External Insulation Research Articles

Design optimization of an assisted living facility to improve summer thermal comfort in warming climates

Assisted living facilities with optimal summer thermal comfort are necessary to ensure improved quality of life for the older individuals in warming climates. Older individuals are exposed to higher mortality risks during periods of excessive heat. This study aims to identify and optimize key design variables for a passive house certified assisted living facility in Belgium with high comfort expectations using EnergyPlus to improve indoor thermal comfort during extreme climates. The sensitivity analysis used the Standard Regression Coefficient method with Latin Hypercube Sampling for eighteen design variables under four categories: layout, envelope, operation, and system. The analysis identified flat roof and external floor insulation as the most influential parameters, whereas lighting gain and cooling setback temperature were the least influential parameters. Furthermore, optimizing the reference building with the most sensitive design variables using a genetic algorithm based on the NSGA-II method found ideal configurations that would ensure minimum thermal discomfort hours during extreme summers. The study findings provide an evidence-based approach for building engineers and designers for early-stage design of assisted living facilities that maintain optimal comfort in mixed humid climates of Europe.

Framework for optimising daylighting and passive indoor thermal comfort in single-banked office buildings in the temperate dry climate of Nigeria

Abstract Many researchers have differed on the optimum values of Daylighting and Passive Indoor Thermal Comfort (DPITC) determinants in tropical climates. The study is aimed at developing a framework for optimising DPITC in singled-banked office buildings, during the activity period (8 a.m. to 5 p.m.), in the temperate dry climate of Nigeria. It was achieved by evaluating the effects of orientation, window-to-wall ratio (WWR), R-values of external wall insulation material, and shading devices on DPITC. A quantitative research design using an explorative design approach was employed in the study as well as an experimental research strategy through simulation method to optimise DPITC. The study used the Federal Secretariat building of Nigeria as a prototype of a single-banked office building. The Google SketchUp Pro 2022 and OpenStudio 3.3.0 simulation tools were used to evaluate the prototype building from January to December 2023. The data generated was analysed using relevant statistical tools (MANOVA, ANOVA, column charts, graphs, and tables). The findings revealed that the best WWR for daylighting and passive indoor thermal comfort are 20% and 15% respectively, while the compromise value was 20%. It was also noted that the R-value of the external wall insulation material does not affect the daylighting of an office building but affects the passive indoor thermal comfort, where the optimum R-value was of 3.26 m2·K/W. The mathematical model was developed as A= 224.58 − 1254.84 WWR+ 102.87 PF − 4.11R … … .1 where A is orientation, WWR window-to-wall ratio, PF projection factor, and R is the R-value of the external wall materials.

Hygrothermal risk assessment of external wall insulation retrofit to non-traditional wall types in an Irish context, using the Glaser method and a heat, air and moisture transient model

The Climate Action Plan 2019 targets the low-energy retrofit of 500,000 existing Irish homes before 2030.1 Up to 80 per cent of building failures can be attributed to moisture risks.2 The literature indicated that external wall insulation (EWI, ETICS) failures are mostly due to moisture ingress at junctions and interfaces. A hygrothermal risk assessment of EWI on three walls with rendered concrete/concrete blockwork/cavity walls in Dublin, Belfast and Belmullet was undertaken using transient numerical simulation and the Glaser method. The guidance, common practice indicates a preference for Glaser. The initial simulation results were compared to assess the appropriateness of Glaser. Material measurements were undertaken and this data was used in the transient numerical simulations. A parametric study was undertaken using a selection of the initial transient numerical simulations stressed with parameters of 1–2 per cent driving rain at different window positions. The results of the initial transient numerical simulations indicate that most retrofit cases, except on cavity walls, are low risk. All cases assessed using Glaser pass the assessments. The parametric study indicated between 40–67 per cent were high risk depending on the wall types. All cases with mineral wool/mineral render were low risk, while most cases with acrylic render were high risk. The research described in this paper indicates that using the Glaser method for hygrothermal assessment of EWI cannot capture the extent of the risk when buildings are leaking.

