Thermal Performance Of Building Envelope Research Articles

Thermal performance of a wooden pipe-embedded building envelope using a low-grade heat source in extreme cold climate conditions

A pipe-embedded wall can effectively reduce building energy consumption in winter. Most of the research on this concept to date has used traditional building materials such as concrete and brick. This paper reports on a wooden pipe-embedded wall allowing more flexible pipe locations, which can be used to reduce heat load in winter. An experimental assessment was developed to investigate the building assemblies thermal performance and the results were used to develop an understanding of its thermal energy saving potential, and as an input for the validation of a numerical model of same. A 3D computational fluid dynamics model of the pipe-embedded wall was developed and applied to assess the thermal performance of the wall under boundary conditions beyond the capabilities of the experimental assessment. Further, the influence of five parameters including the outdoor temperature and pipe positions were studied. A method was proposed for selecting the pipe layer's optimal location. The results show dual thermal impacts of the pipe layer: active heating and passive insulation. Using 8 °C water reduces internal surface heat transfer by 42.5 % under −20 °C outdoor temperature conditions. This is akin to an 18 °C outdoor temperature rise. Furthermore, another interesting result is that increasing the wall material thermal resistance can sometimes increase energy consumption. This study provides a reference for designing and optimizing net zero energy buildings in extreme cold climate conditions.

Cost Benefits of Net Zero Energy Homes in Australia

This paper presents a systematic analysis of energy savings and cost benefits associated with several options for integrating energy efficiency and renewable energy technologies. The primary goal of this study is to assess the cost-effectiveness of achieving optimal net-zero energy (NZE) designs for residential buildings in Australia. Specifically, the analysis combines a series of sensitivity analyses and multi-objective optimizations to account for a wide range of design strategies for detached homes in four cities representing different Australian climates. The results indicate that not only are NZE designs technically feasible for all the considered Australian cities, but they are also highly cost-effective. This cost-effectiveness is attributed to the lower installation costs of rooftop PV systems as well as the beneficial interactive effects of proven energy efficiency strategies. Indeed, it is found that the deployment costs of rooftop PV systems can be recovered in less than 4 years. Moreover, the addition of thermal insulation in walls and ceilings can reduce both HVAC capacities and annual energy end-use by up to 59%. Based on an optimization-based design, NZE homes in Australia can have lower construction costs and, ultimately, lower life cycle costs than dwellings built to meet current energy efficiency standards based primarily on stringent building envelope thermal performance.

Infrared thermography application for in-situ determination of the building envelope thermal performance

During the phase of creating energy audit documentation, many calculations are needed when evaluating the thermal performance of building envelope components due to a large number of distinct components and junctions. Several computer programs are available to assess buildings’ energy consumption, using the thermal performance of building envelope elements as input data. These thermal performances are often provided with varying degrees of accuracy, typically only for the current field of the component, without considering the impact of thermal bridges. However, when using linear heat transfer coefficients ψ, the details provided in thermal bridges’ atlases do not cover all the case studies encountered in the current design, which often requires approximate details. In some cases, the technical documentation of the building is unavailable, which leads to various assumptions about the detailing of the building envelope and a non-realistic picture of the energy performance of the assessed building. The paper presents a methodology and accompanying software called THERMOG that evaluates the thermal performance of the building envelope under actual operating conditions using aerial and terrestrial thermography methods. The paper presents initial findings from some case studies used to calibrate the developed methodology.

Development of an Energy Rating Tool for Australian Existing Housing

Australia aims to achieve net-zero emissions by 2050, and its building sector needs rapid change. The Nationwide House Energy Rating Scheme (NatHERS) is supported by the Australian Government to expand the current building envelope thermal performance energy star rating to a whole-of-home (WoH) energy rating. The NatHERS Administrator supports CSIRO to develop a benchmark WoH energy rating tool for new and existing housing, respectively. The tool for new housing was released in June 2023. This study presents the tool development for Australian existing housing. A case study was conducted using the tool for the eight capital cities of Australian states and territories. It shows that with a detached house built in the 1900s being updated to six or more stars and replacing old equipment and appliances with high-energy-efficient ones, more than 50% of energy can be saved in all the eight cities. To be zero-energy (carbon) housing, 5 kW solar PV needs be installed in Darwin and Hobart, 4 kW in Melbourne and Canberra, 3.5 kW in Adelaide and Sydney, and 3 kW in Brisbane and Perth. It demonstrates that this tool can be used for housing retrofitting to be low/zero-carbon emissions and low operational cost.

