Urban Heat Island (UHI) is a worldwide threat affecting building energy demand, public health, and energy security. Green wall deployment can simultaneously positively impact UHI and building energy ...demand depending on climate zones.
According to the different climate zones worldwide, the present systematic literature review (SLR) investigates the direct effects of green wall installation on building energy use and UHI. 1325 articles were screened, and 51, corresponding to 647 case studies, were selected after removing those with methodological or statistical heterogeneity. The effects of green wall deployment have been explored according to cooling and heating season, weather conditions, daytime, nighttime, green wall typology, green wall orientation, and application scale.
The performed analyses show that green walls: (1) can reduce heating and cooling building energy demand up to 16.5% and ∼51%, respectively, and mitigate UHI up to ∼5 °C in all the investigated climate zones; (2) can decrease to the greatest extent building energy needs when applied in low-density urban contexts where they can be installed on the entire building. Besides, when applied to a single façade, South orientation should be preferred in most climate zones to maximize building energy saving; (3) have the best UHI mitigating potential—up to 8 °C—in highly urbanized areas featured with narrow streets surrounded by high-rising buildings.
Altogether, green walls are a fit-all solution to reduce building energy demand and mitigate UHI, providing healthier living conditions. However, further research is necessary to include quantifiable and unquantifiable effects omitted in the current study.
•Green walls have been investigated in different climate zones.•The effect of green wall deployment on building energy use and UHI was explored.•Green wall deployment decreases building energy needs for space heating and cooling.•Green wall installation may reduce air temperature by up to 8 °C in street canyons.•Large-scale installation of green walls may fully mitigate UHI.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Indoor plants can improve indoor thermal environment, relieve the anxiety, and reduce the CO2 concentration especially in enclosed rooms with air-conditioning and heating. However, owing to the space ...limitation and the light requirement, it is very difficult to maintain traditional large-scale plantings indoors. To improve indoor planting efficiency and thermal environment, the living wall was introduced to be combined with air-conditioning. Two identical rooms were built to analyze the efficiency of combining a living wall with air-conditioning. One room contained a living wall and air-conditioning, while the other room only with air-conditioning was served as a reference. The indoor thermal environment and CO2 concentration were monitored, while the 64 participants were questioned to display their subjective feelings in two rooms. The results showed that combining the living wall lowered the relative humidity by 2.6%, maintained the indoor air speed at 0.20 m/s∼0.30 m/s and reduced the CO2 concentration by approximately 10%, while it increased the uniformity of these environmental parameters. The average skin temperature in the room with the living wall was 0.2 °C higher than that in the referred room and closer to the neutral mean skin temperature. The living wall significantly improved the subjective evaluation on indoor environment, especially in air movement and air freshness, with the thermal comfort level from 0.13 (Slightly higher than ''Neutral (0)'') to 0.73 (Slightly lower than ''Comfortable (+1)'').
•A new method was proposed to improve indoor environment.•Living wall reduced indoor CO2 concentration by about 10%.•Living wall also could reduce indoor relative humidity.•Living wall could improve indoor thermal comfort.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Life-Cycle Assessment (LCA) is a standard approach for evaluating the environmental impacts of products and processes. This paper presents the LCA of Living Wall Systems (LWS), a new technology ...for greening the building envelope and improve sustainability. Impacts of manufacture, operation, and use of the systems selected, were evaluated through an LCA. LWS are closely related to several environmental benefits, including improved air quality, increased biodiversity, mitigation of heat island effects, and reduced energy consumption due to savings in indoor cooling and heating. Two prototypes have been selected, taking into account the modularity and the use of organic substrate as selection criteria. The systems evaluated were a plastic-based modular system and a felt-based modular system. The inventory data was gathered through the manufacturers. The LCA approach has been used to assess the impact of these solutions by focusing on the construction phase and its contribution to both the energy balance and the entire life cycle of a building. This approach has never been done before for LWS. The study found that out of the two systems through the manufacturing, construction, and maintenance stage of the LCA, the felt-based LWS has an impact on almost 100% of the impact categories analyzed, while plastic-based LWS has the lowest influence on the total environmental impact.
