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1.1 This guide provides guidance and considerations related to designing sustainable low-sloped roofing systems, including exposed membrane roofs, membranes covered with vegetative (green) overburden systems, ballasted roofs, and protected membrane roofing assemblies. A sustainable roofing system minimizes environmental impact, conserves energy, and has maximized service life.

1.2 The primary purpose of a roofing system is to weatherproof the building’s top surface. Implementing a sustainable roofing system is the intent of this guide.

1.3 This guide acknowledges that many factors outside the designer’s control affect the longevity of a roofing system. The designer may rely on industry literature (X1.1) and personal experience with roofing systems to estimate the design life.

1.4 The premise of this guide is to focus attention on environmental and other factors that may affect the roofing system over its service life. By considering these factors and incorporating into the roofing system design certain features that mitigate these factors and their potential adverse effects on the roofing system, the roofing system would be expected to have a longer service life.

1.5 This guide includes materials used in roofing systems under jurisdiction of ASTM Committee D08 on Roofing and Waterproofing. The applicability of this guide to other systems and materials has not been determined.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

5.1 This guide is intended to help the user identify and define demands made upon the roofing system by factors such as weather, climate, and building use, in light of the fact that many roofs are specified with secondary features that have quantifiable or non-quantifiable environmental or humanitarian benefit such as alternative energy generation, vegetation, or use as open space. Awareness of the roof’s use as a platform for these secondary functions, as well as the additional demands they make upon the roof, is needed to specify a durable and sustainable roof.

5.2 It is the responsibility of the user of this guide to determine the appropriate prescriptive requirements for implementation of the sustainable roofing system based on considerations listed herein.

5.3 Codes and local ordinances set minimum requirements for roofing systems. Nothing in this guide should be construed to abridge or lessen requirements of codes and local ordinances. Other entities, such as building insurers and system manufacturers, may have requirements for the roofing system.

5.4 Sustainability of a roofing system is site and use specific. A roofing system considered sustainable for a certain site or application may not be sustainable in a different application. There may also be more than one roofing system that achieves an optimal level of sustainability for a given site and application.

5.5 Above-roof vegetative (green) systems and rooftop energy generation systems are discussed herein because they are frequently placed on roofs to reduce the building’s overall environmental impact. These features do not generally contribute to the durability or longevity of the roof. These features may be detrimental to roof system performance and impair the roof’s ability to perform its primary function of protecting the building if their impact is not accounted for in the roof design.

5.6 Design of above-roof systems is beyond the scope of this guide; however, consideration of their potential impacts is outlined herein.