Determination of Materials Used in Green Roofs in Sustainable Structures via Value Engineering

Abstract

The construction industry globally faces the dual challenge of meeting rapid urbanization demands while adhering to environmental sustainability targets. Green roofs have emerged as an effective passive design strategy to mitigate the Urban Heat Island (UHI) effect, enhance building energy efficiency, and manage urban stormwater. However, in developing economies such as Turkey, their widespread adoption is constrained by high initial investment costs and a reliance on imported materials-specifically plastic drainage layers and peat-based substrates. To address these barriers, this research proposes a framework integrating Value Engineering (VE) methodology with a 40-year Life Cycle Cost (LCC) analysis. Using a 2,000 m² commercial Shopping Center (AVM) project in Balikesir, Turkey, as a primary case study, the study investigates the substitution of imported components with locally sourced volcanic pumice (bims). Technical evaluations indicate that the optimized pumice-based system not only complies with structural load limits (135 kg/m²) but also provides enhanced thermal resistance (λ ≈ 0.12 W/mK). The findings suggest that the VE-optimized system achieves a 42% reduction in initial investment costs compared to standard imported green roofs. Furthermore, the LCC analysis indicates that due to notable energy savings and extended membrane longevity, the proposed system amortizes its cost premium over a conventional roof within 6 to 7 years, offering a 34% total lifecycle saving. This research concludes that localized material optimization through Value Engineering positions green roofs as a technically robust, economically viable, and sustainable engineering solution.