Stains on interior ceilings and walls or mold and mildew growth Possible cause: Inadequate or faulty shingle underlayment allowing leakage or inadequate ventilation
Dark, "dirty-looking" areas on your roof Possible cause: Environmental pollutants; vegetation, fungus or algae; loss of granules due to age of shingles
Excessive energy costs Possible cause: Insufficient attic ventilation causes heating/cooling system to run excessively
In warm weather, inadequate ventilation will trap hot air in the attic, causing air c onditioning systems to work harder, or leaving your home's interior hotter and less comfortable. Attic Ventilation: In both hot and cold weather, insufficient attic ventilation may cause moisture in the attic to become trapped and condense on the rafters. This condensed moisture can drip down onto the insulation and reduce its effectiveness.
Excessive energy costs can result.