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Building components in terms of thermal protection are being addressed with standard requirements to related thermal performance design. In this relation, thermal conductivity parameters play a highly relevant role that may affect heat transfer greatly. This represents a key factor in building performance assessments for steady-state conditions and corresponding calculation models on thermal effectiveness as well as temperature distribution of building components. Generally, these parameters are known from declared values given by their producers. For this purpose, standard tests are performed to provide data under steady-state conditions. However, limitations may occur in real cases due to not constant and changing thermal conductivity that is temperature, moisture, and time-depending variables. Therefore, in the design process, several governing factors should be carefully considered in thermal calculations. Accordingly, a standard methodology using the transformation of declared values to design values is adopted in practice. In this paper, the usefulness of transformation formulas based on standard methods is demonstrated and discussed as compared with real subjections obtained in the laboratory. One of the representatives of thermal insulation based on mineral fibrous material was used and studied experimentally to obtain transformation factors on both moisture and temperature relations. Based on the data measured, coefficients of transformation formulas were derived from experimental measurements. Results identify a certain discrepancy between experimental data and theoretically calculated values used by available standard methods. [ABSTRACT FROM AUTHOR]

Paper presents theoretical and real hygrothermal behaviour of the south-east timber wall component. The analysed wall component represents current trends in wooden house design and it is a part of experimental timber building in campus of Mendel University in Brno – woodenHAT experimental module. Long-term exposure of the experimental module to real weather conditions brings information about real of hygrothermal behaviour. The component contains several temperature and moisture sensors which together with the weather station permanently monitor temperature and moisture content in the wall component and conditions in front of the façade during the whole year. Experimental data are compared with results of dynamic simulation earned by well-established software for prediction of heat and moisture transport Delphin which has been developed by Institute of Bauklimatik at TU Dresden. Boundary conditions of the numerical model are based on local weather data as well as reference year for closest places near to Brno. The analysis shows and discusses differences between results of experimental measurement and selected boundary conditions. It represents the validation of HAM-modelling for cases neglecting air flows and insufficient airtightness. [ABSTRACT FROM AUTHOR]

There are still requirements in the building energy research and thermal engineering field to increase the thermal performance of a building and its structural elements. Building envelope made of hollow ceramic bricks are widely used in building engineering for their thermal, acoustic, and structural properties. This type of building element can be considered as one of the most used technologies for the present walls of building envelopes in European region. Various aspects that affect the resulting geometry of brick hollows, changes in the configuration of cavities and currently also the application of filling material with low thermal conductivity may contribute to the increase of thermal properties of these bricks. Another potential approach and further improvements can be based on the reduction of heat loss during heat transfer through the brick cavities aimed at reducing heat transfer by thermal radiation. Therefore, the effect of low emissivity on the thermal performance of ceramic hollow brick is the key subject of this paper. For his reason, inner surfaces of brick cavities were modified with low emissivity coating, experimentally tested using a heat flow meter method and to provide a consequent numerical analysis. Results presented in this study reveals, that depending on the emissivity, the decrease of the thermal conductivity of up to 20% can be theoretically achieved when particular hollow bricks are modelled however this effectivity is not followed by experimental measurement. [ABSTRACT FROM AUTHOR]

The condensation risk of the top envelope of low sloped roofs with air ventilated cavity has an important factor in the designing phase of these building structures. The significance of sky radiation plays an important role in the radiation heat exchange specifically during night-time (winter and transient periods) with regard to heat loss and condensation risk at the top roof envelopes. Basically, the design principles and current development of standard requirements have limited and simplified implementation of this phenomenon. The importance of a relevant design of these types of roofs are being addressed as highly important issue in the building application to predict its reliable hygrothermal performance. In this context, the paper presents results of numerical study, where thy sky radiation effect is carefully taken into account. It provides a numerical analysis on the minimalization of the condensation risk at the top envelope of low sloped roofs with naturally ventilated air cavity. Based on this, a performance prediction of thermal properties degree and its influence due to condensation risk occurrence is obtained, where real climate data for location of Brno, Czechia, is specifically employed. The results demonstrate hour's quantity of condensation risk occurrence in terms of thermal resistance correlation for data obtained through the whole climatic year. [ABSTRACT FROM AUTHOR]

Moisture in materials may affect its technical parameters greatly and plays significant role with close connection to durability and lifespan of building components. Moisture balance analysis and hygrothermal assessment of building components is needed to be provided during the building design stage. Recent trends in architecture integrate lightweight components with application of various foil vapor barriers to control moisture balance. While vapor barrier resistance is often decreased due to perforations in real-world application, the reliable evaluation of moisture transfer in building component is essential in thermal engineering application as well as in building science. This paper presents up to date overview of research focused on vapor diffusion through perforated materials that were conducted already in the past. While perforation of vapor barriers significantly reduces vapor resistance and air tightness corresponded to moisture balance of building element, the effect of vapor tightness decreasing is illustrated in case study based on particular wood frame wall. In this relation, a common engineering practice is compared with the complex numerical approach of heat and moisture transport on a model case with different vapor barrier permeability to identify the overall hygrothermal efficient parameters. Presented results show the importance of real vapor resistance of barriers aiming to point out the knowledge gap in the field of building civil engineering. [ABSTRACT FROM AUTHOR]

The current development of modern building envelope systems predestines the relevance of the application of specific test methods for it to adequately characterize thermo-optical properties of novel transparent building components and systems. Therefore, the intention of this study concerns the investigation of the spectral test method for its potential implementation in analyzing thermo-optical changes in a phase change material based on building components. As solar simulators are considered to be the key methodologies for conducting solar-based research under a well-controlled environment, this study presents a simple design of a low and high flux solar simulator to provide optical testing of specific glass components. The optical system was designed as a lamp of one unit and a parabolic reflector used to irradiate test samples implemented in a squared box with an optical detector. Second, the experimental setup was equipped with a spectrophotometer, and the validity of transmittance data obtained with a reference building's transparent systems, like a simple glass pane and Plexiglas, was tested by measurements comparison with results obtained using a UV/VIS/NIR spectrophotometer in the light transmittance spectra. The results of the experiment revealed light transmittance data obtained from spectrophotometers and compared with reference simple glass systems. [ABSTRACT FROM AUTHOR]