Walls Of Residential Buildings Research Articles

Numerical models for the analysis of shear walls in light steel residential buildings

AbstractIn recent years, the use of steel light housing structural solutions made of cold‐formed thin‐walled profiles (CFS) is becoming increasingly popular. Lightness, high structural efficiency, durability, rapidity and simplicity of erection of the building and its finishes are some of the main advantages of these systems, which make them attractive and competitive with respect to more traditional constructional solutions. In these buildings, which do have a skeleton made of cold‐formed steel profiles completed by sheathings made of various materials, the key role of transmission of both vertical and horizontal loads from the floors to the foundation, is played by the shear walls. Recently, the University of Trento carried out a project aimed to develop an industrialized housing system made of CFS members. In this framework, experimental and numerical studies of the in‐plane lateral response of shear walls were performed. In particular, this paper summarizes first the experimental program and then it focuses on the main features of numerical models and on their validation in both monotonic and cyclic regime. The critical parameters governing the response of these complex systems are finally identified and discussed.

Proposals for standardization the heat transfer resistance of insulated walls of residential buildings in the Republic of Belarus

Introduction. Resistance to heat transfer is considered the main criterion of energy operational efficiency in the design of enclosing structures of buildings and structures. Therefore, the calculation of the values of the normalized resistance to heat transfer, for each locality of the Republic of Belarus, taking into account the actual outdoor temperatures and the duration of the heating season is an urgent task.
 Materials and methods. To assess the energy efficiency of enclosing structures, the value of annual heat losses Q, kWh/m2, through 1 m2 of the structure was adopted. The calculation of the values of the normalized heat transfer resistance for each locality of the Republic of Belarus, taking into account the actual outdoor air temperatures and the duration of the heating season, was carried out according to the method recommended by V.G. Gagarin. A comparative analysis of the results obtained according to the methods recommended by TCP 45-2.04-196-2010* and SP 50.13330.2012 is carried out.
 Results. The calculations determine the values of the normalized heat transfer resistance for each locality of the Republic of Belarus, taking into account the actual outdoor air temperatures during the heating period and the duration of the heating season. To facilitate the design of insulated walls, a map of the recommended (calculated) values of the heat transfer resistance of the external walls of residential buildings for the territory of the Republic of Belarus is constructed.
 Conclusions. According to the results of the performed studies, it was found that the economic efficiency in the design of insulated walls according to the method recommended by TCP 45-2.04-196-2010*, depending on the region of the Republic of Belarus for which the design is being carried out, is on average from 6 to 8 BYN per 1 m2 of insulated wall.

Research on envelope design of ultra low energy consumption passive building in severe cold area

At present, the common solid clay brick structure is widely used in residential building walls, which leads to higher indoor humidity, serious energy loss, waste of economy, environmental pollution and lower people’s comfort. The passive technology of ultra-low energy consumption can improve the insulation performance of the enclosure, reduce the energy consumption of heating and improve the comfort of the owner, and finally achieve the goal of energy saving of low energy consumption buildings in the cold area.

Regional climate effects on the optimal thermal resistance and capacitance of residential building walls

Energy efficiency in residential buildings can be improved considerably by optimizing the allocation of thermal resistance (R) and capacitance (C) of external walls. However, it is difficult to identify which RC allocation yields the minimum heat loss or heat gain for a given climate region, due to a lack of understanding of how regional climate affects optimal RC allocation. In this study, we determine the effect of the climate characteristics on the development of optimal RC allocation by combining the RC network model and the particle swarm optimization algorithm, taking five representative climates in different Chinese cities as examples. The energy efficiency potential and the ratio of heating to cooling load are introduced to comparatively analyse the energy savings after optimization for the five cities. The results indicate that the energy efficiency potential of residential buildings in Harbin is the largest, ranging from 6.2% to almost 20.6% for different total building capacitance. In Harbin, Beijing and Kunming, the energy efficiency potential is larger than those in Guangzhou and Shanghai, which is attributed to the larger heating to cooling load ratio of the former than that of the latter. An approximately linear relationship between the energy efficiency potential and the ratio of heating to cooling load is also built to fast predict the maximum energy savings for any given climate regions. This study could serve as useful references for the optimal design of thermal resistance and capacitance in different climate regions to save energy of residential buildings.

