Wall Insulation Research Articles

Influence of the Building’s Thermal Insulation on Intermittent Heating Mode Efficiency

Abstract The results of mathematical modeling of a building’s thermal insulation influence on the efficiency of intermittent heating mode are presented. This work aim is to assess the influence of thermal insulation on the efficiency of using the intermittent heating mode for the educational building of the Odessa National Polytechnic University’s Heat Engineering Laboratory. The paper analyzes the factors related to improving the efficiency of the programmed heat supply mode. Modeling of the operating modes for heat supply system operated in intermittent heating mode is carried out. There was performed the mathematical modeling of the heating system operation modes for the most unfavorable climatic conditions at low outdoor temperatures, with respective system efficiency indicators obtaining. The potential of energy saving level for administrative, educational, and office buildings depending on the thickness of thermal insulation of external and internal walls is studied. Recommendations have been elaborated for the use of buildings thermal insulation to improve the efficiency of intermittent heating.

Hydrophobic treatments and their application with internal wall insulation

Hydrophobic (or water repellent) treatments have been proposed to mitigate moisture risks associated with internal wall insulation when applied to solid masonry walls. This can reduce risks associated with moisture accumulation within the structure such as mould growth or the deterioration of joist ends and other embedded timber. Where treatments perform well there is a net reduction of moisture content and risk. However, such treatments slow down drying processes, and therefore may result in a net increase in moisture if the treatment is bypassed by, for example, cracks. Some treatments may lead to damage to external masonry surfaces in some situations. Freeze–thaw and salt crystallisation are the two main causes. Hygrothermal simulations may give some indication of risks but techniques to assess the risk of surface damage are either simplistic, impractical outside of the research environment or both. This paper reviews the current field of assessing and predicting the risk of surface damage associated with surface treatments.

Research on the design and thermal performance of vacuum insulation panel composite insulation materials

This study introduces a novel design methodology for composite insulation material aimed at reducing the operational energy consumption of buildings. Vacuum Insulation Panels (VIPs) are recognized for their excellent insulating properties due to their vacuum-sealed nature that minimizes thermal transmittance. However, VIPs are susceptible to damage from temperature stress and abrasion, which can compromise vacuum integrity and degrade performance over time. To mitigate this, a protective layer of rock wool board is adhered to the exterior of the VIP to create a composite insulation material. The thermal conductivity characteristics of the composite insulation materials are experimentally measured and then corroborated with simulations using ANSYS software to affirm the precision of finite element analysis methods. A composite Insulation wall model is constructed using ANSYS to analyze the impact of varying the thickness of the composite insulation materials and the pressure within the VIP on thermal performance. The findings demonstrate that the thermal transmittance coefficient of the composite insulated wall diminishes with increased insulation material thickness and rises with increased pressure within the VIP. Additionally, rock wool boards significantly enhance the durability of the composite insulation material.

Impact of external wall insulation of office buildings on the interior microclimate

Impact of external wall insulation of office buildings on the interior microclimate

Examining the relationship between dwelling energy efficiency and fuel poverty for retrofit strategies: A case study of the United Kingdom

In the midst of a global energy crisis, fuel poverty has become increasingly prevalent. This study examines the effectiveness of energy efficiency retrofits (EERs) in alleviating fuel poverty in the United Kingdom. Using the England fuel poverty dataset with XGBoost and interpretive analyses like Individual Conditional Expectation (ICE) and SHapley Additive exPlanations (SHAP), the research investigates the impact of EERs on fuel poverty. Findings reveal that while energy efficiency enhancements hold potential for improving conditions for vulnerable households, their effectiveness diminishes beyond a certain threshold. The study identifies solid wall and cavity wall insulation, condensing boilers, well-insulated lofts, and central heating systems as the most effective retrofit measures. However, the optimal selection of retrofit methods varies depending on household and dwelling conditions due to interactive effects. Additionally, comprehensive cost-efficiency analyses show that installing condensing combination boilers in homes without existing boilers and adding cavity wall insulation to houses with uninsulated cavity walls are more cost-efficient options. These insights shed light on the complex relationship between energy efficiency retrofits and fuel poverty, informing the development of targeted strategies to address this pressing issue in the UK and globally.

