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This paper discusses experimental and simulated data regarding the thermal bridging effect in a reinforced concrete corner pillar, which belongs to a building dating back to the 1980s and located in Southern Italy. The thermal field determined by the concrete pillar corner has been evaluated, introducing an experimental procedure based on both direct measurements and indirect observations of the inner superficial temperature by means of thermal imaging techniques and surface temperature probes. Moreover, indoor and outdoor air temperature and relative humidity were measured to provide suitable boundary conditions in the numerical simulations, performed with a commercial software tool widely used in Italy based on 2D finite element techniques. The experimental measurements show that, at more than 50 cm from the corner, the surface temperatures become almost constant, meaning that the thermal bridging effect becomes less evident. However, the surface temperature in the corner is around 1.5 °C lower than in the undisturbed flanking walls. In terms of local heat flux, the discrepancy between simulations and measurements is below 3%. Finally, this paper verifies the effectiveness of External Thermal Insulation Composite System (ETICS) renovation in reducing the thermal bridging effect of the corner pillar. The results also include the calculation of the linear thermal transmittance with a series of relations available in well-known atlases for thermal bridges and show that these relations are more reliable in the case of uninsulated pillar than for the insulated one. [ABSTRACT FROM AUTHOR]

This paper discusses experimental and simulated data regarding the thermal bridging effect in a reinforced concrete corner pillar, which belongs to a building dating back to the 1980s and located in Southern Italy. The thermal field determined by the concrete pillar corner has been evaluated, introducing an experimental procedure based on both direct measurements and indirect observations of the inner superficial temperature by means of thermal imaging techniques and surface temperature probes. Moreover, indoor and outdoor air temperature and relative humidity were measured to provide suitable boundary conditions in the numerical simulations, performed with a commercial software tool widely used in Italy based on 2D finite element techniques. The experimental measurements show that, at more than 50 cm from the corner, the surface temperatures become almost constant, meaning that the thermal bridging effect becomes less evident. However, the surface temperature in the corner is around 1.5 °C lower than in the undisturbed flanking walls. In terms of local heat flux, the discrepancy between simulations and measurements is below 3%. Finally, this paper verifies the effectiveness of External Thermal Insulation Composite System (ETICS) renovation in reducing the thermal bridging effect of the corner pillar. The results also include the calculation of the linear thermal transmittance with a series of relations available in well-known atlases for thermal bridges and show that these relations are more reliable in the case of uninsulated pillar than for the insulated one.

The paper is focused on assessing the impact of wood window installation position in terms of wall thickness. The thermal bridge created this way is defined as a linear thermal transmittance [Ψ] of the construction. In this particular case, the thermal bridge is created by the wall and window constructions. For the purpose of this study, one wood window construction was used and compared when installed in various wall constructions. Emphasis was placed mainly on composed walls, which are used mostly in wood panel constructions. Model walls of various compositions, however, having the same thermal performance were evaluated in the study. In order to achieve the same values of thermal resistance of walls, various theoretical materials were used. Following the performed analyses, the course of the dependence between the development of wall temperatures was evaluated. Reference values were represented by a temperature of 0°C and window positions where the system window-wall reaches the minimum value of the linear thermal transmittance of the window installation Ψi,min. The hypothesis that the position of Ψi,min depends on the steepness of the temperature gradient (represented by the temperature curve direction) was not confirmed. Results presented in this study can be used for estimating the window position with Ψi,min at the level of 7 – 11 % of the wall thickness measured from the place in the construction with a temperature of 0°C. [ABSTRACT FROM AUTHOR]

Most apartment buildings in South Korea use internal insulation systems to reduce building energy demand. However, thermal bridges such as balcony slabs in apartment buildings still lead to significant heat loss in winter, because the internal insulation system is not continuous in the balcony slab structure, and floor heating systems are commonly used in residential buildings. Therefore, this study investigates two types of thermal break elements, namely thermal break (TB) and thermal break-fiber glass reinforced polymer (TB-GFRP), to improve the thermal resistance of a balcony thermal bridge. To understand the effects of balcony thermal bridges with and without thermal break elements, the linear thermal transmittances of different balcony thermal bridges were analyzed using Physibel simulations. Then, the heating demand of a model apartment under varying thermal bridge conditions was evaluated using TRNSYS simulations. To understand the effect of insulation systems on heat loss through a balcony thermal bridge, apartments with internal and external insulation systems were studied. Whether the apartment was heating was also considered in the thermal transmittance analysis. Thus, the linear thermal transmittance of the thermal bridges with thermal break elements was reduced by more than 60%, and the heating energy demands were reduced by more than 8%.

