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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.

The present study investigates the impact of different intervention scenarios regarding morphological characteristics of an urban district of Thessaloniki on microclimatic parameters such as surface, air and mean radiant temperature distribution during a typical summer day. The proposed intervention scenarios include the total replacement of concrete pavement and asphalt streets with similar cool materials, increase of the amount of trees and a combination of the above strategies. The three-dimensional non-hydrostatic climate model ENVI-met v.4 is used for the microclimate simulation. The analysis reveals a significant reduction of surface temperatures due to the replacement of conventional coatings with cool materials of higher albedo and emissivity, while changes in air temperature are of lower importance. However, the combined use of cool materials and additional tree planting can contribute to lower air temperatures through shading and leaves’ evapotranspiration.

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.

Towards the zero energy and emission future, near Zero Energy Buildings (nZEBs) lead the path for the building construction sector. European legislation provides normative provisions for the definition of nZEBs and their cost-optimal levels within the context of EPBD recast and Delegated Regulation No.244 (2012). However, that same framework unilaterally assesses the building's impact and considers only the emissions from the operational phase. The present study is a first approach of integrating embodied impact into the context of EPBD recast for the cost-optimal levels of nZEBs, an option provided by its accompanying guidelines. The proposed two-step assessment combines the LCA, LCCA and Energy analysis on the Greek nZEB case study. An extended sensitivity analysis regarding climatic, design and monetary parameters, correlates the effect of embodied impact with the transposition of the cost-optimal levels to building variants with lower material intensity. That same transposition highlights an increase in the primary energy of the cost-optimal level between 0.00 kWh/m2·year and 3.57 kWh/m2·year and a decrease in the share of embodied to the total life cycle emissions and energy between 0.61% and 2.36% and 0.78% and 2.82%% respectively. The effect fades in the total sensitivity analysis scale, where it is located only within the range of results that follow the current energy efficiency regulations’ calculations. Results validate the outcome of a previous companion case study, while both indicate the need for further analysis in order to assess the aspects of nZEBs which are subject of variable definitions across the EU member states.

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.

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.