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Abstract The increasing global energy demand, the foreseen reduction of available fossil fuels and the increasing evidence off global warming during the last decades have generated a high interest in renewable energy sources. However, renewable energy sources, such as wind and solar power, have an intrinsic variability that can seriously affect the stability of the energy system if they account for a high percentage of the total generation. The Energy Flexibility of buildings is commonly suggested as part of the solution to alleviate some of the upcoming challenges in the future demand-respond energy systems (electrical, district heating and gas grids). Buildings can supply flexibility services in different ways, e.g. utilization of thermal mass, adjustability of HVAC system use (e.g. heating/cooling/ventilation), charging of electric vehicles, and shifting of plug-loads. However, there is currently no overview or insight into how much Energy Flexibility different building may be able to offer to the future energy systems in the sense of avoiding excess energy production, increase the stability of the energy networks, minimize congestion problems, enhance the efficiency and cost effectiveness of the future energy networks. Therefore, there is a need for increasing knowledge on and demonstration of the Energy Flexibility buildings can provide to energy networks. At the same time, there is a need for identifying critical aspects and possible solutions to manage this Energy Flexibility, while maintaining the comfort of the occupants and minimizing the use of non-renewable energy. In this context, the IEA (International Energy Agency) EBC (Energy in Buildings and Communities program) Annex 67: “Energy Flexible Buildings” was started in 2015. The article presents the background and the work plan of IEA EBC Annex 67 as well as already obtained results. Annex 67 is a corporation between participants from 16 countries: Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Ireland, Italy, The Netherlands, Norway, Portugal, Spain, Switzerland and UK.

Data availability: Data will be made available on request. ; Copyright © 2023 The Author(s). Urban settings and climate change both impact on energy use and thermal comfort inside buildings. This paper first presents a study of changes in energy demand in residential buildings considering the overlapping effect of climate change and urban heat island intensity in two European locations; Cadiz (Spain) and London (United Kingdom), representing temperate and hot European climates and moderate and dense urban settings. Future-urban weather files were generated and simulations were run considering energy demand and indoor thermal comfort. In hot climate regions such as the one of Cadiz, future climate will increase the cooling demand and the additional impact of the UHI leads to a further increase of up to +28% of total energy demand compared to the current climate without considering urban effects. Future-urban weather conditions will be detrimental also for buildings in London, where the annual energy demand is predicted to increase by up to the 16% if future climate and urban effects are included. This is due to a higher increase in cooling demand compared to the reduction for the heating need. The paper also presents a method to take into account microclimatic conditions in naturally ventilated buildings, especially the effect of wind variations around the building which impacts natural ventilation rates. Air and surface temperature and wind speeds were studied using ENVImet and the resulting microclimatic conditions were used as inputs to the EnergyPlus Airflow Network model for the calculation of the building ventilation rates. It was found that ventilation rates are reduced (in comparison to meteorological weather files) and this reduction impacts negatively on internal operative temperatures. A thermal comfort analysis was carried out indicating that the selection of a suitable weather file and microclimatic conditions is essential for more accurate predictions of internal thermal comfort and will assist in ...

Materials science offers solutions that when are combined can offer important energy savings in the building sector. In this study, high reflectance coating and thermal storage capacity are combined with the aim of improving energy efficiency in buildings. For this issue a multifunctional pigment having a phase change material adsorbed on its surface and a high total solar reflectance has been manufactured. The total solar reflectance of the pigment will make the paint to reflect the sunlight radiation in the infrared part of the spectrum reducing the amount of absorbed radiation. This high reflection provides a surface level effect as is a passive stimulus-responsive solution that acts with sunlight radiation. On the other hand, the thermal storage capability provides a bulk level effect as is passive stimulus-responsive solution acting by temperature changes, making it possible to use constructive materials as a thermal energy storage media. The preparation process is described and the pigment is characterized conveniently. The thermal performance of corresponding pigmented coatings was evaluated by an experiment simulation in which different boxes were covered with the coating containing the multifunctional pigment and traditional pigmented coating on their tops. The indoor air temperature and the interior temperature of the substrate were measured obtaining differences of 4–5°C. European Union Seventh Framework Programme, FP7-NMP-2010-Small-5 (under grant agreement no 280393) Dpto. Educación, Política Lingüística y Cultura of the Basque Goverment, IT-630-13 Ministerio de Ciencia e Innovación, MAT2013-42092-R Engineering and Physical Sciences Research Council, EP/I003932

Abstract To increase the thermal performance of massive masonry walls, exterior or interior insulation can be used. The latter insulation technique is the most risky, though forms for example in cases of historical buildings, buildings with a worth-preserving facade or buildings in the urban context the only solution to increase the thermal performance of the wall. The current article compares the hygric performance of massive masonry walls provided with different interior insulation systems. To do so, small test walls are placed all together in a single hot box–cold box. The total moisture increase in the walls is measured by weighing the test walls. In addition, to investigate the working principle of the insulation systems the moisture distribution across the wall assemblies is investigated using the X-ray projection method. In the analysis capillary active as well as more standard non-capillary active insulation systems are investigated. For the imposed quasi steady-state winter condition, the increase of stored moisture inside walls with a capillary active system is found to be higher than for walls with a traditional vapour tight system.

