1,720,992 research outputs found
Shading and layout influence on flats energy performance of an apartment building
Full text linkGiving the need for environment protection and energy need reduction, especially in the building sector, it is important to clearly understand what influences, and to what extent, buildings’ energy performance. In this work, an apartment building has been considered, and the influence of shadings and of flats layout on the energy performance ratings are evaluated. The case study is a building of the ‘90s, which has been demolished and re-built (2016) according to the actual energy requirements. For each of the 16 flats of the building, the energy certificate has been retrieved in the two configurations: before and after reconstruction. From the analysis of the specific energy consumption, and of their components (i.e. energy need for ventilation, transmission losses, solar gains), in the two configurations, a comparison amongst the flats has been drawn. Results show that the apartment layout influences the solar gains, but this influence (in percentage) is higher in the “ex-ante” configuration than in the “ex-post”. Similarly, the energy gains are more relevant in the “expost” configuration, in which some apartments, although having higher dispersing surface, result to be more efficient due to their favourable exposition
Approaching the validation of building energy models: billing vs indoor environmental data
Full text linkTo understand the real building energy consumption, and to identify the best energy improvements (due to energy refurbishment and/or HVAC replacement), the energy audit is recommended, but it generally entails the realization of an energy model of the building itself. The main issue of this approach is the collection of data, needed to verify the reliability of the energy audit results. Currently, to validate buildings energy model retrieved by hourly semi-stationary software, is it possible to refer to: (i) bills related to energy carrier (i.e. natural gas and/or electricity); (ii) monitored indoor parameters. The aim of the paper is to understand which of the two is more suitable for the purpose. In this work, the two options are investigated considering, as case study, a family house located in central Italy, whose envelope thermophysical properties and HVAC systems are known, and whose bills and indoor environmental conditions (air temperature and relative humidity) were archived since December 2019. Results from the two validation methods are very close to each other; particularly, results show that energy audit performed with indoor environmental parameters better fits the real consumption, but it entails more complex validation procedure
In Situ Thermal Transmittance Assessment of the Building Envelope: Practical Advice and Outlooks for Standard and Innovative Procedures
Full text linkDifferent standard methods for the assessment of the thermal performance of the building envelope are used: analogy with coeval building, theoretical method, heat flow meter measurement, simple hot box, infrared thermography, and thermometric method. Review papers on these methods, applied in situ and in laboratory, have been published, focusing on theory, equipment, metrological performance, test conditions and data acquisition, data analysis, benefits, and limitations. However, steps forward have been done and not been deepened in previous works: in fact, the representative points method and the weighted area method have been proposed, too, whilst artificial intelligence and data-driven methods have begun to prove the reliability also in the U-value prevision using available datasets. Considering this context, this work aims at updating the literature background considering exclusively in situ methods. The work starts from bibliometric and scientometric analysis not previously conducted: this helped to group the methods and to sketch the innovations and the future perspectives. Indeed, from the bibliometric and scientometric literature analysis what emerged was (i) the richness of the background on this topic, especially in the recent years, (ii) two macro-groups (methods with and without measurements), and (iii) the importance of paper keywords (otherwise, interesting papers are eluded by the output of simple database queries). The method study that followed aims at providing (i) a broader view of the thermal transmittance (U-value) assessment procedures, including the utmost recent applications, proposal, and outlooks in this field, (ii) the understanding on the fundamental theories of the techniques, (iii) practical advice for building-envelope assessment, focusing on the advantages and limitations useful for professionals and researchers involved in the energy audit, conservation, or refurbishment of building stock, (iv) the identification of the interconnection between the techniques that often rely on one another, and (v) final remarks and future perspective of the procedures, which embrace the use of artificial intelligence (AI). From the topic analysis, as a result, it emerged that this is an open field for future research, especially with the implementation of AI, which requires good datasets and trials on the models’ architectures, in terms of input layer, number of hidden layer and neurons, and percentage of data to be employed for model training and testing
Thermal comfort monitoring in office buildings: A case study
Full text linkIn the framework of EPBD Directive revision, the EU is pushing Member States to pay more attention to IEQ conditions in buildings, by introducing specific requirements to be verified in the calculation methodology implemented in the national building codes. In this paper, the extensive field monitoring of an office building, carried out in the heating, cooling and intermediate seasons of 2022-2023, is described. Main thermo-hygrometric quantities have been measured in different rooms, considering the occupancy profile, users’ behaviour and appliances use. Results showed overheating conditions in offices exposed to the south façade, mainly due to solar radiation and internal heat gains. Surprisingly, north-facing offices with heating terminals running are colder than south-facing ones with HVAC systems turned off. Further differences were found in the temperature analysis of free-floating conditions, showing deviations up to 4 °C on average, between south and north facing rooms. For each room, thermal comfort issues were assessed in accordance with EN 16798-1, by calculating Fanger Indexes (PMV and PPD), and by adaptive method in the HVAC systems off-work periods. These findings represent the first results of an in-depth analysis of thermal comfort and IEQ conditions, aimed at assessing how the IEQ conditions can address the building energy audit, increasing, at the same time, energy performance and IEQ levels
Field study on heat pump monitoring: challenges and opportunities
Full text linkIn view of the decarbonisation targets in the building sector, heat pump can play a key role, marking the shift towards all-electric buildings. Although the heat pump technology is well known, and its use is ever increasing, some issues (practical and operative) are still open in the assessment of the main aspects that influence the efficiency. These complexities emerge when heat pump monitoring is carried out, allowing to assess the real performance. Therefore, in this work, the challenges and opportunities of heat pump monitoring are presented, from a field study of the tertiary sector. The monitoring of an air-to-water heat pump allowed to: (i) assess its real operating performance; (ii) compare the correlations of results with climate data and load profile; (iii) highlight some critical points, as the importance of data mining and data cleaning phase for the reliability of the results; (iv) assess and identify which is the temporal scale needed for a proper data elaboration
