External Walls Of Buildings Research Articles

A state-of-the-art review of novel aerogel insulation materials for building exterior walls

ABSTRACT The unique network-like framework and nanopore structure of aerogel endow it with excellent thermal insulation performance. The thermal conductivity is as low as 0.012 W/(m·K), far lower than 0.035-0.040 W/(m·K) of traditional thermal insulation materials. Research and industrialization of nanoaerogels as building insulation have gained increasing attention in recent years. This paper discusses the application status, existing challenges, and solutions in the field of building external wall energy conservation and insulation based on nanoaerogel materials. First, it reviews the research progress of nanoaerogels and the development status of traditional building exterior wall insulation materials. The external wall using nano aerogel can reduce the heat loss by about 40%. Second, it focuses on the characteristics and research status of several types of aerogel thermal insulation products for buildings. Some products show that the energy efficiency has been improved to 50% in practical applications. Finally, it analyzes existing challenges of nanoaerogels in the application of building external wall thermal insulation and summarizes the development direction of industrialization research. Building external wall thermal insulation and the application and development of aerogels in the field of building energy conservation are facilitated by this analysis.

Drift when applying biocides to control crawling and flying insects on walls

BackgroundInsecticides are sprayed on external building walls for treatments against crawling and flying insects. These applications can lead to drift into non-target areas and thus to undesirable environmental pollution. This emission pathway needs to be considered during exposure assessments within product authorisations to assess potential environmental risks. However, now, there is only one default value for deposition that is used in all calculations based on the Emission Scenario Document of the Organization for Economic Co-operation and Development at a distance of 50 cm to the treatment area. This is not sufficient for a risk assessment.ResultsWhen applying a chemical barrier of 50 cm at the bottom of the building wall, wind direction had the greatest influence on drift, while changing the nozzle type had no significant effect. Compared with the measured ground sediments, the OECD default value was deemed to be realistic at a distance of 57 cm from the treatment area. When treating the entire building wall, the wind direction as well as the nozzle used show significant influence on the measured values of drift. The default value for deposition proposed for modelling environmental exposure in OECD document ESD PT18 No. 18 was exceeded. Thus, the exposure estimation might not be protective enough.ConclusionDrift values used for the environmental exposure assessment of biocidal products during treatments of building walls should be adapted. This is especially relevant for treatments of entire building walls, where the current default value was exceeded for all distances from the building wall. Wind direction and nozzle type can reduce environmental impact. This finding can be used as a measure to reduce unnecessary exposure in the environment in the future.

Optimizing thermal insulation in building facades: An examination of human-environment dynamics in Nanjing city, Eastern Asia

The external building walls are significant in mitigating adverse weather conditions. Current research on the thermal insulation of exterior walls often overlooks crucial factors such as human comfort, seasonal changes and environmental dynamics. This study introduced a performance evaluation approach for external walls that considered the human thermal zone, annual air temperature and solar radiation. Taking Nanjing City as a case study, the thermal insulation performance of five distinct types of building exterior walls was investigated. The findings highlight the impact of various insulated wall systems on thermal insulation. While different insulated walls exhibited significant variations in effectiveness during extreme weather episodes, these variations were minor over the course of the year. Analysis revealed a spectrum of performance for insulated exterior walls, ranging from excellent to poor: Outer Insulated Wall > Inside Insulated Wall = Sandwich Insulated Wall = Self-Insulated Wall > Mortar-Insulated Wall. The disparity in thermal insulation performance amongst four wall types was minimal, with the mortar-insulated wall demonstrating the lowest performance. The highest temperature recorded for the mortar-insulated wall surpassed 32.2°C over 68 days. This research contributes insights into the nuanced performance of various insulated walls, paving the way for decision-making in climate resilience strategies.

Hygrothermal behaviour of external thermal insulation composite systems (ETICS) to withstand biological colonisation