Abstract Over the past decades, intense urbanization processes have produced built environments with a low energy efficiency and a severe lack of green spaces, which represent the main providers of ecosystem services in cities and play a relevant role in regulating the local microclimate. Among the different natural processes involved in climate regulation, a fundamental role is played by the shading effects of urban vegetation on buildings and built environment. Consequently, urban planning strategies aimed at designing a Green Infrastructure (GI) can have significant impacts on reducing the summer-time energy demand of cities while providing new green spaces for the local community. This is particularly relevant in high density settlements, where urban morphology types such as multi-storey apartment buildings represent an important percentage of the entire built environment. For these morphology types, the implementation of the GI depends on the different possibilities and limitation offered by private open spaces around residential buildings. Despite its importance, the implementation of a GI from public administrations must often challenge the lack of economic resources to acquire and manage private land to be set as new urban green spaces. This article investigates the potential energy savings for multi-storey apartment buildings that can be achieved by shading effect of trees. Particularly, building performance simulations are carried out considering different configurations of key parameters, such as trees species, distance to buildings, orientations of buildings and actual room of open spaces beside buildings where to plant new trees. The simulations are run for a real urban case study located in the metropolitan area of Catania in southern Italy, characterized by different types of urban morphologies. Simulations of shading effect consider three species of trees and 41 different spatial configurations depending on actual availability of open spaces around buildings. Results show that relevant energy savings can be obtained when the entire facades of buildings are shaded. The range of reduction of cooling loads of buildings varies between 2% and 50%, depending on the species and configurations: for half of considered 41 configurations 15% of average reduction is obtained. From an urban design point of view, results also suggest that the distance of trees from buildings and the actual availability of room for trees are key aspects to consider when designing where and how to plant new trees. Not in all configurations simulated, planting trees can result in a significant reduction of cooling energy loads. Findings of this work support urban planning for the choice of different scenarios and alternatives of GI to better balance public and private costs and generate wider benefits for the local communities.

The utilization of solar energy based technologies has attracted increased interest in recent times in order to satisfy the energy demands in buildings. This research work presents a comparative analysis of the energy production and costs of factory made solar heating systems, Thermosiphon Solar Water Heaters Systems (TSWHS) and Forced-circulation Solar Water Heaters Systems (FSWHS), as a function of profile type (high and low) and collector absorber treatment (selective and black painting). We observe that the energy performance and the Levelized Cost of Energy (LCOE) is similar in TSWHS and FSWHS for load volumes below tank nominal volume, black painting absorbers and locations with high solar irradiation. In the case of load volumes greater than nominal, climates with low irradiation and collectors with selective absorbers, the differences in their energy performance can reach a 7% and the LCOE can increase up to 9%. The LCOE is lower for TSWHS systems for all the evaluated scenarios. We have also found that for cold climates, the FSWHS systems present higher net annual energy produced, however, for warm climates TSWHS systems present greater net annual energy production.

Abstract Cities are dissipative structures. As such, cities generate heat, a phenomenon known as urban heat island (UHI). Even though the UHI is one of the most relevant effects of urbanization on urban climate, up-to-date methodologies to include it in the estimation of buildings’ energy consumption are still scarce. During the last 30 years, different methods and software have been developed to measure a thermal building's demand. Building performance simulation is commonly used to calculate heating and cooling demand. However, such techniques do not adequately include the urban heat island effect, which could have an extreme impact on a building's energy consumption. In fact, building operation is doubly connected with the urban environment: on the one hand, buildings generate heat that warms up the environment, and on the other hand, the urban environment alters building performance by the influence of UHI. In this paper, a methodology to incorporate the UHI effect in building performance simulation is proposed. Urban weather data were downscaled at the urban morphology building level to estimate the cooling demand of different types of residential buildings. The global energy penalty for the whole residential building stock was estimated in four South American Pacific coastal cities. The results indicate that when UHI is incorporated, an increase in energy demand between 15% and 200% can be expected. These results challenge the validity of current assessments performed in absence of the UHI effect. At the same time, these results open up the discussion for the inclusion of urban planning measures aiming at reducing the UHI effect on a building's energy demand.