Thermal Bridges Impact on Energy Consumption in Residential Buildings Considering the Brazilian Bioclimatic Zoning

With the considerable increase in electric power consumption, searching for buildings with lower energy impact has become a crucial factor on controlling energy consumption, as well as designing buildings with high thermal comfort. Thermal bridges are weak points in buildings where the thermal resistance varies considerably between two distinct points. Depending on the situation, the existence of thermal bridges in a building can be favorable to the achievement of the expected thermal comfort and lower energy consumption. The aim of this paper is to analyze the impact of thermal bridges of reinforced concrete structure regarding to energy consumption for residential buildings in the Brazilian bioclimatic zones. The used method is characterized by computer simulations of distinct cases configured with and without thermal bridges. The results show that in most bioclimatic zones, the presence of thermal bridges in the wall composition contributes to the reduction of energy consumption for both heating and cooling, and independent of the wall＇s insulation level, solar absorptance is a major factor in the energy consumption levels, walls with smaller absorptance consume less and this consumption increases gradually with increasing absorptance.

Analysis of Thermal Bridge Impact in a Hotel Building for the Eight Brazilian Bioclimatic Zones

This article aims to present an analysis of the influence of thermal bridges on reinforced concrete structural systems regarding energy performance of the envelope of a commercial building located in the bioclimatic zones 1 to 8 in Brazil, using computer simulation. The method used to achieve this goal includes the following steps： （1） definition and configuration of the base case; （2） definition and configuration of the reference model; （3） optimization of energy modeling; （4） energy modeling and comparison of consumption between the base case and the reference model. Main results showed that thermal bridges in reinforced concrete interfere on the building＇s energy performance and that the impact is related to the WWR （window-to-wall ratio） on the building. For hotel buildings with WWR from 30% to 45%, thermal bridges imply a decrease in estimated consumption, which can reach 10%, depending on the bioclimatic zone. For 60% WWR, the non-consideration of thermal bridges can represent up to 5% of increase in estimated consumption, depending on the Brazilian bioclimatic zone.

An integrated computational method for calculating dynamic thermal bridges of building facades in tropical countries

Identifying thermal bridges on building façades has been a great challenge for architects,especially during the conceptual design stage.This is not only due to the complexity of parameters when calculating thermal bridges,but also lack of feature integration between building energy simulation(BES)tools and the actual building conditions.For example,existing BES tools predominantly calculate thermal bridges only in steady state without considering the temperature dynamic behaviour of building outdoors.Consequently,relevant features such as thermal delay,decrement factor,and operative temperature are often neglected,and this can lead to miscalculation of energy consumption.This study then proposes an integrated method to calculate dynamic thermal bridges under transient conditions by incorporating field observations and computational simulations of thermal bridges.More specifically,the proposed method employs several measurement tools such as HOBO data logger to record the actual conditions of indoor and outdoor room temperature and thermal cameras to identify the surface temperature of selected building junctions.The actual datasets are then integrated with the simulation workflow developed in BES tools.This study ultimately enables architects not only to identify potential thermal bridges on existing building façades but also to support material and geometric exploration in early design phase.

Investigation the Correlation between Thermal Bridging and Geometries in Concrete Buildings

This article focuses on the investigation of the correlation between thermal bridging and various geometric configurations. The article employs QuickField software for conducting three-dimensional steady-state heat transfer simulations to investigate the thermal behaviors of diverse geometric shapes. Significantly, this study involves the simulation of four distinct geometries including concrete circular, square, rectangular, and triangular column through an insulated concrete layer while all geometries maintain the consistent surface areas. The simulations yield findings indicating that circular thermal bridging has the best thermal performance, while rectangular thermal bridging displays comparatively the lowest thermal efficiency. Furthermore, the results indicate that alterations in the perimeter of thermal bridge interfaces, while maintaining a constant area, exert a more pronounced influence on the thermal performance of the geometries compared to proportional changes in area while preserving the perimeter. The study’s findings aid building designers and architects in creating more energy-efficient structural and architectural elements by incorporating thermally efficient geometries and forms. .

Building dynamic thermal simulation of low-order multi-dimensional heat transfer

Multi-dimensional heat transfers modeling is crucial for building simulations of insulated buildings,which are widely used and have multi-dimensional heat transfers characteristics.For this work,state-model-reduction techniques were used to develop a reduced low-order model of multi-dimensional heat transfers.With hot box experiment of hollow block wall,heat flow relative errors between experiment and low-order model predication were less than 8% and the largest errors were less than 3%.Also,frequency responses of five typical walls,each with different thermal masses or insulation modes,the low-order model and the complete model showed that the low-order model results agree very well in the lower excitation frequency band with deviations appearing only at high frequency.Furthermore,low-order model was used on intersection thermal bridge of a floor slab and exterior wall.Results show that errors between the two models are very small.This low-order model could be coupled with most existing simulation software for different thermal mass envelope analyses to make up for differences between the multi-dimensional and one-dimensional models,simultaneously simplifying simulation calculations.

