A vapor retarder under the insulation and next to the ceiling to stop moisture from rising into the attic. Enough open, vented spaces to allow air to pass in and out freely. A minimum of 1 inch between the insulation and roof sheathing. The requirements for proper attic ventilation may vary greatly, depending on the part of the United States in which a home or building is located, as well as the structure's conditions, such as exposure to the sun, shade and atmospheric humidity. Nevertheless, the general ventilation formula is based on the length and width of the attic.
Deterioration can occur faster on the sides facing west or south.
When water gets underneath shingles, shakes or other roofing materials, it can work its way to the roof deck and cause the roof structure to rot. Extra moisture encourages mildew and rot elsewhere in a house, including walls, ceilings, insulation and electrical systems. Extremely high winds can cause extensive damage. This blocks proper drainage into the gutter. During the early melt stages, gutters and downspouts can be the first to fill with ice and be damaged beyond repair or even torn off a house or building.