Today, around three in four buildings across the EU are classed as energy inefficient, yet around 85-95% of these buildings will still be in use come 2050, the target year for achieving net zero in the EU.
It is a looming and significant problem that must be overcome if this target is to be achieved. Buildings are responsible for about 40% of the EU’s total energy consumption, and 36% of its total greenhouse gas emissions from energy.
What is airtightness?
One way to improve the environmental and all-round performance of buildings is to invest in improving airtightness.
Airtightness, in simple terms, is defined as the resistance to inward or outward air leakage through leakage points in the building envelope – such leakage points are unintentional as opposed to ventilation systems which facilitate fresh air circulation in a controlled and energy efficient way.
There are many factors which can cause air leakage. These include poor build design, poor workmanship, lack of maintenance or use of inappropriate materials.
Achieving optimal airtightness requires the elimination of all unintended gaps and cracks in the building envelope, which are commonly found where two materials join together (for instance, a window and a wall).
How is airtightness tested?
There are several ways of testing a building’s airtightness levels. Most common is blower door testing, which is sometimes conducted in tandem with thermal cameras.
Blower door testing: This was first standardized by ISO 9972 and has been applied for around two decades in two major ways – the examination of a current situation (I.e., after moving into a building/current state of old buildings), and examination of a building envelope during the construction phase. The test is carried out using a fan, measuring sensors and connected software to register movements of wind and identify any leaking in the building fabric.
Thermal camera testing: In some instances, a thermal imaging camera can help locate the leaks that the blower door test has exposed. These cameras are able to detect patterns that occur when cold air is coming through a leak in the building envelope, air which runs along a surface and cools it down.
Although there are currently no set EU regulations relating to airtightness, most individual EU countries have minimum standards that need to be met.
Airtightness and building performance
If a building fulfills airtightness regulations, then several HSE (health, safety and environmental) advantages are likely to be realized. Indeed, airtightness is a key part of creating a healthy and energy efficient building.
Among the key benefits are:
- Reduced heat loss – 50% of all heat losses occur through the external envelope of a building. Airtight buildings incur less heat loss and thus enjoy improved energy efficiency due to reduced requirements for heating and cooling.
- Enhanced ventilation performance – ventilation is vital in maintaining high indoor air quality (IAQ), an essential part of how buildings can promote health and wellbeing.
- Healthier insulation – less chance of mold and rot building up as moisture penetration is reduced in airtight buildings.
- Greater thermal comfort – airtight buildings are less susceptible to draughts.
Buildings which fail to meet airtightness standards risk comprising on critical performance areas such as energy efficiency, indoor air quality and thermal comfort, as well as deterioration of building materials.
The role of membranes and high-performance tapes
Airtightness can be achieved by installing membranes to provide buildings with protection against unforeseen leakage.
Typically sold in rolls between one and two meters wide, membranes help to control moisture flow both inside and outside the building envelope. There are thus two major varieties of membrane – breathable and non-breathable.
Breathable membranes allow vapor to exit the building while preventing liquid water from entering from the outside, similar to how used for winter sports clothing such as ski jackets. They protect thermal insulation layers and woodwork from humidity and make structures airtight.
Non-breathable membranes are designed for the inner side of the envelope – the interior of the building. These are much simpler solutions, commonly made out of plastic films, that prevent moisture from penetrating into the insulation.
High-performance tapes are needed to apply membranes to walls, roofs, windows and other interior and external surface materials found in the building envelope. They eliminate gaps in the construction to avoid ingress of air and moisture.
Furthermore, they connect (or splice) membrane sheets together and help to navigate awkward structures such as chimneys, skylights, and ventilation installations, ensuring the membrane is tightly applied to the surface (membrane penetrations). Tapes are also used for structure-to-structure applications (membrane connections), connecting membranes to surfaces such as masonry, concrete, plaster, wood, metal, plastics and more.