Fuzzy-stochastic model to assess defects in low-rise residential buildings

Understanding the severity level of defects in buildings can help project managers to take appropriate corrective actions. The objective of this study is to assess the severity of defects in low-rise residential buildings and develop a stochastic model for predicting the likelihood of occurrence of various categories of defects. The defects data for ground floor slabs and walls were extracted from engineering inspection reports of 252 residential buildings in Melbourne, Australia. The analyses were then carried out using Fuzzy Synthetic Evaluation (FSE) and Monte Carlo Simulation (MS) techniques. The outputs of the FSE showed that the severity index of the floor cracks was found to be 3.05 with the equivalent linguistic term of ‘slight’ or 1–2.0 mm in size. Similarly, the severity index of wall cracks was found to be 3.01 with the equivalent linguistic term of ‘slight’ or 1–5.0 mm in size. This indicates that the severity level of defects in floor and wall is low. Likewise, the findings of the simulation analysis revealed that the probability of occurrence of floor cracks with width ranging from 2 to 4 mm is 40.9%, and the chance of occurrence of wall cracks having widths ranging from 5 to 15 mm is 73.6%. The proposed models can assist the regulatory bodies and construction supervisors to assess the probability of occurrence and severity of the building defects in the ground floor slabs and walls of low-rise residential buildings. Further, this study contributes to the body of knowledge by proposing methods to assess defects in buildings.

Analysis of the application of external walls with a screen and an air gap

The article presents the results of the analysis of the investigated external walls of residential buildings with a screen and an air gap in a dry hot climate. The preferred distance between the wall and the screen was set equal to 30–40 cm. With these thicknesses of ventilated air layers, the air temperatures at the wall surfaces behind the screen did not differ from the outside air temperature. An air gap is formed in the process offorming by metal inserts by hollow formers, which are removed after the concrete has hardened. The production of such panels requires special molding equipment of the factory technological lines for the production of external wall panels.

Impact of Wall Constructions on Energy Performance of Switchable Insulation Systems

This paper evaluates the potential energy savings when switchable insulation systems (SIS) are applied to walls of residential buildings located in Belgium and other locations in Europe. The study considers two low-energy prototypical dwellings (an apartment and a detached house) that are representative of post-2010 constructions and renovations in Belgium. Using an 3R2C-based analysis tool, the performance of both dwellings is evaluated with static and dynamic wall insulation systems. First, the switchable insulating system is described along with its associated simple 2-step rule-based control strategy. Then the modeling strategy and simulation analysis tools are presented. In Belgium, it was found that SIS-integrated walls allow energy savings up to 3.7% for space heating and up to 98% for cooling. Moreover, it was found that to further reduce the energy consumption of SIS-integrated buildings in various European climates, thermal mass placement needs to be considered. By optimizing the placement and the parameters of the various wall layers, it is possible to increase the space heating savings by up to a factor of 4 and those of cooling by up to a factor of 2.5.

Durability of interlayer connections in external walls in precast residential buildings

The work concerns the procedure of examination and assessment of the condition of external curtain walls used in typical prefabricated residential construction systems at the end of the 20th century in Poland. External partitions were formed from a concrete structural layer, thermal insulation made of expanded polystyrene or mineral wool with variable thickness and a layer of textured concrete. The insulating and texture layers were attached to the structural panel through connectors known as “hangers”. The durability of the exterior barrier, planned at the design stage for 50 years, is determined by the effectiveness of the execution of both concrete layers’ connections. The technical condition of more than one hundred buildings assembled in the large-panel technology was carried out after 35–50 years of operation, usually prior to the thermo-renovation of the buildings planned by the users or before the end of the designed period of use. Various research techniques were used, non-destructive testing has allowed to limit the required number of destructive tests. The test results, assessing actual physical and mechanical parameters of the materials used for the construction of connections, permitted to build calculation models and verify the effort state of structural elements. As a result of the research, calculations and analyses, a concept of effective reinforcement of threatened connections was developed. In addition, recommendations regarding effective testing of interlayer connections that are difficult to reach were formulated.

Technical and economic analysis of a solar air heating system integration in a residential building wall to increase energy efficiency by solar heat gain and thermal insulation

