Airtightness or air tightness is…
Airtightness is the property of a building that prevents air flows through its structure or fabric, i.e. by infiltration – from the outside to the inside, or by leakage – from the inside to the outside. Airtightness is sometimes confused with wind protection: the purpose of wind protection is to prevent air movements within the fabric of a building, so that its thermal insulation
properties can be retained even when subject to wind forces.
Wind protection is installed to ensure that the thermal insulation can function properly. The demands made on wind protection depend on the properties of the insulating materials used.
The most important reasons for making a building as airtight as possible are to reduce the use of energy in the form of heat, to provide comfort for the residents or users, to provide the right conditions for good ventilation and to avoid moisture problems.
Good airtightness also contributes to preventing outdoor air that might be polluted, for example, by pollen or particles, from making its way into the building. Structural elements between residential units should also be made airtight to reduce the risk of polluted air or smells spreading between them or into other zones. Good airtightness between foundations and the ground underneath help prevent radon from entering other parts of the building. Good airtightness also helps to reduce the transmission of airborne noise, for example, traffic noise.
Airtightness and mechanical ventilation!
An airtight building must have an efficient ventilation system to ensure that a good air quality level is always achieved, irrespective of the weather situation. The simplest way to do this is to install mechanical ventilation, i.e. a system with a fan.
If so-called natural ventilation is used, this presumes that either the building is not airtight or that more or less extensive measures are taken to introduce air into the building so that a sufficient air change rate can be achieved.
In old buildings with natural ventilation a large proportion of the air will enter the building via gaps and holes in the building envelope. If special sealing measures are taken in buildings like these, the air change rate will most probably be insufficient and, in unfortunate circumstances, give rise to moisture problems.