Abstract Roof windows are widely used in northern European countries, contributing positively by giving daylight, passive solar heat and view to the outside. In order to improve their thermal property, triple glazing unit together with external shutter are more and more common on the market. Additionally, the junction part between window and roof is also important since it greatly influences the linear thermal transmittance (LTT) along edges of the window and the daylight level of the room. This research presents a parametric analysis for roof windows with triple glazing unit and external shutter from perspectives of energy, daylight and thermal comfort. The investigation can be described in two parts: • Analysis of thermal and comfort performance for triple glazing unit with an external shutter. • Analysis of combined performance of daylight level and LTT for roof windows. Performances of energy and thermal comfort of triple glazing unit with external shutter can be influenced by different properties, including the width of the cavity between shutter and external pane, air penetration rate through the cavity between shutter and external pane, the tilt angle of the window. The study conducts analysis on the energy and comfort performances of the window by calculating U-value of the entire window and internal surface temperature of the glazing. The calculations are performed by a model developed via state-space modelling using Simulink/MATLAB. The results reveal that the external shutter improves both the thermal and comfort performances of the window. The ways of installing windows on a roof and cutting on the internal wall along window edges also have great influences on the combined performance of daylight level and LTT along the edge between window and roof. Therefore, daylight and LTT are also evaluated with different parameters, including the thickness of roof insulation, installation level of windows on the roof, cutting of lining and extra insulation around the perimeter of windows. The analysis is conducted using DIVA/Rhino and Flixo. The calculations show that the lower installation level and extra insulation around the window frame can decrease linear thermal transmittance of the entire window by more than 60%. [ABSTRACT FROM AUTHOR]

Abstract The goal of the paper is to compare two different methods of calculating the linear transmittance of thermal bridges in order to evaluate the building energy need for heating. As a case study, it was considered an existing non-isolated residential building of '70 years consisting of 30 housing units. All the construction details of the building are known. The energy analysis of the building was carried out using a commercial software. The linear transmittance of the thermal bridges was determined both by the catalogue, provided by the software itself, and by the numerical finite-element evaluation according to UNI EN ISO 10211 standard using a 2-D numerical simulator. Through numerical analysis it is possible to evaluate in a detailed way all the thermal bridges present in the building and therefore it is possible to evaluate the approximation induced by the use of the catalogue. Results show that the detailed analysis leads to a transmission heat exchange through thermal bridges about eight times greater than that estimated through the catalogue and consequently to a higher building energy need of about 12%. The heating energy needs per unit area of the individual housing units were also compared. [ABSTRACT FROM AUTHOR]

The energy consumption in buildings contributes substantially to the worldwide energy use and greenhouse gas emissions. One of the crucial elements defining energy consumption is the building envelope, which in modern designs includes growing share of fenestration. Due to recent improvements of windows and walls, the thermal bridging effects occurring on their connections, become more significant. Window-to-wall connections appear to be especially important and can contribute up to 40% of the total heat loss caused by thermal bridges in building envelope. Thus, this study is investigating thermal properties of window-to-wall connections. The main scope of the work is to determine the most efficient window position in the window opening regarding minimizing thermal bridging effects. Five different wall constructions are investigated along with two windows with different U-values. The thermal simulation results show that the window position has a crucial impact on the amount of energy loss through the thermal bridges. For each wall type, the most energy-efficient position is found, resulting from detailed analysis of sill, head, and jambs construction details. For some cases placing the window in the most energy-efficient position reduces linear thermal transmittance (LTT) over 50%. Among considered positions, the temperatures on the internal surface of the assemblies are weakly influenced by the window position. Example calculations show that significant share of energy losses from the fenestration presence is caused by thermal bridge occurring on window-to-wall. [ABSTRACT FROM AUTHOR]