Empirical study of facade retrofits for optimizing energy efficiency and cooling in school buildings in Saudi Arabia

Educational buildings in Saudi Arabia are characterized by high energy consumption, primarily due to cooling and lighting demands. This study aims to evaluate and optimize facade retrofitting strategies to improve energy efficiency and evaluate economic performance of many scenarios in Saudi school buildings, aligning with the sustainability objectives of Saudi Vision 2030. The research employs a simulation-based optimization methodology utilizing Design Builder software to explore key facade design variables, including Window-to-Wall Ratio, glazing type, local shading devices, and external wall insulation. The methodology is structured in sequential stages: it begins with the collection of base-case data, followed by a data-driven optimization process targeting specific design variables. This is then complemented by an economic and environmental assessment of the optimal retrofit scenarios, ultimately leading to the identification of the most effective energy-saving solution presented at the conclusion of the study. Through an optimization process, the research identifies retrofitting strategies that reduce cooling loads by up to 17 %, lighting energy consumption by 49 % and annual energy costs by 18 %. The study also includes an economic analysis of the retrofits, revealing significant savings in annual electricity costs and a reduction in the building's carbon footprint. This research contributes valuable insights into sustainable building practices, offering practical solutions for improving energy efficiency in the educational sector. The novelty of this study lies in its comprehensive analysis of facade retrofits within the context of extreme climatic conditions, which provides a replicable model for retrofitting educational buildings across the region. The findings have significant implications for policymakers, architects, and sustainability advocates seeking to meet Saudi Arabia's energy conservation goals.

Requirements of the Vapour Barrier in Wood-Frame Walls

This paper examines the water-vapour diffusion resistance (Z-value) of vapour versus wind barriers by determining their Z-value ratio in exterior wood-frame walls thermally insulated with six different materials to prevent mould growth. Using WUFI Pro, the water-vapour diffusion resistance requirements were determined for thermal insulation using mineral wool and biogenic materials: wood fibre, straw, flax, grass, and hemp. Hygrothermal simulations determine the minimum Z-value ratio between these materials with vapour versus wind barriers in temperate and cold climates. Wind barriers with Z-values between 1 and 8 GPa s m2/kg were used in walls with U-values of 0.15 and 0.10 W/m2 K. The indoor moisture load was defined from classes of 1 to 5 with a U-value of 0.15 W/m2 K and classes of 2 and 3 were used for a U-value of 0.10 W/m2 K. The Z-value ratio depends on the Z-values of the wind barrier and thermal insulation material, moisture load class, and U-value. The required Z-value ratio declines with an increased wind-barrier Z-value. The vapour-barrier Z-value approaches a fixed threshold for wind-barrier Z-values approaching lower values (1 GPa s m2/kg) and those approaching higher values (8 GPa s m2/kg), depending on the thermal insulation material. This parameter study examines wind barriers with a Z-value ranging between 1 and 8 GPa s m2/kg, which characterises typical wind barriers used in Denmark For the water-vapour diffusion resistance requirement of the vapour barrier, the Z-value increases for increased moisture load classes and thermally insulated walls with lower U-values. The conversion between the Z-value, the Sd-value, and the water-vapour resistance factor µ can be found in DS/EN ISO 12572:2016.

Multi-objective assessment of the retrofit of traditional walls located in a historical city centre using an urban climate model

Historical city centres face two major challenges in the 21st century: heritage conservation and energy retrofitting. Wall insulation in traditional buildings is at the crossroads of these two issues. When studying the retrofit of the walls, other factors also need to be considered, such as the durability of the walls, the life cycle of the materials used for insulation, the indoor and outdoor comfort in summer. The aim is to propose a method for taking all these objectives into account when choosing the insulation technique for historical walls. To do this, the TEB (Town Energy Balance) urban climate model is used, because it considers the urban microclimate, the energy behaviour of buildings and moisture transfer through walls. A VTT model is integrated into TEB, to include the risk of mold growth. The medieval city centre of Cahors (France) was used as a case study. The retrofit of two types of wall was assessed: “massive” brick walls, and “light” walls with a timber-framed structure, filled with bricks. Six renovation scenarios were studied, including four insulation materials and both internal and external insulation positions. The results obtained underline the need to study the retrofit of the two types of building separately, because the recommendations made for insulation vary depending on the type of wall studied.