ETICS are multilayer building solutions applied to the building external walls to provide an improved thermal performance to the building envelope. However, several questions have been raised concerning the durability of ETICS, namely related to biological colonisation phenomena. Considering the high susceptibility of ETICS to bio-colonisation, the following research questions arise: (i) what is the impact of surface temperature (ST) and surface relative humidity (SRH) fluctuation on mould growth in ETICS facades? (ii) is it possible to predict mould growth on ETICS under fluctuating conditions considering favourable and unfavourable growth conditions? This study aims to investigate the influence of the hygrothermal behaviour of five different ETICS (with thermal mortars and insulation boards) on mould growth. ETICS were exposed for one year at an urban site in Lisbon, Portugal, facing North, during which the ST and the SRH were monitored. Concurrently, numerical simulations were performed to evaluate the hygrothermal behaviour of the ETICS. Three theoretical indices were applied, using numerically and experimentally obtained values of ST and SRH as input to provide an indication of the risk of mould growth. The results were complemented and validated by assessing the bio-colonisation, water performance and aesthetic properties of the ETICS. Index 1 (percentage of time with SRH ≥80%) indicated similar potential of mould growth for all systems. Both index 2 (percentage of time with SRH = 100%) and index 3 (percentage of time with SRH ≥80% and 15 °C ≤ ST ≤ 30 °C) indicated a higher potential of mould growth for the lime-based ETICS and a lower potential for the acrylic-based ETICS with an EPS-based mortar. Moreover, the lime-based system obtained the highest rate of mould growth after one year of outdoor exposure. Therefore, results suggested that indices 2 and 3 are in agreement with field observations and thus can provide an indication on mould growth for the analysed ETICS. Results also showed that an increase of capillary water absorption after ageing to levels higher than 1 kg/m2 after 24 h in direct contact with water can favour mould growth. Thus, the combination of unfavourable microclimatic conditions (SRH <80%; ST < 15 °C or ST > 30 °C) and surface hydrophobicity are fundamental to avoid mould growth on ETICS, regardless of the incorporation of biocide in the finishing coat composition.

Optimum insulation thickness for external building walls for different climate zone in India

Optimum insulation thickness for external building walls for different climate zone in India

Heat loss characteristics of typology-based apartment building external walls for a digital twin-based renovation strategy tool

Information about existing building structures is necessary for creating a renovation strategy. Older buildings are often built using typical building envelope structures. However, this information is presented in the building register at a general level, specifying the material type but not its characteristics. For a cross-regional reconstruction strategy, it is necessary to link the scarce information in the building register with the heat loss characteristics of the building envelope structures. In the current study, we classified external wall solutions according to building typologies and linked this with building register information. The typology database includes log, timber frame, brick, concrete, and aerated lightweight concrete external wall structures. Comparing the typology-based values and the actual situation showed that the wall structures’ expected and actual heat loss characteristics agreed. However, there were also significant deviations, primarily because the data from the building register did not allow for precise classification. Nevertheless, data showed that building typology-based heat loss properties are necessary for developing a district-based renovation strategy.

Semi-automated visualization method for visual inspection of buildings on BIM using 3D point cloud

Regular diagnosis of a building can identify structural safety and latent hazards and establish efficient maintenance strategies. Traditional diagnoses are based on personal perspectives or knowledge of experts; therefore, they are laborious, time-consuming, and subjective. Moreover, the results may be unreliable. In addition, an undefined data format makes its practical use difficult. This study proposes a visualized semi-automated approach to extract building condition data and integrate them with BIM using Dynamo. The proposed framework uses Python code to improve efficiency when extracting coordinates. First, 3D point cloud data on the external walls of buildings obtained using a laser scanner are processed, and the relevant information, such as coordinates, is extracted. Second, the BIM model is implemented based on a point cloud using supplementary modeling tools. Finally, the extracted defects are modeled as new objects, and each BIM object is colored according to the modified criteria. To validate the feasibility of the proposed method, it was applied to actual buildings, improving the efficiency and accuracy of building inspections. This is expected to facilitate a reduction in building maintenance work and the identification of deterioration patterns.

Optimum thermal performance of green walls systems and design requirements against heat transfer of conventional external walls of low-rise concrete buildings in hot regions

This paper presents a study on how the thermal performance of conventional external walls of concrete building could be improved against heat transfer in hot regions. 45 buildings were visited to observe the heat transfer from the warmer side of the external wall to the cooler side. The measurements showed that the conventional walls are insufficient because of high indoor temperatures. This study introduced three environmentally friendly scenarios to enhance the efficiency of the concrete wall against heat transfer. In the first scenario, a continuous air layer was added at the middle of the wall to form an aired-concrete wall. In the second scenario, a living green layer was added on the exterior side of the wall to form a living-concrete wall. The third scenario merged the previous two insights to form a living-aired-concrete wall. Thermal models were prepared to conduct thermal analysis. The results showed that the air layer deactivates the work of thermal bridges and improves the thermal resistance of the wall 5 to 15 times. In the aired-concrete wall, the results showed that the minimum depth of the air layer should be at least 6 cm, to secure a convenient indoor environment with indoor temperature not more than 25 °C. Furthermore, the results showed that adding only an outdoor living green layer to the conventional wall is insufficient in all thermal zones of hot regions. Finally, the best thermal performance against heat transfer was found in the living-aired-concrete wall using outdoor Perennials plants and 5 cm middle air layer.