A New Method of Building Envelope Thermal Performance Evaluation Considering Window–Wall Correlation

A New Method of Building Envelope Thermal Performance Evaluation Considering Window–Wall Correlation

Prediction of urban residential energy consumption intensity in China toward 2060 under regional development scenarios

With global commitments to carbon neutrality, restraining the rapid growth of building energy consumption becomes crucial. Several building energy consumption predictions for China were conducted, but the regional heterogeneity and urban residentials’ special characteristics were not considered in these models. Thus, a “bottom-up” physical model with regional scenario assumptions was proposed for existing, newly-built, and renovated urban residential energy consumption prediction in five building thermal zones in China. Large-scale investigations were conducted for regional energy-use status and energy-use-related advanced technology development status both in China and developed countries. Regarding building envelope thermal properties, types, possession quantities, and performance of energy-use equipment, occupant energy-use behavior, and renewable energy utilization, Benchmark (B), Medium control (M), and Strict control (S) scenarios were assumed considering the spatial differences among each zone and temporal difference between 2020 and 2060. Results showed fluctuating trends, but all zones peak in 2035 under the B scenario, and before 2025 under the M and S scenarios. The intensity for newly-built urban residentials under the S scenarios in Severe cold, Cold, Hot Summer and Cold Winter, Hot Summer and Warm Winter, and Mild zones by 2060 are 4.07 kgce/(m2·a), 6.8 kgce/(m2·a), 6.53 kgce/(m2·a), 6.5 kgce/(m2·a), and 5.21 kgce/(m2·a), respectively.

Simplified Model of Heat Load Prediction and Its Application in Estimation of Building Envelope Thermal Performance

This study provides a reference for estimating the building envelope thermal performance at the initial stage of design for nearly zero-energy buildings in different climate zones. A simplified model of heat load prediction, which combines the quasi-steady-state thermal balance calculation procedure in ISO 52016 and the variable-base degree-days method, was proposed. Therefore, a building energy performance evaluation tool BPT V1.0 was developed. Subsequently, the simplified model was validated through comparative analysis with the Building Energy Simulation Test (BESTEST) standard procedure. To conduct a feasibility analysis of the development tool, case studies were performed on the performance evaluation of building envelopes of residential and office buildings in different climate zones in China. Compared to the simulation results from EnergyPlus, the deviation of heat load calculated by BPT V1.0 was within 10%, which further verifies the applicability of the tool under different climatic conditions. Annual heat load under different thermal performance building envelopes was calculated through BPT V1.0. The building energy efficiency improvement rates were found to range from 30 to 60% in nearly zero-energy buildings in different climate zones in China. The study results can provide a reference for energy managers and a basis for estimating the building energy efficiency performance with different envelope thermal properties in the region.

Challenges and opportunities in quantitative aerial thermography of building envelopes

The use of small unmanned aerial vehicles (UAVs) equipped with an infrared (IR) camera has created opportunities for qualitative and quantitative thermal assessments of building envelopes. However, it is currently unclear how successful this method is at quantifying heat losses through the building envelope. The inconsistency in findings indicates that sources of error that affect the accuracy of surface temperature measurements are not well understood by thermographers and that recommendations to minimize the errors in aerial thermography measurements have yet to be determined. In this study, laboratory and field experiments were conducted to investigate the scientific reasons for discrepancies between aerial (i.e. dynamic) and conventional stationary infrared thermography (IRT) observations. A set of practical approaches were presented to minimize the sources of error in UAV-IRT measurement. The results of field experiments showed a non-linear and dramatic variation of measured surface temperature during flight, where the deviations of results between dynamic and stationary thermography were beyond the manufacturer-reported accuracy of ±5 °C. Additionally, the results indicated that induced convection from drone propellers affects microbolometer stabilization with surrounding environmental conditions, which significantly influences the IR camera measurement accuracy. Finally, subsequent investigations utilized a shield around the camera to minimize the convective turbulence on the lens and thermal sensors, successfully achieving temperature deviations of less than 1 °C. These findings may inform manufacturers about the limitations of current IR camera technology during aerial surveys and therefore provide opportunities to define a more robust thermal imaging protocol for the quantification of building envelope thermal performance.

