scholarly journals Determining Thermal Specifications for Vegetated GREEN Roofs in Moderate Winter Climates

2015 ◽  
Vol 9 (13) ◽  
pp. 208
Author(s):  
Christoph Maria Ravesloot
Keyword(s):  
Thermal Insulation ◽  
Thermal Performance ◽  
Energy Use ◽  
Green Roof ◽  
Green Roofs ◽  
Physical Parameters ◽  
Winter Climate ◽  
Theoretical Contribution ◽  
Winter Conditions ◽  
U Value

<p class="zhengwen">Because local weather conditions in moderate climates are changing constantly, heat transfer specifications of substrate and vegetation in vegetated green roofs also change accordingly. Nevertheless, it is assumed that vegetated green roofs can have a positive effect on the thermal performance of construction in winter conditions. Is there proof from scientific research and field testing for this assumption? To answer this question, research is conducted with the main research question: Which parameters defining thermal performance for vegetated green-roof construction for a moderate winter climate like that in the Netherlands can be determined from existing literature, and how do these parameters influence thermal performance? Literature research was executed on monitoring and testing of thermal specifications of vegetated green roofs. Models with physical parameters on vegetated green roofs were studied and compared. The first goal was to make a list of all physical parameters and corresponding variables valid in the Dutch moderate-winter climate. None of the models that were found in the literature seemed to cover all physical processes. These models use parameters and variables to calculate the overall u-value of substrate and vegetation. Nevertheless, one nearly complete model was used for a sensitivity test on variables. Maximum and minimum values of variables were calculated in the model to determine the influence on the outcome in terms of u-value. From this analysis, a distinction could be made between variables influencing the u-value strongly and other variables influencing the outcome weakly.</p><p class="zhengwen">The modelling showed that three variables were influencing the model calculations moderately strongly and therefore the thermal performance of the vegetated green-roof substrate and vegetation. These variables are not consistent with parameters modeling or calculating u-value in constructions. This finding means that contribution to thermal insulation by extensive vegetated green-roof substrate and vegetation in terms of u-value would be negligible. Only a small theoretical contribution to thermal insulation can be argued from weak variables. To be sure about this small theoretical contribution to the u-value of the roof construction, this u-value was used as input for energy-use calculations for residential buildings. These calculations show that such a small increase of the u-value leads to no visible reduction in energy use for heating in winter conditions. The contribution is negligible compared to the influence of the u-value from extra insulation under the roof.</p>For vegetated green roofs in such moderate winter climates as in the Netherlands, additional u-value will have to be proven specifically, because the modelling shows that, in general, no contribution to thermal insulation can be expected.

Research and simulation analysis of thermal performance and hygrothermal behavior of timber-framed walls with different external thermal insulation layer: Cork board and anticorrosive pine plate

2020 ◽  
pp. 174425912093672
Author(s):  
Haiyan Fu ◽  
Yewei Ding ◽  
Minmin Li ◽  
Yu Cao ◽  
Wenbo Xie ◽  
...  
Keyword(s):  
Thermal Insulation ◽  
Thermal Performance ◽  
Simulation Analysis ◽  
Living Environment ◽  
Wall Structure ◽  
Cold Winter ◽  
Winter Climate ◽  
Hygrothermal Behavior ◽  
Building Wall ◽  
Mold Spore

In order to improve the comfort of the living environment, the thermal performance and temperature–humidity regulation of the exterior walls of two timber-framed structure buildings is theoretically calculated and experimentally studied in this study. Both of the two buildings are located in Nanjing, China, the hot-summer and cold-winter zone. Then WUFI is used to simulate and predict the changes of temperature, relative humidity, and water content of the two timber-framed structure buildings, to strengthen the theoretical analysis of the thermal and humidity coupling of the external walls, and to propose an optimal design scheme for the insulation and temperature and humidity regulation of the external walls. The main results show that the tested thermal conductivity is basically consistent with the predicted value, which prove that WUFI simulation can effectively predict the thermal insulation performance of the external wall. The two timber-framed structure buildings are both suitable for the cold areas, and the reasonable optimization of the design of the structure is the key to the insulation of the building wall. Timber-framed structure is proved to have good temperature–humidity regulation effect. The moisture content of the two timber-framed structure buildings is stable, and the annual temperature and winter humidity are within the appropriate humidity range, which indicates that the wall design is suitable for Nanjing hot-summer and cold-winter climate zone. Four types of wall structure indoor mold spore germinations are less likely, which is not easy to produce the mold. The above research aims to optimize the design of the energy-saving wall of the timber-framed structure and create a comfortable and healthy living environment.

