Moisture content of materials

[Michael Hurd]

It is difficult to know how much water a given material can have build up within the material before it causes a problem. If you run a calculation and the moisture content of the material stays below the typical "built in" moisture that WUFI assigns, is it safe to assume the product can withstand this level of moisture without degradation? For instance, WUFI assigns a built in moisture for gyp board USA of .39, when I run calcs and the moisture level stays below that figure, I assume the product is at a water content level that would not damage the product over time - is this a good general rule of thumb for materials that can be damaged by moisture? For the purpose of this discusssion I am ignoring the potential of mold growth and am specifically interested in water damage to the materials.

[Manfred Kehrer]

It is difficult to know how much water a given material can have build up within the material before it causes a problem. If you run a calculation and the moisture content of the material stays below the typical "built in" moisture that WUFI assigns, is it safe to assume the product can withstand this level of moisture without degradation?

No, the typically buit-in moisture is just a kind of initial state for the materials.

For instance, WUFI assigns a built in moisture for gyp board USA of .39, when I run calcs and the moisture level stays below that figure, I assume the product is at a water content level that would not damage the product over time - is this a good general rule of thumb for materials that can be damaged by moisture? For the purpose of this discusssion I am ignoring the potential of mold growth and am specifically interested in water damage to the materials.

The Rules for the Evaluation are not yet clearly defined. A common accepted rule is for the yearly mean value to stay below 80% RH at all positions of your assembly.

Please see also this post:
http://www.wufi-forum.com/viewtopic.php?t=169