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Development and use of preconstruction have been exhibited for several decades. Numerous modules, ranging from the simplest to the most advanced concepts, have been suggested to ameliorate the layout of building structures, with respect to a broad spectrum of needs. This study aims to unfold the fire defensiveness of an innovative precast concrete sandwich wall-system subjected to the ISO 834 fire, such as this is provided for in EN1991-1-2. In light of a rapidly evolving environment that should shield structures against fire, this investigation emphasises on the vulnerability of precast panels with a varying thickness of insulation by means of a numerical methodology and a versatile heat transfer-model. A finite-element analysis is carried out with COMSOL Multiphysics® simulation software. In a following step, as fire risk should be vigorously tackled, the research is extended to validate numerical predictions of the model by means of an experimental setup for wall specimens arranged in the laboratory. Therefore, an additional goal of this research is to assess temperature discrepancies for both addressed cases. Despite various approximations of the model, an excellent agreement between numerical and experimental results is shown, confirming the rationality of computational simulations in terms of temperatures’ precision. It has been revealed that for all examined cases, the insulation ability (I) has been maintained for more than 3 h regardless of the positioning of the insulation. Further evidence though suggested that is not the case for the loadbearing capacity (R), as the installation of a fire exposed insulation layer resulted in lower stability systems. Also, the effect of the insulation thickness is not that dominant as on average and maximum temperature deviations among marginal assemblies (d\ud \ud EPS\ud = 2 cm and d\ud \ud EPS\ud = 10 cm) did not exceed 5 °C and 10 °C at t\ud \ud fire\ud ≈ 100 min.

Subject of this study is the analysis of the Smart Readiness Indicator (SRI), as well as its application for a residential building in Greece. The indicator, which was firstly introduced in the revised EPBD in 2018, assesses the buildings’ smart readiness through the examination of the presence and the evaluation of the functionality level of smart services. Its goal is the promotion of buildings that are energy efficient, adaptive to their users’ needs, and flexible in respect of their electricity demand, according to the three key - functionalities, as stated by the Directive. A smart building is not only characterized by its sustainability but also by its adaptiveness to the environmental conditions and its users’ preferences. Smart buildings are a basic component of smart cities, which utilize a great range of smart technologies aiming at the improvement of their citizens’ lives. The Smart Readiness Indicator as well as the sub indicators evaluate the smart buildings using a multicriteria assessment method, which is thoroughly described in this paper. Finally, the indicators’ calculation is executed for a residential building in Greece leading to results, which are discussed along with identified methodology shortcomings and difficulties.

Construction and Demolition Waste (CDW) effective management is of vital importance, especially regarding the climate-neutral economy target set for 2050. The common practice of landfilling them during the past decades and ignoring the environmental impacts is now obsolete, with countries around the world adopting national regulations for their proper treatment. The lack of data on the CDW volume produced every year both in the European region and at the Greek national level is evident, in contrast with Asian or American regions, and introduces a great uncertainty in the field. This study aims at estimating the CDW quantities produced by a typical multi-storey residential building in Greece, built in the mid-20th century, made of reinforced concrete and filling masonry walls. The subsidized renovation programs by the European Union, which have a great impact on the Greek domain, are also considered, so two renovation procedures are considered during the building’s lifespan, resulting in an extended lifetime of the building along with additional CDW quantities produced on each renovation procedure. Challenges regarding the disposal, recycling and reuse potential and alternatives of the distinct CDW types produced are presented, based on the international literature available data.

Climate change has a major impact on the urban built environment, both with respect to the heating and cooling energy requirements, but also regarding the higher probability of confronting extreme events such as heatwaves. In parallel, the ongoing urbanization, the urban microclimate and the formation of the urban heat island effect, compounding the ongoing climate change, is also a considerable determinant of the building’s energy behavior and the outdoor thermal environment. To evaluate the magnitude of the complex phenomenon, the current research investigates the effect of climate change and urban heat island on heating and cooling energy needs of an urban building unit in Thessaloniki, Greece. The study comparatively evaluates different tools for the generation of future weather datasets, considering both statistical and dynamical downscaling methods, with the latter involving the use of a regional climate model. Based on the output of the regional climate model, another future weather dataset is created, considering not only the general climatic conditions, but also the microclimatic parameters of the examined case study area, under the future climate projections. The generated future weather datasets are then used as an input parameter in the dynamic energy performance simulations with EnergyPlus. For all examined weather datasets, the simulation results show a decrease of the heating energy use, an effect that is strongly counterbalanced by the rise of the cooling energy demand. The obtained simulation results also reveal the contribution of the urban warming of the ongoing climate change, demonstrating the need to perform a holistic analysis for the buildings’ energy needs under future climate conditions.