The energy consumption in buildings has continuously increased, and in some countries it reaches almost 40% of the total energy use. Therefore, there are various efforts to minimize energy consumption in buildings, and the regulations on building envelope insulation have been tightened up gradually. For vacuum insulation panel (VIP) in buildings, various researches have been conducted over the last several years and its application has been extended in building industry. VIP application in buildings enable thinner building envelope while maintaining the same thermal performance by a greatly lower thermal conductivity than conventional insulation materials. On the other hand, VIP applied in buildings may cause thermal bridges, which reduce the thermal performance of VIP envelope due to the very low thermal conductivity compared with other building materials. Therefore, the thermal performance of building envelope with VIP depends on how the VIPs are applied to the building envelope and that is affected according to the installation method of VIP with other building materials. This study aims to analyze the thermal performance of VIPs, and to evaluate the effective thermal transmittance (U-value) of building walls with VIPs. For this study, the VIPs-applied walls were designed to minimize thermal bridge effect and their linear thermal transmittances were evaluated by BISCO program. [ABSTRACT FROM AUTHOR]

Renovation of old apartment buildings is a topic of current research interest throughout the Eastern Europe region where similar typology is derived from the period of 1960–1990. Thermal bridges, essential components of the transmission heat loss of a building, have to be properly evaluated in the energy audit during current state-of-the-art situation as well as in the comparison of renovation solutions. Resulting from field measurements and calculations, we propose linear thermal transmittances Ψ of thermal bridges for four types of apartment buildings: prefabricated concrete large panel element, brick, wood (log), and autoclaved aerated concrete. Our results show that thermal bridges contribute 23% of the total transmission heat loss of a building envelope before renovation. After renovation thermal bridges account for only 10% if windows are repositioned into additional external thermal insulation and balconies are rebuilt as best practice. Inversely, impact of the thermal bridges might be up to 34%, depending on the wall insulation thickness. We have also found that the relative percentage of thermal bridges after renovation increases and the negative impact of the thermal bridges of certain junctions cannot be compensated with thicker wall insulation. Results obtained in this paper are useful for energy audits. [ABSTRACT FROM AUTHOR]

The major aim of this study was to create a numerical model of thermal bridges in a wooden structure and to discover differences between factual values of linear thermal transmittance utilized in the finite-element (FE) modelling and values given by the European normative method (EN ISO 14683). Thermal bridges of wooden structures were detected using thermocamera FLIR S65 for infrared detection. These measurements allow displaying the temperature distribution of the thermal scan and proving the positive correlation between heat flux and change in the evaluated temperatures of a thermal bridge. A three-dimensional FE model of the structure was prepared for the thermal analysis using the engineering software ANSYS Workbench 13. The transmission heat loss coefficients of a prefabricated wooden house were established based on the Czech normative method (ČSN 730540-4). Linear thermal transmittance values calculated from the thermal analysis and the normative method given by EN ISO 10211 were compared. The results show that even if the transmission heat loss coefficients meet the requirements designated by standards, the real heat losses are increased by thermal bridges involved in the construction. Their influence is determined by the linear transmittance value which is usually not exactly established. [ABSTRACT FROM PUBLISHER]

Nowadays, the building sector is one of the main sources emitting pollutant gases to the atmosphere due to its deficient energy behaviour. Among the elements of the envelope, the thermal bridges are where the heat losses and gains mainly occur, depending on the season of the year. To reduce the effect of the thermal bridges, there are different patented technologies which give provide solutions. In this paper, the thermal behaviour of five patented slab front (slab-façade) thermal bridges are analysed in a case study located in the south of Spain. Moreover, the influence of the thermal bridge on the energy demand from the building analysed was evaluated, both in the current scenario and future ones (2020, 2050 and 2080). The results reveal that the use of the patents in slab fronts can mean reductions by up to 95.74% in the linear thermal transmittance. Likewise, due to the improvement of the thermal bridge of slab fronts by using the patented designs which offered the best features, a savings in the global energy demand for heating higher than 18% as well as a savings in the global energy demand for cooling higher than 2.80% could be achieved in all the time scenarios considered.