Improving the Thermal Performance of Building Envelopes: An Approach to Enhancing the Building Energy Efficiency Code

Cities on the east Mediterranean coast, especially in Palestine, are struggling to move towards sustainability as they are vulnerable to climate change and lack natural resources, especially energy resources, and this situation is further aggravated by high energy prices. The problem is the building sector, which is the most challenging sector when it comes to cities’ sustainability and, specifically, energy sustainability. In Palestine, this sector is the main consumer of energy but it lacks energy efficiency measures, such as up-to-date building energy codes. This study analyzed building thermal performance under different scenarios with a focus on building envelopes. We aimed to evaluate the benefits of introducing an updated building energy code—mainly addressing U-values for building envelopes—on future reductions in energy demand. We used a simulation tool (DesignBuilder) to evaluate typical existing building-envelope thermal and energy performances. Then, we undertook a comparison between the existing conditions and the proposed application of different scenarios, including the existing Palestinian building energy code and green building guidelines, the ASHRAE code for building envelopes, and the Jordanian building energy code, in order to introduce an updated building envelope energy code. The results showed that the current situation—building without applying any energy code or applying the existing Palestinian building energy code—is far from the high-energy performance that could be achieved by applying international or local green building codes. The use of thermal insulation could reduce the energy demand for heating by 83 to 43%, depending on the building type, climatic zone, and U-value. We recommend utilizing different U-values for building envelopes in different climatic zones to achieve high thermal performance. The results from this study have implications for construction industry professionals, local governments, and researchers seeking to establish high-energy-performance building envelopes.

Thermal and visual remote sensing of residential buildings by UAV

This paper is aimed to define an innovative method to evaluate building envelope thermal performance over the time by infrared thermography. The remote sensing is carried out by infrared camera and digital camera. An Unmanned Aerial Vehicle (UAV) is used for the sake of image acquisition. Firstly, flight and measurement protocols are defined to guarantee a correct detection and a new dimensionless parameter (β) is introduced to compare images taken in different time instants and environmental conditions. Successively, thermal and visible 3D models of the investigated building are analyzed, and a first draft of a 3D β-map is realized.

Energy savings for a junior high school classroom that actively uses daylighting and sensitivity study on the effect of the building envelope thermal performance

AbstractThis paper analyzes the energy‐saving potential of lighting, including its effect on heating and cooling, and analyzes the effect of the thermal performance of a building on the annual energy consumption of a classroom actively using daylighting. The subject of this study is M Junior High School, located in Gifu, Japan. This school has a classroom design with a sloping roof, allowing the installation of large windows from north to south. The window‐to‐wall ratio of 56% for the south wall and 41% for the north wall takes advantage of daylight. Simulation results of illuminance in the classroom were validated through comparison with field measurement data. The result demonstrated that daylight utilization decreases lighting electric power consumption by 66.6% when artificial lighting is controlled in the classroom. The results confirmed that there was no significant heat load increase for heating and cooling even though the window surface area was larger than that of a typical classroom. The sensitivity study showed that the thermal performance of the building envelope mainly affects the heating energy consumption, but it has no significant effect on cooling and lighting energy consumption. In terms of the thermal performance of the building envelope and the amount of energy saving by daylight utilization, it is necessary to consider the appropriate thermal performance to determine cost‐effectiveness.

Prediction of the impact of climate change on the thermal performance of walls and roof in Morocco

Abstract Climate change has become a real challenge in different fields, including the building sector. Understanding and assessing the impact of climate change on building energy performance is still necessary to elaborate new climate-adaptive design measures for future buildings. The building energy consumption for heating and cooling is mainly related to the building envelope thermal performance. In this study, the winter heat loss and summer heat gain indicators are proposed to assess and analyse the potential impact of climate change on opaque building envelope elements for different climate zones in Morocco over the next 40 years. For that purpose, a one-dimensional heat transfer model is used to simulate the heat transfer through the multi-layer structure of the wall/roof. A medium climate change scenario is considered in this study. The results showed that the current average walls and roof summer heat gain is expected to increase of about 19.2–54.3% by the 2060s depending on the climate zone, versus a less important decrease in winter heat loss varies between –10.6 and –20.6%. This paper provides a reliable evaluation of the climate change impact on building envelope thermal performance, which leads to better adjustments in future building envelope designs.

