Life cycle integrated multi-criteria decision model for roof assessment

Abstract

Roofs significantly impact urban microclimates and indoor environments. However, selecting a suitable roof typology is complex due to environmental, social, and economic issues. This study aims to propose a method that comprises four parameters to support the selection of the most sustainable roof typology: life cycle energy assessment, urban heat island, life cycle cost analysis and thermal comfort. A top-floor flat in a multifamily residential building model with conventional (fibre cement), cool and green roofs, with and without thermal insulation, was used as a case study. The Brazilian climatic contexts of Florianópolis, Curitiba, and Brasília were considered. Computer simulations on EnergyPlus and data from the literature, technical specifications, a Brazilian database for quantifying materials and services and market prices were used to assess the roof typologies’ performance in each parameter. A questionnaire was applied to a panel of building experts to define the relative importance of each parameter. A multi-criteria decision-making (MCDM) method combining Analytic Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was used to weigh the parameters and select the most energy-sustainable roof alternative for each climatic context. The cool roof was the most sustainable in Florianópolis and Brasília, whereas the green roof was in Curitiba. Conventional roofs performed worst in all cities due to lower environmental and social efficiency. The method proposed herein offers valuable guidance for selecting energy-sustainable roofs and urban planning strategies, with adaptability to other roof typologies and countries, enabling tailored roof solutions for local conditions.