects of the building specification in order that the building meets overall targets for emissions.

No. Air tightness testing applies to:

  • All new dwellings (based on a sampling rate)
  • All new buildings other than dwellings
  • ‘Large’ extensions to buildings other than dwellings

Air permeability is an important factor in assessing the overall carbon emission of a building via the appropriate calculation methodology:

Standard Assessment Procedure (SAP) for dwellings under 450m² floor area – accredited software has been developed to make calculation easier.

If you are building a new domestic property or commercial property of a certain size, it will need to undergo air tightness testing. This assesses the building for ‘air permeability’, checking for air leakage through gaps, holes and other areas. The Government has SAP (Standard Assessment Procedures) in place for air tightness testing, setting standards buildings must comply with to be energy efficient.

Residential properties and those over a certain size (500 m2) must undergo air tightness testing. Small developments of one or two properties must have one of the buildings undergo air tightness testing. However, if the properties are of different construction then both must be tested separately.

With larger developments, a proportion of the buildings must be tested, depending on the size and construction of the properties. There are exceptions to this and if you have any questions regarding how many need to be tested or about the exceptions, please contact us and we will be happy to help.

In a property where air tightness is below the recommended standard, the following problems can occur:

  • unwanted heat loss
  • discomfort for occupants (cold homes)
  • increased heating bills (to counter the cold)
  • greater CO² emissions (as result of additional heating required)
  • negative impact on the wood, masonry, or metal used to construct the property

Airtightness primarily focuses on the elimination of all unintended gaps and cracks on the external envelope of the building.  Airtightness is an essential part of creating a healthy, comfortable, energy-efficient living environment.

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Luke Hickman

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