Study on Preparation Technology of Novel Fluorosilicone Rubber Composite Insulator

Abstract Currently, commonly used external insulation materials for power products lack operational stability compared to high-temperature vulcanized silicone rubber. The excellent hydrophobicity of PTFE provides a direction for further enhancing high-temperature vulcanized silicone rubber. By utilizing fluorinated occupation directional design technology and improving the dispersion degree of the dispersed phase, we have successfully prepared high-temperature vulcanized fluorine silicone rubber. After testing its flammability and other aspects, the prepared material achieved HC1-level hydrophobicity, surpassing conventional silicone rubber insulators in terms of self-cleaning performance.

Fabrication of a novel high electrical conductivity Si3N4 matrix composite with Cu three-dimensional network structure by spark plasma sintering

Silicon nitride (Si3N4) ceramic matrix conductive composite materials have shown great promise as conductive layer materials for electrical transmission components. However, existing conductive phases struggle to form a three-dimensional (3D) interconnected network in Si3N4 matrix, resulting in poor electrical conductivity. This study proposed a spark plasma sintering (SPS) process utilizing Si3N4 as the substrate and Cu particles as the reinforcement phase to fabricate a novel electrical conductivity Si3N4/Cu composite material. The results indicated that the diffusion of Si atoms in Si3N4 facilitated the formation of copper silicide (CuiSi) interface between the two constituents during sintering, creating a strong chemical bonding for high conductivity. Simultaneously, composite materials with optimized Cu content formed a 3D interconnect network structure, providing a continuous path for electrical conduction. At Cu content of 30 vol%, the Si3N4/Cu composite exhibited a satisfying electrical conductivity of 295.37 S/m, which was 14 orders of magnitude higher than that of Si3N4. The composites also demonstrated a percolation phenomenon, with a theoretical percolation threshold of Cu particles at just 0.1 vol%, an order of magnitude lower than that of carbon reinforcement particles. Furthermore, an integrated design featuring external insulation and internal conductivity was achieved by wrapping a Si3N4 insulation layer around the conductive Si3N4/Cu composites. The fabricated insulation layer exhibited higher resistivity (1.12×1014 Ω) and a lower wear rate (1.3×10−6 mm3/N·m) compared to some contemporary insulation ceramics, while the conductive layer had a lower calorific value, making them excellent candidates for electrical transmission component materials.

Field Natural Experimental Study of Ice Growth Characteristics of Split Conductor and Single Conductor on Hybrid Freezing Icing

Abstract Transmission line icing seriously endangers the safe operation of transmission lines. At present, most of the research on transmission line icing is based on numerical simulation, and the growth law of transmission line ice in a natural environment has not been explored and studied. In this paper, natural ice-covering experiments are carried out in the Xuefeng Mountain Field (Natural) Ice Covering Test Base of Chongqing University, and single conductor, three-split, and four-split conductor ice-covering change rules in the mixed rime ice environment are explored. Test results found that the wind direction has a greater impact on the ice, and the windward side of the conductor ice is much larger than the leeward side. The downwind side of the ice of both single conductor and split conductor is smaller than the upwind side. The weight of ice on the split conductor line on the downwind side is about 86% of that on the upwind side. The results can provide a reference for the design of external insulation of UHV DC transmission lines.

Measurement analysis of large-area elements of External Thermal Insulation Composite Systems using 3D scanning techniques

Measuring the deformation of large-area objects with non-uniform rough textures using traditional techniques is technically challenging and time-consuming. This article presents a comprehensive solution that enables the precise measurement of the deformation of large-area elements of external thermal insulation composite systems (ETICS). The laboratory tests for environmental resistance were conducted in a climatic chamber. The surface of the wall underwent irregular deformation owing to thermal and humidity cycles. The deformation state at different stages of exposure was recorded using 3D scanning techniques. Scanning results were paired using a simplified cause-effect graph, and the deformation was measured by engineering inspection. Evaluation criteria were developed using measurement uncertainty and a straightforward binary acceptance principle. Finally, compliance tests were performed to confirm the reproducibility and repeatability of the method.

