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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.

Despite the multiple advantages of prefabricated compared to conventional buildings, such as significant reductions in cost and time, improved quality and accuracy in manufacture, easy dismantling and reuse of components, reduction in environmental degradation, increase of productivity gains, etc., they still share a small part of the European building stock, mainly in the Mediterranean. This paper attempts to highlight the potential of prefabricated buildings to achieve advanced levels of performance, particularly as regards their thermal and energy behavior. More specifically, in this paper the energy needs of a single-family building constructed with prefabricated elements is analyzed, considering different climate contexts. The prefabricated elements comprising the building envelope were developed in order to address specific requirements with respect to their structural, hygrothermal, energy, fire, acoustical, and environmental performance, within the research project SUPRIM (sustainable preconstructed innovative module). The new multifunctional building element, also incorporating phase change materials for increased latent thermal heat storage, has been proven to be beneficial in all the examined climate zones. The results of the relevant studies will highlight the contribution of the new prefabricated element to the sustainability of the overall construction, as well as its advantages when compared with conventional constructions.

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.

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.

Electricity generation on site is a design challenge aiming at supporting the concept of energy-autonomous building. Many projects worldwide have promoted the installation of photovoltaic panels on urban buildings, aiming at utilizing a large area to produce electricity. In most cases, photovoltaics are considered strictly as electricity generators, neglecting their effect to the efficiency and to the thermal behaviour of the building envelope. The integrated performance of photovoltaic ventilated fa?ades, where the photovoltaics are regarded as part of a complicated envelope system, provides design challenges and problems that cannot be overlooked within the framework of the Nearly Zero Energy Building concept. In this study, a finite volume model for photovoltaic ventilated fa?ades is developed, experimentally validated and found to have a significant convergence to measured data.

This paper aims to analyse the changes that the new Hellenic Regulation on the Energy Performance of Buildings (REPB) has brought to the Hellenic residential buildings, which is in line with the European Directive 2010/31/EC. These changes refer to construction techniques, construction costs and energy performance. Our assessment is based on the numerical analysis of two typical residential buildings, a single and a multi-one. Both buildings were studied according to the requirements set before and after the application of the REPB for all (four in total) climate zones of Greece. The cost for implementing the two regulations was evaluated, as was also the energy consumption cost. Based on these costs we estimated the operating costs for heating, cooling and domestic hot water of the two buildings of this study. The implementation of the REPB significantly reduced the required heating loads for space heating in all climate zones by 37%–48% for both building types; this is mainly attributed to the improvement of the thermal properties of the building envelope and the improved energy performance of the electromechanical systems. The required cooling load was low and the implementation of the REPB did not change it significantly. Significant energy savings, in the range of 51%–58% were also achieved by installing flat plate solar collectors for Domestic Hot Water heating.

In this paper, some well-known buildings’ environmental performance assessment tools and methods are reviewed with regard to the consideration of visual comfort in their structure and assessment process. Specifically, the parameters used for visual comfort's assessment in widely used tools (BREEAM, LEED, SBTool and CASBEE - versions for office buildings) are examined; the type and the kind of criteria used for the assessment, the weightings applied and references to relative standards are reviewed and comparatively assessed. Although the presented results cover the issue of visual comfort as a whole, emphasis is given on daylighting–related factors.

The paper presents the ventilated facades as an intervention for efficient energy upgrade of new and, mainly, existing buildings. It focuses on the requirements that this specific building element should fulfill, with regard to legal, technical, social and financial aspects. More specifically, legal aspects concern mainly the regulations that determine the element's behaviour with respect to the hygrothermal, energy, sound and fire performance, as well as other legal restrictions (i.e. urbanism/planning rules or listed buildings). The technical aspects involve structural issues, architectural concerns and aesthetics, as well as functional matters. Finally, the social aspects refer to the acceptance of the element by building users and architects/engineers, while the financial aspects interrelate the ownership with the economic incentives and the investment feasibility. All the above are presented and discussed in the paper in order to highlight the applicability of ventilated facade systems in residential buildings.

