Introduction to Air Tightness Testing

Air permeability/air leakage/air tightness is the uncontrolled flow of air in and out of the building through the gaps, cracks and envelopes. The process of measuring air permeability/air leakage/air tightness in a building is called as air testing. Air testing is important as it helps in reducing the large portion of the energy getting wasted due to the uncontrolled flow of air in buildings.

According to the Building Regulations in UK, It is essential to keep up to the standards in order to reduce the carbon emission or carbon foot print in newly constructed building or existing buildings. It improves the atmosphere of the building area and protects the overall health conditions of residents in buildings. Through Air tightness testing the leakage of the air in the fabric of buildings is quantified. It is like medium to check the wastage of energy resulting in increasing the loads for space heating / cooling due to the uncontrolled flow of air in gaps, cracks and envelopes in the building.

Air Tightness Testing: Ensuring Compliance and Efficiency

Pressure testing is an extremely crucial step that can help ensure that your buildings meet the UK Building Regulations properly; and among these regulations, the most important one is Part L1.

This mandatory test that needs to be conducted by every building owner tells us exactly how much air escapes and infiltrates your structure as a result of gaps and cracks. The chief target behind such a test is to effectively promote your building's efficiency and comfort levels.

Why is Air Tightness Testing a must for every property owner?

Air tightness testing is highly important for newly built structures, it can help you gain your testing certificates. If you fail to meet these Part L1 standards, it means you will have to face refusals, serious inspections and even long delays in the commissioning process and other extra expenses.

However, if you are carrying out air tightness tests, it can help you with successful and assured outcomes. These tests aid in revealing whether your building performs under the Part L legal standards or requirements. All these reasons make testing necessary.

  • Energy efficiency With unchecked air infiltration rates, a home will need more energy to heat during winter and cool during the summer. By identifying leakage points, you, as a developer can easily resolve these problems, thereby saving a good amount of energy and even raising the thermal performance of your developments and structures. This not only helps in shrinking the running costs but also helps the building maintain a low carbon footprint and stay on friendly terms with nature.
  • Drastic improvement in air quality Any air leaks can allow different sorts of allergens, pollutants and humidity into a building, thereby bringing on health problems such as respiratory diseases and more. with proper sealing, you can improve the air quality and inhibit mould growth too, thus contributing to a healthier living and working environment for your loved ones or tenants.
  • Comfort and Durability The air leakage that is caused by drafts can even cause temperature levels to be erratic in certain localities. Proper testing will enable you to avoid such problems and maintain a constant, uniform temperature in every room of a house or structure. Moreover, by reducing the amount of air that gets into your building, you can also help to protect its structure from moisture-related damages or issues.

How Air Leakage Testing Works?

An air leakage testing procedure is all about getting your home properly tested for any leaks; this can be done by applying pressurisation or depressurization techniques by using fan sets at your building's external doorways.

Through this highly controlled process, it's possible to test the amount of airflow that needs to be generated to effectively maintain a certain pressure difference. This will tell you exactly how much leakage is possible in your building. The main points in the process involve:

  • Check if all the external doors and windows are closed
  • Sealing off ventilation and extraction points is also an equally important point to keep in mind
  • You will have to use a blower door fan to test the place for leakage

Another fact to know is that test results are expressed as air tightness and are measured in cubic metres of air leakage per hour per square metre. To meet these standards and requirements, our results need to meet or stay below the well-known Design Air Permeability (DAP) standards.

Key Advantages for Developers and Building Users

  • Cost Effective: Thoroughly sealed buildings not only help in cutting down energy costs but also increase your property's value because of its excellence in the areas of environment compatibility and comfort.
  • Simply Constructed Projects: Although a pre-emptive approach in identifying air leakages may require some extra effort in the early stages, it will eventually end up saving you time and money in the long run without fail.
  • Helping the Environment: With fewer chances for air leakage, the direct energy demand is reduced too. This is particularly in line with the global sustainable development targets and thus, you can ensure that fewer greenhouse gases are emitted by your building.

If you want air tightness testing services in Hampshire, Wiltshire and Dorset, do contact us or thoroughly check out our website to know more.

