Once water gets underneath shingles, shakes or other roofing materials, it can work it’s way to the roof deck and cause the roof structure to rot. Extra moisture encourages mildew, mold and rot elsewhere in a house. Condensation can result from the build-up of relatively warm, moisture-laden air. Moisture in a poorly ventilated attic promotes decay of wood sheathing and rafters, possibly destroying a roof structure. Sufficient attic ventilation can be achieved by installing larger or additional vents and will help alleviate problems because the attic air temperature will be closer to the outside air temperature. High winds can lift shingles’ edges (or other roofing materials) and force water and debris underneath them. Extremely high winds can cause extensive damage.