1,720,969 research outputs found
Green roofs to reduce building energy use? A review on key structural factors of green roofs and their effects on urban climate
No full textIn the next decades, the increase in global population will lead to further urbanization determining, on the one hand, an increase in building energy use and, on the other hand, a surge in urban temperature, which, in turn, affects building energy demand. Since the building sector greatly contributes to the use of energy globally, the amelioration of this sector is an urgent issue to contribute to climate stabilization. Published literature shows that green roofs affect both directly and indirectly building energy use, delivering the message that green roofs are fit-all solutions. However, the efficacy of the deployment of green roofs varies depending on climate and on their specific design. The present study contains a geographically explicit review of the potential building energy benefits deriving by the installation of green roofs depending on their specific design aiming at answering to the following research questions: - Are green roofs fit-all solutions for decreasing building energy use in diverse climates? - How insulation, growing media, and plant selection of green roofs should be calibrated in different climates to maximize their effect on building energy use? - How green roofs can contribute to urban heat island-mitigation in different climates? Answering these research-questions, this study provides urban decision-makers and planning agencies useful insights to, not only prioritize strategies, but also efficiently design by-laws and local regulations to maximize the potential positive effect of urban-wide green roof deployment on building energy use
Numerical comparisons between Gauss-Legendre methods and Hamiltonian BVMs defined over Gauss points
No full textBuilding integrated vegetation effect on micro-climate conditions for urban heat island adaptation. Lesson learned from Turin and Rome case studies
Full text linkThe proposed study investigates the effect of urban heat island mitigation scenarios by applying extensive green roofs, green façades, and living walls to two built areas within Turin and Rome, Italy. Three mitigation scenarios and a baseline one have been developed in ENVI-met software for each built area and run for a typical winter day, summer day, and summer day with a heat wave. The simulation results show that building integrated vegetation technology-application on a single building has an irrelevant effect on local temperatures; contrariwise, building integrated vegetation technology-wide application can effectively mitigate urban warming. Furthermore, the effect of green roofs and green walls on urban temperature is negligible in winter, likely because of the limited plant activity and the reduced amount of incoming solar radiation. Results also show that green façades are more effective than green roofs in mitigating pedestrian-level air temperature when installed on high-rise buildings, and green walls are more beneficial in mitigating summer urban heat island when installed in canyons parallel to wind direction than in perpendicular ones. Depending on the mitigation scenario, average decreases in urban temperatures up to 1 °C can be reached in the whole selected built area, alleviating urban warming
Development of predictive indices for evaluating the UHI adaptation potential of green roof- and wall-based scenarios in the Mediterranean climate
Full text linkUrban heat islands can jeopardize urban inhabitants, but the installation of green roofs (GRs) and walls (GWs) can contribute to mitigating urban overheating. The present study provides novel indices to easily predict the spatial median variation in air temperature at pedestrian heights related to the application of GR- and GW-based scenarios during the hottest hours of a typical summer day by varying the building height (BH), coverage percentage, and leaf area index. The indices are meant to be applied to built areas with 0.3–0.4 urban density in the Mediterranean climate and are derived from regression models fed with the outputs of 281 simulations of three urban areas developed and run in ENVI-met software. The developed models are all highly significant. The GR model shows that mitigation is influenced by all three parameters, and it can estimate mitigation with a root mean square error of 0.05 °C. Compared with the other parameters, the GW models revealed that the BH did not influence the decrease in air temperature. The green façade and living wall (LW) indices predict mitigation with errors of 0.04 °C and 0.05 °C, respectively. However, for the LW model, further parameters should be considered to improve its reliability
Heat island effects in urban life cycle assessment: Novel insights to include the effects of the urban heat island and UHI‐mitigation measures in LCA for effective policy making