•Two prototypes of modular living wall systems analyzed through Life Cycle Assessment (LCA) method.•Life cycle approach to evaluating environmental impact and energy savings on buildings of the living wall systems as a passive system.•The environmental performance of living wall systems can be improved by selecting materials according to LCA results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Green infrastructure (GI) is already known to be a suitable way to enhance air quality in urban environments. Living wall systems (LWS) can be implemented in locations where other forms of GI, such ...as trees or hedges, are not suitable. However, much debate remains about the variables that influence their particulate matter (PM) accumulation efficiency. This study attempts to clarify which plant species are relatively the most efficient in capturing PM and which traits are decisive when it comes to the implementation of a LWS. We investigated 11 plant species commonly used on living walls, located close to train tracks and roads. PM accumulation on leaves was quantified by magnetic analysis (Saturation Isothermal Remanent Magnetization (SIRM)). Several leaf morphological variables that could potentially influence PM capture were assessed, as well as the Wall Leaf Area Index. A wide range in SIRM values (2.74-417 μA) was found between all species. Differences in SIRM could be attributed to one of the morphological parameters, namely SLA (specific leaf area). This suggest that by just assessing SLA, one can estimate the PM capture efficiency of a plant species, which is extremely interesting for urban greeners. Regarding temporal variation, some species accumulated PM over the growing season, while others actually decreased in PM levels. This decrease can be attributed to rapid leaf expansion and variations in meteorology. Correct assessment of leaf age is important here; we suggest individual labeling of leaves for further studies. Highest SIRM values were found close to ground level. This suggests that, when traffic is the main pollution source, it is most effective when LWS are applied at ground level. We conclude that LWS can act as local sinks for PM, provided that species are selected correctly and systems are applied according to the state of the art.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Vertical vegetation systems are an innovative passive method for decreasing the thermal energy demand of buildings while increasing the quality of urban life. The main objective of this work is to ...calculate the effectiveness of vegetation in reducing thermal loads analytically. For this purpose, the thermal energy performance of the modular living wall was compared with a traditional double façade construction system to evaluate the influence of vegetation using Stochastic Differential Equations models.
The research was carried out experimentally using a real-scale PASLINK test cell. The thermal behaviour of a double leaf bare wall and the same double leaf wall converted into a modular living wall were calculated for different summertime and wintertime periods. In both studied cases, the temperature of the exterior surface of the bare wall is taken at the same place regardless of whether or not there is greenery system in the energy balance. With this simplification, the effect of the modular living wall can be identified within the estimated coefficients.
The thermal resistance of the conventional double façade increased 0.74 (m2 K)/W over the non-greened wall, which represents a weighted increase of 49%. Additionally, the experimental results showed that the evapotraspiration processes that take place in the living wall lead to an increase in the combined convection-radiation coefficient, which reduces the overheating of the façade. Moreover, the effective solar absorptivity value of the outermost surface of the bare wall has been reduced an 85% thanks to the living wall, which confirms the high capacity of the living wall to reduce solar heat gains.
