MIL-HDBK-1001-5 Roofing And Waterproofing S/S By Mil-Std-3007This handbook sets forth guidelines for design of roofing, LAYOUT 1 and waterproofing systems for building construction. It covers design of new low-slope and steep roof systems, reroofing of existing buildings, and waterproofing, and dampproofing systems.

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MIL-HDBK-1001/SA

relative humidity.  In warm, humid climates, e.g., Hawaii and Guam, however, vapor flows downward through the roof toward an air-conditioned interior.  Placing a vapor retarder on the deck and below the insulation is harmful in a tropical climate.  It

prevents venting of water vapor to the interior, entrapping it in the roof sandwich where it may condense in the insulation (refer to Section 4).

This difference in predominant vapor-flow direction may influence the proper choice of roof system:  conventional

assembly with insulation sandwiched between the deck below and membrane above, or a protected membrane roof (PMR) assembly, with membrane and insulation positions reversed, i.e., with insulation above the membrane.  In a cold climate where the predominant

vapor-flow direction is upward from a heated interior, the membrane in a PMR doubles as a vapor retarder. This is an efficient arrangement.  In a humid tropical climate, however, where the predominant vapor-flow direction is downward, the conventional roof assembly's position with the membrane above the insulation may be more efficient, with the membrane again functioning both as waterproofing and vapor retarder.

1.4.1        Solar Radiation.  Solar radiation embrittles asphaltic materials and thermoplastic sheets.  Plasticizers are lost through the combined effects of heat and sunlight.  Shielding of the membrane and flashings is important.  Aggregate, mineral granules, or heat-reflective coatings may be used as shields to increase the membrane's service life and cut cooling-energy costs.

1.4.2     Wind Velocity.  Wind velocity has an impact on roof design apart from the obvious requirement of better anchorage (or heavier ballast) in high-wind areas. Loose aggregate ballast should not be used in high-wind areas.  "Windstripping" of aggregate-surfaced built-up bituminous membranes has been noted

in such diverse locations as Guam and Grand Forks, ND.

1.S       Roofing Material Selection.  See Table 1 below for selection of low-slope membrane roofing.  See Table 2, in Section

9, for selection of materials for steep roofing.

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