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Condensation computation

With the aid of our database, you can easily calculate the condensation online by the Glaser method in accordance with DIN 4108-3. Simply select the materials of the outer wall or roof structure from the menu below.

+ thermal resistance inside
thermal resistance outside
There is no condensation in the construction.

Delete all layers

Name Thickness Lambda water vapour resistance value
+ SWISS KRONO OSB 12 0.13 167
+ SWISS KRONO OSB 15 0.13 135
+ SWISS KRONO OSB 18 0.13 115
+ SWISS KRONO OSB 22 0.13 100
+ SWISS KRONO OSB 25 0.13 100
+ SWISS KRONO DP50 15 0.09 11
+ SWISS KRONO WP50 15 0.09 11
+ Gypsum Paper Board 9.5 0.25 8
+ Gypsum Paper Board 12.5 0.25 10
+ Gypsum Fibreboard 10 0.31 10
+ Gypsum Fibreboard 12.5 0.31 10
+ Vapour Barrier 0.2 1 100000
+ Structural Timber 60 0.13 41
+ Structural Timber 240 0.13 41
+ Fiber insulation 0.032 1
+ Fiber insulation 0.035 1
+ Fiber insulation 0.04 1
+ EPS 0.035 100
+ XPS 0.03 250
+ Wood fiber 0.045 5
+ PU insulation 0.025 150
+ Polystyrene 0.038 80
+ Chipboard 13 0.13 50
+ Plywood (500 kg/m³) 15 0.13 70
+ Lime Render 15 0.87 35
+ Pore Concrete 240 0.29 5
+ Breather Membrane 0.2 1 100
+ Air 22 7.73 1
Name Thickness Lambda water vapour resistance value

The computation tool does not show how much condensation is formed. Nevertheless you can assess how safe the construction is on the basis of the details supplied:

  1. If the Actual figure is significantly lower than the Sat figure, we can say the construction is safe.
  2. If the Actual figure is only just above the Sat figure, condensation will be formed but this will not necessarily lead to damage.
  3. If the Actual figure is significantly higher than the Sat figure, the structure will definitely need to be improved.

What is condensation anyway?

Depending on the temperature and air pressure, air absorbs varying amounts of moisture in the form of water vapour. Condensation is created when warm air cools as cold air absorbs less water. When warm, moist air from inside cools down on its way through the wall or roof, condensation can be the result. When a building is constructed, care must be taken to ensure that this condensation does not soak and thereby damage any element of the building. To prevent condensation, less water vapour must reach the element from the warm interior than can escape on the cold exterior.

The condensation computation by the Glaser method

Benannt nach seinem Erfinder Helmuth Glaser stellt die Tauwasserberechnung nach Glaser eine vereinfachte, standardisierte Methode dar. Dabei geht man immer von folgenden Werten für die Umgebung aus:

  • Interior: 20 °C, 50 % humidity, 8.7 g water/m3
  • Exterior -10 °C, 80 % humidity, 1.7 g water/m3

This means there is a difference in vapour pressure between the interior and exterior. The vapour or moisture permeates the various layers of the wall or roof from inside to out by way of diffusion. To ensure that the moisture can penetrate the wall or roof to the outside without causing condensation, the individual layers of the building must exhibit differing degrees of resistance. Materials with high diffusion resistance are therefore used on the warm side and with lower diffusion resistance on the cold side. So the set-up must be more impermeable on the inside than on the outside. In this way, the moisture finds its way to the outside without meeting the cooler surface of an element on which it could condense.

Whether an element exhibits capillary action is irrelevant for the computation of condensation by the Glaser method. Only climate conditions in the individual layers are taken into consideration here and analysed to determine whether condensation will form at these points. The capillary effect is considered in significantly more complex building physics programs, e.g. WUFI (transient heat and moisture transfer) in hygrothermal simulations. For example, this type of software can also be used to keep records of flat roof constructions which tend not to be open to diffusion and in which downward drying occurs in summer. However, the SWISS KRONO computation tool for the formation of condensation permits a reliable assessment of whether condensation will occur in the chosen construction or not. Several values are used for the computation:

  • Water vapour diffusion resistance (µ): Water vapour resistance of the structural element
  • sd value: focuses on the diffusion equivalent air layer thickness, calculated from the water vapour resistance (µ) and the thickness (d) of the product in metres (µ x d), example: If a product has an sd value of 5 m, this corresponds to the resistance of a 5 m layer of air.
  • Thermal conductivity value (λ): Ability of a material to conduct heat in W/mK
  • Vapour pressure: Water vapour pressure in the material layer in PA The Actual value is the value calculated for the material layer. The Sat value or vapour saturation value indicates the point from which condensation is formed. If the Actual value is larger than or equal to the Sat value, “condensation formation” is displayed.

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