Buildings are the major energy consumers, especially when they are located in severe climatic conditions where the energy requirements for heating and cooling are very high. Implementation of renewable energy sources in buildings to reduce their energy consumption and thus the fossil fuel consumption is a priority measure to reduce energy bill costs and greenhouse gas emissions, respectively. Although the initial cost of purchasing and installing renewable energy systems remains high, the costs associated with the operation and maintenance of these systems are negligible. This study aimed to analyse the integration of renewable energy sources in the building sector, namely the solar air heating system (SAHS), to assess the techno-economic-environmental performance of this system on reducing building energy consumption, economic benefits, and greenhouse gas emissions reduction. The paper analyses the annual efficiency of the SAHS integration into the building envelope, in a temperate-continental climate, with hot summers and cold winters. Finally, the proposed SAHS system was evaluated against the natural gas boiler heating system. The results of the financial analysis showed that the simple payback period of SAHS investment will recover in a period between 14 years to 5 years when the subsidies granted by the state are between 0% and 50%. The SAHS proposed here is economically feasible for the weather conditions and the building geographical orientation analysed and system implementation is a good solution to reduce buildings’ energy consumption by using renewable energy. The results show that the implementation of SAHS efficiently reduces, depending on weather conditions, the dependence on fossil fuels by reducing the thermal energy need to heat the building by a minimum of 15.53% in 2011 and a maximum of 24, 68% in 2007. Installing SAHS on the building wall, it will reduce the building heat loss through the wall, achieving a lost heat recovery at a rate ranging between 9.8% and 12.51%. Besides the economic benefits, the paper also highlights the environmental benefits of reducing CO2 emissions. Thus, the use of this system will reduce yearly CO2 emissions, depending on weather conditions, between 38 t CO2/year (2014) and 44 t CO2/year (2007).

Modulating thermal load through lightweight residential building walls using thermal energy storage and controlled precooling strategy

Precooling is a recognized technique for reducing cooling energy in buildings during peak hours by shifting load to off-peak hours. This technique is particularly effective in buildings with high thermal mass, because of their large thermal energy storage capacity, and in commercial buildings due to their variable electricity pricing based on time-of-use rates. Precooling in residential buildings has been a matter of limited interest in the past because of their low thermal mass and typically uniform electricity pricing rate. While previous studies on precooling primarily focused on cost savings, an important aspect of precooling is the thermal load modulation, which could be very effective in managing peak demand in lightweight residential buildings integrated with thermal energy storage systems. In this study, we examine different precooling strategies to manage the heat gains in lightweight building walls integrated with phase-change materials. We create nine different precooling profiles by controlling the interior temperature, and then evaluate the influence of the precooling profiles on four key building energy performance parameters: total heat gain, peak heat gain, maximum heat gain during peak hours, and time at which peak occurs. To thoroughly understand the fundamental physics, we first consider hypothetical climates and obtain the optimal precooling strategy required to achieve maximum peak shedding and shifting while minimizing the total heat gains. We then extend the model to Baltimore, Maryland, and estimate the benefits of the optimized precooling strategy under real conditions. The optimal precooling strategy proposed in this study can shift the peak heat gain by up to 14 h, thereby reducing the heat gain during peak period by up to 95%, at the expense of 23% increase in the total heat gains.

Experimental and numerical investigation on innovative masonry walls for industrial and residential buildings

This study proposes efficient exterior concrete walls (consisting of blocks, mortars, and plasters) to reduce the heat transfer to or from buildings for minimizing energy consumption due to air conditioning or heating processes. Different blocks were treated by partially or totally replacing coarse and fine aggregates with insulation materials. Mortars and plasters were also treated by partially replacing sand with certain insulation materials. A control block (without treatment) was also produced with three-row rectangular cavities to reduce the effective thermal conductivity. Experimental tests were performed to determine the thermal conductivity of blocks, mortars, and plasters, and to validate a developed three-dimensional model (using ANSYS-Fluent program). The model results showed a substantial increase in model accuracy (about 15%) by involving the estimation of radiation heat transfer in the block cavities. The thermal and economic performance of treated masonry walls showed that the optimal performance was obtained from a wall having volcanic scoria-treated blocks (200-mm thick) and 15% vermiculite-treated mortar (10-mm thick). The thermal performance was enhanced by 15% and 318% (for thermal resistance increase) and 13% and 76% (for heat flux reduction) more than those of the control and market walls, respectively. Adding 15% vermiculite-treated plaster (2 × 15-mm thick) to the wall enhanced the thermal performance remarkably. The total cost of the improved wall (having the highest thermal resistance) was reduced by 1.39 and 3.67 times over the control and market walls (Dhahran, Saudi Arabia), respectively. This improved wall is a promising candidate for exterior walls in residential and industrial buildings.

Analysis of dynamic thermal performance of the walls in residential buildings in Serbia

In this paper, analysis of dynamic thermal performance of multilayer insulation wall in residential buildings in Serbia is performed. Considering that the final goal is to build a residential structure with the highest level of efficiency, that is, with the lowest energy consumption for heating and cooling, it is necessary to determine good thermal characteristics of a multilayer wall. The first type of walls, which were analyzed had the same structure with different thicknesses of individual layers. The second type of analyzed walls had the same structure, but the thermo-insulating layers occupied different positions. The third type of walls had different structures, but the same total thickness. Based on the results presented in the paper, it can be concluded that in walls with similar structures, the same total thickness and different thicknesses of individual layers, there are differences in the external temperature variation shift. The position of the thermal insulation layer for the same wall structure does not significantly affect the change in temperature oscillation caused by the change in the outside temperature. Changing the wall structure, however, has significant influence on the thermal capacity. This analysis offers the possibility to choose the optimal solution for the wall structure with the highest energy efficiency.