To achieve national greenhouse gas reduction in the building sector, heating and cooling energy in buildings should be reduced. The government has strengthened regulations on insulation performance for building energy savings. However, the building envelope has various thermal bridges. In particular, a metal panel curtain wall comprises a number of thermal bridges at joints between the panels and the fixing units, thus degrading the overall thermal performance. To reduce building energy, it is necessary to reduce thermal bridges in building envelopes. This study aims to analyze the energy saving potential achieved by reducing thermal bridges. For this, the insulation performance and building energy needs of the existing and alternative metal panel curtain wall were evaluated. The alternative metal panel curtain wall that uses plastic molds at joints between panels and the thermally-broken brackets was suggested to reduce heat loss through thermal bridges. As results, the effective U-value of the alternative metal panel curtain wall was reduced by 72% compared with the existing metal panel curtain wall. In addition, annual heating energy needs of the alternative metal panel curtain wall building was reduced by 26%, and annual total energy needs was reduced by 6% because annual cooling energy needs of it slightly increased compared with the existing metal panel curtain wall. In conclusion, the alternative metal panel curtain wall considerably influenced the savings in building energy needs by reducing thermal bridges. [ABSTRACT FROM AUTHOR]

This paper presents a study on using the steady-state three-dimensional heat transfer software HEAT3 for evaluating the heat flow of heat transfer through different elements of the building envelope in order to establish the linear thermal transmittance of the linear thermal bridge. The linear thermal transmittance is obtained according to the one-dimensional steady- state heat transfer calculation formula for the plane walls using the heat flow values obtained through the method specified above. The results presented in this paper are part of a wider study on evaluating the heat transfer through building's envelope elements by evaluating as accurate as possible the thermal bridges effect of the most common building structures. As a case study, it was considered the steady-state heat transfer through an opaque outer wall of a building considering the thermal bridges for the following elements: outer walls intersection, inner and outer wall intersection and outer wall with intermediate floor intersection. [ABSTRACT FROM AUTHOR]

Vacuum Insulation Panels (VIPs) are characterised by very low thermal conductivity, compared to traditional insulating materials. For this reason, they represent a promising solution to improve the thermal behaviour of buildings, especially in the case of energy retrofitting (where a higher performance and less thickness is desirable). VIPs are insulating components in which a core material is surrounded by an air tight envelope which allows a high degree of internal vacuum to be maintained. Such features, on the one hand, allow excellent thermal insulation properties to be achieved, but, on the other, require the manufacturing of prefabricated panels of fixed shape/size. This means that the use of these super insulating materials in the building envelope involves the problem of joining the panels to each other and of fixing them onto additional supporting elements. As a result, purposely studied supporting structures or systems are required. However, these structures and systems cause thermal bridging effects. The overall energy performance of the resulting insulation package can therefore be affected to a great extent by these additional elements, and can become significantly lower than that of the VIP panel alone. In order to verify the incidence of thermal bridges on the overall energy performance of an insulation system that makes use of VIP panels, an experimental campaign has been carried out using a heat flux metre apparatus and analysing different joint materials/typologies. First, a measurement method was proposed, tested and verified on the basis of data from the available literature. A series of measurements on different samples was then performed. The experimental results were then used to calibrate and verify a numerical model that allows the performance of various “VIP packages” to be predicted and the performance of the overall package to be optimised. [ABSTRACT FROM AUTHOR]

The thermal losses on the edges of vacuum insulation panels (VIP) are influenced by the thickness of the panels, the type of edge design (single- or multi-layered foils), the inorganic barrier material and the thickness of the barrier layers. Additional thermal bridging effects result from applications and constructions, e.g., the material used in the joint between two panels (e.g. elastomeric foam), the covering layers on the panels and the mechanical fasteners used for mounting and fixing. Via numerical simulations for VIP of varying thickness, the thermal bridging effects are determined for different influencing factors. The impact of the linear thermal transmittance on thermal resistance of panels of various sizes is calculated and equivalent thermal conductivity of the panels determined. [ABSTRACT FROM AUTHOR]

