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-1001/5A

cycle cost.  Roof thermal resistance should meet or exceed agency criteria and requirements for Federal buildings.

3.2.6.1   Documents.  The NRCA Energy Manual and the 1985

American Society of Heating, Refrigerating and Air Conditioning

Engineers (ASHRAE) 1985 Handbook - Fundamentals, Chapter 20,

contain discussions on heat-flow calculations and economic

insulation thickness for building envelopes.

3.2.6.2   Variations.  High levels of thermal resistance are not always life cycle cost effective.  Refer to the discussion on "Buildings With Dominant Internal Loads" in Chapter 20 Errata of the ASHRAE 1985 Handbook - Fundamentals.

3.2.7     Evaluation.  An energy evaluation should be conducted for each building to determine if the roof insulation thermal resistance should be higher or lower than set forth above.

3.2.7.1   ASHRAE Methods.  Chapter 28 of the ASHRAE 1985 Handbook

- Fundamentals, provides a number of methods for estimating

energy consumption associated with roof insulation.  Hour by

hour, detailed computer simulation methods are preferred.  At

least three levels of thermal resistance should be evaluated for

the roof over each type of space in each building.

3.2.7.2   Life Cycle Cost.  Economic evaluation of roof

insulation should be carried out in accordance with NAVFAC P-442,

Economic Analysis Handbook, or equivalent.

3.2.7.3   Important Considerations

a)  Where some space heating is accomplished by means of heat recovery, or where some space cooling is accomplished by free cooling methods such as economy cycle, or cooling tower, or cooling resulting in lower purchased energy requirements, lower levels of thermal resistance can be justified on a life cycle cost basis.  Where energy is expensive, higher levels can be justified.

b)  Each area of a building may vary.  The level of thermal resistance for each area of the building does not necessarily have to be the same throughout.  Quite often, areas with long hours of operation and high internal heat gains will require less insulation than areas with little or no internal heat gain and/or short hours of operation.  Compensate for reductions in R-value due to fasteners and structural members.

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