Analysis of Influential Parameters in Green Roof Design for Reducing Energy Consumption and Carbon Emissions in Tehran

Document Type : Research Paper

Authors

1 Master of Architectural Technology, School of Architecture, College of Fine Arts, University of Tehran.

2 Assistant Professor, Department of Architectural Technology, School of Architecture, College of Fine Arts, University of Tehran, Tehran, Iran.

Abstract

Energy consumption in buildings accounts for approximately 40% of global energy use and contributes to 33% of greenhouse gas emissions, making it one of the most critical environmental challenges. Green roofs have emerged as a sustainable solution to mitigate energy consumption and enhance urban environmental conditions. By improving thermal insulation, reducing the urban heat island effect, and supporting biodiversity, green roofs offer significant environmental, economic, and social benefits. This study analyzes and evaluates key parameters such as soil thickness, plant species selection, and vegetation characteristics in green roof design aimed at reducing energy consumption and carbon dioxide emissions in Tehran.
This study underscores the importance of proper green roof design and plant selection in enhancing urban sustainability and mitigating the impacts of climate change. The findings highlight how integrating ecological design principles into urban planning can lead to more energy-efficient and environmentally friendly buildings. Policymakers and architects are encouraged to adopt green roof design as part of broader efforts to create resilient urban environments capable of withstanding climate challenges.
Selecting suitable plant species for green roofs is of paramount importance. These plants must be well-adapted to  local climate conditions and resistant to environmental changes such as high temperatures, severe cold, and drought. Proper selection ensures efficient energy performance and resilience to Tehran's climate, contributing to both environmental protection and energy conservation.
This research investigated plant characteristics such as Leaf Area Index (LAI), leaf reflectivity, and leaf emissivity using 133 simulation scenarios conducted with the Design Builder software. Eight plant species suitable for Tehran's climate were identified based on their effectiveness in reducing energy loads and providing year-round thermal comfort. These species included Thymus vulgaris, Mesembryanthemum cordifolium , Salvia Rosmarinus , Sedum, Lavandula angustifolia, Achillea millefolium, Frankenia thymifolia , and Hedera helix. These species not only improve insulation and energy efficiency but also play a crucial role in mitigating urban temperature fluctuations by enhancing thermal stability.
The results indicate that green roofs can achieve up to 25% energy savings in cooling and heating loads when appropriate plant species are combined with optimized soil layers. During warm periods, plants with higher LAI values (above 3.5) effectively reduced cooling loads through shading and transpiration. Conversely, during colder periods, plants with moderate to low LAI values (between 1 and 4) demonstrated better heat retention, significantly lowering heating loads. These findings highlight the importance of selecting plants with LAI values suited to seasonal energy needs, enabling year-round efficiency.
A soil thickness range of 15 to 20 centimeters was identified as optimal, balancing energy savings during both warm and cold seasons. Thicker soil layers enhance water retention and thermal mass, boosting the efficiency of green roofs under temperature extremes. The study also demonstrated that these eight plant species reduced energy consumption by 19% to 24% while significantly lowering CO₂ emissions, ranging from 5.54 to 9.51 kg/m² per year, through improved insulation and shading properties. As a result, green roofs are recommended as a key strategy for promoting sustainable urban development, particularly in cities like Tehran.

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References

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Journal of Fine Arts: Architecture & Urban Planning
Volume 29, Issue 4
February 2025
Pages 59-74

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