Everyone is talking about airtightness but only a few people know the meaning and the facts about:
Dampness, Heatloss and Energy Consumption are one of the main criterias for buildings today.
The best insulated building is worthless without a proper building sealing, which consists of various sealing solutions to protect the building structure against the weather, dampness and heatloss.
Mostly a breathable barrier protects the building on the outside, like for example a roof membrane. This layer prevents the penetration of
dampness and moisture. The same function is covered by the external plaster on the walls.
On the inside of the building structure, the most buildings need a special vapour control barrier on the inside of the building structure.
This barrier prevents that damp warm air, coming from the room, will enter the building structure.
The internal barrier has also to protect the building against the heatloss, caused by unwanted escape of warm room air through joints and other leakages.
This will be mostly called "Airtightness", but please don´t forget how important it is to have a vapour control barrier either. Internal plaster is airtight but not great for vapour inhibiting.
The easy principle for a proper building sealing means:
The external sealing has to be weatherproof but breathable whilst the internal sealing must be airtight & vapour inhibiting.
The inside sealing has to be tighter than the outside sealing.