Why An Air Tightness Test Is Essential For Energy Efficiency In Your Home

20 February 2023 | Construction, General

What is an air tightness test?

Air pressure testing, or air tightness testing, is a method used to assess the level of uncontrolled air escape through crevices and openings within a building. These gaps are often too small to be detected visually, which is why a pressure test is conducted to measure the extent of air leakage across the entire structure.

What is a good air tightness test result UK?

In the United Kingdom, there are specific guidelines for Air Permeability, with the maximum limit set at 10 m3h-1m-2. However, for new homes, it is recommended to maintain an Air Permeability of 5 m3h-1m-2 or less.

Usually, if the reading falls between 3 to 5 m3h-1m-2, building control and your SAP assessor would consider it acceptable.

If the reading goes below 3 m3h-1m-2, it may indicate that the building is too tightly sealed, which can lead to problems such as mould and condensation. In such a scenario, it is essential to have an adequate ventilation system in place.

Is it worth getting an air tightness test?

Yes, it is worth getting an air tightness test as it can significantly impact the energy efficiency of your dwelling.

Air leakage through uncontrolled gaps and cracks in the building fabric can result in significant heat loss, leading to higher energy consumption and costs for heating and cooling.

An air tightness test helps to identify these gaps and leaks, enabling you to take steps to address them and improve the energy performance of your building. Additionally, a more energy-efficient building can lead to a more comfortable living environment, improved indoor air quality, and potentially increased resale value.

How do you test air tightness?

To test air tightness, passive ventilation in the building is temporarily sealed, and all doors are fixed open internally.

The external envelope and all its openings are also closed. Air testers then install blower door testing equipment to an external opening, which pressurizes the building and measures the overpressure difference.

This overpressure forces air to flow in through any gaps or cracks in the building, helping to identify areas that require fixing. By measuring the rate of air leakage at a standard pressure, air testers can determine the air tightness of the building.

How do I know if my house is airtight?

You can inspect various areas of your house, both inside and outside, for cracks and gaps that could cause air leaks.

Focus on areas where two different building materials meet, such as all exterior corners, outdoor water faucets, and where the foundation and the bottom of exterior brick or siding meet.

Additionally, inspect around electrical outlets, switch plates, door and window frames, electrical and gas service entrances, baseboards, weather stripping around doors, fireplace dampers, attic hatches, wall- or window-mounted air conditioners, cable TV and phone lines, where dryer vents pass through walls, vents, and fans.

Look for gaps around pipes and wires, foundation seals, and mail slots. You can also check windows and doors for air leaks by seeing if you can rattle them or if you can see daylight around the frame.

Additionally, you may consider replacing old windows and doors with newer, high-performance ones or installing low-cost plastic sheets over the windows.

Do all new builds need an air test?

According to building regulations, new build residential properties and those over a certain size (500 m2) must undergo air tightness testing before being sold.

However, small developments of one or two properties that are exactly the same must have only one of the buildings undergo air tightness testing, and the larger developments must test a proportion of the buildings, depending on their size and construction.

Are homes with air tightness healthy?

The question of whether air tight homes are healthy is a complex one.

While poor filtration, bad ventilation, homeowner behavior, and off-gassing from household products and finishes can cause indoor air to contain pollutants, there is a recent push by homebuilders to make indoor air quality healthier than outdoor air.

This is made possible with improved building codes, increased awareness, designing for health, product innovations, and transparency. There is a growing trend toward homes becoming clean-air sanctuaries and safe zones from high levels of outdoor air pollution.

Therefore, it is possible for homes with air tightness to be healthy with the appropriate measures in place to maintain good indoor air quality.

How long does an air tightness test take?

The duration of an air tightness test depends on various factors such as the size of the building and the level of air leakage. On average, it should take under two hours, and if successful, you should receive a test score either the same or following day.

How do you prepare for an air test?

To prepare for an air tightness test, you should ensure that all windows and doors are fully fitted and well-sealed, and access doors, including internal garage doors, are airtight and cannot be temporarily sealed in advance of the test.

Bathrooms should be fully fitted and complete with air leakage paths fully sealed before fitting bath panels, extractors, vanity unit covers, and any boxing in. Skirting boards should be sealed above and below, and lights, power outlets, and appliances should be fitted and well-sealed.

Kitchens should be fully completed, with appliances, extractor fans, and boxing-in all in place, and cavities behind cupboards should be sealed.

Finally, loft hatches and storage doors leading to roof voids must be fitted with draft excluders, and rad pipes and manifolds should be double-checked to ensure they are sealed.

What is a good EPC score?

A good EPC score will vary depending on your circumstances. The EPC rating is graded between A and G, with A being the highest level of efficiency and G being the lowest. In most homes, an energy performance certificate rating of D is the most common.

However, for buy-to-let landlords, a minimum E rating is required before taking on new tenants or renewing existing contracts. Ultimately, the higher the EPC rating, the more energy-efficient your property is considered to be.

EPCs also provide valuable recommendations on measures that can be taken to improve the energy efficiency of your home, as well as the estimated costs associated with these measures.

What will fail an EPC?

Technically, you cannot “fail” an EPC assessment. However, if your home does not achieve a minimum energy performance rating of E, it cannot be let out to tenants.

Additionally, properties with an EPC rating of F or G are not eligible for buy-to-let mortgages, which may affect the ability to sell the property.

While some exemptions do apply, such as for period properties or holiday homes, these exceptions must be registered by the landlord. It is important to note that an EPC does not represent a pass or fail, but rather an assessment of the energy performance of the property and recommendations for improving it.


  • Danielle Stone

    She has been writing professionally for 8 years, with articles published in various print and online publications. She is an avid researcher and strives to bring her readers the most up-to-date information and insights on the topics she covers. Danielle is also an expert on home renovation, interior design and construction, and she loves helping homeowners turn their dreams into realities. When she’s not writing or editing, Danielle enjoys spending time with her family, gardening and exploring nature.

    View all posts