Innovative Approach for Detecting Early-Stage Partial Discharges in Instrument Transformers via Ultrasound and Random Forest Analysis

This article introduces a novel technique for detecting and classifying Partial Discharges in Instrument Transformers, addressing the gradual breakdown of external insulation in high-voltage electrical equipment through ultrasound measurements. The use of hand-held probe-microphones for ultrasonic sensing gains prominence for its versatility and online diagnostic capabilities. The proposed method combines insights into partial discharge types and the pollution level within the equipment, thereby transforming ultrasonic readings into useful information and facilitating informed decision-making. Laboratory tests simulate real-world conditions to which current and voltage transformers of 145 kV and 245 kV are subjected. These tests result in ultrasonic and apparent charge measurements, also known as Phase-Resolved Partial Discharges (PRPD). A random forest model achieves over 92 % accuracy in classifying ultrasonic signals into eight class: normal, light partial discharge, light corona, corona, light superficial, light saline pollution, moderate saline pollution and heavy saline pollution; enhancing the understanding and predictive maintenance of instrument transformers.

The impact of window opening behavior on the indoor thermal environment and coping strategies in passive houses

China is actively developing passive houses to improve energy efficiency and reduce primary energy use. These buildings have low actual load characteristics, resulting in a smaller air conditioning terminal heating capacity. However, owing to this limited heating capacity, the air conditioning terminal provides modest indoor air regulation. In practice, occupants of passive houses often open windows for ventilation in winter, resulting in an indoor temperature that is lower than the set value, and it takes a long time for the temperature to return to the desired level. There are few studies that have investigated this issue. Two possible solutions to this issue are proposed: first, altering the external wall structure can enhance the thermal response rate, reducing the time needed for temperature recovery. Secondly, limiting the window-opening area can minimize heat loss during ventilation, thereby maintaining a reasonable indoor temperature. Notably, this may inconvenience occupants. Taking a passive house in Qinghai as a case study, this study discusses the influence of window-opening behavior on the indoor thermal environment. Simulations were conducted to study the window-opening behavior considering different window-opening areas and wall structures. Three different wall structures were considered: internal insulation combined with external insulation (IAE), sandwich insulation combined with external insulation (SAE), and external insulation structures. The results indicate that the IAE and SAE structures cannot effectively improve the indoor thermal environment after opening a window. Overall, changing the wall structure does not reduce the time required to restore room temperature. However, by limiting the opening area of the window, the room temperature can be effectively controlled. Under the given window opening ratio, the room temperature can be stabilized above 18 ℃. This study offers a practical method for controlling and enhancing the indoor thermal environment, which is applicable to the construction and development of passive houses.

Nanosecond photography observation of the discharge process across the 220 kV/500 kV insulators in lightning impulse

Long air gap discharge is the basis for the study of lightning protection and external insulation design of high voltage lines. However, there is a lack of detailed and comprehensive observation of the long air gap discharge process at the ns-level, as well as higher voltage insulator discharge observations. In this paper, the lightning impulse discharge/flashover tests are conducted on 220 kV glass insulators and 500 kV glass/composite insulators. Firstly, the U50% test is performed to determine the U50% value of each insulator under standard lightning impulse, and 1.1U50%, slightly higher than U50%, is applied to ensure the breakdown of the insulator. Subsequently, emICCD is utilized with a very short exposure time (minimum 10 ns) to obtain repeated single shots of discharge images under different delays, exposure times and light intensity gain. These images were spliced together based on time sequence to create a continuous discharge process. The discharge processes of 220 kV glass insulator and 500 kV glass/composite insulator are compared and analyzed. The results show that in the early stage of discharge, the discharge processes at the low voltage end of both 220 kV and 500 kV glass insulators are more intense. Additionally, the downward leader is faster than the upward leader in the discharge process of 500 kV composite insulators.

