Abstract: Given the adverse implications of both urbanization and global climate change for cities, specifically regarding issues such as human health and comfort, local air quality, and increased summertime energy use in buildings, it is becoming imperative to develop models that can accurately predict the complex and nonlinear interactions between the surrounding urban fabric and local climatic context. Over the past years, a number of comprehensive tools have been widely applied for the generation of near-surface urban climatic information. In this paper, we report on the potential of two alternative approaches to urban climate modeling. Specifically, we compare the climatic output generated with Urban Weather Generator (UWG) and the Weather Research and Forecasting (WRF) model. The WRF model has been widely applied due to its capability of downscaling global weather data to finer resolutions, thus representing the location-specific microclimatic information, while considering the interactions with the surrounding urban and regional context. However, this approach is computationally intensive. The UWG was recently introduced as a simpler alternative to such complex models. The tool morphs rural weather data to represent urban conditions given a set of location-specific morphological parameters. In the present paper, WRF and UWG methods were compared based on empirical data pertaining to air temperature, wind speed, and humidity, collected from 12 locations in the city of Vienna, Austria, over 5 distinct time periods. In general, our results suggest that, as compared to the WRF model, the UWG model results are closer to monitored data. However, during the extreme conditions in summer, the WRF model was found to perform better. It was further noted that the discrepancy between the two models increases with decreasing temperatures, thus revealing a higher offset between UWG and WRF output during the winter period.
Abstract: To reduce the energy and resource consumption in the building sector this study is focusing on a design optimisation of life cycle oriented buildings. In order to optimise the performance of the buildings and in consequence also to achieve improved results for the mandatory Austrian energy certificate a simulation-based rapid design approach is used for the early stage design phase of the buildings, in particular for the architectural design of the buildings.Methods like the Window to Wall Ratio, at the very beginning of the design process, a parametric simulation with EnergyPlus or a more detailed optimisation approach with GenOpt are integrated in this study applied to example buildings. The results are showing that the method can be used in a circular approach for improving the heating demand of the Austrian energy certificate for this case study by more than 25 % compared to the preliminary design
Abstract: The present study investigates waste generation during the production and erection phase of a prefabricated single family house in Austria as a basis for identifying waste prevention potentials. Therefore, the material composition of a case study building (wood frame construction) is compared to waste generated during production and erection. In order to assess the whole life cycle of prefabricated buildings the use phase as well as the end-of-life phase are also considered. Examples are given to show how different measures can impact the generation of waste directly and indirectly. The results show that production and erection are already very efficient with regard to waste generation and prevention potentials mainly exist in further offcut reduction and optimization in packaging. The use phase and the end-of-life of the building are more complex to investigate and waste prevention potentials are less tangible. However, important measures for waste reduction are related to the easy exchangeability of building components as well as their reusability. The lifetime extension of the building and building components, which can be achieved through proper operation and maintenance, can be considered a key issue for preventing waste in the building sector.
Abstract: A quality aspect of buildings pertains to their disposition to provide their inhabitants with effective means of indoor environmental control. Most buildings incorporate a number of elements and devices meant to influence indoor environmental conditions (i.e., windows, blinds, luminaires, radiators, fans). Inhabitants may be provided with different interfaces to operate these devices. In contrast to some other aspects of building performance (e.g., energy efficiency), there is a lack of systematic procedures for objective evaluation of buildings' indoor environmental control devices and their human interfaces. The present contribution entails some general thoughts on the path toward definition and implementation of such procedures.
Abstract: Architectural competitions are regarded an important way to find close-to-optimal solutions for given building design tasks. In recent years, sustainability criteria within architectural competitions increased in importance. However, the question how to cleverly integrate sustainability criteria into the required deliverables that architects have to provide in competition entries remains widely unsolved. Even if energy calculations or tabular data are stipulated, both meaningfulness and impact on the jury decision seem to be highly doubtful. This might be due to a number of reasons: First of all, architectural competitions regularly address early design stages. In other words, large uncertainties regarding construction assemblies, glazing properties, and HVAC-systems (Heating, Ventilation, Air Conditioning) persist at this moment, thus energy evaluations come with a high level of inaccuracy. Moreover, juries that evaluate competition entries regularly consist of domain specialists for the later building usage and architects, but not necessarily encompass energy efficiency specialists. This is understandable, given the multitude of requirements within building design, where sustainability is only one out of many. Furthermore, there is no common understanding regarding clear decision criteria pertaining to sustainability. Even if certain scalar KPIs (Key Performance Indicators) are demanded, these numbers can regularly not describe the overall performance of a building design. Another important aspect is that entries to architectural competitions regularly are checked onto formal issues, but not regarding the plausibility of their content. As such, it cannot be expected that the winning and running-up projects of competitions automatically resemble the most sustainable projects. Literally, any sustainability or energy performance description has to be taken for granted, but can rarely be validated. Commonly it is argued that the winning projects of competitions are regularly the competition entries that show the most balanced mix of different attributes. This, however, is difficult to evaluate. In the present contribution we illustrate the methodology and results of a recently conducted empirical experiment. Thereby, we asked undergraduate and graduate students of architecture to subjectively evaluate a set of competition entries of a recent architectural competition for a high-density, low-energy residential housing project. The project entries were the winning project as well as the five runner-up projects. The students were provided with principle information about the competition and its principle goals and then had to rank the projects regarding different criteria. The comparison of this subjective evaluation was then compared with the competition result. Some differences between the jury’s ranking and the subjective evaluation could be observed.
