Mold comes in to the house in many ways. Always when there is water present.
1. Exterior water – infiltration (through the siding or the roofing)
Improper installation of the siding – no building paper or a house wrap was installed. Roofing again improper installation of roofing and flashing allowing the rainwater into the building shell.
2. Exterior water – under ground.
High level of ground water is big problem pushing hydrostatic pressure against the foundation wall, forcing the water into the foundation. The causes of high level of water are over watering the garden next to the foundation, rainwater coming off the roof then runs to the foundation. Following the wall downward adding to the ground water. Basement floors that have pour, or not properly installed drainage system can have 50 gallons of water evaporating in a 1000 SF basement per day
3. Interior water – leaking pipes and/or sweating pipes
4. 4. Interior water- high humidity comes from cooking, showers, people them selves sweat and put a lot water into the air.
When humidity levels go above 65% mold has the ability to start growing. The higher the humidity above 65% with temps above 68°, the quicker the mold responses to it environment. Lets look at a Refrorator very high humidity but low temps the mold is held in check because of the low temperature.
This time lets look at the cabinet under the sink there is a leak about a drop per minute. The temp in the house is 70° and the humidity is 45%. But in the cabinet the temp is 68° and the humidity is 80% or better. The house air has no way to dry out the cabinet allowing it reduce the humidity, therefore in about 1 week mold will start to grow. In one year the entry interior sink base cabinet will be covered in mold. Now lets apply this to a stud cavity, humidity get trapped between the exterior wall sheathing and the interior sheetrock or finished surface. But this time you have no idea it’s happening and no way to check on the condition of the framing. Using a porous type of insulation in your stud spaces on the exterior walls is like begging for mold to inhabit you home on all sides of you.