Resent developments on the requirements regarding the thermal efficiency of buildings and building envelopes, have increased the need for energy retrofit of building envelopes. Cladding systems and ventilated facades are among the most attractive solutions to these problems due to a variety of reasons, including aesthetics, moisture control, serviceability and resistance to environmental factors. Despite all the benefits of these structures, their actual thermal efficiency has not been studied extensively yet. In many countries, the thermal performance of these structures is treated in the same way as more simple structures like ETICS. Within the framework of the European project E2VENT, an thorough study of the nature of thermal bridges has been performed – among others- in order to reveal the nature and the magnitude of thermal bridge effects in such structures, to investigate the design parameters that can assist in minimising their contribution in overall heat flows and to improve the overall thermal efficiency of the building envelope. Results shows that thermal bridges in metal cladding systems can be a significantly weak point in thermal insulation protection if no special care is given during the design and the construction process. By simply neglecting point thermal bridges due the lack of specific requirements, to the insufficient knowledge or by considering that only the use of thermal-break products can efficiently treat it, can significantly decrease the thermal insulation quality of the facade, leading to undesirable results.

Heading towards more energy-efficient buildings, legislative requirements are becoming increasingly demanding. A decade ago, the thermal bridge effect was a known deficiency of building facades but, beyond design guidelines, no qualitative or quantitative requirements occurred in order to minimize its impact. The implementation of international standards in many national building codes has shown that the thermal bridge effect may significantly contribute to heat flows through building envelopes. Due to the multifaceted nature of heat flow through thermal bridges, its magnitude is usually estimated on the basis of predefined values or as a surcharge of the overall heat transmission loss. This study aims to investigate the differentiation and inaccuracies derived by the use of such simplified approaches with respect to the determination of the exact solution. In the context of this study, a multifamily building is assumed as a base case and its thermal bridge typologies are identified and analysed. By using an advanced numerical tool, the magnitude of thermal bridges heat flows is calculated for different building envelope thermal transmittance requirements (ranging from slightly to highly thermally insulated elements), representing the envelope thermal transmittance range currently found in most European countries. Results are compared to the respective ones derived from four prevailing methodologies highlighted in modern building codes aiming at calculating the heat flow through thermal bridges. This study reveals that existing approaches for implementing thermal bridges effect have not followed the progress achieved in thermal insulation requirements and the relevant framework should be updated to better support the effort for more rational and precise results.

The paper concerns the development of an innovative building module with advanced thermophysical and mechanical properties that will be used in constructing sustainable prefabricated buildings with high structural, hygrothermal, energy, acoustic, fire and environmental performance at the minimum possible time and cost. In this paper, the configuration of the new building element, as well as its hygrothermal, energy, acoustic and environmental performances are presented. In addition, its contribution to forming a sustainable, energy efficient, affordable building is investigated.

The complicated nature of indoor environmental quality (IEQ) (thermal, visual, acoustic comfort, etc.) dictates a multi-fold approach for desirable IEQ levels to be achieved. The improvement of building shells&rsquo, thermal performance, imposed by the constantly revised buildings&rsquo, energy performance regulations, does not necessarily guarantee the upgrade of all IEQ-related aspects, such as the construction&rsquo, s acoustic quality, as most of the commonly used insulation materials are characterized by their low acoustic performance properties. From this perspective the SUstainable PReconstructed Innovative Module (SU.PR.I.M.) research project investigates a new, innovative preconstructed building module with advanced characteristics, which can, among other features, provide a high quality of acoustic performance in the indoor space. The module consists of two reinforced concrete vertical panels, between which the load bearing steel profiles are positioned. In the cavity and at the exterior surface of the panel there is a layer of thermal insulation. For the scope of the analysis, different external finishing surfaces are considered, including cladding with slate and brick, and different cavity insulation materials are examined. The addition of Phase Change Materials (PCM) in different mix proportions in the interior concrete panel is also examined. For the calculation of the sound insulation performance of the building module the INSUL 9.0 software is used. The results were validated through an experimental measurement in the laboratory in order to test the consistency of the values obtained. The results indicate that the examined preconstructed module can cover the sound insulation national regulation&rsquo, s performance limits, but the implementation of such panels in building constructions should be carefully considered in case of lower frequency noise environments.