Seismic behavior and failure analysis of prefabricated foamed concrete composite walls for passive houses

In view of the lack of research on the failure mode and seismic behavior of high-performance insulation walls utilizing lightweight concrete as the structural material, this study presents experimental findings from a seismic behavior investigation of prefabricate foamed concrete composite walls (PFCCWs) for passive house in China. The PFCCWs incorporate low thermal conductivity and high-strength foamed concrete, polyurethane, decorative magnesium straw slabs to provide excellent thermal and mechanical properties for prefabricated passive houses in hot summer and cold winter area. The seismic behavior of PFCCWs under different influence factors were elaborated using quasi-static test data and observation of external damage. The lightweight and porous nature of foamed concrete leads to significant crack formation during failure. The findings suggest that the skin effect of magnesium straw slabs and polyurethane impedes crack development and improve the load-bearing capacity with ductility enhancement. Additionally, reducing the aspect ratio and substituting post-cast column concrete with common concrete are effective to improve the seismic behavior. The window opening changes the worst damage area of the wall and notably weakens the seismic behavior. The enhanced integrity of cast-in-place wall leads to the difference in the failure mechanism and increases in load-bearing and deformation capacities. Meanwhile, design suggestions for the foamed concrete insulation walls are also proposed by comparing the failure mode and hysteretic response of various wall types.

Analyzing Passive Design Retrofits using Pareto Front Optimization to Reduce Operational Carbon in Commercial Laboratory Spaces

Buildings are one of the leading sources of carbon emissions in the world. Most of the carbon emissions are released during the operation phase of the building. It is essential for buildings to provide thermal and visual comfort for the users. In the case of existing buildings, it is necessary to offer retrofit solutions so that the operational carbon emissions can be reduced without compromising on the other essential factors. In this study a Multi-Objective Optimization (MOO) of passive design strategies was conducted for a commercial laboratory in India situated in a moderate climate zone. The design variables considered for the study are wall and roof insulation, glazing material, window-wall ratio (WWR), depth of shading device and the number of shading devices used. The objective functions are: 1. reduced energy use intensity and operational carbon emissions, 2. increased thermal comfort hours and 3. increased daylight autonomy. Rhinoceros and grasshopper software along with Ladybug and Honeybee plug-ins were used for the study which resulted in 1296 iterations. MOO technique namely Pareto front optimization was used to optimize the objective functions. Out of 1296 solutions (excluding base case), 72 solutions were non-dominated. Two methods are described in the study to identify the recommendations for retrofit. The first method describes a Heuristic method of selection using Design Explorer recommending 5 good solutions. In the second method a factor is evolved to identify the 5 best solutions in sequential order. The overall study recommends the use of EPS insulation for the RCC roof, WWR of 20% on all sides, 3 horizontal shading devices of depth 0.75 m for all window openings. When compared with the base case scenario, this solution minimizes the EUI by 3.7%, maximizes average TCH by 106.6% and maximizes average DA by 66.9%. The overall operational carbon emissions are reduced by 7095.6 kgCO2.

Study on properties and simulation application scenarios of flame retarded modified konjac glucomannan organic and inorganic composite aerogel

In this paper, a new organic-inorganic biomass composite aerogel was prepared by freeze-drying method with glucomannan, hydrophilic isocyanate, water-soluble flame retardant, and water glass as raw materials. Biomass Konjac glucose mannan (KGM) was used as the main network framework, KGM was chemically cross-linked and alkali-cross-linked with hydrophilic isocyanate and Na2SiO3 solution, and flame retardant modified with water-soluble flame retardant and water glass. The microstructure showed an obvious organic-inorganic interpenetrating network structure. The compressive strength of sample K2S4P2 was 4.751 ± 0.089 MPa, and the compression modulus of sample K2S4P1B modified by boric acid hydrolysis of Na2SiO3 was 63.76 ± 1.81 × 103 m2/s2. The introduction of boron ions contributes to the thermal stability of organic components. The peak and total heat release rates of sample K2S4P1A4 decreased by 80.3 % and 50.8 %, respectively. In addition, the thermal simulation calculation of the external wall in winter and summer using ANSYS software showed that the thickness of the insulation layer with the best insulation effect is 40–60 mm. The organic-inorganic composite aerogel provides a simple and environmentally friendly method for the application of external wall insulation systems in low-energy buildings with both mechanical properties and flame retardant properties.