Design of a short perturbation method for on-site estimation of a building envelope thermal performance

On-site measurement of the actual thermal performance of a building envelope could considerably benefit to the building sector by securing an effective performance of newly built or retrofitted buildings. Current methods to estimate the Heat Transfer Coefficient, for example, suffer however from either excessive equipment downtime and therefore large costs, or fail to achieve a reasonable accuracy. This paper aims therefore at developing and assessing an original 24-h perturbation method for estimating a whole-building Heat Transfer Coefficient. Based on a binary heating signal, the proposed method exploits the data collected with stochastic RC models.The paper first presents a numerical comparison of 398 binary signals along with variable initial indoor temperatures to bring out common characteristics of signals that achieve highly accurate HTC estimations. An experimental campaign in a highly insulated wooden-framed house then implemented one particular signal and assessed its reproducibility under variable weather conditions. The paper shows that the proposed 24-h method indeed achieves a highly accurate estimation when performed in cold weather. In mid-season conditions, the method shows a better robustness from 30- to 36-h measurements. The results invite to further investigate other building types in variable weather conditions to validate the proposed method.

Effect of Thermal Bridges of Different External Wall Types on the Thermal Performance of Residential Building Envelope in a Hot Climate

In this paper, the thermal performance of residential building envelopes including thermal bridges (TBs) in a hot climate, using four different exterior wall types, is modelled and assessed. TBs at the junctions between columns and walls and between walls and slabs of the ground floor, roof, and intermediate floors are considered. The tested wall types are classical (two layers of cement blocks with insulation in between), autoclaved aerated concrete bearing (AAC-B), AAC column and beam (AAC-CB), and exterior insulation and finish system (EIFS). The results indicated that thermal bridges have a considerable effect and determine the best external wall type which was the EIFS that has a continuous exterior insulation. EIFS proved to reduce the heat transmission with the outdoor environment for residential buildings by 101.8, 51.2, and 13.9% than the AAC-CB, AAC-B, and classical walls, respectively. Thermal bridges effect on the building envelope using the EIFS is insignificant as the thermal resistance of the envelope and wall differs by less than 1% for small areas. The overall heat transfer coefficients for small buildings are larger than those for large buildings by 8–26%. As the number of intermediate floors increases from 1 to 50, the envelope overall heat transfer coefficient increases by 4.5% for the EIFS, 14.1% for classical, and 19.5% for AAC-CB walls. The AAC-CB, as the common practice wall structure in many hot climate countries, has the lowest performance among the tested wall types.

Infrared thermography for quantitative thermal performance assessment of wood-framed building envelopes in Canada

Since many buildings in Canada were built prior to the advent of national and provincial energy codes and standards, quantifying building envelope thermal performance is an important step in identifying retrofit opportunities in existing buildings. This study aimed to use external quantitative infrared thermography (IRT) to estimate effective U-value of opaque building envelopes (considering the effect of thermal bridging sources) of a conditioned at-scale structure comprised of four wood-framed wall assemblies commonly used in Canada. Furthermore, the effect of vignetting artefacts on effective U-value measurements was assessed, followed by a practical approach to correcting for it to improve accuracy of U-value estimation and calibration of energy models. Additionally, a comprehensive uncertainty analysis was performed to evaluate the impact of input variables on the accuracy and uncertainty of results. Finally, apart from qualitative and quantitative thermal assessment of the building envelope, a novel relative quantitative infrared index (IRI) methodology was proposed as a means to facilitate rapid evaluation and subsequent ranking of building envelope thermal performance. The results indicated that vignetting effect has an adverse impact on the accuracy of results, in particular for well-insulated walls where deviations of −42.31% to −83.33% were observed. However, when the proposed practical approach was implemented, substantial improvements in accuracy of walls’ U-value were obtained, ranging from −2.33% to −12.50% after correction versus −13.95% to −58.33% without correction. Moreover, the results indicated that the energy model was substantially more accurate when the effect of thermal bridges were accounted for, and the adverse effect of vignetting was addressed in the estimation of U-value. In this case, ASHRAE Guideline 14 criteria were satisfied: Normalized Mean Bias Error (NMBE) < 5%, and Coefficient of Variation of the Root Mean Square Error (CVRMSE) < 15%. The findings of the uncertainty budget demonstrated that the influence of parameters on U-value depends on the type of wall assembly. Ultimately, wall thermal performance rankings based on IRI were consistent with their U-value rankings, implying that IRI can be a reliable metric for relative quantitative comparison of building envelope thermal performance, regardless of boundary conditions.