Water-resistant gypsum expanded-clay concrete technology

The results of studies on the technology of preparation and hardening of the expanded-clay concrete under various conditions, prepared on the basis of a water-resistance complex gypsum binder (CGB), are presented. It is shown that CGB-based expanded-clay concrete can be used to erect the outer walls of residential and civil buildings. The optimal preparation methods and temperature and humidity conditions for hardening water-resistance CGB-based expanded-clay concrete are given.

Fundamental Properties and Thermal Transferability of Masonry Built by Autoclaved Aerated Concrete Self-Insulation Blocks.

This paper performed a detailed study on the fundamental properties and thermal conductivity of autoclaved aerated concrete (AAC) self-insulation block, and the mechanical properties and heat transfer resistance of the AAC self-insulation block masonry. Different kinds of joints and the plastering surface were used to build the masonry specimens. The distinctive feature of the blocks and mortars is the lower thermal conductivity with expected strength. Compared to those with larger thickness of insulation mortar joints, the masonry with thin-layer mortar joints had better compressive performance and lower shear strength. The compressive strength of masonry was related with the block and mortar strengths, the shear strength of masonry along mortar joints was related with the mortar strength. The stress–strain relationship of masonry in compression could be predicted by the similar expression of conventional block masonry. The tested heat transfer coefficient of AAC self-insulation block masonry with thickness of 250 mm without plastering surfaces was (0.558 ± 0.003) W/(m2·K). With the plastering surfaces, the heat transfer coefficient reduced by 4.4% to 8.9%. Good agreements in values of heat transfer coefficient existed by using the test, theoretical computation and ANSYS (ANSYS Inc. Canonsburg, PA, USA) analytical methods. Based on the extensibility analyses, the heat transfer coefficients of AAC self-insultation block masonry with different thickness are proposed. The best thickness is proposed for the outer walls of residential buildings in different cold zone to meet the design requirement of energy conservation.

INVESTIGATION THE EFFECT OF OUTDOOR AIR INFILTRATION ON THE HEAT-SHIELDING CHARACTERISTICS THE OUTER WALLS OF HIGH-RISE BUILDINGS

The influence of infiltrating outdoor air on the thermal protection characteristics of the exterior walls of modern residential and public buildings is considered. The review of sources devoted to this problem confirmed its relevance at the present time, especially for high-rise buildings. The authors of the article analyzed the influence of longitudinal and transverse air infiltration on the thermal protection characteristics of the outer wall of a 25-storey building built in Samara. The results of the calculation showed a significant decrease in the reduced resistance to heat transfer of the outer wall when air infiltrates through it. To confirm the calculated data, the results of a full-scale study of external walls are presented. Based on the results of the study, general recommendations are given for the interior decoration of the exterior walls of high-rise buildings.

We need to talk about timber: fire safety design in tall buildings

The construction industry is characterised by ignorance, indifference, and lack of clarity on roles and responsibilities. There is a culture across the sector which can be described as a ‘race to the bottom’. There is insufficient focus on delivering the best-quality building possible. This, in May 2018, is how Dame Judith Hackitt described the UK construction industry – with her specific focus on buildings. Her interim report, Building a Safer Future, was intended as ‘a call to action for an entire industry’ – recognising that ‘true and lasting change will require a universal shift in culture'. The UK government’s immediate response to Hackitt was to ban combustible materials for use in the external walls of residential buildings with a height greater than 18m3. The government’s impact study in support of the ‘ban’ explicitly identified that the engineered timber industry would see significantly reduced growth due to post-Grenfell regulatory changes. Has the use of a material that has been increasingly of interest to the tall building industry suddenly been ‘scuppered’? Why was mass timber not included within the government’s list of exemptions? It would surely have been easy to draft some text to exempt timber from the ban.