This paper presents the primary findings of a research project, aiming to introduce an innovative building module with improved thermophysical and mechanical properties that will serve as a bearing element and/or as an internal partition wall in prefabricated residential buildings. This new building module will comply with current requirements as regards its operation and performance. For the purposes of this investigation, the overall performance of the considered building elements is ensured by the proper configuration and assembly of the involved layers and is verified through analytical and experimental analyses, as well as through measurements at accredited laboratories. The objective of this innovative building element is to establish a building envelope with a high structural, hygrothermal, energy, acoustic, fire and environmental performance, while reducing both the time and cost required to complete its construction. Evidently, the accomplishment of this objective suggests various benefits on both the business sector and the research community. Moreover, the utilization of this building module is influential in terms of social impact, as it promotes the construction of buildings with advanced energy and environmental performance that can furthermore mitigate and adapt to the climate change impacts.

Urban sustainability has been connected to form and compactness of the urban tissue. At the same time the relationship between urban form and energy efficiency is strongly affected by climate. This paper investigates the effect of climate conditions on the relation between urban morphology and energy efficiency of urban blocks, focusing on the Greek city context. A set of building block typologies is analyzed with regard to their form factors such as S/V ratio, coverage ratio and building ratio for the climatic conditions of two cities, each one belonging to a different climatic zone. Heating and cooling loads are calculated at an urban block scale for the climate of the city of Thessaloniki (zone C) and of the city of Heraklion (zone A) in order to draw conclusions about the relation between geometry factors and energy efficiency. The results of the research indicate that there is a strong relationship between urban morphology factors and energy efficiency and that the total load demand of urban blocks can be described as a function of form parameters. Results of the research, concerning the energy demand calculation, are valuable since they indicate the energy profile of each typology according to climate and can be used for defining different urban strategies towards sustainability in a context-based climate dependent analysis.

Cladding systems have become an attractive solution in energy renovation of existing buildings since they combine multiple benefits. In such systems, the use of a metallic frame and brackets, which penetrates the thermal insulation layer, creates point thermal bridges that are usually neglected by thermal insulation regulations due to their calculation complexity and their supposed small magnitude in overall heat losses. The objective of this study is to perform a parametric analysis to quantify the magnitude of this thermal bridging effect. All necessary calculations are performed using a detailed 3-dimensional numerical analysis approach in order to overcome oversimplifications found in most thermal bridge estimation methods. Results of the analysis are applied in a refurbishment study of an existing office building in order to underline the significance of the problem under investigation, in practice. As it is shown, point thermal bridge effects in cladding systems can constitute a significant part of buildings’ thermal balance. Neglecting their presence can lead to significant underestimation of actual heat flows which can account for 5% to almost 20% of total heat flows through the building envelope, depending mostly on the thermal transmittance of the load bearing wall and the ventilation characteristics of the air cavity.

The paper focuses on the assessment of the windows’ contribution to the energy performance of buildings in the warmer regions of Europe. This is derived by calculating the cooling energy index qc and the area weighted energy needs for different window configurations installed on a reference room for two different building uses, office and residential. The examined window types differed with regard to their thermophysical and optical properties (U- and g-value), geometry (frame and window fractions) and orientations. The energy parameters used for the performance assessment were calculated with the help of a dynamic simulation tool for a location with a representative Mediterranean climate. The extensive multi-parametric analysis exhibited interesting results. It was found that for the cooling mode the energy performance of windows in warm climates is influenced significantly by their thermophysical properties. More specifically, the impact of solar transmittance is significant and its optimal selection can contribute in minimizing the energy consumption, especially in environments with controlled ventilation, such as offices. On the contrary, advanced fenestration products with low thermal transmittance seem to behave unfavorably, since their extremely low thermal transmittance prohibits the dissipation of heat toward the ambient environment and results ultimately in higher cooling energy loads.

