Green roofs can serve as natural insulators to save on energy costs for heating and cooling while mitigating urban heat island effects by lowering overall city temperatures.
Recycled rainwater tanks can help filter rainwater, alleviating strain on city drainage systems while adding beauty and character to any building.
1. They Increase Roof Load
Green roofs add considerable weight to a building, increasing its likelihood of leaks and necessitating structural modifications. Furthermore, irrigation and watering needs for their soil-and-plant-composed roof are ongoing requirements.
Green roofs can help boost biodiversity in cities by creating habitat for birds and insects in limited natural spaces. Green roofs also contribute to mitigating urban heat island effect – where bricks, concrete and asphalt absorb solar radiation more than surrounding areas to raise temperatures; by contrast, vegetation on green roofs reduce this effect through evapotranspiration, cooling the city while conserving energy.
Green roofs serve a dual purpose by acting as an insulator to decrease air conditioning usage, thus cutting energy costs and emissions of greenhouse gases. Furthermore, their vegetation helps remove pollutants from the air through dry deposition as well as carbon sequestration and storage – thus making green roofs an integral component of low-impact development strategies.
2. They Increase Energy Costs
Green roofs can add aesthetics and value to buildings, yet require maintenance for proper functioning. Furthermore, the weight of plants and soil on green roofs puts stress on roof structures causing leakage or structural damage which often results in leakage and structural failure.
Green roofs can be beneficial to both the environment and energy costs if not maintained properly. They have the power to reduce cooling energy by insulating against sunlight and slowing water runoff; additionally, they help mitigate urban heat island effect by absorbing and dissipating heat.
Airflow roofs may provide significant energy-efficiency benefits; however, their U-Value ratings cannot be given an exact value as their performance depends on climate conditions and plant phenology. Therefore, they may be less efficient in terms of reducing energy consumption and cooling loads than cool roofs.
3. They Increase Maintenance Costs
Green roofs use plants and soil to insulate buildings, cutting energy costs and the urban heat island effect caused by concrete and asphalt cities absorbing sunlight, while through evapotranspiration they remove greenhouse gases and pollutants from the air.
Wildlife habitats provide valuable ecosystem services while their acoustic properties help insulate against noise pollution from heavy traffic and aircraft noise pollution, such as in office buildings planted with indigenous grasses and wildflowers near San Francisco International Airport and under its flight path that experienced decreased noise levels as a result of their installation.
Extensive and intensive green roofs require additional structural reinforcement of a rooftop to support the added weight of planting materials, which is one factor contributing to their cost. A lightweight growing medium such as perlite, expanded shale, pumice or crushed terra-cotta won’t degrade over time as the growing medium. Furthermore, green roofs also need waterproof and root repellant layers, drainage capabilities as well as vapor control features to make up its total cost.
4. They Are Expensive
Green roofs can be more costly than their standard roofing counterparts and add weight to any building they adorn, so older structures that cannot bear this additional load may require reinforcement to handle its weight.
Green roofs feature plants and soil that add an additional layer of protection between the intense sunlight and roof membrane, thus decreasing energy use for cooling during summer months.
Green roofs help cities reduce sewer system loads by filtering rainwater and absorbing excess rain, making flood and erosion control easier for cities. Furthermore, their green plants help remove particulates matter and gaseous pollutants from the atmosphere while supporting food justice security by allowing people to grow produce on them themselves and contributing green space and beauty into urban environments.