scholarly journals Technical considerations in green roof retrofit for stormwater attenuation in the Central Business District

2015 ◽  
Vol 33 (1) ◽  
pp. 36-51 ◽  
Author(s):  
Sara Wilkinson ◽  
Jessica Lamond ◽  
David G Proverbs ◽  
Lucy Sharman ◽  
Allison Heller ◽  
...  
Keyword(s):  
Built Environment ◽  
Focus Groups ◽  
Energy Use ◽  
Relevant Literature ◽  
Green Roof ◽  
Green Roofs ◽  
Environmental Benefits ◽  
Design Stage ◽  
Due Diligence ◽  
Content Type

Purpose – The key aspects that built environment professionals need to consider when evaluating roofs for the purpose of green roof retrofit and also when assessing green roofs for technical due diligence purposes are outlined. Although green or sod roofs have been built over many centuries, contemporary roofs adopt new approaches and technologies. The paper aims to discuss these issues. Design/methodology/approach – A mixed methods design based on a systematic review of relevant literature from parallel disciplines was used to identify and quantify the social, economic and environmental benefits of retrofitted green roofs in commercial districts. The technical issues of concern were drawn from a desk-top survey of literature and from stakeholder focus groups undertaken in Sydney in 2012. Findings – There are perceptions amongst built environmental practitioners that may act as artificial barriers to uptake. There is little direct experience within built environment professionals and practitioners, along with a fear of the unknown and a risk averse attitude towards perceived innovation which predicates against green roof retrofit. Furthermore projects with green roofs at inception and early design stage are often “value engineered” out of the design as time progresses. There is a need for best practice guidance notes for practitioners to follow when appraising roofs for retrofit and also for technical due diligence purposes. Research limitations/implications – The focus groups are limited to Sydney-based practitioners. Although many of these practitioners have international experience, few had experience of green roofs. A limited number of roof typologies were considered in this research and some regions and countries may adopt different construction practices. Practical implications – In central business districts the installation of green roof technology is seen as one of the main contributors to water sensitive urban design (WSUD). It is likely that more green roofs will be constructed over time and practitioners need knowledge of the technology as well as the ability to provide best advice to clients. Originality/value – The benefits of green roofs as part of WSUD are increasingly being recognised in terms of reduced flood risk, reduced cost of drainage, improved water quality and lower energy use, as well as other less tangible aspects such as aesthetics and amenity. This research highlights the lack of understanding of the short- and long-term benefits, a poor appreciation and awareness of these benefits; a lack of technical knowledge and issues to be considered with regard to green roofs on behalf of practitioners. The study has highlighted the need for specific training and up-skilling in these areas to provide surveyors with the technical expertise needed. There is also a need to consider how the emerging retrofit and adaptation themes are best designed into the curriculum at both undergraduate and postgraduate levels. Clearly, if the potential benefits of green roofs are to be realised in the future, building professionals need to be fully conversant with the technology and be able to provide reliable and accurate advice.

scholarly journals COBERTURA E FACHADA VERDE:

2019 ◽  
Vol 8 (2) ◽  
pp. 89-100
Author(s):  
Thiago Youzi Kussaba Kayano ◽  
Nuria Perez Gallardo ◽  
Bruno César dos Santos ◽  
Mauricio Sanches Duarte Silva ◽  
Rafael Perussi ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Thermal Performance ◽  
Green Roof ◽  
Green Roofs ◽  
Sao Paulo ◽  
Test Cell ◽  
São Paulo ◽  
Control Test ◽  
Green Façade ◽  
Green Facade