During the last decade, several countries worldwide established systems for the energy rating of windows, which allow for the direct comparison of different window products on a common basis and enable the consumers and designers to select windows with regard to their energy performance. Most of the existing methodologies do not take into account the influence of the windows on the cooling needs, but indicate only their performance during the heating season. However, at the present time the cooling performance is becoming a significant parameter for evaluating the overall building energy performance in Europe.Within this context the current paper attempts to propose a new system for assessing the cooling performance of the windows at a pan-European level. The paper starts with a brief presentation of the existing window energy rating systems found worldwide. In order to propose a new rating system which can be applied across Europe, climatic zones were defined. A detailed analysis of the energy performanc...

The exploitation of forest and agricultural biomass residues for energy production may offer significant advantages to the energy policy of the relevant country, but it strongly depends on a number of financial, technological and political factors. The work in hand focuses on the investigation of the energy, environmental and financial benefits, resulting from the exploitation of forest and agricultural biomass residues, fully substituting the conventional fuel (diesel oil) for building space heating in Greece. For this investigation, the energy needs of a representative building are determined using the EnergyPlus software, assuming that the building is located across the various climate zones of Greece. Based on the resulting thermal energy needs, the primary energy consumption and the corresponding emissions are determined, while an elementary fiscal analysis is also performed. The results show that significant financial benefits for the end-user are associated with the substitution examined, even though increased emissions and primary energy consumption have been derived.

This paper aims at identifying the energy benefits deriving from the installation of a new technological solution developed for the retrofit of existing buildings within the research project E2VENT. The E2VENT system comprises an advanced ventilated facade, a heat exchanger, a heat storage and a smart management system, and as such it addresses both the heat losses through the building envelope and the poor air quality problems often prevailing in older buildings. The performance of the E2VENT system is assessed for a typical residential multi-family building unit with different thermal insulation levels located in different climates. It is compared to the baseline scenario, assuming that no thermal insulation exists, and also against the conventional renovation scenario of external thermal insulation composite system (ETICS). The results show that the E2VENT system performs better when compared to the conventional ETICS scenario. In all cases the heating loads are significantly reduced, while the cooling loads are also reduced, but at a more moderate rate.

In this study the variations of concrete density and concrete thermal conductivity of various wall assemblies are considered to analyse their influence on the dynamic thermal characteristics, such as the decrement factor and time lag. The assemblies under study refer to insulated walls with variable concrete density and the concrete placement in one or two layers. The insulation is also placed as one or two equivalent layers giving rise to a total of six typical wall configurations. The thermal inertia parameters are determined using the thermal-circuit modelling approach and the analysis is based on the nodal solution method. Density and conductivity variations of the concrete layers are seen to interrelate non-linearly with the walls’ RC-sections corresponding parameters with consequences on its inertia parameters. As such variations, together with the studied insulation placements, affect the decrement factor and time lag in a different fashion, metrics for assessing the walls’ thermal behaviour from a proportional (PDM, PTM) and a relative (RDM, RTM) point of view are introduced. Computer results, showing the impact of the variations of concrete density and conductivity on the decrement factor, time lag and the proposed metrics are presented for all the studied wall assemblies.

This paper presents a feasibility analysis for the installation of ground source heat pump systems in Cyprus. Two reference buildings, a single- and a multi-family one, are designed and analyzed using the EnergyPlus software, in order to calculate their energy needs for heating and cooling for the climate conditions of Cyprus, one of the warmest areas in Southern Europe. These energy needs are assumed to be covered by the conventional heating and cooling systems that are most widely used in Cyprus or alternatively by a ground source heat pump system, which consists of a vertical ground heat exchanger and water-to-water heat pumps and is analyzed using an in-house developed and validated code. Primary energy consumption and the resulting CO2 emissions for both the conventional and the alternative systems are calculated and compared. Results show that the installation of the ground source heat pump system achieves in most cases substantial reductions in primary energy use for both types of buildings. As regards carbon emissions, the findings are less clear: Emissions of the geothermal system are higher than those of the conventional system for the single-family building but considerably lower for the multi-family one. From an economic perspective, the geothermal system compares favorably with the conventional systems in many cases, particularly for the multi-family building.

