1,720,986 research outputs found
On the relation between urban climate and energy performance of buildings. A three-years experience in Rome, Italy
No full textClimatic conditions strongly affect the energy performance of buildings, and due to the synergy between global climate change and the Urban Heat Island (UHI) effect, the climatic conditions inside and outside the city are highly different. However, weather data collected at airports are commonly used for building energy simulations and these data do not take into account real temperature distribution in cities. Many studies in the literature address the topic but mostly considering only a couple of urban and non-urban stations. In this paper, the urban climate in Rome, Italy, is analysed after monitoring of the air temperature and relative humidity in four selected neighbourhoods and one reference station from October 2014 until September 2017. Rome is characterised by a composite urban pattern and high variability of building types, of which the four selected areas are representative. The heating degree days decrease up to 18% and cooling degree days increase up to 157% in the urban area with respect to the rural reference and the area most affected by the UHI is the city centre. The UHI is more intense in summer than in winter (average increase between 0.7 °C and 1 °C); while the diurnal and nocturnal UHI depends on the season and the neighbourhood. Then, the energy performance of a representative apartment block and a typical office building was computed using the measured data. Regarding the predicted energy performance, comparing the four urban sites and the reference site, the UHI causes a reduction of heating consumption up to 21% in residential building and 18% in the office building. An increase of cooling consumption up to 74% is instead computed for the residential building and up to 53% for the office building. © 2018 Elsevier Lt
Survey and solutions for potential cost reduction in the design and construction process of nearly zero energy multi-family houses
Full text linkWhile the day in which nearly zero energy buildings is quickly approaching, their construction cost remains higher than minimum requirements' ones, in this framework operates CoNZEBs (Solution sets for the cost reduction of new Nearly Zero-Energy Buildings) Project, funded EU Horizon 2020. This paper explores a critical point identified by the project: potential cost reductions in the design and construction process. Starting from current costs and assessed the lack of available data, a survey is carried out focusing on two main stakeholders: i) design and planning process actors; ii) construction companies and contractors. About 100 answers are collected within the participant countries (Denmark, Germany, Italy, Slovenia), providing insights about issues and potential solutions for the process cost reductions. The results show differences among countries in terms of expectations for the potentials solutions, mainly related to the national market characteristics. The survey also shows the critical issue of the increase for construction costs respect to the originally planned ones Another session presents the impact of exemplary solutions aimed at optimising the design and construction process costs; they are grouped in three categories: specific building envelope and energy system technologies, specific design solutions, innovative project management systems. Quantitative examples are provided for each category
Assessment of construction cost reduction of nearly zero energy dwellings in a life cycle perspective
Full text linkConcerning Nearly Zero Energy Buildings, it is important to guarantee energy efficiency, thermal comfort and indoor environmental quality, while keeping construction and operational costs low. In this framework, this paper explores the efficacy of applying different scenarios, for reducing construction costs of new nearly zero energy multi-family houses in a life cycle perspective. Conversely to the standard cost-optimal approach, a real Italian case study building was chosen. Alternative and unconventional combinations of solutions for envelope and technical systems were adopted. Calculations were performed in two Italian cities (Rome and Turin). Three types of analysis were developed thermal comfort, energy performance and financial calculation. Results of the thermal analysis show that the installation of active cooling to prevent summer overheating can be avoided by applying low-cost passive strategies. All the proposed low-cost scenarios (4 alternative scenarios in Rome and 5 in Turin)reached the highest grade of energy performance, with a reduction of the non-renewable primary energy consumption up to 46% compared to the base case in Rome and 18% in Turin. From the economic perspective, all the scenarios in the two climate zones allow both reductions in the construction costs, up to 26% in Rome and 15% in Turin, and a Net Present Value after 50 years up to 163 €/m2 in Rome and 158 €/m2 in Turin
Towards the development of a smart district: the application of an holistic planning approach
No full textThe most important challenge for planners and administrations is to identify optimal strategies for improving city life from a global point of view. Urban Planning models should therefore provide solutions in a coordinated and holistic way and should be flexible and adapted to different contexts and territorial levels. Currently, a global approach to the development of Smart Cities is still missing. In this paper the authors developed a planning methodology based on the qualitative and quantitative evaluation of the reciprocal impacts among Smart strategies applied at the district level. The aim is to assess if and to what extent these actions would influence the performance of the district from a global perspective (Economy, Energy, Mobility, Community, Environment)compared to the base case scenario. The methodology has been applied to a sustainable district ideally located in the suburb of Rome and seven Smart scenarios have been modeled and simulated (with Matlab ® - Simulink). Absolute results show the differences among the seven scenarios; the application of the normalized and a-dimensional Smart Performance indicators allowed also to identify the best scenario from a holistic perspective
The impact of humidity on vortex creation around isolated buildings
No full textThe effect of humidity on the climatic conditions and the turbulence around an isolated building has not been yet investigated in literature. This paper analyses the simultaneous effect of architectural and environmental parameters on the vortex creation around a building, focusing on the impact of relative humidity. Sixty-four 3D computational fluid dynamics simulations have been performed, coupling 4 values of inlet velocity, air temperature, solar radiation and building height with 4 values of relative humidity. Results demonstrated that the inclusion of humidity in the simulations has an impact on the vortex creation. Differences in values and trends of the vortex dimensions (Hc, Xc, and Lc) were obtained compared to previous studies where relative humidity was not considered. The highest percentage difference between the two studies regards the building height, where the addition of relative humidity made the Xc value decrease by up to 56%. Among the analysed environmental parameters, building height has the higher impact on the characteristics of the vortex, followed by air velocity. The results have been compared with the analytic formula of the ASHRAE Handbook. Cubic mathematical equations have been developed correlating the vortex dimensions with building height, air velocity and relative humidity
