Insulation Thickness Of Walls Research Articles

Energy and structural optimization of mid-rise light-frame timber buildings for different climates and seismic zones in Chile

AbstractLocation determines not only the climatic condition but also the structural loads that the structure must withstand. Given the broad variety of climatic and seismic requirements of Chile, the design of lightweight timber buildings considering both energy and seismic design parameters and boundary conditions becomes a difficult task. The main objective of this research is to analyze and quantify the effect of climates, seismic loads, lateral anchorage, and story number on the optimal energy design solutions, including the seismic behavior in a light-frame timber building. Furthermore, the optimal design was parametrically analyzed considering five Chilean cities that consider different climates, seismic zone, number of stories, and lateral anchorage systems to prevent rocking (overturning) due to lateral seismic forces. The optimal wall insulation thickness, stud spacing, and thermal mass exhibited significant variations depending on the buildings' number of stories, lateral anchorage system, climate, and seismic zone. Therefore, the results of this investigation reinforce the necessity of integrating energy and seismic designs for light-frame timber buildings. The optimal designs obtained in this investigation showed considerable variations depending on the combination of climatic and seismic loads as well as the number of stories and anchoring systems. The article's main contributions are the evidence of the structural and energy design interconnection of light-frame timber buildings and how design variables, such as stud spacing, floor concrete thickness layer, and wall insulation thickness, are related and change according to the different climates, seismic loads, lateral anchorage, and story number.

Optimization of insulation thickness of walls and roofs using energy, exergy, economic and environmental (4E) analyses

Optimization of insulation thickness of walls and roofs using energy, exergy, economic and environmental (4E) analyses

Impact of grey energy on optimal wall insulation thickness

AbstractFor decades efforts have been made to reduce the greenhouse gases emissions of buildings by reducing their energy demand with governmental regulations in Europe, pushing towards very low thermal transmittances (U‐values) with ever thicker insulation layers for new buildings. However, there is no linear relationship between the insulation thickness and the heat losses. Therefore, above a certain thickness the consumption of buildings does not decrease significantly. Hereafter a life cycle analysis, including emissions before the building becomes operational is applied to evaluate the impact of the increasing thickness of components on the overall emissions. Publicly available product data sheets are used to compare four insulation materials under three scenarios. These analyses yield interesting results showing that energy‐intensive insulation materials lead to a negative impact in the overall energy balance after a certain thickness. Even though there is not always a pronounced optimum insulation thickness, it is logical that further reductions in U‐value for new buildings should hence be carefully evaluated. The results show that the optimal thickness is around 20 cm for most materials, while the important major savings come from the first 10 cm.

Multi-Stage Sensitivity Analysis of the Energy Demand for the Cooling of Grain Warehouses in Cold Regions of China

The early design parameters exert a considerable influence on the cooling energy demand of a granary building in operation. In order to investigate the impact of various parameters on energy use, a grain warehouse energy model was constructed using the Ladybug + Honeybee tools on the Grasshopper platform. Three global energy sensitivity methods were used to analyze the model, and the sizes of the influential parameters were determined and ranked. The study uncovered that the cooling energy demand of the grain warehouse was primarily influenced by factors such as the cooling set-point temperature, roof solar absorptance, roof and exterior wall insulation thickness, window type, and orientation. On this basis, a local sensitivity analysis was conducted for the highly sensitive parameters to identify their influence trend and optimal design range. The results showed that the cooling energy demand of the grain warehouse increases faster as the cooling set-point temperature decreases, with the highest growth rate occurring at a temperature below 18 °C. Lower solar absorptance of the roof is conducive to reducing the cooling energy demand of the grain warehouse. When the thickness of the roof thermal insulation is less than 120 mm and the thickness of the external wall thermal insulation is less than 60 mm, energy use decreases more quickly with greater insulation thickness. It is advisable to use traditional or new windows with thermal insulation and shuttered windows. Furthermore, the optimal position of the long side of the granary was between 10° west and 10° east of north. This research could provide guidance for the energy-saving design and renovation of granary buildings in cold regions of China.

The Potential of Green Engineering Solutions for Energy Conservation in Residential Buildings Towards Sustainability: A Case Study of Saudi Arabia

Developing countries in hot climate regions such as Saudi Arabia have witnessed rapid population growth, which has led to greater resource consumption as a result of the increased demand for new buildings. This research proposes a multi-objective evaluation of the potential green engineering solutions to conserve energy using a building within the ROSHN housing project, which is one of the mega projects in Saudi Arabia, as a case study for this paper with the aid of simulation software, taking into consideration the context of the sustainability concept. The results showed that traditional passive architectural design, whether courtyards or Mashrabiya, had the nearly greatest influence, with percentages ranging from −4% to −5.15% for varied parameters and designs compared to the base case energy usage. Furthermore, energy efficiency solutions for the building envelope’s external insulation and finish system (EIFS) enabled a drop in the U-value that lowered energy usage to −5.40%. However, the wall insulation thickness beyond 300 mm in this system has no substantial influence on energy savings. This research’s most clear finding is that a P2P system for PV panels on a district scale can supply enough energy to meet its needs after implementing the optimal strategy of the other proposed solutions.