Research on Insulation Configuration of 220 kV Bushing in High-Altitude Polluted Areas

The external insulation strength of the power equipment sleeve in the substation and converter station will be reduced with the increase in altitude and atmosphere pollution. The weakness of external insulation seriously threatens the safe operation of electrical equipment. At present, there are few studies and conclusions that focus on the flashover characteristics of power equipment bushing in high-altitude polluted areas. Therefore, this paper takes the 220 kV voltage level bushing as the research object and studies the Alternating Current (AC) pollution flashover characteristics and lightning and switching impulse flashover characteristics at low pressure. The insulation configuration at high-altitude polluted areas is analyzed. Finally, the insulation configuration scheme, which is suitable for high-altitude polluted areas, is proposed. The results show that the AC pollution flashover voltages of the bushing decrease with the decrease in the atmospheric pressure and the increase in the salt density as a power exponent function. The impulse flashover voltages also decrease with the decrease in the atmospheric pressure as a power exponent function. The atmospheric pressure/pollution impact characteristic index is related to the type of voltage, the value of the atmospheric pressure, and the value of the salt density. The test bushing does not meet the insulation configuration requirements in some high-altitude polluted areas. Through the analysis and calculation of the test results, the bushing insulation configuration scheme in high-altitude polluted areas is proposed. The research results can provide a reference for the external insulation design of bushings in substations and converter stations in high-altitude polluted areas.

Experimental study on reinforced concrete beams strengthened with Basalt and Carbon Textile Reinforced mortars at elevated temperatures

Reinforced concrete members strengthened with Fibre-Reinforced Polymer will suffer degradation when exposed to elevated temperatures or fire without an external insulation. Textile Reinforced Mortars (TRMs) can alleviate these problems posed by Fibre Reinforced Polymer epoxies at elevated temperatures. The present study deals with the thermo-mechanical behaviour of reinforced concrete beams strengthened with Textile Reinforced Mortar at elevated temperatures. Reinforced concrete beams were strengthened with Basalt and Carbon textiles and tested while the specimens were maintained in hot conditions. Carbon and Basalt TRMs were applied as one-layer and one- and three-layer, respectively. All the test specimens were heated to 200 °C, 400 °C, 600 °C, and 800 °C, followed by mechanical loading to evaluate their flexural behaviours. Strengthened members experienced common degradation of flexural strength when subjected to higher temperatures except at 400 °C. The test results revealed that Textile Reinforced Mortars can sustain temperatures up to 600 °C, but the concrete and steel underwent degradation at this temperature. At 800 °C, the Basalt textile showed signs of annealing, whereas the carbon textile oxidised from the textile reinforced mortar matrix. The study also evaluated strengthened members' thermal response and mechanical failure patterns at elevated temperatures.

Retrofitting of an Existing Cultural Hall into a Net-Zero Energy Building

The energy efficiency of existing buildings is a crucial factor in addressing energy consumption challenges in European countries, accounting for nearly 40% of the total energy usage. One such country is Cyprus, which faces significant challenges in transforming its existing building stock into energy-efficient and sustainable structures. To face this situation, extensive focus has been made by the government on the energy-efficient retrofit of non-residential public buildings erected before 2010, which lack any energy efficiency measures. This study examines the case of the Pano Polemidia Cultural Hall (PPCH), which represents the building stock of that period. Through the simulation of two scenarios, before and after the adoption of retrofit measures, the existing energy performance is initially evaluated and then the adoption of sustainable solutions, which improve substantially the energy efficiency and can be easily adopted from the relevant authorities, is explored. These retrofit measures include installation of HVAC system, covering of the shell of the building with external thermal insulation, lighting replacement with LED devices, installation of PV system and solar panels, and replacement of the external openings with aluminum windows. The results derived show that the energy consumption of the building was reduced from 468 to 218 kWh/m2·yr, with renewable energy sources (RESs) contributing 177 kWh/m2·yr, the CO2 emissions were reduced from 136.73 to 11.5 kg/m2·yr, while the reduction in energy consumption per sector ranged from 25% in lighting to 83% in hot water. Therefore, it is evident that a comprehensive retrofitting plan can transform the PPCH into a near-zero energy consumption building that also provides value to the local community and can act as a successful example for any other non-residential buildings with similar characteristics.

