A B S T R A C T
Addressing urban requirements has become a serious concern as the population of both developing and developed cities grows rapidly. Green roofs are viewed as a realistic option with clear environmental, economic, and social benefits.This study looks at how green roofs can improve air quality and save energy in residential buildings in Tabriz, a city with a cold and dry climate. To explore this, two scenarios were created using DesignBuilder energy simulation software: one with vegetation on the roofs and another without. The analysis compares the effects of both roof types on energy use for heating and cooling, CO2 emissions, and urban air quality throughout a year, considering local weather conditions. The results show that in August, the hottest month in Tabriz, a building with a standard roof used around 2000 kWh of energy, while one with a green roof used only 1200 kWh. This difference suggests that green roofs can significantly reduce energy consumption compared to conventional roofs. These findings provide useful insights for designing more energy-efficient buildings in cities, contributing to smarter and more sustainable urban development.
Extended Abstract
Introduction
Sustainable development has been a key concept in global strategies and United Nations reports since the 1980s. It focuses on economic, social, and environmental dimensions. Sustainable architecture, such as green roofs, is considered an effective solution to reduce energy consumption and carbon emissions. Green roofs create shade, transpiration, and thermal insulation, reducing roof surface temperature and temperature fluctuations. Research shows that green roofs can reduce internal temperatures from 4.3 to 5.0 degrees Celsius, leading to significant energy savings. They also play a role in reducing urban heat islands (UHIs) by an average of 0.68 degrees Celsius. In urban areas like Beijing, green roofs can reduce daily air temperature by 0.41 degrees Celsius. Integrating green roofs in building information modeling can optimize their design and performance, reducing environmental challenges like climate change and energy resource management. This research evaluates the performance of green roofs in cold and dry climates using Design Builder energy simulation software. The results can be used as a strategic tool for urban planners and architects to achieve sustainable development goals.
 
Methodology
This research explores how green roofs affect energy consumption in residential buildings in Tabriz City. A one-story, two-bedroom house, covering 88 square meters, was selected for energy simulations using DesignBuilder software, which accurately models building energy performance and compares different roof types. The model includes six thermal zones, with control applied to all except zone 6. The building falls under type A with significant urban use, showing a primary need for heating and energy savings in group 1. Roof thermal conductivity was calculated within the software, and the data is detailed in relevant tables. Simulations ran for a full year across four seasons, with results recorded monthly and every 20 minutes. The building features double-glazed windows, LED lighting, and an average of four occupants per unit. Local meteorological data was incorporated into the simulation via an EPW file, reflecting Tabriz's cold, dry climate. The roof is modeled as flat, with materials selected accordingly, and the green roof includes a soil layer reduced to 20 cm in thickness. This high level of accuracy ensures that the results provide valuable insights for optimizing energy use and minimizing environmental impacts.
 
Results and discussion
The study shows that energy consumption in colder months, such as January and February, is significantly higher without a green roof, highlighting its role as effective thermal insulation. In contrast, during hotter months like July and August, energy consumption decreases when a green roof is in place. The use of Frankenia thymifolia, a common cover plant species, prevents the roof from overheating and lowers the building's cooling needs. The simulated green roof system with Frankenia was successful in optimizing energy use year-round, cutting consumption by roughly 462,526 kWh annually. This energy reduction is due to the green roof's unique thermal properties, which limit heat exchange between the building and its surroundings. During hot seasons, the green roof lowers roof surface temperatures, decreasing reliance on cooling systems. In cold seasons, it helps retain heat inside, reducing the need for heating. These thermal benefits also reduce strain on air conditioning and heating systems, extending the lifespan of the building's mechanical equipment.
The results also indicate that the green roof's impact varies depending on specific weather conditions and building characteristics. For example, in regions with more extreme temperature fluctuations, the energy savings from a green roof may be even more pronounced. Additionally, the type and thickness of the soil layer, as well as the choice of plant species, can significantly influence the roof's thermal performance. The study found that Frankenia thymifolia, with its dense foliage and drought-resistant properties, was particularly effective in maintaining stable roof temperatures. However, different plant species might yield varying results depending on local climate conditions. The effectiveness of green roofs in mitigating urban heat islands was also evident, as the lower roof surface temperatures contributed to a cooler microclimate around the building. This not only reduces the building's energy consumption but also has broader environmental benefits, such as improving outdoor air quality and reducing the overall urban heat island effect. These findings underscore the importance of carefully selecting and designing green roof systems to maximize their environmental and energy-saving benefits.
 
Conclusion
Green roofs are a promising solution for sustainable urban development, offering environmental, economic, and social benefits. They reduce heat islands in cities by 30 degrees Celsius, contribute to effective runoff management, improve urban air quality, and provide thermal insulation, saving up to 21.2 kWh/m2 of energy consumption for heating and cooling. The adaptability of green roofs to different weather conditions allows for maximum energy savings. Studies have shown that the construction of green roofs can lead to energy savings between 3.2% and 9.1%.
Green roofs also reduce CO2 emissions by optimizing parameters and reducing the amount of CO2 produced by buildings. However, their effectiveness can vary significantly based on specific weather conditions and types of buildings. A study conducted in Tabriz, East Azerbaijan, evaluated the effect of creating a green roof with a common cover plant and a traditional roof without vegetation. Results showed that green roofs significantly affect energy consumption during peak temperatures, but they also reduce heating and cooling energy consumption.
However, the study has limitations, such as the challenge in accurate modeling of complex urban environments and the lack of access to data for long-term studies. Additionally, the effect of green roofs on indoor air quality has not been studied, and the thermal performance of green roofs with architecture design is not yet fully understood.
 
Funding
There is no funding support.
 
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
 We are grateful to all the scientific consultants of this paper.