Com a busca de alternativas para melhorar o conforto ambiental em ambientes construídos, os sistemas de fachadas e tetos verdes aparecem como uma opção para melhoria, em especial, do conforto térmico. Utilizando-se de um episódio climático representativo no mês de junho de 2016, analisou-se comparativamente o comportamento térmico de uma célula de teste com fachada e teto verde e uma célula de controle para avaliação do desempenho térmico em dia crítico experimental de frio. O experimento foi realizado no Centro de Recursos Hídricos e Estudos Ambientais (CRHEA) da Universidade de São Paulo (USP), em Itirapina-SP. Os resultados indicaram que a célula de teste com fachada e teto verde possui um melhor desempenho térmico em comparação à célula de controle. Palavras-chave: desempenho térmico, episódio climático representativo, comportamento térmico, fachada verde, cobertura verde. Abstract In searching for better thermal behavior alternatives in building environments green facade systems and green roofs emerge as an improvement option, particularly in thermal comfort. Using a representative climate episode to analyze the month of June of 2016 we studied the thermal performance of a green façade and green roof test cell and a control test cell in experimental critical cold day. The experiment was made in Water Resource and Environmental Studies Center (CRHEA) of University of São Paulo (USP), in Itirapina-SP. The results indicated the green wall and green roof test cell have a better thermal performance than control test cell. Keywords: Thermal performance, climatic representative episode, thermal behavior, green façade, green cover.

Reed as a Thermal Insulation Material: Experimental Characterisation of the Physical and Thermal Properties

2022 ◽  
Author(s):  
Raphaele Malheiro ◽  
Adriana Ansolin ◽  
Christiane Guarnier ◽  
Jorge Fernandes ◽  
Lívia Cosentino ◽  
...  
Keyword(s):  
Thermal Insulation ◽  
Thermal Performance ◽  
Carbon Emissions ◽  
Building Materials ◽  
Energy Use ◽  
Low Cost ◽  
Insulation Material ◽  
The European Union ◽  
Building Stock ◽  
Thermal Insulation Material

The building sector plays a significant role in reducing global energy use and carbon emissions. In the European Union (EU), the building stock represents 40% of total energy use and in which cooling and heating systems represent over 50%. Portugal is one of the EU countries where the consequences of energy poverty are most evident due to the families' financial inability to adequately climate their homes. The reasons are several, but they are mainly linked to buildings' poor passive thermal performance, resulting from inadequate adaptation to the climatic context and reduced thermal insulation. Thus, it is necessary to develop solutions to increase buildings’ thermal performance and reduce their potential environmental impact, which arises mainly from the significant use of active systems. In this sense, natural building materials are a promising solution, reducing energy use and carbon emissions related to buildings. This research studies the potential use of reed found in Portugal (Arundo donax) as a thermal insulation material. Its physical characterisation and the influence of geometry configuration on its thermal performance are evaluated. Its durability was studied too. Reed stalks were used to carry out the physical and durability tests. A reed board (150 x 150 mm) was built, and its thermal performance was tested in a hotbox. According to the results, the characteristics of reeds found in Portugal make it suitable to be used as a building material. Furthermore, regardless of the configuration studied, the reeds have a satisfactory thermal performance to be used as thermal insulation, under the requirements defined by Portuguese thermal regulation, Re ≥ 0.30 (m2.oC)/W. There is a trend to the mould growth in the reed, but only under favourable conditions. Additionally, considering the abundance of reed throughout the Portuguese territory, this is an eco-friendly and low-cost option that gathers all requirements to be more used in the construction market.

scholarly journals A Comparison of Energy and Thermal Performance of Rooftop Greenhouses and Green Roofs in Mediterranean Climate: A Hygrothermal Assessment in WUFI

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2030
Author(s):  
Mansoureh Gholami ◽  
Alberto Barbaresi ◽  
Patrizia Tassinari ◽  
Marco Bovo ◽  
Daniele Torreggiani
Keyword(s):  
Thermal Performance ◽  
Mediterranean Climate ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Building Envelope ◽  
Considerable Proportion ◽  
Urban Context ◽  
Cooling Period ◽  
The Impact