Low-energy residential building optimisation for energy and comfort enhancement in semi-arid climate conditions

The application of energy-efficient strategies in buildings, such as the Green Building Concept, can significantly impact human comfort and resource consumption. However, due to the complexity of decision-making factors and the variety of available materials, computational models are necessary to identify the most effective solutions and optimise building energy performance. This study presents an integrated framework that uses machine learning algorithms and a Petri Net control system to optimise the thermal, comfort, and energy efficiency of both vertical and horizontal building envelopes in semi-arid climate zones. The framework incorporates several passive techniques for building energy parameters, including material thickness and melting point, window types, wall insulation thickness and thermal emissivity, wall solar absorbance, window wall ratio, fenestration position, air tightness, roof solar reflectance, roof insulation thickness and conductivity (W/(m·°C)), and floor insulation thickness. An experiment design was developed using Box-Behnken Design-Response Surface Methodology (BBD-RSM) for statistical optimisation, which was coupled with Design Builder simulation model. The methodology was demonstrated by applying it to a residential building in Mexico. Meta Additive Regression was used to analyse the output factors, which showed higher confidence compared to REP Tree and M5P Tree algorithms in green buildings. The results demonstrate that an annual energy reduction of 50 kW/m2 per household can be achieved by using an optimised building envelope.

Multi-objective optimization of school building envelope for two distinct geometric designs in southern Brazil

The standard Brazilian school projects (EMEIs) were created for the Proinfância [Pro-Childhood] program to respond to the growing national demand for public schools. Unfortunately, the project disregards the Brazilian local climate, leading to an inadequate architectural design, especially in terms of energy performance. Within this context, this research aimed to assess the impact of a new geometric design and envelope proposal on the energy performance of a Brazilian school building. The study object is a standard project (EMEI) of the Proinfância program located in Pelotas, Brazil. Two distinct multi-objective optimizations were performed based on EnergyPlus coupled with the Strength Pareto Evolutionary Algorithm 2 (SPEA2), in which the objective functions were defined to minimize heating and cooling Energy Use Intensity (EUI) for different geometric designs (Base and Linear models). The design variables considered were window-to-wall ratio (WWR); thermal insulation thickness for walls and floor; solar absorptance values for walls and roof; and solar orientation. A total of 74.520 simulations were carried out, and the results indicated that the new geometric design combined with bioclimatic envelope strategies was capable of reducing 52% of the Energy Use Intensity when compared to the standard school project.

Energy and environmental assessment of the chilean social housing: Effect of insulation materials and climates

The impact of the envelope insulation and location of a Chilean single-family dwelling on the energy and environmental performance remains understudied. To figure this out, this study proposes to develop a life cycle assessment of a social housing with different thermal insulation materials and thicknesses (1–15 cm) in seven cities located in different thermal zones. The impact of the insulation and climate conditions is evaluated through the dwelling heating demand and the environmental impact, which allows determining the overall impact of improving the housing envelope by considering a cradle-to-grave approach. The functional unit considered in this study is 1 m2 of the total dwelling floor area. As expected, the heating demand showed notable differences between cities, being more energy-intensive (134–236 kWh/m2 yr) in cities located in Chile's extreme south, such as Punta Arenas. On the other hand, the major environmental impacts were registered in Puerto Montt (600–850 Pt/m2), although this city does not present a high heating and electrical energy consumption.Regarding the insulation material performance, increasing the wall insulation thickness (1–15 cm) decreased the U-value by 31 and 89%, resulting in an energy saving of 57–60% and reducing the environmental impact by 18 and 29%. These findings suggest that the actual thermal standard could be improved for reducing energy consumption and the environmental impact in the cities located in southern Chile. Moreover, the results demonstrate that the environmental impact depends more on the energy resources used to produce heating, electricity and domestic hot water than on the location of the city. It allows to identify potential opportunities to implement feasible and more sustainable solutions for social housing design considering site-specific conditions.

