Building assemblies are generally more vapor permeable than air permeable because
A)vapor is not really a gas.
B)vapor is only a small part of the air- vapor mixture.
C)vapor has only water molecules, while air is a mixture of nitrogen and several other gases.
D)vapor pressure differential between the inside and the outside air is much greater than the corresponding air pressure differential.
E)vapor molecules are heavier than air molecules.

Question

Quizplus · Accepted Answer

Vapor pressure differential refers to the difference in pressure between the inside and outside of a material due to the presence of water vapor. This is often the driving force behind moisture movement through building assemblies. Since vapor molecules are smaller and more easily pass through small openings than air molecules, vapor permeability tends to be higher than air permeability in building assemblies.

Building Assemblies Are Generally More Vapor Permeable Than Air Permeable