In urban areas, a considerable proportion of energy demand is allocated to buildings. Since rooftops constitute one-fourth of all urban surfaces, an increasing amount of attention is paid to achieving the most efficient shapes and component designs compatible with every climate and urban context, for rooftops of varying sizes. In this study, three types of rooftop technologies, namely insulated, green roof, and rooftop greenhouse, are evaluated for energy and thermal performance using computer simulations. Water surface exposure, absorption, and intrusion are the three important factors in the calculation of hygrothermal models that impact energy consumption and building envelope performance; however, a few studies are specifically focused on providing realistic results in multi-dimensional hygrothermal models and the assessment of the impact of moisture in roofing solutions. This paper aims at evaluating the performance of three different roofing technologies through a two-dimensional hygrothermal simulation in software WUFI. To accomplish this, a precise localized microclimate model of a complex urban context on the scale of a neighborhood was employed to evaluate the cooling and heating loads of the buildings, the impact of the water content in the green roof on the thermal behavior of the roof surface, and the feasibility of designing a building with nearly zero cooling needs. A two-story building in the city center of Bologna, Italy is modelled. Simulation results have shown that during the cooling period, the performance of the designed rooftop greenhouse is the most effective by 50% reduction in cooling loads. Besides, the impact of moisture in green roofs has been detected as a negative factor for thermal and energy performance of the building in the Mediterranean climate. The results ultimately highlighted the capability of passively-designed rooftop greenhouses to create a building with nearly zero cooling needs.

scholarly journals Impact of Vegetation, Substrate, and Irrigation on the Energy Performance of Green Roofs in a Mediterranean Climate

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2016 ◽  
Author(s):  
Gomes ◽  
Silva ◽  
Valadas ◽  
Silva
Keyword(s):  
Mediterranean Climate ◽  
Energy Use ◽  
Soil Depth ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Area Index ◽  
Vegetation Height ◽  
Energy Needs ◽  
Irrigation Levels

Green roof energy performance is still a challenging topic, namely in a Mediterranean climate since it depends on building characteristics, roof type, and also on climatic conditions. This paper evaluates green roof buildings’ energy needs and use in a Mediterranean climate. An experimentally calibrated numerical model was used to perform a parametric analysis and identify the influence of key parameters in heating and cooling energy needs, as well as annual energy use. The vegetation height, the soil depth, and LAI (leaf area index) were identified as the key parameters. The irrigation levels were also crucial for the energy performance of green roofs, particularly during the summer period and in a Mediterranean climate. Heating energy needs were mainly associated with soil depth due to higher thermal resistance, whereas cooling energy needs depended mostly on LAI, which influenced evapotranspiration and shading effects. A reduction of soil depth from 1.0 m to 0.1 m increased winter energy needs by up to 140%, while low values of LAI increased cooling energy needs up to 365%. Annual energy use in a Mediterranean climate showed a higher dependence on soil depth, with oscillations of up to 115%, followed by LAI and vegetation height. Finally, irrigation levels impacted the annual energy use more significantly for lower watering flow rates. Reductions of about 500% were obtained when changing watering flowrates from 0 mm/day to 6 mm/day in intensive green roofs. Since green roofs with native species expect low values of watering, this may increase their cooling energy needs.

scholarly journals Cement blocks with EVA waste for extensive modular green roof: contribution of the components for thermal insulation

2017 ◽  
Vol 10 (1) ◽  
pp. 92-106 ◽  
Author(s):  
A. B. DE MELO ◽  
T. N. M. MENDONÇA
Keyword(s):  
Thermal Insulation ◽  
Green Roof ◽  
Internal Surface ◽  
Green Roofs ◽  
Additional Contribution ◽  
Surface Temperatures ◽  
Air Temperatures ◽  
Footwear Industry ◽  
Hot And Humid Climates ◽  
Typical Summer

