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4. Water vapor transfer index (WHTI)
We have just characterized the physical quantities that define the hygrothermal state of humid air in time (at a given instant) and space.
In other words, it corresponds to a static state of humid air in a given environment.
What happens when a construction element separates two different hygrothermal environments?
4.1 Fick's Law
Consider a homogeneous wall separating two environments in which temperatures T 1 and T 2 are equal: T 1 = T 2 , but where HR 1 and HR ...
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Water vapor transfer index (WHTI)
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Standards and norms
New standards
- - NF EN ISO 7783-1 - 09.1999
- Détermination du coefficient de transmission de la vapeur d'eau. - NF EN ISO 7783-2 - 07.1999
The first describes the free-foil capsule method. The second determines and classifies water vapour transmission rate (permeability).
They now have the status of French standards and are part of the NF EN 1062-1 to 1062-11...
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