| Use multiple calculations (based on simple Glaser method) to calculate the probability of condensation.
Not vapor barrier give a 14% of risk of condensation, while 0% risk (no condensation) with a vapor barrier.
ABSTRACT
Knowledge of how often we have condensation on the surface or in the construction are important. I make diffusion calculations on a typical timber wall. Calculations are done with a statistical risk method. Each parameter in the calculation is assigned an assumed distribution of values. A computer program for generation of random values makes 1000 random cases by selecting a random value from each distribution. The result is for instance the percentage of cases with condensation. The method is used on 2 cases.
The first is a wall with or without a vapor barrier. With a normal water barrier, there is no condensation risk. Without a vapor barrier there is 15% risk of condensation.
The second case is a comparison of risk for cases with different moisture resistance of inside layer (vapor barrier) and outside layer (wind barrier) . The risk of condensation is 40%, if the both resistances are equal. There will be no condensation risk, if the moisture resistance of the vapour barrier is more than 5 times greater than the wind barrier's resistance.
The statistical method with random values is practical for cases, where we do not know all parameters accurate. We can find out the risk of getting values above or below a certain level. |