•Thermal model characterization of PASLINK test cell.•High energy savings in cooling and small increase in heating.•Modular living wall did not provide any thermal benefits in cold winter.•Modular living wall installation may reduce building surface temperature by up to 10 °C in summertime.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Green walls that effectively treat greywater have the potential to become a part of the solution for the issues of water scarcity and pollution control in our cities. To develop reliable and ...efficient designs of such systems, the following two research questions were addressed: what would be the optimal design of a green wall for greywater treatment, and how tall should the system be to assure adequate treatment. This paper reports on (i) a long-term pollutant removal comparison study of two typical green wall configurations: pot and block designs, and (ii) a short-term profile study exploring pollutant retention at different heights of a three-level green wall, across different plant species. Removal of suspended solids (TSS), nitrogen (TN), phosphorus (TP), chemical oxygen demand (COD) and Escherichia coli was tested, as well as various physical parameters. Pot and block designs were found to exhibit similar pollutant removal performance for standard and high inflow concentrations, while the block design was more resistant to drying. However, due to its multiple practical advantages, pot designs are favoured. The greatest removal was achieved within the top green wall level for all studied pollutants, while subsequent levels facilitated further removal of TSS, COD, and TN. Interestingly, colour, pH, and EC increased after each green wall level, which must be taken into account to determine the maximum height of these systems. The optimal size of the system was found to be dependent on plant species choice. The results were used to create practical recommendations for the effective design of greywater treatment green walls.
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•Pot and block green wall designs have similar pollutant removal performance.•Block designs more resilient to drying, while pot designs are more practical.•Top green wall level has highest pollution removal, minor effect of other levels.•Colour, pH and EC accumulate in green walls, limiting maximum height.•Two- or three-level pot green wall with appropriate plants is the most viable.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Expansion of modern cities reduces green areas, especially within city centres where the urban heat island has become a significant problem. In an attempt to increase greenery in cityscapes and to ...provide passive cooling, vertical greenery systems (VGS), an old practice of covering building façades with plants, are receiving attention from architects, engineers, building planners and researchers. This paper systematically reviews available publications on VGS and classifies them according to 13 distinct themes. Research into VGS has increased over recent years and the trend shows the approach to this field of research is changing. Thermal research remains the most prevalent theme compared to others, representing almost half of all publications (76 out of 166), with the top three most highly-cited articles all related to thermal properties of VGS. Nevertheless, the systematic review shows a strong trend of diversification into cross-disciplinary research. The proportion of VGS papers reporting on two or more themes has grown from 25% in 2011 to more than 60% in 2017. The review has revealed that among the limiting factors to VGS are cost and maintenance. The outcomes of this systematic review allow recommendations to be made to architects, designers, planners and owners of VGS regarding the need to account for maintenance in the overall design and operation of these systems. On the basis of this review, future research into VGSs will be increasingly multidisciplinary and will need to consider the interconnected dimensions of the system and how they determine both its cost and effectiveness.
•Systematic review on VGS identified 1000 articles from Scopus and WoS; 166 articles included in final review.•Increasing research trend in VGS with 42 articles reviewed published in 2017, from 8 in 2010.•Included top ten journals publishing VGS research and top ten cited articles in VGS research.•Trend towards multidisciplinary research with growing number of articles relating to more than one discipline.•Identified emerging research and new technologies in VGS field.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Currently no sustainable, economical and scalable systems have been developed for the direct removal of roadside air pollutants at their source. Here we present a simple and effective air filtering ...technology: botanical biofiltration, and the first field assessment of three different botanical biofilter designs for the filtration of traffic associated air pollutants – NO2, O3 and PM2.5 – from roadside ambient air in Sydney, Australia. Over two six month research campaigns, we show that all of the tested systems filtered NO2, O3 and PM2.5 with average single pass removal efficiencies of up to 71.5%, 28.1% and 22.1% respectively. Clean air delivery rates of up to 121 m3/h, 50 m3/h and 40 m3/h per m2 of active green wall biofilter were achieved for the three pollutants respectively, with pollutant removal efficiency positively correlated with their ambient concentrations. We propose that large scale field trials of this technology are warranted to promote sustainable urban development and improved public health outcomes.
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•Botanical biofiltration of NO2, O3 and PM2.5 was achieved at roadside environments.•NO2 was removed most efficiently, with a single pass removal efficiency of 71.5%.•Pollutant clean air delivery rates of 40–121 m3/h per 1 m2 plenum were achieved.•All pollutant removal rates were positively correlated with ambient concentrations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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