Methods of Mathematical Statistics in Analyzing Probabilistic Characteristics of External Insulation

Methods of Mathematical Statistics in Analyzing Probabilistic Characteristics of External Insulation

Energy performance analysis of alternative building retrofit interventions for the four climatic zones of Greece

Climatic conditions determine which retrofit strategy can result in a satisfactory improvement of a building's thermal performance. This study systematically investigates alternative retrofit actions, as standalone and in combination, and assesses their energy performance. The retrofit actions include i) insulation on the external walls, ii) the incorporation of phase change material (PCM) on the roof and the increase of the building thermal inertia, iii) a mechanical ventilation system with a summer period operation, and iv) a cool roof coating. The energy analysis concerns a typical two-story family building and the four climatic categories of Greece and is conducted with the INTEMA.building tool, a dynamic energy analysis software developed in Modelica language. The importance of the present study is that it serves as a guideline for the selection of the energetically optimum single retrofit or multiple-retrofit strategy regarding a building's location climatic data, and provides calculations concerning the annual heating and cooling loads, and the corresponding heat pump electricity consumption. The retrofit actions of external wall insulation and PCM roof addition are characterized as more effective in reducing a building's heating energy loads, while the mechanical ventilation system and cool roof coating are more effective in reducing a building's cooling loads. The quadruple retrofit strategy results in the maximum electricity savings for Heraklion (28.01%), Athens (21.15%), and Thessaloniki (16.54%), while the triple retrofit strategy which does not include the cool roof coating, results in the maximum electricity savings for Kastoria (10.79%). Lastly, an economic analysis of the energetically optimum renovation strategies is conducted.

Enhancing the fire resistance of light gauge steel framed floor-ceiling systems through external insulation

Light Gauge Steel Framed (LSF) floor-ceiling systems, composed of thin-walled cold-formed steel (CFS) structural components, offer a high strength-to-weight ratio and cost-effectiveness, leading to their widespread adoption in modern construction. However, research on the fire behaviour of LSF floor-ceiling systems is limited. The industry-standard approach of using two 16 mm gypsum plasterboards for ceilings achieves a maximum Fire Resistance Level (FRL) of 90 min, mainly due to the significant fall-off associated with gypsum plasterboard. Traditional methods for increasing FRL involve adding more layers of gypsum plasterboard; however, the efficacy of achieving a 120-min FRL with three 16 mm gypsum plasterboards remains uncertain. This paper addresses these issues by developing innovative LSF floor-ceiling systems that incorporate external insulation (rigid stone wool) to mitigate the impact of critical ceiling fall-off behaviour and enhance FRL. The research includes dimensional stability tests of rigid stone wool, thermal and structural finite element modelling, and load-bearing small-scale fire tests. The new LSF floor-ceiling system has been shown to achieve an FRL of 130 min, approximately 45 % higher than conventional floor-ceiling systems, offering enhanced fire resistance and increased thermal comfort as a single, integrated solution.

Research on multi-physical field analysis and assessment technique of virtual connection defects in cluster cable joints based on digital twin technology

As the “blood vessels” and “nerves” of the power grid, cables are important carriers for transmitting electric energy, and their failures will affect the safe and stable operation of the power grid. In this paper, a digital twin model of thermal characteristics is constructed for 10 kV YJV×400 cluster cable and its joint model. Based on the multi-physical field coupling analysis method, the fluid field, temperature field and current-carrying capacity of the cluster cable are analyzed. The temperature rise and airflow distribution characteristics of the joint and its external insulation when the defect of joint false connection occurs are analyzed. Based on the fuzzy analytic hierarchy process (FAHP), weights are assigned to the locations of multiple measurement points of the cable external insulation, and the temperature distribution of each measurement point is combined with the digital twin technology to calculate the hot spot temperature of the cable, so as to assess the defects of the joints of the cables. The digital twin platform is used for real-time monitoring of cable status and assessment of defects. The temperature rise experiments of cables under different carrying capacity and joint defects show that this method can accurately and efficiently calculate hot spot temperatures and assess defects of joints in cluster cables.