Uncertainty analysis of envelope retrofits for existing residential buildings in underdeveloped areas: A case study of Daokou, China

Current envelope-related uncertainty analysis (UA) focuses mostly on the physical properties of materials. However, the uncertainties of retrofit strategy selection, building element selection and construction quality are especially significant in underdeveloped areas due to their low economic and technical levels. To obtain more reliable energy analysis results and to correctly support decision-makers, a new UA method combining an orthogonal experiment (OE) and Latin hypercube sampling (LHS) is proposed to investigate the uncertain outputs caused by the three mentioned aspects. Furthermore, important factors affecting the uncertain outputs are screened by two global sensitivity analysis (GSA) methods: the standard regression coefficient (SRC) method and the treed Gaussian process (TGP) method. The UA results show that considering the uncertain inputs, the envelope energy-saving rates fluctuate from 46 %∼65 %, 70 %∼92 %, 48 %∼67 %, and 71 %∼90 % separately for the four typical retrofit scenes. The retrofit scene with the best energy-saving effect is always accompanied by the highest uncertainty. The GSA results show that the top three sensitive factors account for approximately 80 ∼ 100 % of the output variance. Infiltration and wall insulation thickness are the two most important factors for energy consumption in most cases. The results of the SRC and TGP methods are in general agreement, while TGP has the advantage of distinguishing the nonlinear relationship between glazing type and cooling energy. Therefore, it is advisable to apply design schemes that can make a trade-off between energy savings and robustness when performing envelope retrofits in underdeveloped areas.

Application of model predictive control to building design optimisation

Optimisation algorithms offer a valuable tool for enhancing the energy efficiency of buildings by fine-tuning specific design parameters. Model Predictive Control (MPC) emerges as a compelling technology to address the rising need for improved efficiency and adaptable operation within building energy systems. A simulation study using MATLAB and EnergyPlus was conducted to examine the influence of MPC and building design optimisation (BDO) on wall insulation thickness and internal mass area. The focus was on their impact on heating energy use and indoor thermal comfort in an office room located in Brussels, Belgium. The study revealed that the sole implementation of MPC led to a 7.6% decrease in heating energy use, while the application of BDO resulted in a more significant reduction of 12.8%. Remarkably, the fusion of MPC and BDO yielded the highest energy savings, cutting heating electricity usage by 23.4% compared to the baseline model. Moreover, MPC effectively maintained indoor temperature within the desired thermal comfort boundaries. The optimal wall insulation thickness and internal mass area were also ascertained through BDO, both of which exceeded the levels set by the baseline model. BDO, in conjunction with MPC, demanded the maximum permissible insulation thickness of 320 mm for the external north and south walls. Interestingly, when BDO was combined with MPC, the requirement for the internal mass area reduced by 11.7 m2 compared to utilising BDO alone. The study’s results underscore the potential of integrating MPC with BDO to elevate building energy efficiency. Furthermore, this strategy may be adaptable to optimising other building parameters at the early design stage, thereby augmenting overall building energy efficiency.

A whole life, national approach to optimize the thickness of wall insulation

Insulating external walls has great potential to reduce post-retrofit operational energy consumption and thus carbon emissions, but determination of the optimal insulation thickness still remains a challenge in the building industry. Although life cycle performance assessment has been introduced into the optimization of wall insulation thickness, there is still a lack of studies conducted at the building stock level. Moreover, the impact of variations of future climate conditions and the carbon intensity of the electricity grid are rarely studied. This study aims to fill this gap, by developing and demonstrating a holistic whole life approach to determine the optimized wall insulation thickness of the English housing stock. The study assesses both the reduced post-retrofit operational energy and carbon, as well as the additional embodied energy and carbon from wall insulation. There are three different optimization aims, namely: maximize the whole life carbon emissions reduction, maximize the whole life energy consumption reduction, and maximize both the whole life energy consumption and carbon emissions reduction. The results revealed that the optimized glass wool insulation thickness varies from 0.010 m to 0.275 m, increasing wall insulation thickness further than optimized value will result in negative effects. Ignoring future variations could lead to overestimation of the reduction potential of insulation installation on whole life energy consumption, and thus emissions reduction. The overestimation percentage for stock level whole life energy consumption reduction varies from 20.5% to 26.7%, and the overestimation percentage for stock level whole life carbon emissions reduction varies from 421.3% to 502.0%.

