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Constructions and related matters relevant to environmental health
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
John Bryson, Stephen Battersby
“Cool” roofs (usually light in colour) are roofing systems that can deliver high solar reflectance (albedo) and have the ability to reflect the visible, infrared and ultra-violet wavelengths of sunlight and reduce heat transfer to the building. They also have high thermal emittance (the ability to radiate absorbed or non-reflected solar energy). “Green roofs”, sometimes known as “living roofs”, are roofs that are partially or wholly covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. They serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, and helping to lower urban air temperatures. Both forms of roof counter the heat island effect. An urban heat island is an urban area that has significantly higher temperatures than surrounding rural or less densely populated areas.
Stormwaters: Management
Published in Yeqiao Wang, Fresh Water and Watersheds, 2020
John C. Clausen, Michael E. Dietz
Vegetated or “green” roofs have been used for centuries in northern Europe. Benefits of green roofs include retention of rainfall, and in some cases, energy cost savings.[16] The traditional or “intensive” green roof consists of a thick soil layer capable of supporting grasses, plants, and sometimes even trees. As would be expected, the building structure below a green roof needs to be specially engineered to support its weight safely. An “extensive” green roof consists of a shallow media (10–15 cm) of expanded clays or other light materials. The advantage of the extensive system is that the weight is much less, so the system can be applied with less structural support. However, this type and thickness of media cannot support shrubs or trees. Typically, extensive green roofs are planted with Sedum species, which are highly tolerant of the harsh conditions that exist on a rooftop (Figure 23.6). The amount of rainfall that is retained by a green roof depends on the type of roof, the vegetation, as well as the regional climate. Retention can be a substantial portion of annual precipitation.[17] The green roof is an ideal BMP for highly developed urban areas where little greenspace exists for traditional BMPs, but open rooftops are plentiful.
Biological Engineering Designs
Published in Paul H. King, Richard C. Fries, Arthur T. Johnson, Design of Biomedical Devices and Systems, 2018
Paul H. King, Richard C. Fries, Arthur T. Johnson
Green roofs are designed to absorb rainfall, delay water runoff, save on summertime cooling, reduce rooftop maintenance, and improve the aesthetic appearances of urban building rooftops. They consist of water-impermeable rooftop layers covered with a thin layer of plant growth medium (soil), and covered with plants grown for their hardiness under difficult conditions. The plants must be able to absorb water very quickly during storms either frequently or infrequently timed, but survive during drought conditions between rainfall events. Thus, many of the plants used for green roofs are succulants that can internally store large amounts of water. Irrigation may be used to help the plants survive long periods between rains, but the water use for irrigation actually helps to cool the building underneath as it is evaporated through transpiration. Roofs are usually the sight of the greatest heat loss in the winter and the hottest temperatures in the summer. Green roofs reduce the amount of stormwater runoff and also delay the time at which runoff occurs, resulting in decreased stress on sewer systems at peak flow periods. The plants used on green roofs improve urban air quality and turn otherwise unusable roof space into pleasant outdoor areas for social and private occasions.
Socioeconomic feasibility of green roofs and walls in public buildings: The case study of primary schools in Portugal
Published in The Engineering Economist, 2021
Catarina Almeida, Inês Teotónio, Cristina Matos Silva, Carlos Oliveira Cruz
Besides the costs, several studies have demonstrated the green infrastructure’s benefits. For example, green roofs and green walls contribute to the reduction of pollutants’ concentration in the atmosphere (Bianchini & Hewage, 2012a, 2012b; Rowe, 2011; Yang et al., 2008). They also help to regulate the air temperature which has an impact on the mitigation of the urban heat island effect and its consequent carbon footprint (Bianchini & Hewage, 2012b; Getter et al., 2011). Green roofs, in particular, contribute to improve the rainwater quality and management through the retention and delay of the water flow (Getter & Rowe, 2006; Hashemi et al., 2015; Rowe, 2011; Vijayaraghavan, 2016). Finally, both green systems play an important role in the well-being and physical, social and psychological health of citizens (Bowler et al., 2010; Dadvand et al., 2016; Salthammer et al., 2016).
Green infrastructure and urban sustainability: A discussion of recent advances and future challenges based on multiyear observations in New York City
Published in Science and Technology for the Built Environment, 2019
The two major green roof categories include extensive green roofs, whose substrates are typically 15 cm thick or less and feature short-rooting, drought-resistant plants such as sedum, and intensive green roofs, whose substrates are greater than 15 cm thick and may be sowed with deeper rooting plants including shrubs and trees. Due to their lower cost, reduced maintenance requirements, and lighter weight per unit area, extensive green roofs are more frequently adopted than their intensive counterpart (Hakimdavar et al. 2016). For this reason, the majority of green roof studies engaging the author and her colleagues involve extensive green roofs. Figure 4 provides the location of three of these extensive green roofs, each of which encompasses a popular construction type. W118 is a Xero Flor America XF301 + 2FL vegetated mat system with a substrate depth of 32 mm, ConEd is a GreenGrid-G2 modular tray system with a substrate depth of 100 mm, and USPS is a Tecta Green built-in-place system with a substrate depth of 100 mm. All three roofs are planted with sedum species. Monitoring of green roof performance began in 2009 and has been almost continuous since then. Further information on the characteristics of each green roof, monitoring equipment, and setup can be found in Carson et al. (2013).
Urban and architectural design from the perspective of flood resilience: framework development and case study of a Chinese university campus
Published in Journal of Asian Architecture and Building Engineering, 2023
Xu Ke, Wang Yang, Lin Misheng, Zhao Ranting
The NBS catalogue focuses on intensive and extensive green roof types. The natural processes that green roofs are associated with are evapotranspiration, temporary storage and buffering of rainwater, and sunlight absorption. Extensive green roofs are basic lightweight systems characterised by minimal maintenance and management. The NBS catalogue sets a performance threshold for extensive green roofs. They should have at least 25 L/m2 storage capacity and 95% coverage after three years. Intensive green roofs are accessible for public or recreation purposes and also need regular maintenance, which leads to higher costs compared with extensive green roofs.