Highlights: [•] The thermal performance of fiber-reinforced polymer thermal breaks is investigated. [•] The new thermal breaks have a linear thermal transmittance <0.10W/m2. [•] Related to the opaque building envelope, thermal losses can be reduced by 18%. [•] Heating requirements of a building with an optimum envelope can be reduced by 41%. [Copyright &y& Elsevier]

Most apartment buildings in South Korea use internal insulation systems to reduce building energy demand. However, thermal bridges such as balcony slabs in apartment buildings still lead to significant heat loss in winter, because the internal insulation system is not continuous in the balcony slab structure, and floor heating systems are commonly used in residential buildings. Therefore, this study investigates two types of thermal break elements, namely thermal break (TB) and thermal break-fiber glass reinforced polymer (TB-GFRP), to improve the thermal resistance of a balcony thermal bridge. To understand the effects of balcony thermal bridges with and without thermal break elements, the linear thermal transmittances of different balcony thermal bridges were analyzed using Physibel simulations. Then, the heating demand of a model apartment under varying thermal bridge conditions was evaluated using TRNSYS simulations. To understand the effect of insulation systems on heat loss through a balcony thermal bridge, apartments with internal and external insulation systems were studied. Whether the apartment was heating was also considered in the thermal transmittance analysis. Thus, the linear thermal transmittance of the thermal bridges with thermal break elements was reduced by more than 60%, and the heating energy demands were reduced by more than 8%. [ABSTRACT FROM AUTHOR]

Abstract: The use of vacuum insulation panels in buildings has gradually increased in the past few years and developments in their production have occurred in parallel. This has mainly lead to an optimization of different hygro-thermal properties of both the core material as well as the envelope. The issue of thermal bridges caused by the 300nm thin metallic layers of the barrier envelope and by the joints between two adjacent panels remains. The present study investigates the influence of these thermal bridges on the effective thermal conductivity of a staggered double-layer of vacuum insulation panels. For this purpose a series of guarded hot plate measurements on single- and double-layers of vacuum insulation panels was carried out. The variety of the existing thermal bridge situations was accounted for by different panel size compositions. The results hereof were compared to those of a simplified numerical model. The target is to determine the effective thermal conductivity by a minimum number of required tests and the simplest numerical model. This will enable the determination of additional heat loss induced by the mentioned thermal bridges for a specific envelope laminate type without knowing the details of its composition especially the metallic layers. [Copyright &y& Elsevier]

Abstract: The building''s energy performance is the result not only of material and component performances, but also of the way the components are interconnected. Concerning windows, their energy performance, which is usually evaluated by using the glass and frame heat transfer coefficients and the linear heat transfer coefficients of the glazing spacer, depends also on the frame installation. In this paper the entity of thermal losses due to the frame installation has been evaluated in terms of linear thermal transmittance calculated in accordance with the standard EN ISO 10211:2007 using THERM 5.2. The analysis of thermal bridges between a wooden frame window installed into two different kinds of external clay block walls has been carried out. The linear thermal transmittances have been calculated for three cases regarding the position (external, internal, and intermediate) and three concerning the insulation of the hole perimeter (non insulated, insulated and with insulation over fixed frame). The impact of the window installation on thermal losses has been estimated and its dependence on different sizes has been evaluated. A new graphical representation has been suggested. The frame position and the configuration of the window hole insulation result to have a relevant impact on the overall thermal performance of the considered window. [Copyright &y& Elsevier]

