Mold and mildew thrive when the relative humidity remains high in your home for even a short period. Their growth rate is quite rapid; the fungi starts to form on damp surfaces in as little as 24 to 48 hours. Soon after, the fungi begins to produce spores that are released into the the air. The spores can cause moderate to severe health problems in individuals. Mold may also damage the wood, drywall and other surfaces of the home.