Double-skin facades (DSFs) are a technology that lies behind innovative energy efficient facade systems. While it provides a potential for high energy efficient buildings, other important parameters, like point thermal bridge problems, are in most cases overlooked. The aim of this study is to investigate the magnitude of this approach and the effect it might has on the overall heat flow estimation in buildings. The study performs a numerical analysis of heat flow through the points where such effects are found, in order to analyse their nature under different design parameters selection like the use of thermal breaks, the substrate wall material, the thermal insulation thickness and the type of anchors used to securely connect both facade skins. The results are then applied to a case-study office building aiming at quantifying the overall contribution of point thermal bridges to heat flows through the building envelope. As the analysis shows, point thermal bridges in well-insulated envelopes have a heat-loss similar to the one from 1 m2 of facade’s wall. The overall effect at DSFs can surpass 25% of total envelope heat flow, leading to a large underestimation of actual heat flows through the building envelope. Overlooking their contribution, as many European national energy efficiency regulations currently do for the shake of simplicity, has a significant effect in widening the gap between predicted and actual energy efficiency of buildings.

Several studies underline the dramatic changes that are expected to take place in nature and environment due to climate change. The latter is also expected to affect the built environment. Particular emphasis is currently given to the impact of climate change on historical structures. Within this context, it is important to use simple methods and novel tools in order to investigate pecific case studies. In this study, the climate change impact on the hygrothermal performance of the log walls in a historic timber building is presented. The building under investigation is the Fadum storehouse, also known as ‘the coated house’, located in Tønsberg, Norway. The storehouse dates to the late 18th century. It has a particular design with the main features of stumps or piles up to which it stands and the ‘coating’ that covers its outer walls. The main damage of the construction is related to the biological degradation of the wood. The hygrothermal performance of the log walls, as well as the exterior and interior climate, have been monitored and the results have been used to validate a Heat, Air and Moisture transport (HAM) model. The validated HAM model is then used to examine the performance of the log walls for both current and potential future climate conditions. The transient hygrothermal boundary conditions serve as the input parameters to a biohygrothermal model that is used to investigate the biological deterioration of the building components. The findings reveal that currently there is no mould risk for the main body of the construction, which is in accordance with the visual inspection. The passive systems of the building are highly conducive to these results, since they protect it from driving rain and other sources of moisture and eliminate the potential impact of future climate change risk scenarios. This work is a part of the HYPERION project. HYPERION has received funding from the European Union’s Framework Programme for Research and Innovation (Horizon 2020) under grant agreement No 821054.

The increased rates of urbanization and industrialization of the 20th and 21st centuries have dramatically changed the land use and cover of modern cities, contributing to the degradation of the urban microclimate and the rise of the ambient urban air temperatures. Given the multiple negative energy, environmental and social consequences of urban warming, the present paper summarizes the findings of previous studies, assessing the main causes of the phenomenon along with the key investigation methods involving experimental and computational approaches. There follows a description of the most common mitigations, and adaption strategies towards the attenuation of urban warming are described. The analyzed elements include the addition of green spaces such as trees, grass and green roofs; changes on the albedo of the urban surfaces and water-based techniques, as well as a combination of them. The discussion of the reported findings in the existing literature clearly reflects the impact of urban morphology on the outdoor thermal environment, providing also useful information for professionals and urban planners involved at the phase of decision-making.

The most common action for the buildings' energy upgrade across Europe is the addition of thermal insulation on the external walls. Such interventions, although simple on their construction, cause significant changes on the building's behavior, not only on its energy needs, but also on the hygrothermal and visual performance. The effects are not always positive; for example, thicker insulation may result in lower thermal transmittance and better thermal energy performance, but on the other hand the thermal bridging effect is amplified, and the daylight levels are decreased. This research intends to quantify these impacts by analyzing the relevant parameters for different regions of Europe. The analysis aims at explaining the complicated interrelationships on the building physics' aspects encountered through interventions on the building envelope, but also at identifying appropriate measures that could counterbalance the negative impacts and enhance the overall building performance.