BIM-based retrofit method (RBIM) for building envelope thermal performance optimization

Retrofitting building envelope thermal performance is crucial to ensure adequate interior thermal comfort of the building, minimize cooling load rate and, therefore, reduce overall building energy consumption. The retrofit process of an existing building envelope involves the design team selecting the best performing building materials and components based on various design variables and predefined design objectives. Worldwide, an overall thermal transfer value (OTTV) metric has been developed and used for assessing heat transfer through the building envelope. However, the application of OTTV implicates dealing with many design variables and much information, which makes the design decision-making process time-consuming and complicated. Furthermore, selecting the most appropriate design alternative in terms of OTTV performance while considering the most cost-effective design option could be a very challenging task. Therefore, this research proposes a method for retrofitting building information modelling (RBIM) to achieve a tradeoff design set between two conflicting objectives, namely minimizing OTTV and minimizing the retrofit cost. The prototype system derived from this method integrates BIM authoring tools (e.g., Autodesk Revit®), visual scripting (e.g., Dynamo), and a non-dominated sorting genetic algorithm (NSGA-II) customized in MATLAB®. The applicability of the proposed system is validated with a case study of an office building. The results show that the developed system provides a valuable design decision support system for retrofitting building envelope thermal performance while considering the retrofit cost. Additionally, the system shows an improved level of automation in terms of data management compared to the conventional methods.

Evaluation of a retrofitted heritage building in downtown Cairo as a best-practice example

Energy retrofitting standards and guidelines, together with benefitting from best existing experiences, are effective in retrofitting heritage buildings towards low-carbon emissions. In Downtown Cairo, many heritage buildings are exposed to adaptive reuse practices, after moving to the ‘New Administrative Capital’. Integrating energy saving in said practices has become a crucial aspect. Therefore, the aim of this study is to evaluate a recent retrofitted heritage building called ‘La Viennoise’ as an example of best practice for retrofitting processes in Downtown Cairo. The study carried out a field survey for data gathering. A monitoring-based simulation model was created and calibrated, and the building envelope and energy use were evaluated. The simulation results are presented into two cases. The first includes the original state as a base case, showing a very low building envelope thermal performance. The second includes the current state as an improved case. A comparison of both cases shows that the implemented retrofitting scenarios in the case study effectively improved its building envelope and reduced annual energy consumption, and CO2 emissions. This paper allows further benefit from such example by setting a retrofitting guideline to expand this concept in other buildings with similar conditions to achieve a low carbon-built heritage.

Developing Double Walls System to Improve Building Energy Performances in Dry Tropical Climates

This paper deals with building envelope thermal performance through a comparative study of the use of two types of construction materials, such as CEB and cement blocks, in order to introduce the use of double walls in sustainable buildings' construction. The building envelope participates in providing thermal comfort to users and in the optimal management of building energy consumption. This study begins with a survey of public preferences for building materials used in Burkina Faso. The results indicate that 76% of the people surveyed opt for cement blocks over local materials. Concerning the thermal and specific energy performance, three variants of building envelope were studied: CEB walls, cement blocks and the double-wall (CEB + Cement blocks). It appears that the CEB walls are more efficient than the cement block walls. The introduction of double envelopes leads to the thermal resistance of 357.37m².K/W and reduces the heat flow from 85.32% to 90.24% compared to the wall made with CEB and cement blocks. This approach, which consists in mixing construction materials for good thermal insulation, allows improving the envelope thermal performance and the overall building energy performance.

Performance Assessment of the Overall Building Envelope Thermal Performance—Building Envelope Performance (BEP) Metric

Performance Assessment of the Overall Building Envelope Thermal Performance—Building Envelope Performance (BEP) Metric

Evaluating thermal performance of vertical building envelopes: Case studies in a Canadian university campus

Campus buildings at the University of Victoria (UVic) were largely constructed before the advent of building energy codes. The University is in the process of commissioning vertical building envelope upgrades/retrofits with added intention of addressing potential energy and greenhouse gas (GHG) savings in their building stock. The aim of this paper is to present the methodology adopted to evaluate potential energy savings from vertical envelope retrofits of 49 non-residential buildings across the campus portfolio, and to further validate those savings through more detailed energy models for a subset of buildings. To this end, the thermal performance of a building envelope was quantified based on its heat loss coefficient (UA), obtained from multiplying its surface area (A) by its thermal transmittance (U-value). Heat loss (UA) calculations were used as an energy loss metric to inform envelope rehabilitation prioritization, in addition to data gathered from building envelope condition assessments (BECAs). UA data were also analyzed against other building data such as floor area, vertical envelope area, vertical area to floor area ratio (VFAR), window-wall ratio (WWR), age, and type of construction for potential correlations. Finally, archetype energy models were used to evaluate the impacts of envelope retrofits on energy and GHG savings on three selected buildings. The outcomes of this study allow the University to weigh the benefits of improved energy performance from envelope retrofits against associated capital cost expenditures.