Retrofitted green roofs and walls and improvements in thermal comfort

Abstract

Abstract. Increased urbanization has led to a worsening in the quality of life for many people living in large cities in respect of the urban heat island effect and increases of indoor temperatures in housing and other buildings. A solution may be to retrofit existing environments to their former conditions, with a combination of green infrastructures applied to existing walls and rooftops. Retrofitted green roofs may attenuate housing temperature. However, with tall buildings, facade areas are much larger compared to rooftop areas, the role of green walls in mitigating extreme temperatures is more pronounced. Thus, the combination of green roofs and green walls is expected to promote a better thermal performance in the building envelope. For this purpose, a modular vegetated system is adopted for covering both walls and rooftops. Rather than temperature itself, the heat index, which comprises the combined effect of temperature and relative humidity is used in the evaluation of thermal comfort in small scale experiments performed in SydneyAustralia, where identical timber framed structures prototypes (vegetated and non-vegetated) are compared. The results have shown a different understanding of thermal comfort improvement regarding heat index rather than temperature itself. The combination of green roof and walls has a valid role to play in heat index attenuation.

Uso de sistemas vegetados e os impactos na promoção da saúde

“…Various studies have reported the efficiency of green roofs and walls in attenuating indoor temperatures 9,10,11,12 .…”

“…Wilkinson & Castiglia Feitosa 10 found temperatures as much as 14.8ºC lower in prototypes with retrofitted green roofing compared to those without green technology. Castiglia Feitosa & Wilkinson 12 also assessed the heat sensation in prototype buildings in Sydney, Australia, based on characterization of the risk of human exposure to heat according to the U.S. National Weather Service (NWS) 13 . The authors found that modular green systems fitted to walls and roofs were capable of reducing the proportion of extreme heat conditions (> 41ºC, categorized as "danger" and "extreme danger"), from 11.7% to only 0.4%.…”

“…The fact that a system can be applied without commercial intermediaries essentially means a cost reduction. Similar systems using trays with lids can be used to cover walls, also using affordable and accessible materials on the market 12 . Importantly, however, green walls and façades are more complex than green roofs, since they require specific materials for their attachment, such as brackets, scaffolds, etc.…”

Improving the Indoor Environment through an Indoor Green Curtain System

“…Vertical greenery systems have shown their advantages in different climates, as green walls improve the thermal comfort of indoor environments, and can also reduce a building's energy consumption during the summer and winter seasons [27][28][29][30]. Moreover, the cooling load was reduced by 20% when plants were used as green walls instead of blinds under the same solar radiation intensities [31].…”