Airtightness is a fundamental property of modern buildings and it ultimately stands for good quality of the overall build of a residential object.

Why is that?
An efficient level of airtightness is achieved ONLY upon carefull attention to every connection. It is something that is done directly on the construction site and it depends non only on the skills of designers but also on the skills of the workers that physically put together the assembly.

As consequence, in order to achieve a good airtightness, one must have a good design combined with outstanding implementation.

Air is very thin.
…and it will find its way through every small opening left uncover.
In the external walls and roof, special membrane are used to ensure proper airtightness. Those membranes must then be sealed one to each other by using special sealing tapes. In a house there are hundreds of meters of tape.
It is easy to understand that with such amount of taping it is quite possible to miss a spot.

Well, if the pressure tests gives a good value than both membranes and tape have been applied correctly and the work can be considered flawless.

Why airtightness is important?
Airtightness is not only indicator of good quality of design and implementation.
Benefites of airtightness are:

1) less cold air penetrating the building in winther, resulting in better indoor comfort (especially at floor level)
2) avoid condensation of vapour inside the walls where the cold air penetrates the building. This humidity would cause molding in warmer seasons!
3) avoid uncontrolled loss of warm air = uncontrolled loss of Energy. An airtight building saves Energy!

There, now you know why you should care.