What is air tightness and how can we solve it?

What is air tightness?

So what air tightness? Air tightness, or air leakage, is a measure of the amount of unwanted air that leaks in or out of a building through gaps and cracks in the walls, floors, and ceilings.

If your home has a room that’s always cold in the winter, even with the heating on, or if you’ve ever sat in a restaurant and felt a chilly draught around your ankles, there’s a high probability air is being drawn in and is escaping!

In the UK, there are two measures for air tightness:
1. through air permeability, or
2. through air changes.

Both measures assess the volume of air leaking in or out of a building per hour, with air permeability comparing the volume of lost air to the square metres of the building fabric (walls, floor and ceilings), and air changes comparing the volume of lost air to the total volume of the air within the building envelope.

Building Regulations and air tightness testing

UK Building Regulations measure air tightness using air permeability, while international standards such as Passivhaus and the International Energy Conservation Code (IECC) use air changes. If you’d like to read more about this, please click here to view Passivhaus Trust’s air tightness guide.

Pre-2022, air tightness has been part of UK Building Regulations but was only required for specific types and/or sizes of buildings. With the push for Net Zero and improving UK housing stock, from June 2022 air tightness testing became a requirement in all new build dwellings and most commercial buildings.

Reducing energy usage by eliminating air leakages

Similarly to having the air conditioning on in the car but leaving the windows open, if a building has a lot of leakage points through the walls, floors or roof, heating or cooling systems have to work overtime to keep the building at a constant temperature.

This study published by the Grantham Institute at Imperial College London reports that an average UK home looses heat three times faster than a home in Continental Europe.

So, how can we solve this?

The key is to consider ventilation and air movement during the design and build process and invest just as much time in this as you would do choosing windows, insulation and internal finish options!

By building active ventilation into your new home or a new building and ensuring the main envelope is leak-free and air tight, there are huge energy savings to be made for all new or retrofit builds.

This can either be uncontrolled or controlled, with the most basic options such as trickle vents right the way through to mechanical ventilation with heat recovery (MVHR) systems. All types of intentional ventilation are a step in the right direction, and different systems interact with air tightness in different ways – the most energy-efficient and air tight structures require systems to ensure the healthiest internal environment that can be offered.

With modern insulation, glazing and a full ventilation system, a typical home could see energy reductions of around 40% if air leakage is reduced from Building Regulations standards down to Passivhaus levels.

Traditional methods of sealing a building are often extremely time-consuming and labour-intensive, and the manual process involves the installation of tapes, membranes and sealants. This is why Passivhaus builds often cost more! AeroBarrier is the only ‘plug-and-play’ automatised system in the UK which guarantees you a specific level of air tightness through a measured and intelligent sealing process – reducing your energy usage while saving you time and money during your build and in the future.

How does AeroBarrier work?

In just four hours and four simple steps, the AeroBarrier system finds and eliminates building air leakages and draughts… Please click here to discover how.