1. Sometimes, humidity or dampness (water vapor) in the air can supply enough moisture for mold growth. Indoor relative humidity (RH) should be kept below 60 percent — ideally between 30 percent and 50 percent, if possible. Low humidity may also discourage pests (such as cockroaches) and dust mites. Humidity levels can rise in a building as a result of the use of:

• Humidifiers
• Steam radiators
• Moisture-generating appliances such as dryers
• Combustion appliances such as stoves
• Showers
• Heat escape from the attic floor to roof deck

2. Heat escape from the living space is a big contributor to mold growth as a result of cold air from the soffits or roof vents hitting warm air from the living space that leaked out through the attic floor seams. This is evident from the exterior when icicles are present. Often the attic sheathing (roof deck) will have mold, why? Because the heat escapes from the house's living space, it is creating both condensation and warming of the roof deck.

In addition to proper insulation levels, and air tight attic floor, in the attic, when passive power fan ventilation which is thermostat controlled does not remove excess heat escape from the living space the heat will prematurely melt roof snow creating a serious situation with icicles and the potential for ice dams.

• Ventilation can dissipate the heat moisture and condensation will feed mold growth.
• The best solution is to prevent heat escape from the pressure barrier of the living space and conditioned building envelope.
• Mold remediation means treating the cause along with the affected surfaces.