Moisture and water vapor move in and out of a house in three ways:
- with air currents;
- by diffusion through materials; and
- by heat transfer.
Of these three, air movement accounts for more than 98% of all water vapor movement in building cavities. Air naturally moves from a high-pressure area to a lower one by the easiest path possible—generally, through any available hole or crack in the building envelope. Moisture transfer by air currents is very fast—in the range of several hundred cubic feet of air per minute. Thus, to control air movement, a house should have any unintended air paths thoroughly and permanently sealed.
Latest studies about homes built in Humid areas like Florida show that buildings need to have all holes and cracks sealed to prevent humid air from finding its way to the interior spaces. Contractors will use the latest ZIP systems, or building wraps to keep out the rains we see, but it what we do not see that we need to also stop. The relative humidity outside in the hot air will bring in lots of water if not stopped.
Why do you want to keep this water vapor out of the interiors? To prevent water damage. I have been trained to spot common types of moisture problems in buildings during an inspection. Most (if not all) moisture-related problems can become serious and expensive if not taken care of quickly and completely. Therefore, it is important for me to call out or recommend further evaluations and/or repairs by qualified professionals when any moisture intrusion is discovered.