Although modern prefabricated buildings may offer many advantages, such as a significant reduction in cost and time, improved quality and accuracy in manufacture, easy dismantle and reuse of its components, etc., they have not gained the attention they deserve in the construction market yet. In this paper, a holistic approach for the formation of prefabricated buildings of advanced performance is presented. Within this context, a new, innovative prefabricated building element is developed, designed to exhibit optimized structural, hygrothermal, energy, acoustic, fire and environmental performance. The improved properties of the building element are ensured by the proper configuration of the layers that compose it with respect to the design objectives; for example, in order to support the heat storage and the control of indoor temperatures, the integration of PCMs in the element's layers is investigated. Furthermore, in order to indicate the contribution of the new building element to the sustainability of the overall construction, the performance of a building formulated with the new element is analyzed in terms of energy and environmental behaviour. The new building element and construction system are expected to systemize the prefabricated element's production, leading eventually to the improvement of the building quality, as well as to the reduction of time and cost of building's erection. In parallel, the new certified and optimized building performance will increase the share of prefabricated buildings in the Mediterranean countries, where housing needs are gradually growing, while at the same time, energy efficient and environmentally friendly construction will be promoted.

Increased urban air temperatures due to urbanization affect the buildings’ energy performance and the outdoor thermal comfort. Aiming on the establishment of adaption strategies, urban microclimate studies using numerical simulation tools are gaining great scientific attention. The ENVI-met model is one of the most widely employed dynamic simulation tools. Considering its increasing use, this review aims to perform a meta-analysis of the reported evaluation results, reflecting the capability of the model to accurately calculate the diurnal profile of microclimatic variables. The analysis relies on the definition of the range of the reported metrics and on the investigation of the relationship between the various indices, applied for the model evaluation. Secondly, the study assesses the existing ENVI-met simulation results, indicating the cooling potential of urban greenery and cool materials regarding air, surface and mean radiant temperature modifications. The analysis revealed that the model can be considered as a helpful tool for urban climate analysis, provided that its limitations and features are accounted for by the user during the interpretation of the simulation outcome. Concerning the performance of the examined mitigation strategies, the most popular technology is the urban greenery while the mitigation potential is increased when different strategies are combined.

Aiming at the improvement of a dense urban area’s microclimatic conditions, this study examines by simulation means, the application of highly reflective materials as a mitigation strategy. However, as significant albedo changes may occur due to weathering and aging, the study investigates the surface (Tsurf) and air (Tair) temperature cooling potential of cool paving materials, both for the design and the aged values of solar reflectance; the aged albedo values are issued from previously reported experimental campaigns. Since the majority of the existing studies evaluate the cool materials’ impact at the pedestrian’s height, the current work aims to provide further insight on the vertical profile of the achieved Tair reduction due to cool pavements, at different heights of the study area’s canyons. The analysis revealed that the Tsurf and Tair decrease due to cool pavements is reduced by 50%, when the aged albedo values are considered, while the obtained Tair reduction is negatively related to the distance from the ground. The accurate assessment of the high albedo materials’ effect on the urban microclimate imposes thus the consideration of the albedo degradation due to weathering and aging whereas extra effort should be given on the development of cold materials standing the test of time.

Predicting buildings’ heating and cooling needs through dynamic simulation methods requires the input of hourly weather data, so as to represent the typical meteorological characteristics of a specific location. Hence, the so called ‘typical weather years’ (TWY), mainly deduced from multi-year records of meteorological stations outside the urban centres, cannot account of the complex interactions between solar radiation, wind speed and high urban densities which lead to the formation of the urban heat island effect and to higher ambient air temperatures. As the assumption that climatic parameters at a reference location of a meteo station are similar for a densely built up area can lead to miscalculations of the heating and cooling needs, the aim of this study is to present a computational method for assessing the urban climate's effect during the generation of typical weather data for dynamic energy calculations. In this vein, a typical ‘urban specific weather dataset’ (USWD), reflecting the microclimatic conditions in front of a building unit inside an urban district in the city of Thessaloniki, Greece is created based on microclimate simulations with the Envi-met model; it is then compared with a typical reference weather dataset (RWD), representing climatic conditions at a reference location of a meteo station. The results indicate that the proposed method can capture microclimate characteristics; higher dry bulb temperatures were reported during the year inside the urban canyon, compared to the corresponding values at the reference location, with indicative mean daily deviations up to 1.0 °C and 0.75 °C in February and July respectively. Wind speed, near the building facade is generally found lower than the corresponding values at the reference location, due to wind sheltering by neighbouring constructions. Given that climatic parameters strongly influence the output of energy simulations the proposed computational method provide a contribution for higher accuracy of building energy simulation in the urban context. Future work will involve energy performance simulations of a typical building unit with the generated USWD file so as to evaluate the urban climate's influence on energy needs.