On the cost reduction of a nearly zero energy multifamily house in Italy: Technical and economic assessment
No full textTwo important issues concerning NZEB development are: from one side to guarantee specific heating-cooling balance for each climatic condition, taking into account thermal comfort and indoor environmental quality, and from the other side to enhance the reduction of construction and management costs, ensuring the fulfillment of NZEBs standard requirements. In this paper these two aspects have been analyzed. Numerical analyses under transient thermal conditions demonstrated that passive design (night ventilation and shadings) allow to minimize the overheating risk in summer season and consequently to avoid the installation of an active cooling system: up to 65% average cooling demand reduction can be obtained; 1.5 air change rate of night ventilation allowed to reduce the overeating risks to 16 hours only. Furthermore, the development of low-cost technical solutions in the construction phase guarantees up to 25% reduction of investment costs and high final savings, considering operational costs over the entire building life cycle (50 years). The Net Present Value of the four scenarios range from 63 €/m2 to 140 €/m
On the cost reduction of a nearly zero energy multifamily house in Italy: Technical and economic assessment
Full text linkTwo important issues concerning NZEB development are: from one side to guarantee specific heating-cooling balance for each climatic condition, taking into account thermal comfort and indoor environmental quality, and from the other side to enhance the reduction of construction and management costs, ensuring the fulfillment of NZEBs standard requirements. In this paper these two aspects have been analyzed. Numerical analyses under transient thermal conditions demonstrated that passive design (night ventilation and shadings) allow to minimize the overheating risk in summer season and consequently to avoid the installation of an active cooling system: up to 65% average cooling demand reduction can be obtained; 1.5 air change rate of night ventilation allowed to reduce the overeating risks to 16 hours only. Furthermore, the development of low-cost technical solutions in the construction phase guarantees up to 25% reduction of investment costs and high final savings, considering operational costs over the entire building life cycle (50 years). The Net Present Value of the four scenarios range from 63 €/m 2 to 140 €/m
On the potential of switching cool roofs to optimize the thermal response of residential buildings in the Mediterranean region
No full textCool materials are a well established solution to mitigate urban overheating. Notwithstanding, their net energy and cost impact might turn negative in year-round assessments, owing to space heating penalties. Thermochromic materials, that are able to switch from a prevalent absorbing to a prevalent reflective behaviour, may overcome this problem. Several studies at the material level show advantages and limits of the technology, however no marketable solution exists yet. This study aims at quantifying the energy saving potential of switching cool roofs to optimize the thermal response of residential buildings in the Mediterranean Basin. The task is performed by simulation in transient regime, drawing on different material modelling approaches. The analysis is carried out in three cities: Barcelona, Palermo and Cairo, representative of different areas of the Basin. Several scenarios are considered, different in terms of building insulation, transition temperature and switching magnitude. Thermochromic materials exhibit potential annual energy savings up to 8.5% and 19% with respect to cool and conventional roofs, respectively, when the solar reflectance switches from 0.15 to 0.75. Smaller annual energy savings are achieved as the switching magnitude is decreased. Due to several factors, thermochromic cool roof can also lead to annual energy penalties compared to static roofs. Further modelling and experimental efforts are needed to better predict the response of the material during the transition phase and refine the optimization process
A step towards the optimization of the indoor luminous environment by genetic algorithms
No full textBuildings are heavily responsible for energy consumption and CO2 emissions. Increasing their energy efficiency is in the direction of the EU strategies; and this is consistent with EU Energy Performance of
buildings Directive (EPBD 2010/31/EU), 2010. In this view the design and management of daylight and artificial light can play a fundamental role. In this paper, a method to optimize indoor lighting design from energy efficiency, economic and environmental viewpoints is presented. The optimization was developed through the Genetic Algorithms technique and the optimal layout in terms of number, location and mounting heights of luminaires in a generic office room was evaluated. Solutions with different types of light sources, nominal luminous flux and photometric distribution curves were compared and the cost effectiveness of these alternatives was also considered. The systems resulting from the optimization show increased uniformity of illuminance, a reduction of the number of luminaires and a decrease of the maximum UGR values, proving the effectiveness of the technique in the lighting design field. Results show that current methods for lighting design can still be improved to achieve optimal configurations in terms of energy efficiency and cost effectiveness
On the Validity of Daylight Factor for Evaluating the Energy Performance of Building
No full textThe Daylight factor is internationally recognized as the synthetic parameter to relate indoor visual task lighting requirements and daylight availability. Nevertheless, problems related within its static nature and the absence of connection with environmental parameters and geographic location, have been repeatedly highlighted in the literature. From an energy point of view, it is used in the European standard EN 15193:2008 for evaluating daylight penetration in buildings. Standard sky for D calculation (Overcast sky) has been defined as the most conservative, and from an energy point of view, this is very useful because represents the condition of peak energy consumption for artificial lighting. The aim of this study is to verify if D calculated under other sky conditions could be more conservative from an energy point of view. Whenever this case would occur, in order to keep results on the safe side, appropriate corrections should be applied to the D in the EN 15193:2008
- …