Microencapsulated waste cooking oil derivatives for building thermoregulation

The utilization of waste resources and the intelligence of building materials are of great significance to the sustainable development of human society. A novel type of microencapsulated phase change material (MPCM) with a phase change heat storage capability was prepared in this paper through the suspension polymerization method using methyl palmitate (MP) derived from waste cooking oil as core materials. Meanwhile, the response of foamed concrete containing MPCM to ambient temperature change was investigated. According to the experimental findings, the MPCM's phase change temperature, phase change enthalpy, and decomposition temperature are respectively 20 °C, 68 J/g, and 215 °C, which is extremely suitable for the external walls of buildings to adjust the indoor temperature. Moreover, the particle size of the MPCM is about 100 μm-220 μm, which can fill part of the voids in foam concrete to increase its strength. Additionally, the infrared thermal imaging experiment indicates that the foam concrete containing 10 wt% MPCM can maintain 4 °C-5 °C gap with the ambient temperature, which demonstrates that the MPCM can significantly mitigate the impact of ambient temperature on buildings. The findings of the study contribute to the intellectualization of building materials and the recycling of waste resources.

Wind loads tests of external walls blocks masonry of noncombustible polystyrene concrete

Introduction. Blocks of non-combustible polystyrene concrete of D300 density grade, B1 compressive strength class with normalized thermal conductivity λ0 = 0,078 W/(m·°C) and frost resistance grade not lower than F75, developed by LLC “Institute VNIIZhelezobeton”, were used in masonry with a thickness of 375 mm without special fireproof lining. Such masonry successfully passed standard fire tests for fire hazard and fire resistance, which showed the possibility of its use in external non-bearing energysaving walls of multi-storey buildings (up to 25 floors inclusive, about 75 m high).Aim. Evaluation of the strength and deformation characteristics of non-combustible wall masonry made of noncombustible polystyrene concrete blocks with a density of D300 at design wind loads at a height of about 75 m. Materials and methods. Fragments of uncoated wall masonry 375 mm thick, 2,7 m high and 1,2 m wide of noncombustible polystyrene concrete blocks mounted on a mortar with over-all dimensions of 295 × 375 × 595 mm were tested.The test procedure is in accordance with State Standard 8829-2018.Results. The destructive bending load exceeded the calculated one by an average of 4,1 times, while the deflection in the middle of the fragment was 1,9 times less than the permissible one.A methodology has been developed for calculating the strength and deformability of masonry of polystyrene concrete blocks under wind loads, taking into account the influence of horizontal and vertical masonry joints, which is scheduled to be reflected in Amendment No. 1 SP 434.1325800.2018.Conclusions. The results of wind load tests showed that for unlined masonry made of non-combustible polystyrene concrete blocks with a density of D300 and a thickness of 375 mm, the requirements for strength and deformability are met with a significant margin. The results of tests for wind and fire effects of the specified block masonry make it possible to use it in nonbearing external walls of multi-storey residential energyefficient buildings up to 75 m high in virtually all regions of Russia.

Evaluation of energy efficient building envelope alternatives for sustainable cities

This study is aimed to create an exemplary project to present the contribution of the new buildings to energy savings when the residential buildings are transformed into green buildings. To create a sustainable built environment in residences, this study emphasizes that low-energy building strategies be combined with efficient and high-performance natural-sourced materials. Our findings show that using a natural-sourced material as the building envelope material has an impact on the use of primary energy and energy costs of the alternatives studied. In this study; In the case of replacing the building external wall components of an existing construction designed with internal insulation in the climatic conditions of Ankara, the change in energy performance has been investigated. The analysis was done with the help of BIM-based Revit Program and “Green buildings studio” where energy simulations were created. In the study, 54 different wall combinations were created by modeling combinations of different construction (porous, gas concrete, and pumice bricks), insulation (glass wool, rock wool, sheep wool, PUR, XPS, and EPS) and, roof (tile, asphalt shingle, and green roof) materials. When the outputs obtained from the analyzes were evaluated, the lowest energy consumption values were observed in the combination of pumice brick wall, green roof, and polyurethane insulation materials. In this scenario, the annual fuel consumption per square meter is determined as 30000.6 MJ/m2. On the other hand, the highest energy consumption values were observed in the combination of porous brick wall, tile roof and sheep wool insulation materials. In this scenario, the annual energy consumption per square meter is determined as 30026.6 MJ/m2. Although there are not high numerical differences between the findings, it has been observed that the results give consistent results with the thermal conductivity coefficients of the materials used in the combinations.