Heat transfer through windows accounts for a significant proportion of energy used in the building sector for covering both heating and cooling needs, since the optical and the thermal characteristics of conventional fenestration products constitute them more “vulnerable” in energy flows when compared to opaque building elements. In this study, an approach for evaluating the cooling energy performance of residential windows is presented. It is based on a parametric study, which aims at highlighting the impact of the window configuration on its energy behavior in terms of geometrical characteristics, thermophysical and optical properties, as well as orientation and shading levels. The results underlined the magnitude of the relationship between the thermal and optical properties of the transparent elements with respect to their orientation; especially for residential buildings, the solar transmittance determines at a considerable extent the cooling energy performance of fenestration, at least in the warmest part of Europe. Furthermore, the statistical analysis of the derived data provided mathematical expressions, which can be used in praxis for predicting the cooling energy performance of windows with respect to their thermal and optical characteristics.

Fenestration has always been regarded as the weak element in the building envelope due to its role in determining of the energy balance of a building. At the same time, cooling performance is becoming a significant parameter for evaluating the energy performance of buildings in Europe. Due to the plethora of window products with advanced properties currently existing on the market, it is not always easy for engineers to select the optimum solution. In this paper, the cooling performance of windows in the warmest part of Europe is evaluated with regard to their geometrical, thermophysical and optical characteristics, as well as their shading provisions. The analysis shows that the contribution of the windows in determining cooling loads is maximized when their solar transmittance is high and their thermal transmittance is low. Moreover, in the Mediterranean regions the increased thermal efficiency of transparent elements in buildings with controlled ventilation, such as offices, prohibits the dissipation of heat toward the ambient environment and ultimately result in higher cooling energy loads.

Nowadays, subjects such as eco-design requirements, product rating or code compliance with regard to energy efficiency are expanding towards a pan-European level. This leads to the necessity of defining zones within the European region, which share common climatic characteristics and will further facilitate the quick estimation of building energy performance. Towards this direction stands the current paper; it presents an approach for defining climatic zones in Europe on the basis of the amount of heating and cooling degree days. It is applied for the climate classification of selected European cities and is compared with the conventional scheme based solely on heating degree days. Since the approach is orientated mainly towards the assessment of building energy performance, its outcomes are evaluated with regard to the actual heating and cooling energy needs of a reference building unit with office use located in representative cities of the proposed climatic zones and facing the four cardinal orientations. The classification of climatic zones on the basis of both heating and cooling degree days leads to more realistic results, since nowadays cooling needs form a substantial part of the energy balance of the building, especially in the Mediterranean regions.

Sustainability, environmental performance and energy efficiency have become main subjects not only for the profession of architecture, but for every profession, as well. Within the scope of this conference, and more specifically the overall energy performance of buildings, the section dealing with the higher technical education has special relevance. The need for incorporating sustainability and energy parameters in higher education has been recognised for some considerable time now. As academic staff members teaching in technical courses at the Faculty of Architecture, University of Zagreb, we are always under time pressure in keeping up with the newest performances in structure and technology facing the question: How to realise and improve the graduate framework and the learning and teaching plan of environmental issues in the courses that we teach? The paper examines available study programme ‘Architecture and Urban Studies’ within the master degree programme at the Department of Architectural Technology and Building Science. The new compulsory course Architecture and Technology 1 (AT1_2018/2019) addresses the topics of building energy consumption and emissions, rational use of energy, environmental impact, high performance efficiency and sustainable building. By comparing a selection of students’ works in different groups conducted experimentally for the first time, the paper will discuss the project approach, give a critical evaluation of the selected case studies and some lessons learned from attempts to incorporate environmental issues into the unit syllabus. Through this paper we attempt to share information and deepen the discussion within the academic community. Finally, as a contribution, it is expected to increase the ways by which parameters of energy and environmental sustainability can become an integral guiding principle in the design and delivery of all academic courses offered at the Faculty.