Passive Discomfort Index as an alternative to Predicted Mean Vote and Predicted Percentage of Dissatisfied to assess occupant’s thermal discomfort in dwellings

Besides energy poverty, a certain tolerance to discomfort justifies Portugal’s low heating energy consumption. Once Portuguese buildings stock, previous to 1990, has a weak energy performance, it is crucial to reflect on how to make renovations with more assertive benefits (besides energy), such as those related to the health and comfort of occupants. Hence, we have studied a single house in the TRNSYS dynamic simulation tool. We performed a sensitivity analysis by simulating the same building in three locations based on Portuguese climatic winter zones: I1 — Santarém, I2 — Santa Maria da Feira, and I3 — Guarda, for two ranges of wall insulation thickness, in free float. Considering Fanger’s Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) as the Passive Discomfort Index IDP, results suggest that lowering 20 mm on the insulation thickness does not substantially impact occupants’ discomfort in winter. As the variations between scenarios considering PPD > 15%, PMV < −1, or IDP (Tair < 18 °C) are very similar, IDP could be an alternative to PMV/PPD for assessing thermal discomfort in dwellings.

Integration of energy and seismic-structural design variables through the optimization of a multi-story residential light-frame timber building with different seismic lateral connectors and building stories

The structural and energy performance of the light-frame buildings is intrinsically linked, but the design process of both domains is not. Light-frame timber buildings are subjected to overheating due to the lack of thermal mass. A solution to eliminate or mitigate overheating is adding thermal mass, but the main drawback is increasing the seismic forces the building needs to withstand. Furthermore, the length of exterior shearwalls, fenestration openings, and studs spacing affect both the energy and structural performances. This paper aims to analyze and integrate energy and seismic-structural design variables for a light-frame residential timber building with different lateral seismic connectors and building stories. An Energy and Structural Timber Building Optimization (ESTIBO) methodology is proposed to integrate energy and seismic-structural design variables by optimizing the building energy performance. ESTIBO is based on GenOpt optimization software using a hybrid multidimensional optimization algorithm, while the energy simulations are performed on EnergyPlus using the Rhino's Grasshopper plugin. A structural model is implemented in Matlab under a modal response analysis of the building structure. The main results show that integrating critical design variables achieves different optimal values considering feasible structural solutions with reduced heating and cooling loads. It was found the four main variables that primarily reflect the link between energy and seismic-structural performances are stud spacing, wall insulation thickness, wall insulation type (high or low specific heat capacity), and floor concrete layer thickness. This paper contributes to improving the understanding of light-frame timber buildings' performance regarding the interaction of energy and structural-seismic design variables. Moreover, ESTIBO demonstrated to be able to provide optimal energy and seismic-structural solutions. Thus, it can support the early design stage of light-frame timber buildings.

A Study on Optimum Insulation Thickness in Walls of Chinese Solar Greenhouse for Energy Saving

Chinese solar greenhouses (CSGs) are characterized by unique walls to reduce the transmission of heat and promote the energy conservation in winter production, which promotes cultivation in the northeast region of China in winter. Effective selection of insulation material is important for the CSG based on the energy consumption and economic analysis. However, choosing the thickness of the insulation material in walls often discussed with the structure of CSG. There is a lack of research combing the optimal insulation thickness for improving the energy conservation. The aim of this study was to find the optimum insulation thickness during the energy conservation based on the structure of walls, the energy consumption in local climatic conditions, the cost of insulation material, and economic payback period over a lifetime. By the economic analysis of insulation thickness, thermal resistance, lifetime energy saving, and payback period, three kinds of typical walls (clay brick (CB), hollow concrete block (HCB) and fly ash block (FAB)) combed with four insulation materials including the expanded polystyrene, the foamed PVC, the perlite, and the rock wool were calculated. The optimum insulation thickness can be found when energy savings reached the maximum. In the northeast region, the association of FAB with rock wool as the insulation layer was the most economic composite wall structure. The optimum insulation thickness was 0.05 m, with the cost only 5 USD/m2. The thermal resistance of composite wall had a significant effect on the payback period. When thermal resistance increased from 0.2 to 1.2 m2K/W, the payback period varied from 0.4 to 4.3 years. What is more, the energy consumption in local climatic conditions had a more significant effect on payback period. It can be assumed that insulation materials are more favored in cold climatic regions where heating degree-days over 1600 °C days for payback periods is less than 2 years. These results have strong practical and economical significance in saving energy and improving the environment of CSG.