Effective wall structures with use of flax straw concretes

The modern building technologies are technologies of green construction, near zero-energy and active buildings with bioclimatic design, optimized energy consumption and CO2 emissions. Prospective enclosing structures of such buildings are structures using available, low cost, and environmentally friendly materials based on plant raw materials. In this paper the evaluation of technical solutions of wall enclosing structures using flax concrete based on lime binder with a density of 300-350 kg/m3 was carried out, taking into account their heating and cooling loads in residential buildings. It is shown that the provision of the necessary indicators of the external walls of energy-efficient buildings is achieved by using multilayer structures with a heat-insulating layer of flax straw concrete or a single-layer structures made from flax straw concrete in frame construction technology.

Bushfire Resistance of Lightweight Masonry Blocks Made with Diatomite Aggregate

‘Diatomite’ is a naturally occurring soft material that contains fossilized skeletal remains of diatoms. It is lightweight, and the porous structure of the aggregate possesses low thermal conductivity. This study was aimed at developing masonry (i.e., cement) blocks using diatomite aggregate and assessing their suitability for use in bushfire shelters and external walls of buildings in bushfire-prone areas. First, the chemical and physical properties of mix components (i.e., cement, sand, and diatomite aggregate) were determined. Then masonry block cement mixes including a cement-sand (i.e., standard) and three different cement-diatomite (i.e., diatomite) mixes were developed by absolute volume method. The properties of fresh mixes; slump and fresh density and properties of hardened mixes; density, compressive strength, and water absorption were investigated, while bushfire and building fire resistance of developed masonry blocks were examined by exposing them to the standard fire curve for 30 min and three hours, respectively. The obtained results from this experimental study showed that diatomite mixes have a negative correlation between the amount of diatomite aggregate and the density and compressive strength, while a positive correlation for water absorption and bushfire and building fire resistance. All the developed diatomite blocks are ultralightweight, loadbearing, and have three hours of building fire resistance. Further, the obtained results were compared with those of the standard and two other previously developed lightweight masonry blocks/mixes using expanded perlite and pumice aggregates. In comparison to the standard and other diatomite, expanded perlite, and pumice blocks, blocks made with 60% of diatomite aggregate are recommended for use in bushfire shelters and other buildings in bushfire-prone areas.

Thermal performance assessment of double hollow brick walls filled with hemp concrete insulation material through computational fluid dynamics analysis and dynamic thermal simulations

Thermal insulation is the most widely used solution to reduce the energy consumption of buildings. In order to minimize the cost and time needed to build an insulated wall as well as to decrease greenhouse gas emissions, this manuscript proposes to incorporate a bio-based insulation material into the air cavities of hollow bricks constituting the external walls of buildings. Therefore, the aim of this paper deals with the assessment of the thermal performance of Moroccan external building envelope constituted of double hollow brick walls filled with hemp concrete and separated by a 5 cm air layer thickness. Three configurations composed of three types of hollow bricks were studied (8-, 12- and 16-holed bricks). Firstly, using numerical simulations based on a two-dimensional Computational Fluid Dynamics (CFD) method, a parametric study was conducted in order to determine which of the three configurations meet with the requirements imposed by the Moroccan thermal building regulation. In terms of thermal resistance R and thermal transmission coefficient U, results have shown that double brick walls with 12 and 16 hemp concrete filled holes were the only configurations meeting the requirements of Moroccan Thermal Regulation. Afterwards, the study was revolved at a whole building scale and a dynamic thermal simulation considering various internal parameters was performed using TRNSYS software. Furthermore, an economic and environmental analysis was conducted and a comparison with Moroccan thermal regulation shows that our results perfectly meet the requirements of this regulation and are more efficient from thermal, economic and environmental perspectives. Finally, the insulation technique used in this investigation can be widely applied around the World and similar thermal performances can be achieved for the case of different regions characterized by the same Mediterranean warm climate considered in this paper.

Experimental study of the influence of external factors on the functionality of a regenerative decentralized ventilation unit

The article presents an experimental field study of the influence of environmental factors on the functionality of a commercial decentralized ventilation device for regenerative utilization of heat from the exhaust air, intended for installation in an external wall of buildings. The experiments included measurements during the winter and summer seasons. Real operating situations with two regenerative heat exchange matrices are presented and tested. The results of the experiments show that the functionality of the ventilation and heat recovery device does not meet the characteristics that the device shows under standard laboratory conditions.