Frequently Asked Questions

Pressure testing, air-tightness testing, or blower door testing, is a test that determines the amount of uncontrolled air infiltration through the external envelope of a building. The test assists in the identification of a property that complies with Part L of the Building Regulations.

It examines gaps, cracks or construction weak points where air can escape or enter without being a part of the designed ventilation system. This is aimed at enhancing energy efficiency by determining where heat can be lost, so that developers, builders and homeowners can seal their buildings properly and make them work as they should.

A good air-tightness result depends on the type of building and its design targets. For new residential properties, the Building Regulations typically require an air permeability rate of 10 m³/h·m² or less at 50 Pascals. Nevertheless, most homes that are well constructed would be targeting results between 3 and 5.

The lower the values, the more airtight the building is, and the more energy-efficient it is, and the less heat it loses. In Passivhaus or high-performance houses, the goal is usually less than 1. An effective outcome will mean reduced heating costs, increased comfort and energy performance standards being met during the process of approving the building.

To test air-tightness, a specialist uses a calibrated blower door system. The equipment is fitted into an external doorway to pressurise or depressurise the building. Sensors measure the airflow required to maintain pressure, revealing how much air escapes through gaps and cracks.

Before testing, all windows and doors are closed, and vents are sealed where necessary. The results provide an air permeability figure, which is used to check compliance with Part L of the Building Regulations. The test helps identify weak points in the building fabric and supports energy efficiency improvements if needed.

An air-tightness test typically takes 1 to 2 hours for a standard residential property. The duration depends on the size of the building, its layout, and how well-prepared it is for testing. The process includes setting up equipment, sealing vents and openings, and running a series of measurements at different pressure levels.

If issues are found, extra time may be needed for remedial advice or a follow-up test. Once complete, results are calculated on-site and a certificate is usually issued the same day or the next morning. Larger commercial buildings may require additional time.

Yes, air tightness testing is mandatory for most new buildings in the UK. Under Part L of the Building Regulations, developers must prove that the building meets required standards for air permeability. This applies to new residential properties and many commercial buildings.

Without a valid test and supporting certificate, building control will not issue final approval. The test confirms that the building is energy efficient and that heat loss through leaks is within acceptable limits. It is also a key requirement for energy performance calculations and achieving SAP or EPC ratings.

Air tightness testing is typically carried out near the completion stage of construction. It must be done after windows, doors, and finishes are in place, but before final decoration. This allows for accurate measurement of the building’s performance and gives time to fix any leaks if the initial test fails.

For new homes, the test is usually booked once all mechanical systems and service penetrations are sealed. Developers must ensure the test is completed before applying for a completion certificate. Testing is also required in many renovation or conversion projects involving multiple dwellings.

You need an air tightness test to demonstrate that your building meets energy efficiency and regulatory standards. It checks whether unwanted air is leaking through the structure, which can cause heat loss, higher energy bills, and discomfort.

The test is required under Part L of the Building Regulations for most new and refurbished properties. It is also essential for calculating your building’s energy performance rating. Failing to carry out the test could delay project approval. It helps builders find and fix problems before handover, ensuring better quality, lower emissions, and improved living conditions.

To prepare for an air tightness test, ensure the building is as complete as possible. Close all windows and doors. Seal gaps around service pipes, cables, loft hatches, and ventilation ducts. Check that all insulation is properly fitted, and skirting boards or wall junctions are sealed.

Cover or block off extract fans and trickle vents. The goal is to test the actual fabric of the building, so only intended ventilation should remain open. Good preparation not only ensures a more accurate result but also increases the chance of passing on the first attempt.

You can book premium air-tightness testing services with Southern Assessors. They provide UKAS-accredited testing across Hampshire, Wiltshire, and Dorset for both residential and commercial buildings. Their team handles every step, from test preparation and on-site measurement to reporting and compliance certification.

Whether you are a developer, contractor, or private homeowner, Southern Assessors helps you meet Part L regulations efficiently. They also offer guidance on improving results and retesting where required. With fast reporting, expert engineers, and reliable service, they are a trusted name for air tightness testing in the region.

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