A well-insulated, airtight, thermal bridge free building envelope is a key factor for nearly zero energy buildings (nZEB). However, increased insulation thickness and minimised air leakages increase the effect of thermal bridges on the overall energy efficiency of the nZEBs. Currently, the calculation of linear thermal transmittance follows ISO 10211, which requires the separate numerical assessment of combined thermal bridges, where two or more junctions are positioned in close proximity within delimiting cut-off planes. This poses a practical problem, as the number of different combinations (mainly related to window to wall connections in combination with corners, intermediate ceiling etc) is too large in practice to follow the standard procedure. In this study, a parametric numerical assessment of different thermal bridges in well-insulated constructions showed that with linear thermal transmittance up to 0.2 W/(mK) in lightweight construction and up to 0.1 W/(mK) in heavyweight construction the reduction of flanking element length from 1.440 m to 0.288 m (80% reduction) had no effect on numerically calculated linear thermal transmittance in steady-state conditions. For thermal bridges inside heavyweight construction with linear thermal transmittance below 1.1 W/(mK) the flanking element length could be reduced by 50% without any effect and by 70% with marginal effect (<2%) on linear thermal transmittance. The shorter flanking element length, roughly equal to its thickness, can then be used to minimise the amount of combined thermal bridges in complex building envelopes. Compared to ISO 10211 requirements, the amount of different combined thermal bridges in two exemplary building envelopes was reduced by 35% to 76%, depending on the building type, and allowed deviation of 0.5%, 1.0% or 2.0%, thus significantly reducing the working hours of practitioners. [ABSTRACT FROM AUTHOR]

Although vacuum insulation panels (VIPs) are excellent thermal insulators, edge effects decrease their overall thermal performance. Moreover, they are often used with protections, such as integration into a panel. These panels typically use spacers that cause a significant additional thermal bridge. The effect of this thermal bridge is either determined accurately with numerical simulation tools or estimated with simple thermal resistance networks. The first approach is laborious, while the latter approach lacks accuracy. This study therefore presents and validates an analytical approximation model for calculating this thermal edge effect. A comparison of this model with numerical simulation shows that it can be applied with an inaccuracy of <10%. The total inaccuracy, however, also includes an error due to the schematization of the edge of the building panel. Yet, this model appears to be very useful for estimation of the linear thermal transmittance of the edge of building panels. [ABSTRACT FROM AUTHOR]

Although vacuum insulation panels (VIPs) are thermal insulators with very low center-of-panel thermal conductivity, their effective thermal conductivity is raised significantly due to large edge heat fluxes caused by a continuously enveloping high barrier laminate, especially if metal based foils are applied. This study therefore presents and validates two analytical approximating models for calculating this thermal edge effect for thin high barrier laminates around VIPs. A comparison of these models with numerical simulations shows that they can be applied with an inaccuracy of <5% for idealized barrier laminates, considering the limitations specified. These models also demonstrate that the linear thermal transmittance, representing this edge effect, amongst others depends on envelope thickness and thermal conductivity, panel thickness, and center-of-panel thermal conductivity. Moreover, this study shows that these models are able to estimate the linear thermal transmittance resulting from more realistic VIPs with seams near their edges, as well. For these realistic panels, deviations between numerical data and prediction model maximally amount to about 9%. Using the presented models then, enables VIP designers, architects, and building engineers to estimate the overall thermal performance of a VIP. [ABSTRACT FROM AUTHOR]

Abstract: The thermal behaviour of a balcony board with integrated glass fibre reinforced plastic (GFRP) elements replacing the compression reinforcement rods, is investigated by means of measurement as well as numerical analysis. For this reason a specimen consisting of an externally insulated brick wall and a representative part of a balcony is tested under a steady state temperature gradient of 30K in a guarded hot box. Additionally to the normative requirements, temperature sensors are placed on critical sites within the construction, prior to the pouring of cement, to help the verification of the numerical analysis carried out simultaneously. Measured and calculated results are compared and some numerical parameter studies are carried out to quantify the advantage of glass fibre reinforced plastic elements over conventional balcony boards from a thermal point of view. [Copyright &y& Elsevier]

