Low-slope shed roofs that range in pitch from nearly flat to 4-over-12 are common in the Southwest and in dense urban neighborhoods of the Northeast. These roofs are either framed with deep trusses or framed with rafters that are separate from the ceiling joists. Because of their limited space between the sheathing and the ceiling joists, these roofs are often difficult to insulate properly. Although some builders insulate a low-slope roof with the same techniques used for a house with a big attic, they should be using a different approach. If the roof is vented, the ceiling must be air-sealed to prevent moisture-laden air from reaching the attic. If the roof is unvented, there are several ways to efficiently insulate the space either from the exterior, from the interior, or from a combination of both.
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