Is a self-sufficient building energy efficient? Lesson learned from a case study in Mediterranean climate
No full textIn this paper, the energy performance of an energy self-sufficient residential building, located in the outskirt of L'Aquila city, in central Italy, is presented. The aim of this study is to demonstrate that even a self- sufficient building, that represents a still uncommon construction in the Mediterranean area, can have optimization margins. The analysis is performed via calibrated model carried out with EnergyPlus⢠engine coupled with DesignBuilder. The results of this study show a substantial discrepancy between the high efficiency of the envelope, and the poor performance of the heating system. Therefore, five possible scenarios, that differ for the technological plant, were hypothesized. Based on the total thermal energy consumption of the heating system as it is, equal to 29.9 kWh/m2y, the proposed multi-scenario analysis allows to identify a solution that ensures energy savings up to 67.1%. In this study, these results indicate that a proper a priori study of building's thermal load by considering different plant typologies could help to choose the better solutions for realizing efficient buildings
Quantification of heat energy losses through the building envelope: a state-of-the-art analysis with critical and comprehensive review on infrared thermography
No full textThe large majority of the building heat losses occur through the building. Hence, theaccurate evaluation of energy leakages, quantified by the thermal transmittance (U-value), is necessary, especially for energy labelling or city energy planning purposes, to foresee proper retrofit intervention and energy strategies. Among the techniques for the U-value assessment, the one that employs the quantitative infrared thermography (IRT) has spread in the last years, thanks to the possibility of easing the abovementioned processes due to reliable results, fast inspection, measurement carried out on large areas. However, a work that collects all the available techniques, explaining their weak and strength points, together with analogies and differences among the literature experiences, and which focuses on IRT, has not been carried out until now.
This study starts from the common approaches for the U-value evaluation (analogies with coeval buildings, the calculation method, the in-situ measurements and the laboratory tests), with the underlying standard procedures and the most important advantages, problems, and potential sources of errors defined by the literature. Then, the IRT technique, and its development through the years, is detailed and discussed, focusing on analogies and differences among the available literature sources. Also, several recurring energy related problems, such as the detection and estimation of thermal bridging as well as the assessment of the ε-value of building materials, are shown. Finally, the qualification of IRT personnel and the perspectives in the building sector are briefly explained, to remark the need for specialized thermographers who deal with an ever evolving methodology
The Potential of Optical Profilometry in the Study of Cultural Stone Weathering
No full textThe problem of deterioration of marble or stone monuments on display in the open air was raised in scientific terms around the mid-nineteenth century, correctly sensing the close dependence between the increased speed of surfaces alteration and air pollution. However, only more recently, around the years 1980–1990, emerged a need for quantitative data to assess the degree of degradation and the relative danger in the future projections. Non-destructive techniques can be an important aid in assessing the state of degradation and, above all, its speed, directly on the most important monuments exposed to the urban environment. In this work we discuss some non-destructive techniques able to evaluate the alteration of the surface shape of artefacts exposed to the environment through a non-contact survey of their surface shape. Advantages and disadvantages will be highlighted, as well as the problems still open
A comparison between thermographic and flow-meter methods for the evaluation of thermal transmittance of different wall constructions
No full textOne of the key parameters that "meter" the energy performance of the whole structure of buildings is the thermal transmittance. This parameter can be evaluated with a theoretical approach, regulated by standard ISO 6946, once the stratigraphy of the envelope and the properties of the constituent materials are known, or by using a heat flow meter (HFM), following the recommendations provided in standard ISO 9869. Recently, the use of quantitative IR Thermography (IRT) has been proposed by several researchers; this method allows to determine the overall transmittance of an envelope in a short time (especially in comparison with HFM method). However, the theoretical or experimental transmittance, measured on real buildings having walls composed by different materials, can be rather distant from those calculated or measured with different procedures. For this reason, for a correct certification of the thermal performance of a building envelope, it is necessary the availability of experimental procedures for a direct and reliable evaluation of the thermal transmittance, suitable for different walls. Research has found that, especially in historical constructions, faults in the building envelope and the age of the materials can greatly affect the HFM measurements. The aim of this work is to analyze in situ the thermal performance of three different walls which have been selected according to: different materials, different age, and different construction. On each envelope, a comparison between U-values, measured by HFM and IRT, and computed according the standard procedure, has been effected
Room and window geometry influence for daylight harvesting maximization – Effects on energy savings in an academic classroom
Full text linkLighting systems have a fundamental role for the overall buildings energy consumption. Therefore, remarkable efforts are required for optimizing the lighting systems energy use and for finding new daylight harvesting solutions. In this paper, the impacts on daylight harvesting provided by different room and window geometries and their effects on energy savings are presented. An academic classroom with only one window is chosen as case study and it is supposed that the window orientation is modified according to the four cardinal points. A climate-based approach was chosen for the multiple simulations, carried out via DIVA software, by assuming: square and rectangular classroom geometries with the same total area; square and rectangular window shapes having Window to Floor Ratios (WFRs) equal to 8% and 12%; two different dimmable lighting systems, in order to quantify the energy savings, by considering fluorescent and LED dimmable lamps. The daylight analysis, performed by evaluating both the Daylight Factor (DF) and the Daylight Autonomy (DA), showed that room and window geometries have high influence on daylight harvesting maximization, allowing remarkable energy savings (up to 48.5%) with respect to non-dimmable lighting system. In particular, the best energy result, equal to 467.5 kWh/yr, was obtained with rectangular room and window geometries coupled with LED lamps and WFR equal to 12%
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