Abstract: A concrete wall externally insulated with six expanded polystyrene boards, each containing three vacuum insulation panels, was investigated both experimentally and numerically. The main goal of this study was to determine the thermal performance of vacuum-insulation panels applied to walls in building constructions. Comparisons were made with conventional insulation and also with systems including damaged, i.e., vented vacuum panels. Since the vacuum insulation panels are encased in a metallized laminates as barriers against permeation of moisture and gas, special attention was given to the edge effects. Stepwise adjustment of the measured and calculated results reported here provide a general assessment of the efficacy of this insulation system applied on different wall materials. A functional representation of the measured data, for steady-state conditions, is introduced. Moreover, infrared thermography was used to confirm the three dimensionally calculated temperature distributions on the surface. The present investigation was part of the research programme “High Performance Thermal Insulation in Buildings and Building Systems” of the international energy agency (IEA). [Copyright &y& Elsevier]

In architecture, the outstandingly low thermal conductivity of vacuum insulation panels (VIPs) of ≈4 × 10-3W/(m K) allows to realize thin thermal insulation layers. Typical U-values are 0.2W/(m² K) for a 2cm-thick VIP. On the other hand, with vacuum-insulated façades the relative effect of thermal bridges is much stronger than that for conventionally insulated buildings. In this work, different thermal bridges are investigated. Especially with VIPs with laminated Al foils (here the aluminum foil is ≈8 μm thick and laminated on both sides with plastic foils of 15 μm PET and 50 μm PE), strong thermal bridges around the perimeter of the VIPs occur. Also the mounting system can have a strong negative effect on the thermal performance of VIP-insulated walls. As our calculations show, the effect of the thermal bridge depends strongly on the thermal contact of the VIPs with the wall. Therefore, it is necessary to optimize every vacuum-insulated construction in order to make the best use of the low thermal conductivity of VIPs. As an example, we describe how VIPs were effectively integrated into a renovated gable façade and into a new ultra-low energy timber building. [ABSTRACT FROM AUTHOR]

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This study presents a non-computerized calculation procedure for steady state two-dimensional conductive heat losses through thermal bridges. The heat flow is divided into distinct flow paths based on physical considerations. A resistance is derived analytically for each flow path. These resistances are combined into a net work. The network simulates the construction. Calculating the total resistance of the network gives the thermal resistance of the construction. The algorithm is compared with a finite forward difference method. The relative error on the linear thermal transmittance of the thermal bridges calculated does not exceed 10%. The absolute error on the mean surface temperature is approximately 1°C and independent of the type of construction. The minimum inside surface temperature can be estimated in only a few cases; the absolute error is approximately 0.5°C. The algorithm is devel oped mainly for designers. Its simplicity and the possibility it offers for quick and ac curate control calculations makes it an ideal design tool. It can be programmed in Lotus for specific applications of a designer. It is ideal for prevention of condensa tion, more so than predicting heat loss (or gain). [ABSTRACT FROM PUBLISHER]

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. • Prevalent methods for thermal bridge estimation are comparatively examined. • The comparison takes place for different levels of thermal insulation. • Results depend on thermal bridge geometry and building elements insulation capacity. • Significantly different results for a selected multi-storey building are observed. • Simplified approaches in building codes may lead to considerable inaccuracies. [ABSTRACT FROM AUTHOR]

• FEM simulations of different construction joints for the wall-foundations-ground node. • Regression equations for all the configurations to evaluate linear transmittance. • Correlations to evaluate the ground-contact thermal bridges in existing buildings. • Tests for more than 1000 practical cases confirmed accuracy of proposed correlations. The issue of transmittance of thermal bridges in existing buildings has been addressed aiming to achieve correlations able to evaluate the ground-contact thermal bridges. A bi-dimensional steady state FEM model has been implemented to simulate wall-to-floor structural node and then validated in accordance with the EN ISO 10211:2017 standard. Different construction joints have been then simulated for the structural node foundations-vertical elements up to a total of 19 configurations, from which 1700 cases have been derived varying walls and floor stratigraphies and ground properties. Correlations for the linear thermal bridge transmittance have been calculated through regression technique for all the configurations, together with their validity ranges expressed in terms of 95% confidence interval values. Tests performed for more than 1000 practical cases confirmed the accuracy of the proposed correlations. Through those correlations ground contact thermal bridges in existing buildings can be hence analyzed in a simple and operative way, offering technicians in the sector a tool that covers most of the possible situations. [ABSTRACT FROM AUTHOR]