• Energy Research

This study examined the atmospheric urban heat island (UHI) phenomenon within the city of Rome (Italy) and its effects on building energy demand. Weather data from 2020 and 2022 collected from six meteorological stations were considered. A Geographic Information System (GIS) was used to analyze the landscape, correlating the percentage of impermeable surfaces with UHI intensity values in each area. Dynamic simulations were conducted using different climatic data to estimate the heating and cooling energy demands for two representative residential buildings. The findings revealed significant differences in the climatic conditions between urban and rural areas, primarily due to temperature increases. The UHI intensities reached maximum values of 4.67 °C and 3.54 °C in 2020 and 2022. In urban areas, the UHI has positive effects on the heating energy demand but results in a significant increase in energy demand for cooling. Considering a building type constructed between 1900 and 1950, a variation of up to 33.03% in the heating energy demand in urban areas compared to rural areas was calculated, along with a variation of up to 81% for cooling. In contrast, considering a more recent building type constructed between 1991 and 2005, the corresponding values reached up to 36.47% and 75.7%.

This paper presents differences in calculations of annual heating and cooling energy need performed by numerical dynamic simulations software IDA ICE and those carried out by the modification of simple hourly method from EN ISO 13790 EN ISO 13790, widely used for determining building energy need. A simple model of a nearly-zero energy building was created and all heat gains and set-points that could lead to a mismatch in initial or boundary conditions were analysed. The impact of those on the annual heating and cooling energy need was examined by adding and/or removing every single one of them. Boundary conditions in numerical dynamic simulations were set up to match those in simple hourly method. Such an approach enables evaluation of differences in results and definition of their origin. The comparison of results has shown that in most cases, annual energy need for heating and cooling calculated using numerical dynamic simulations software differs from that calculated using EN ISO 13790. Among the others, more detailed heat accumulation model of heat gains in building’s envelope in IDA ICE software was marked as the main reason. Fact that solar heat gains seem to be underestimated by EN ISO 13790 and differences in heat transfer towards ground contribute to the differences in results as well.

The EN ISO 52016-1 standard presents a new simplified dynamic calculation procedure, whose aim is to provide an accurate energy performance assessment without excessively increasing the number of data required. The Italian National Annex to EN ISO 52016-1, currently under development, provides some improvements to the hourly calculation method; despite many works can be found in literature on the hourly model of EN ISO 52016-1, the National Annexes application has not been sufficiently analysed yet. The aim of the present work is to assess the main improvements introduced by the Italian National Annex and to compare the main results, in terms of energy need for space heating and cooling. To this purpose, an existing building representative of the Italian office building stock in Northern Italy was selected as a case study. The energy simulations were carried out considering both continuous and reduced operation of the HVAC systems. The options specified in the Italian National Annex were firstly applied one by one, and then all together. The variation of the energy need compared to the international base procedure is finally quantified. For the premises and the scope above discussed, the present work is intended to enhance the standardisation activity towards the adoption of more accurate and trustable calculation methods of the building energy performance.

This chapter reports the analysis of the correlation between the seasonal thermal energy needs of different building solutions and their climatic locations, assuming the variety of the Italian context taken as representative of southern Europe. The case-studies, simulated through a detailed dynamic tool, are representative of common practices from three main construction ages (newly built, 1960/80 and very old), and therefore include both different envelope characteristics and window percentages. Consideration is also given to the implementation of passive cooling strategies, such as shading and night ventilation, and to the adoption of variable set-point temperatures, directed towards climate-related user expectations, i.e. adaptive comfort. The graphic representation, according to the heating and cooling degree days adopted for supporting the climate-related analysis, can also be useful for extending the assessment to other locations within the same climatic area through simple interpolation. The data sheets reporting the detailed results of the case-studies, on the other hand, can be used directly for assessing the building energy needs of similar locations.

Abstract The goal of the paper is to compare two different methods of calculating the linear transmittance of thermal bridges in order to evaluate the building energy need for heating. As a case study, it was considered an existing non-isolated residential building of ‘70 years consisting of 30 housing units. All the construction details of the building are known. The energy analysis of the building was carried out using a commercial software. The linear transmittance of the thermal bridges was determined both by the catalogue, provided by the software itself, and by the numerical finite-element evaluation according to UNI EN ISO 10211 standard using a 2-D numerical simulator. Through numerical analysis it is possible to evaluate in a detailed way all the thermal bridges present in the building and therefore it is possible to evaluate the approximation induced by the use of the catalogue. Results show that the detailed analysis leads to a transmission heat exchange through thermal bridges about eight times greater than that estimated through the catalogue and consequently to a higher building energy need of about 12%. The heating energy needs per unit area of the individual housing units were also compared.

Abstract Adoption of energy metering systems in apartments with centralized heating plant will lead to greater awareness of the users on energy consumptions. Moreover control systems allow to manage internal temperature according to kind of occupation of the apartment. Starting from the energy consumption of a case study, an apartment block in Bologna, this paper shows the results, based on dynamic simulation, of reduction of energy needs resulting from retrofitting on the building envelope and the effects of thermoregulation systems. Different setting of the internal temperature in adjacent apartments can lead to a variation of energy consumption up to 30%.

Abstract Highly reflective roofs, widely known as cool roofs, can reduce peak surface temperatures and the energy required to cool buildings, mitigate urban microclimates, and offset CO 2 . However, weathering, soiling, and biological growth affect their solar reflectance. In this study, the solar spectral reflectances of 12 roofing membranes were measured before the exposure and after 3, 6, 12, 18, and 24 months of natural ageing in Roma and Milano, Italy. The membranes with an initial solar reflectance greater than 0.80, for example, decreased in reflectance by 0.14 in Roma and 0.22 in Milano after two years. Then, for a typical highly insulated commercial building, the annual cooling load savings were calculated to be reduced by 4.1–7.1 MJ m −2 y −1 per 0.1 loss in reflectance. When the buildings are non-insulated, the savings reduction is 58–71 MJ m −2 y −1 in Milano and 70–84 MJ m −2 y −1 in Roma. Ageing yielded a reduction of the cooling load savings that could be achieved with a new white membrane of 14–23% in Roma and of 20–34% in Milano. Moreover, in Milano, an aged, white, highly insulated roof, which has a solar reflectance of 0.56, may reach a surface temperature 16 °C higher than a new roof, which has a solar reflectance of 0.80.