Eliminating Fastener Thermal Bridging in Low Slope Roofs: Energy Efficiency Savings versus Installation Costs

Low-slope roofing assemblies include a wide range of insulation and single ply membrane attachment methods. Previous studies have shown that mechanical attachment using metal fasteners leads to significant thermal bridging and consequent loss of insulation value and reduction of long term thermal efficiency. This study calculates the costs associated with mechanical attachment in terms of lost insulation value, increased long-term energy costs, and the material and labor costs associated with installation of these common systems. Energy efficiency reductions using metal fasteners were modeled for eight US cities in a range of climate zones. From the data, it was possible to calculate target costs (labor plus materials) that would make adhered systems cost effective. There are many options available to adhere single ply roof system components, such as solvent-based adhesives and low-rise urethane foams, together with different application approaches such as broom, spray, and ribbon methods. The cost targets derived in this study can help optimize the use of such materials and application methods such that the thermal bridging due to fasteners could be substantially reduced or eliminated.

Engineering phonon thermal transport in few-layer PdSe_(2)

Engineering phonon transport in low-dimensional materials has great significance not only for fundamental research,but also for thermal management applications of electric devices.However,due to the difficulties of micro and nano processing and characterization techniques,the work on tuning phonon transport at nanoscale are scarce.In this work,by introducing Ar+plasma,we probed the phonon transport in two-dimensional(2D)layered semiconductor PdSe_(2)under different defect concentrations.By using thermal bridge method,the thermal conductivity was measured to decrease by 50%after a certain Ar+irradiation,which implied a possible phase transition.Moreover,Raman characterizations were performed to show that the Raman sensitive peaks of PdSe_(2)was red-shifted and finally became disappeared with the increase of defect concentration.“Defect engineering”proves be a practical strategy in tuning the phonon thermal transport in low-dimensional materials,thus providing guidance for potential application in designing thermoelectric devices with various emerging materials.

Design Details of Low-Energy and Passive Houses Using Composites from Waste Raw Materials

The article deals with potential use of waste materials in construction industry, specifically use of high density polyethylene （HDPE）. The article is focused in particular on recycled polyethylene application in products designed for construction industry, especially for passive houses. Currently certain building details of passive houses are not perfect or their solution results in higher economic demands related to house purchase and its further use. For the purpose of this thesis details of windows installation in external walls and elimination of thermal bridges in wall footing have been chosen. Products were subject to mathematic modelling of thermal technique and statics. The executed mathematic models documented that products are fully functional and that the suggested product successfully eliminate insufficiencies of some currently applied solutions.

Simulations of Heat and Moisture Conditions in a Retrofit Wall Construction with Vacuum Insulation Panels

Vacuum insulation panels provide unprecedented possibilities for renovating the existing building stock in a manner that reduces the thermal losses through the building envelope. This study is focused on the implementation of VIPs （vacuum insulation panels） in energy retrofit projects with rendered outer walls. Particular emphasis is put on reducing the thermal bridges due to mechanical fasteners and at the joints of the panels. These are evaluated through a parametric study of the impact of the thermal conductivity of the joints of the panels and the adjacent insulation layer as well as the material of the fasteners. The study is carried out with 3D FEM （finite element method） simulations software. Furthermore, the moisture conditions in the construction are studied. The dynamic moisture behavior of a wall construction is modeled with a two dimensional FEM model. The long term effects of vapor diffusion are investigated in terms of accumulated moisture and the risk of condensation. The results illustrate that vacuum insulation on the outside of the wall construction does not pose a moisture problem to the construction. The simulations are based on a draft of a new technical solution for the refurbishment of a building that is typical for the great Swedish building program of the 1970s.

Lecablock, an Alternative Construction Material for the Exterior Walls of Passive House

In this paper it is attempted to investigate the Leca blocks as sustainable construction material for the exterior walls of passive house. The building physical properties of Leca design wall structure are studied along with the environmental impact and load-bearing capacity. To compare the results, a similar analysis is carried out considering the traditional wooden wall construction of passive houses. The results showed that Leca design wall structure can be an alternative sustainable solution to the traditional wooden wall structure of passive house, mainly due to its low U-value, its ability to handle moisture, and comparable structural load-bearing capacity. However, the wooden wall structure is more environmentally friendly than the Leca blocks due to its lower emissions to the environment and reduced energy use, especially during the manufacturing process.