Insulation

Outside humidity penetrates building shells and can be stored in considerable quantities by concrete, screed, masonry, and conventional building materials. This stored moisture is emitted continuously into the air indoors. This applies to cellars and to ground floors and upper storeys, as well as free-standing garages, halls, and so on. The amount of water which penetrates depends mainly on the type and design of the insulation used. Old buildings without any insulation, or with only a little, are penetrated much more readily by outside moisture than newer buildings.

The other extreme occurs with super-tight insulation and tight-sealing windows, which may not let any moisture in from outside, but which are so moisture-proof that the air humidity emitted and produced indoors cannot escape despite ventilation and heating, and as a result the air humidity rises continuously.

Interior insulation can also cause serious moisture problems. Inside insulation can reduce the temperature of masonry (heat is kept away from the wall), which causes moisture in the air inside to condense on the cold masonry. This condensation can cause mould and mildew to grow, and can lead to building damage-damage which can remain undiscovered for a long time because it is behind the insulation.

The following figures give you an idea of the amount of moisture which different building materials can absorb. They show just how much water can be stored in building structures.

Building material	Max. water retention
Solid brick	90 - 190 l / m³
Lime-sand brick	180 - 270 l / m³
Heavy concrete	140 - 190 l / m³
Aerated concrete	280 - 290 l / m³
Plasterboard	360 - 490 l / m³