Study on thermal physical detail of gas block wall structure without single source

This article presents the results of theoretical and experimental studies carried out at the physical heat level in a sample of an outer wall with a small block of a non-code gas block in order to improve the energy efficiency of the outer walls of newly built residential and public buildings. As a result of the studies, the overall thermal conductivity resistance of the outer wall consisting of a non-code small block block, the thermal conductivity coefficient of the wall layers, the temperature flow passing through the wall, the temperature in the wall layers and the heat resistance of the wall for the summer season were revealed. The theoretical thermophysical studies carried out are comparable to experimental studies on the wall model, recommendations have been developed to improve the energy efficiency of the external walls of buildings under construction on the basis of modern projects.

Integration of PCM as an external wall layer in reducing excessive heat of building walls

Innovative building approaches, which take advantage of heat energy in buildings, have recently appeared as part of a global effort to save energy. Incorporating phase change material (PCM) into the building envelope helps in reducing energy consumption and regulating energy demand by managing the thermal inertia of designed PCM thermal characteristics. A study was conducted to assess the performance benefits provided by the latent heat of the concrete wall combined with PCM. This study focuses on developing and testing heat barrier performance by incorporating PCM into wall external finishing, i.e. cement plaster and gloss paint. The effect of PCM inclusion in building wall were investigated by experimental work. The results indicate that incorporating PCM into the building wall reduced the surface temperature by up to 9 °C. Furthermore, the application of the PCM in the plaster layer is more reliable in reducing the internal wall surface temperature by a value of 8.1 °C when compared to the PCM in a painted coating. Painted wall panels experienced more significant temperature reduction differences than other wall panels, i.e. 9.2 °C and 9.5 °C, respectively. However, painted wall panels experienced higher internal surface temperatures than external surface temperatures compared to plastered wall panel at night. This could be due to the paint reactions, which are ineffective at releasing internal heat from the building at night. The yearly energy demand is decreased by 64.3% by incorporating PCM to the building wall, with a total annual electricity bill savings of 42.3% (8695.8 kWh yr−1). Therefore, it was concluded that wrapped PCM integrated into plaster layers on external surface building walls could decrease the indoor building temperature and thus contribute to conserving the energy required for an air conditioning system.

An Assessment of External Wall Retrofitting Strategies Using GRC Materials in Hot Desert Regions

Due to urbanization, population growth, and the consequences of climate change, the usage of energy for cooling has increased considerably in recent years. Passive climate measures, on the other hand, could alleviate the situation by reducing energy use in buildings. This study examined the environmental and financial benefits of utilizing glass fiber-reinforced cement in the external walls of a communal social hub building in New Aswan city, taken an example of the hot desert region. Utilizing Design Builder software, the effect of various outside wall alternatives on cooling energy consumption was explored and analyzed. In addition, a cost–benefit analysis utilizing the simple payback period was conducted to aid decision-makers in selecting the most suitable exterior wall materials for public buildings in hot desert regions. Using cement plaster, cement brick, glass wool, and glass fiber-reinforced cement as an outside wall resulted in a significant improvement rate, according to the data. Compared to a typical wall (cement plaster, cement brick, and cement plaster), it can save up to 41% of energy. In addition, it has the lowest simple payback period value when compared to other examined solutions (10.86 years). In general, the results indicate that glass fiber-reinforced cement walls embedded in thermal insulation materials and incorporated into cement brick walls are more energy-efficient in terms of necessary cooling energy and economic viability.

An empirical study on the thermal behavior of rice husk in eco-friendly brick for external walls of buildings

An empirical study on the thermal behavior of rice husk in eco-friendly brick for external walls of buildings

Investigation into the viability of the properties of porous glass-ceramics produced from granite dust and maize cob for use in thermal insulation of external walls of residential buildings

Given the enormous need for cost-effective wall insulation materials in the developing countries and Nigeria specifically, this study, explores the viability of porous glass-ceramics production from granite dust and maize cob using one-step sintering technology. The chemical compositions of the locally sourced materials used including granite dust, ball clay and maize cob were obtained using XRF. 300µm of granite dust and ball clay as well as 425µm of maize cob powder were used. Different amount of granite dust and maize cob powder were mixed with constant amount of a mixture of NaOH and Na2SiO3 in three different groupings to formulate the porous glass-ceramics samples. The formulated samples were uniaxially pressed at 10MPa and sintered in a gas kiln at 850oC for 3 hours. The sintered samples were subjected to experimental tests. The results showed water absorption, apparent porosity, bulk density, compressive strength and thermal conductivity of 25.6%–46.7%, 43.5%–75%, 1.45g/cm3 –1.9g/cm3, 0.7MPa–9.7MPa and 0.11W/m.K–0.53W/m.K respectively. The mineralogical properties of the sintered samples were obtained using XRD. The results indicated a viable material for use in thermal insulation of residential buildings.