Abstract Green roofs can contribute in many ways to the quality of the environment, being known for reducing the heat transfer to the interior of the buildings. Amongst the available techniques for the execution of this type of covering, the use of light cement blocks which are compatible with the system of extensive modular green roofs is proposed. For the light cement blocks, produced with EVA aggregates (waste from the footwear industry), an additional contribution in the capacity of thermal insulation of the proposed green roof is expected. In the present article, the demonstration of such contribution is intended through measurements carried out in prototypes in hot and humid climates. After characterizing the capacity of thermal insulation of the proposed green roof, with different types of conventional covering as a reference, an additional contribution of the component used in this green roof was identified by making comparisons with measurements collected from another green roof, executed with cement blocks without the presence of the EVA aggregates. In the experiments, external and internal surface temperatures were measured in each of the prototypes' coverings, as well as the air temperatures in the internal and external environments. From the analysis of the data for a typical summer day, it was possible to prove that the proposed green roof presented the lowest temperature ranges, considering the internal air and surface temperatures. The presence of the EVA aggregates in the proposed blocks contributed to the decrease of the internal temperatures.

Thermal Performance Evaluation of Green Roofs in Warm Humid Climates: A Case of Residential Buildings in Madurai, India

2016 ◽  
Vol 692 ◽  
pp. 82-93 ◽  
Author(s):  
A Madhumathi ◽  
S. Radhakrishnan ◽  
R. Shanthipriya
Keyword(s):  
Thermal Properties ◽  
Thermal Performance ◽  
Energy Demand ◽  
Residential Buildings ◽  
Green Roof ◽  
Green Roofs ◽  
Outdoor Environment ◽  
Thermal Mass ◽  
Second Phase ◽  
Rapid Urbanization

Green roof application on real residential buildings in Tamilnadu, India is very limited and mostly concentrated in major cities mainly for visual purposes. There is not enough research has been conducted to boost up the benefits of green roof system in Warm and Humid weather in India. Green roofs have the potential to improve the thermal performance of a roofing system through shading, insulation, evapotranspiration and thermal mass, thus reducing a building’s energy demand for space conditioning. To quantify the thermal performance and energy efficiency of green roofs an experimental investigation was done in residential buildings of Madurai, Tamilnadu, India. This paper refers to the analysis of the thermal properties and indoor thermal performance study of the green roof. The investigation were implemented in two phases: during the first phase, extended surface, air temperature and relative humidity measurements were taken at the indoor and outdoor environment of the buildings where the green roof had installed and during the second phase of the study, the thermal properties of the green roof, as well as, the cooling potential were examined. Results showed vegetative roofs reduced heat gain compared to the white reflective roofs and conventional reinforced cement concrete due to the thermal mass, extra insulation, and evapo-transpiration associated with the vegetative roofing systems. The results also proved that green roofs provide acceptable indoor thermal performance with respect to the other conventional roofs while re-establishing the relationship between human and environment, which have been destroyed due to the rapid urbanization.

THERMAL PERFORMANCE OF AN EXTENSIVE GREEN ROOF UNDER SEMI-ARID CONDITIONS IN CENTRAL ARGENTINA

2021 ◽  
Vol 16 (1) ◽  
pp. 17-42
Author(s):  
Lelia Imhof ◽  
Edgardo Suárez ◽  
Natalia Cáceres ◽  
Federico Robbiati ◽  
Cecilia Cáceres ◽  
...  
Keyword(s):  
Thermal Performance ◽  
Green Roof ◽  
Green Roofs ◽  
Climatic Conditions ◽  
Urban Environments ◽  
Climate Conditions ◽  
Average Temperature ◽  
Arid Conditions ◽  
The Difference ◽  
Extensive Green Roofs

ABSTRACT Extensive green roofs improve the provision of ecosystem services in urban environments, particularly in semiarid regions. The aim of this paper is to compare their thermal performance during six months between two rooms, one with a green roof and the other with a conventional roof, in Córdoba (Argentina). The room with a green (planting) roof showed a lower inside surface temperature since the beginning of the study than the control room (between 5–6°C of difference). During the selected period, the indicators such as temperature amplitude (the difference between the maximum and the average temperature) and the anti-interference characteristics of the layers to the outdoor air temperature are produced a better performance for the green roof compared to the conventional roof. The pattern of a better performance was consistent across the study for the green roof, characterized by a higher cooling and warming of the roof surface during the day and night, respectively. The green roof was more effective at blocking an upward heat flux during the day and suppressing heat loss during the night. Evaporation, conductive flux and climatic conditions seem to dominate the thermal performance of green roofs in areas with semiarid climate conditions.

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