Abstract: The Glaser method is an assessment procedure for the risk of moisture accumulation in building mono-dimensional structures, that could be used to evaluate mould risk and interstitial condensation risk.It is based on a simplified model that does not represent the real phenomenon and its limitations are well-known qualitatively.This work provides a comparison in terms of moisture content between the Glaser method and WUFI Pro, an advanced heat, air and moisture transfer prediction tool. First the influence of material properties is evaluated on four fictitious materials walls, then six different building envelope typologies for six weather files from Central and Southern Europe are modelled to evaluate the Glaser method results.The effects of the Glaser method simplifications are quantified in terms of moisture content percentage difference.
Abstract: The goal of this paper is to assess two ultra-low-energy family houses from thermo-physical aspects and environmental perspectives. Thermo – physical evaluation, done in two-dimensional PC software Area, has shown results that consent with the newest standards for designing critical details in two ultra-low-energy family houses. Both cases show correctness in design in regards to thermo-physical properties. Both critical spots – corners are well insulated with surface temperatures over 17°C, which indicates low risk of mold occurring. Most of the embodied energy is in roof construction with value of 3084 MJ in house A and 1943 MJ in house B. In terms of indicator of global warming potential, most emissions were calculated in bearing walls of house B (593 kgCO2eq/m2). From the acidification potential, the most emissions were determined in the roof construction B (1.02283 kgSO2eq/m2). It can be stated that financial expenses on groundwork and preparing polystyrene casing for a reinforced concrete slab is significantly higher (family house A) than for foundation insulated from the exterior side with extruded polystyrene (family house B).
Abstract: In recent years, many researchers have focused on the energy efficiency and performance of existing buildings. In order to predict the hygrothermal performance and minimize the risk of moisture damage in retrofit cases, user-friendly moisture calculation tools have been developed. However, concerns have been raised as to how to increase the reliability of such tools. In this context, the present study uses simulation to investigate the retrofit potential of the historical building façades via application of silica aerogels on the external walls. Monitored data provided the basis for generation of a more accurate initial simulation model, as well as the evaluation of the predictive performance of the model.
Abstract: This paper deals with creating of the unique measurement units on the building façade, which enable the possibility to conduct a full-scale measurement of the outdoor climate parameters around the building. The façade of the Research center building, which is a part of University of Zilina campus, is equipped with 36 weather stations to measure the outdoor climate conditions and impact of the building on the approaching wind flow, air temperature distribution, solar radiance impact on the façade etc.In this article, the change of temperatures within the time and place on the facade (sides, position, time), is monitored. This takes into account the surroundings of the building and the temperature on the façade and comparison to the measured “basic” air temperature.
Abstract: Aerodynamics is a relatively young scientific discipline, which started developing in the 50´s of last century. There are known several methods for calculating and measuring of the aerodynamic variables – in-situ measurements, wind tunnel measurements, CFD simulations and calculations according to national standards. Each method has its advantages and disadvantages. Nowadays a large focus is on experimental verifying the findings achieved with calculations help and CFD simulations. One of the verification possibilities are measurements in wind tunnels. The submitted paper deals with construction and using of the wind tunnel by the Slovak University of Technology in Bratislava. This device was put into operation after experimental verification in 2012, so this wind tunnel is one of the newest of its kind in Europe. The concept of the construction of individual structural elements and the wind tunnel parts has been designed in collaboration with the Aeronautical Research and Test Institute (Czech Republic) and was based on previous made analysis of aerodynamic tunnels. Its structure was designed and realized by Konštrukta Industry (Slovak Republic). We could it characterized as atmospheric boundary layer wind tunnel with open test section. It is unique with two test sections – front and back measuring space, where the front measuring space is used for uniform flow and the back measuring space is used for turbulent flow. That is why it is not only usable in the civil engineering sector (buildings, bridges, chimneys etc.), but also in city urbanism (pedestrian wind comfort and wind safety, dispersion of air pollutants), aircraft and automotive industries.