Optimization of Insulation Thickness of External Walls of Residential Buildings in Hot Summer and Cold Winter Zone of China

It is important to reduce primary energy consumption and greenhouse gas emissions associated with residential buildings in the hot summer and cold winter (HSCW) zone of China. Changing the insulation thickness of the external walls of residential buildings (ITEWB) is regarded as an effective way to manage such problems within a budget. This paper aims at developing an innovative way to select the optimal insulation thickness of external walls for residential buildings (OTWRB) in the HSCW zone of China, considering economic, energy and greenhouse gas emissions issues associated with the ITEWB. Four different cities and two different operation modes of the air conditioners (continuous and intermittent) are considered in this study. To explain the selection process, typical hypothetical buildings are simulated in Wuhan, Changsha, Hangzhou and Chengdu. Expanded polystyrene is chosen as the material of the insulation layer while split air conditioners are selected as the equipment for space heating and cooling. Integrated Environmental Solutions-Virtual Environment is used for the dynamic operational energy consumption of buildings. Life cycle cost method is adopted to calculate the economic impact of ITEWB on building performance. The Chinese life cycle database is used to quantize the impacts of ITEWB on building performance in the aspect of energy and greenhouse gas emissions based on the life cycle theory. The most appreciated insulation thickness is chosen from the thickness range of 30 mm to 150 mm. We find that for continuous operation mode of air conditioners in Wuhan, the optimal economic insulation thickness is 70 mm, whereas when considering only energy and environmental aspects, the OTWRB is 150 mm. These are all larger than the current insulation thickness which is 30 mm. When the weighting efficiencies of the economy, energy, and greenhouse gas emissions are different, the OTWRB varies from 70 mm to 150 mm for continuous operation mode. The different cities have little influence on the OTWRB while the different operation modes of air conditioners have some influence on the OTWRB.

АНАЛІЗ ПРОТИПОЖЕЖНИХ ЗАХОДІВ У КОНСТРУКЦІЯХ ЗОВНІШНІХ СТІН ІЗ ФАСАДНОЮ ТЕПЛОІЗОЛЯЦІЄЮ ТА ОПОРЯДЖЕННЯМ ШТУКАТУРКОЮ

Метою роботи є аналіз протипожежних заходів у конструкціях зовнішніх стін із фасадною теплоізоляцією та опорядженням штукатуркою, а також аналіз особливостей їх облаштування, враховуючи досвід інших країн. Розглянуто та проаналізовано види, конструктивні особливості, призначення та функції протипожежних поясів та обрамлення віконних (дверних) прорізів, виконаних з негорючих матеріалів, які влаштовуються в конструкціях зовнішніх стін із фасадною теплоізоляцією та опорядженням штукатуркою. Наголошено на значну роль протипожежних поясів та обрамлення віконних (дверних) прорізів із негорючих плит з мінеральної вати у забезпеченні пожежної безпеки будівельних об’єктів. Зроблено висновки про те, що в Україні на національному рівні в нормативних документах процедура облаштування протипожежних поясів та обрамлення навколо віконних та дверних прорізів недостатньо технічно описана (розкрита), що призводить до випадків неправильного трактування цих вимог або взагалі їх нехтування.

Optimal Design of Wall and Ceiling Structures According to the Mechanical Safety and Comfort of the Internal Environment

The article describes an approach to the optimal design of load-bearing structures of walls and ceilings, taking into account not only the factors of strength and stiffness, but also the internal environment of the premises. The problem of optimization of structural systems, taking into account safety, reliability and comfort is currently particularly relevant. Most scientific studies consider each factor separately, which can lead to deterioration of both the functional process in the premises and the onset of the risk of an emergency. An evolutionary modeling scheme is proposed, which operates with discrete sets of parameters and allows to obtain design solutions of minimal cost based on a joint integrated consideration of strength, deformability, thermal protection and acoustic comfort of walls and ceilings. The minimization of the structures cost is assumed as a goal function. Stresses, strains, thermal resistance to heat transfer and the value of airborne sound insulation index are considered as active constraints. Two problem statements are considered. The first one takes into account the design of walls according to the criteria of strength and heat engineering, and the second one is the design of the ceilings with ensuring strength, stiffness and acoustic comfort. Examples of the optimal design of the residential building walls and floors with regard to the conditions considered are given.

Analysis of physico-chemical processes under maintenance of masonry enclosing structures

Technical condition of exterior brick walls of Ufa residential buildings built in 40-70s together with defects and damages detected is assessed herein, diagnostics of both physico-chemical and physico-mechanical values for serviceability of structures of 40s, 70s and 2000s is made. The expected protection mechanism is proposed to be used in every considered level of rehabilitation to maintain the residual service life and to increase serviceability of damaged residential building walls. The proposed levels of rehabilitation have been tested in cities of the Republic of Bashkortostan under the Program for total renovation of multi-apartment residential buildings.