Optimization of external wall insulation thickness in buildings using response surface methodology

Optimization of external wall insulation thickness in buildings using response surface methodology

Optimal insulation thickness of walls using improved Particle swarm optimization

Uninsulated external walls and inappropriate insulation of buildings are the main reason for energy losses. In this study, novel configurations of multi-layer pre-fabricate wall elements were used to enhance the ability of energy-saving and decrease the payback periods and investments in residential houses in five cities in Iran with different energy demands. Also, an optimization strategy is applied to determine optimum insulation thickness for external walls. The evaluation process is based on using natural gas and electricity in Iran’s buildings for heating and cooling, respectively. The optimum required insulation thickness in Cities with different climates according to their degree/day value for four different insulation materials (extruded polystyrene, glass wool, rock wool, and polyurethane) is achieved using a novel optimization method (Improved PSO). According to the obtained results, annual cost saving for of the wall in case of simultaneous heating & cooling is more than cooling and heating alone. However, for the payback period, simultaneous heating & cooling has a lower payback period than cooling and heating alone. The results revealed that the cost of rock wool is higher, and the cost of polyurethane is higher than the cost of all other insulating materials in Ardabil. Also, the optimal insulation thickness for the Ardabil city with hollow brick walls and heating and cooling needs is and for the XPS, respectively.

Evaluation of condensation reduction performance of thermal breaker according to wall insulation thickness

Evaluation of condensation reduction performance of thermal breaker according to wall insulation thickness

Optimisation of wall insulation thickness using energy management strategies: Intermittent versus continuous operation schedule

In contrary to current studies in the literature, mostly concerning continuously operation system, this paper explores the effect of heating/cooling operation schedule on the determination of optimum insulation thickness (OIT) and location by studying different intermittent heating and cooling strategies. With this aim, two different cases, corresponding to house and office, were investigated for the climatic conditions of Ankara, Turkey, and compared with the continuous case. Performed analyses show that the optimum insulation thickness is highly dependent on the operation mode of buildings. When an intermittent heating and cooling strategy is applied, the OIT values remarkably differ from the continuous case (reducing by up to 2 folds), showing potential savings resulting from the energy management system. Locating the insulation material at the external wall surface was found to be more effective irrespective of the operation mode of the building. Furthermore, effects of applying OIT under the intermittent operation on the indoor air temperature fluctuations, energy consumption and level of greenhouse gas emissions are investigated. Most profound energy savings are observed for heating mode. For all the studied cases, the reduction in the total energy and global warming potential is between 52–74%, and 37–62%, respectively.

Energy, Economic and Environmental (3E) Analysis of a Tank-in-Tank Solar Combisystem

In this study, the thermal performance of a tank-in-tank solar combisystem is dynamically simulated to investigate the effect of various parameters such as collector type and area, storage tank volume, building specifications, heat exchange terminal units, and climatic conditions on system performance. The results showed that by increasing the collector area, tank volume and thickness of wall insulation, the solar fraction increases. It was also found that the use of floor heating instead of a radiator system improves the system performance. The solar fraction using the evacuated tube solar collector is 2.3% higher than that using flat plate solar collector. The annual solar fraction of 45.6%, 63.4%, 41.2%, 34%, 57.3%, and 88.1% is obtained in Hot-Dry (Tehran), Hot-Dry (Yazd), Cold-Dry (Tabriz), Moderate-Humid (Rasht), Hot-semi Humid (Abadan), and Hot-Humid (Bandar Abbas), respectively. The environmental analysis indicates that using the proposed solar combisystem could save 2241.3 m³ natural gas and offsetting 4731.5 kg less CO2 emissions during a year. The life cycle cost analysis shows that the payback time of the proposed system for the economic conditions of Iran is 7 years.

Optimal Combination of External Wall Insulation Thickness and Surface Solar Reflectivity of Non-Residential Buildings in the Korean Peninsula

To delay fossil energy depletion and implement the Paris Climate Change Accord, the South Korean government is attempting to reduce greenhouse gas emissions with the establishment of the 2030 Roadmap. The insulation performance of external walls is being continuously enhanced in the architectural domain. However, Korea’s policy and construction market focuses only on the heat resistance of buildings’ external walls to enhance the insulation performance, leading to an increased thickness of the insulation materials. In this study, the relationship between the surface reflectivity and insulation thickness of external walls was examined to formulate an effective insulation strategy for buildings in Korea. Office buildings of 12 regions in the Korean Peninsula were considered. The dynamic energy simulation program EnergyPlus was used to perform the heating and cooling load analyses. The present worth method was adopted to perform the economic analysis. The analysis of the cooling and heating loads indicated that a change occurred not only in terms of the latitude but also between the Eastern and Western regions. The energy consumption could be reduced by increasing the reflectivity in the Southern region and lowering the reflectivity in the Northern region, based on the total load. In addition, a higher latitude corresponded to a higher energy saving effect owing to the increased insulation thickness. In the case of Jeju Island and Busan, regions with a relatively large cooling load and small heating load, the total load is little affected by insulation thickness at high reflectivity. If the external skin was considered to have the optimal reflectivity, the regions for optimal insulation thickness could be divided into three categories: north, central and south.