Wall-applicable metamaterial: mitigating resonance dip for enhanced sound transmission loss

In recent years, there has been a significant advancement in thermal insulation technology, allowing for the implementation of energy-efficient solutions in existing buildings while preserving their architectural and cultural significance. This recognition has led to the widespread adoption of External Thermal Insulation Composite Systems (ETICS). However, this brings the common challenge in acoustic engineering, the resonance dip, into the spotlight. When the frequency of an incident sound wave coincides with a mass-spring-mass resonance of the thermally insulated wall, the sound insulation drop occurs, possibly resulting in a reduction in transmission losses. This study introduces a wall-applicable design of Plate-type Acoustic Metamaterial (PAM) to effectively enhance sound transmission loss. We investigated in development a transfer matrix method combined with the effective mass density of PAM to model the ideal metamaterial wall and further compared it with the results based on mass-law methods. Design strategies to construct the ideal bandgap were developed by analyzing dispersion curves.

Fabric Retrofit of a Hard-to-Treat, Pre-1919 House in Preparation for Heat Pump Use

The uptake of low-carbon domestic heating systems is a significant strategy towards global targets of reducing greenhouse emissions and mitigating climate change. Pre-1900 hard-to-treat houses will still be existing in the next 25 years, and they have the greatest potential for improved energy-efficiency. This study investigates the potential of fabric retrofit to prepare an older, hard-to-treat house type for heat pump use. The house type was modelled in DesignBuilder and validated using the Ulster University test house. The wall, loft and floor insulation, as well as glazing upgrades can yield up to 50% reduction in heating demand for a hard-to-treat house type, thereby preparing it for heat pump installation. Additionally, upgrading insulation and glazing in line with the current building standards was cost-effective, with a net present value of approximately GBP 12,000.

House FIRSTLIFE in student contest and in Living Lab

Abstract The paper comments on selected measurements and observations related to the FIRSTLIFE house demonstration unit, which was prepared by the team of the Czech Technical University for the international competition Solar Decathlon Europe 21/22 with its final at the Solar Campus in Wuppertal, Germany. The paper comments on the measurement results obtained during the competition in the field of building physics (thermal and moisture comfort, measurement of air permeability, measurement of sound insulation of the perimeter wall and dynamic co-heating test). The second part of the paper describes selected follow-up activities. For the purposes of the Living Lab, eight of the competition houses remained on the Solar Campus for at least another 3 years. This allowed long-term monitoring and targeted experiments to be carried out and some of the earlier measurements to be repeated under different climatic boundary conditions. For this phase, additional sensors were added in the Czech house, such as a meteorological station and temperature and heat flow sensors in the perimeter wall. Part of the data comes directly from the building management system. The paper comments on first results from Living Lab period.

In-situ measurement of thermal transmittance of building walls: Evaluation of stored heat flux in heavy-weight walls during the cooling season

The conventional heat flow meter (HFM) method is used to measure the thermal performance of building walls. Typically, this method is applicable for measurements on lightweight walls and when the difference between the indoor and outdoor temperatures exceeds 10 °C. However, modern buildings are constructed using highly insulated high-performance heavy-weight walls. Therefore, an in-situ measurement method is required to overcome the limited measurement environment of the conventional HFM method. In this study, a novel stored heat flux (SHF) method is proposed to overcome the limitations of the existing HFM method. This method estimates the stored heat flux in the wall using the thermal energy-conservation equation of the enclosed system and uses a decrement factor and time lag to calculate the thermal transmittance (U-value). The proposed method can be applied to heavy-weight walls in the cooling season when the difference between the indoor and outdoor temperatures is less than 10 °C. Furthermore, the design U-value can be estimated with higher accuracy than that observed in the conventional HFM method. The results of the relative error analysis for the U-values show that the conventional HFM method was approximately 68 % of the design U-value, while the proposed SHF method was approximately 15 %.

Experimental investigation on shear performance of ECC sandwich insulation wall panel with GFRP connectors

The problem of high energy consumption in buildings is becoming increasingly prominent. Sandwich insulation wall panel is used to reduce the heat loss of building because it has the same life span as the main structure of the building. Engineered Cementitious Composites (ECC) is a material with significant multi-crack cracking ability and strain hardening characteristics, and replacing ordinary concrete with ECC as the inner and outer plates of sandwich insulation wall panels contributes to solve the problems of easy cracking and poor durability of the plates. Therefore, starting with the form of GFRP connectors, this thesis studied the influence of different connector forms on the shear performance of ECC sandwich insulation wall panel through experiments, and evaluated its safety. The results show that the specimen with X-shaped connector had the highest vertical shear stiffness and bearing capacity, but its lateral shear stiffness and bearing capacity were very low, which could not be used as a two-way shear connector. The shear stiffness and bearing capacity of the I-shaped connector and the modified X-shaped connector were similar, but the toughness index of the modified X-shaped connector was much higher than that of the I-shaped connector. All connectors could meet the requirements of relevant specifications for shear bearing capacity and deformation. In comparison, the shear performance of the modified X-shaped connector was more excellent.