Circular Renovation of an Apartment Building with Prefabricated Additional Insulation Elements to Nearly Zero Energy Building

Construction and demolition waste constitute more than one-third of the total waste generated in the European Union. The pursuit of sustainable renovation must progress further to encompass elements that ensure reuse or recyclability. A fundamental transformation, involving extensive renovation and a transition to circular renovation practices, is indispensable in effectively addressing the pressing challenge of decarbonization for the entire building stock in Europe. In this study, we have developed a circular deep renovation solution using prefabricated modular external additional insulation elements to achieve a nearly Zero Energy Building (nZEB). Circular prefabricated modular external additional insulation elements were formulated, manufactured, and installed. The potential for disassembly and reutilization of materials was developed and demonstrated for both a prototype and the complete deep renovation. The analysed prefabricated modular solutions exhibited greater potential for circularity compared to the traditional External Thermal Insulation Composite System (ETICS) due to their superior demountability and reusability characteristics. The overall cost of the renovation, which included the installation of a new heating system, replacement of water and sewer pipes, addition of 50 kW photovoltaic (PV) panels on the roof, installation of new balconies, addition of a balanced ventilation system with heat recovery, and replacement of the electricity system in common areas, amounted to 505 €/m². Following the deep renovation, the Energy Performance Value was measured to be 92 kWh/(m²·a), resulting in an EPC class of A. This implies that the building now meets the requirements for nZEB in accordance with Estonian legislation, with no performance gap.

Theoretical studies of the expedient radius of thin pipe insulation

Decentralized ventilation systems with exhaust heat recovery are an energy-efficient solution for organizing and maintaining comfortable microclimate parameters in apartments and individual residential buildings. Such supply and exhaust systems do not require additional space for the distribution network of air ducts and significant intervention in the interior of the premises. One such device is the Vents TwinFresh regenerative installation. Twin Fresh install in the structure of the outer wall. The task of follow-up is to increase the efficiency of its work. Studies of heat exchange processes in the thin channels of the heat regenerator carried out. Channels with different thermophysical properties are studied. Experimental uncertainty decreases with better thermal insulation of the investigational stand. It is confirmed by the decrease in overheating and the heat transfer coefficient of the external surface thermal insulation when its thickness increases. Overcoming the critical diameter of the insulation of the experimental installation allows to minimize the measurement error, which takes into account the influence of heat exchange processes of the outer surface of the insulation with the environment. It is necessary to determine not the critical but the expedient diameter of the insulation. When using the appropriate thickness of thermal insulation, the temperatures on the inner and outer surfaces of the pipe have practically the same value. Thus, it is possible to take temperature readings of thin tubes from the outside, not from the inside, with the same accuracy. Accordingly, the design of the test stands for experimental research is simplified. The scope of application of the appropriate diameter of thermal insulation is not limited only to studies of heat transfer. This concept can used in any systems, equipment, and techniques that require insulating materials.

Multi-Span Greenhouse Energy Saving by External Insulation: System Design and Implementation

To address the issues of excessive heat loss from the roofs of multi-span greenhouses and high energy consumption for heating during winter production, we propose an approach for the external insulation of the roof of multi-span glass greenhouses and have developed an external insulation system (EIS) to practice this approach. The system achieved full coverage of the greenhouse roof through mechanized unfurling and furling of external thermal blankets, thereby achieving energy-saving insulation. This paper describes the overall design and working method of the EIS, providing detailed design and structural parameters for critical components such as the traction rope transmission mechanism and the rail-type sealing structure. Through a system verification experiment, the specifications of the traction rope were determined and the rationality of the EIS’s thermal blanket unfurling and furling time was confirmed. An insulation performance experiment indicated that the average heat flux of the greenhouse roof covered with the external thermal blanket over 14 continuous nights was 54.2 W/m2, compared with 198.6 W/m2 for a single-layer glass roof. Covering the roof with the external thermal blanket reduced heat loss from the glass roof by 72.7%. The average heat flux of the roof of the Venlo-type multi-span greenhouse with double-layer internal insulation was 99.9 W/m2 during the same period, indicating that the heat loss from the roof using external insulation was only 50.3%. This study provides a novel thermal insulation approach and an energy-saving system for multi-span greenhouses.