Full text linkUrbanization often entails a surge in urban temperature compared to the rural surroundings: the Urban Heat Island (UHI) effect. Such a temperature increase triggers the formation of pollutants worsening the urban air quality. Jointly, bad air quality and UHI affect ecosystems and human health. To alleviate the impacts on the population and the environment, it is crucial to design effective UHI‐mitigation measures. Life Cycle Assessment (LCA) is an assessment tool able to capture the complexity of urban settlements and quantify their impact. Yet, as currently implemented, LCA neglects the interactions between the built environment and the local climate, omitting the resulting impacts. This study reviews the existing literature, showing the lack of studies that organically include interactions between the built environment and local climate in LCA. This forms the basis to identify the unsuitability of the current LCA framework for comprehensively capturing the impact of urban settlements. To overcome this limitation, this research offers a pathway to expand the LCA methodology, indicating the necessity to (a) couple the LCA methodology with climate models or physical relations that quantify the interactions between the local climate and the built environment; (b) include novel impact categories in LCA to address such interactions; and (c) use existing or ad hoc developed characterization factors to assess the impacts related to the UHI effect. The LCA community can build on the frame of reference offered by this research to overcome the current limitations of LCA and enable its use for a comprehensive assessment of the impacts of UHI and its mitigation measures
Life Cicle Assessment dei solai di copertura: il contributo dell’albedo
No full textIl Life Cycle Assessment nell’applicazione all’edificio o alle sue componenti non considera le caratteristiche ottiche, come ad esempio l’albedo, in grado di influenzare gli impatti finali sull’ambiente.
In questo lavoro di ricerca è stato indagato l’impatto relativo alle fasi d’uso e manutenzione di un solaio finito con guaina nera in gomma e un altro con gomma sintetica bianca ad alta riflettanza (EPDM) considerando in entrambi i casi gli effetti dovuti all’albedo. Al fine di stimare gli impatti diretti dell’albedo, valutati nella categoria di danno Climate Change, è stato applicato un modello climatologico in grado di calcolare i forzanti radiativi
relativi alla variazione dell’albedo urbano e di esprimerli in termini di CO2 equivalenti. Mediante dati sperimentali raccolti in situ relativi alle temperature superficiali dei due solai ubicati sul Con Edison ‘Learning Center’ a Long Island City, è stato calcolato il flusso di calore attraverso le due coperture. Le analisi condotte evidenziano che la maggiore albedo dell’EPDM contribuisce ad una diminuzione totale dei flussi attraverso il solaio di circa il 9% (effetto indiretto dell’albedo). Tale valore equivale ad un abbattimento degli impatti relativi al consumo di energia elettrica o di gas naturale per il riscaldamento e per il raffrescamento, calcolati col software SimaPro 7.1 mediante il metodo IMPACT 2002+, pari al 10%. L’effetto diretto dell’albedo sul global warming è stato invece valutato nel breve (cinquanta anni) e nel lungo periodo (cento anni) mediante l’utilizzo di un modello
climatologico. In entrambi i casi la maggiore albedo determina una diminuzione degli impatti relativi alla categoria climate change pari a circa il 10-30% del totale
Effect of green wall installation on urban heat island and building energy use: A climate-informed systematic literature review
No full textUrban 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
Recent advances on the parallelization of Gauss methods
No full textWe introduce a new formulation of Gauss collocation methods for the numerical solution of ordinary differential
equations. These formulae may be thought of as Runge-Kutta methods with rank-deficient array and may be specified in order
to allow an easy parallel implementation. We show some preliminary results on Gauss methods of order 4, 6 and 8
Hamiltonian BVMs (HBVMs): implementation details and applications
No full textHamiltonian Boundary Value Methods are one step schemes of high order where the internal stages are partly exploited to impose the order conditions (fundamental stages) and partly to confer the formula the property of conserving the Hamiltonian function when this is a polynomial with a given degree v. The term "silent stages" has been coined for these latter set of extra-stages to mean that their presence does not cause an increase of the dimension of the associated nonlinear system to be solved at each step. By considering a specific method in this class, we give some details about how the solution of the nonlinear system may be conveniently carried out and how to compensate the effect of roundoff errors. © 2009 American Institute of Physics
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