Microclimate Effect on Cooling Energy for Buildings in Hot, Humid Climates: A Comparative Analysis of Shaded and Unshaded Environments

This paper explores the influence of microclimates on changes in air temperature and the often-overlooked aspect of their effect on energy savings across varying microclimatic conditions. The study compares the cooling energy requirements of two identical single-story buildings in distinct microclimates: one characterized by concrete ground devoid of shade and the other featuring soil ground with tree shade. Climatic environmental data were collected over 15 days in the concrete-exposed field and shaded area beneath the trees to conduct the investigation. These datasets were input into EnergyPlus 9.6 to model the energy demands and consumption of buildings subject to the specified climatic conditions. The validation of the simulated model against actual energy demand data from a classroom building demonstrated agreement. The findings reveal notable differences in air temperature, with the shaded area experiencing temperatures 0.8°C to 8.0°C lower than the concrete-exposed monitoring location. The building in the tree-shaded microclimate exhibited a lower peak cooling load than its concrete-exposed counterpart, resulting in a 35% reduction in the electrical energy requirements for the air-conditioning system. The study recommends implementing 0.08-m polyurethane insulation for the building walls and roof to equalize the energy demand and consumption of the concrete-exposed building with that of its shaded counterpart. Furthermore, building design in shaded areas can maximize the window glass area while consuming less energy than buildings on concrete-exposed grounds. The study advocates leveraging the microclimate associated with surrounding buildings in the design process to enhance the overall energy savings.

Evaluation of insulation effectiveness for thermal comfort in summers: experimental and CFD numerical study

We evaluate the thermal performance of PUF-insulation boards embedded in the roof of an office-sized room. Two rooms were constructed: one with and the other without insulation. The thermal comfort was evaluated by performing an experimental study according to ANSI/ASHRAE Standard 55-2017. The inside air temperature, humidity, wall and ceiling temperatures, air velocities and thermal flux were measured for the summer April–June 2023. Using these measurements, the PMV and PPD values were computed. The effectiveness of the insulation material with regard to thermal comfort is judged by the reduction in values of these indices. During a typical day, a reduction of around 30% is achieved just by adding the insulation. Nusselt number correlations are proposed to predict the convective heat transfer from the walls. Detailed CFD simulations were performed and a parametric study to understand the effect of insulation thickness, wall insulation, roof thickness and room dimensions on thermal comfort was undertaken.

Comprehensive Cost–Energy Evaluation of Wall Insulation for Diverse Orientations and Seasonal Usages

Comprehensive Cost–Energy Evaluation of Wall Insulation for Diverse Orientations and Seasonal Usages

Geopolymer-based insulated wall incorporating construction and demolition waste: Experimental assessment of thermo-physical behavior

The benefit of the application of geopolymers in the building sector is nowadays undisputed. In addition to good structural characteristics, these are characterized by interesting thermophysical properties, obtained through a production process, that reduces CO2 emissions and could incorporate recycled material, thus responding to environmental sustainability. However, it is noted the lack of studies regarding the in-field thermal performance. Thus, the aim of the present study is to investigate the thermal performance, under real conditions, of an innovative geopolymer-based insulated wall. It incorporates over 70% of net weight of Construction and Demolition Waste materials. The wall is conceived within the European project called “Green INSTRUCT” aimed to realize modular prefabricated building elements, for retrofitting and new construction of buildings. Two wall prototypes are analysed, which differ for the type of lightweight aggregate of geopolymer matrix, 3% by weight: expanded polystyrene or extruded polystyrene. The study refers to almost one year of continuous monitoring within a full-scale test room located in southern Italy. The method developed consists of 5 different phases and it involves also a normative-insulated reference wall. The results show higher insulation level of the proposed wall package, with a reduction of the heat flux of about 66% and more stable indoor thermal conditions, compared to the reference wall. Also the inertial properties are satisfactory, showing an experimental decrement factor equal to 0.05 and a time-shift of decrement factor higher than 6 h. All told, the experimental results can provide valuable insights into the real impact of innovative technology on energy efficiency and indoor thermal comfort.