In relation to air-transported moisture, let us take into
consideration another movement of the air that contributes to high
humidity in your home; this is called the Stack Effect. This occurs
when warm air rises and exits the house through upper passageways such
as windows or vents. This creates a negative pressure in your crawl
space creating an unbalanced mixture of humidity and temperature. This
pressure forces external humidity to permeate through your crawl
space. This will keep on going on if not properly controlled
immediately.
This is a natural occurrence around us and it applies to many
things because it is all about the actual behavior of water. The
idea as to how water permeates through a towel, cloth, or soil, is
the same with your foundation. An effective way of preventing this
is applying a capillary break such as plastic, metal, or any other
impermeable material when your house is still being constructed.
Moisture/vapor
diffusion through foundation walls
Vapor is considered to be highly diffusive. Given external changes
in weather that promotes a high production of vapor, it is a
fairly easy job for vapor to permeate through your foundation
walls and condensate to your crawl space interior. This is a very
common problem, especially for houses built in concrete, as they
are more susceptible to moisture absorption.
Especially during the summer, when many homeowners opt to open
their windows and provide extra air circulation in their crawl
space, air-transported moisture is highly to occur. While opening
windows might provide temporary drying to your space, this will
not be the same case long term. Doing it will actually increase
your crawl space’s humidity that will eventually lead to wall
drips and dampness.