Residential Buildings In Korea Research Articles

Neural network-based nonintrusive calibration for an unobserved model in digital twin-enabled building operations

The digital twin (DT) model is the key to enabling DT-enabled applications and services by mathematically expressing the physics, dynamics, and indoor environment of a target building. However, the DT model may provide substandard performance owing to various operational uncertainties; as such, in-situ calibration is essential in building operations. This study proposed a neural network-based nonintrusive calibration (NNNC) method for a DT prediction model. A field application study was conducted on a prediction model developed for a district heating substation serving real residential buildings in Korea. The case study demonstrated (1) the operational uncertainty of the prediction model and (2) the dependence of the calibration accuracies on different indirect calibration approaches. The NNNC method showed a better calibration accuracy for the target prediction model than existing Bayesian inference-based nonintrusive calibration. Specifically, NNNC, using a correction function with a multi-layer perceptron, reduced the prediction model errors by 38.6% and 34.7% for bias and random errors, respectively. The results demonstrate the effectiveness of NNNC in DT-enabled building operations. Therefore, the NNNC ensured the applicability and reliability of the prediction model.

Comparison of Heat Treatments by Floor Heating and Fan Heating for Bed Bug Control

Background: Non-chemical methods are as important as pesticides to control bed bugs. The most effective method is heat treatment. Underfloor heating is widely used in residential buildings in Korea, and the benefits of floor heating can be utilized in heat treatment for bed bug control.Methods: Simulations of indoor air flow and heat transfer were performed to compare and analyze the temperature distributions with different heating methods for bed bug control using floor heating and fan heater methods.Results: Even though the average indoor temperature of floor heating was lower, it was more uniform with floor heating than that of fan heating under the assumed conditions. Local cold spots disappeared with the floor heating method.Conclusions: It was confirmed that floor heating has advantages over fan heating to achive uniform high temperatures during heat treatment for exterminating bed bugs.

Simultaneous in-situ calibration for physical and virtual sensors towards digital twin-enabled building operations

Digital twin-enabled building operations heavily rely on a building sensor network to collect operational data. Virtual sensing, in combination with physical sensors, has great potential in establishing a reliable and informative sensing environment. However, physical sensors can experience hardware errors or systematic errors due to the working environment within building systems. Virtual sensors are also subject to their model uncertainties arising from input physical sensor errors and changes in system operations. These virtual sensor errors have a negative effect on the in-situ calibration accuracy of corresponding physical sensors. To address these issues, this study proposes a simultaneous in-situ calibration (SIC) method designed to calibrate multiple physical and virtual sensors with varying errors in the context of digital twins. The SIC problem is mathematically formulated, including two types of distance functions (direct and indirect) and defining correction functions to calibrate various types of virtual sensors (such as backup, validation, replacement/virtualization, and observation sensors). Importantly, the proposed method tackles the challenges posed by the unknown calibration environment in operational systems. A field application study was conducted for two physical sensors and three different virtual sensors operating in a district heating substation serving real residential buildings in Korea. The case study shows how the different calibration accuracies for each sensor depend on the calibration approaches, such as physical-targeted (existing Case 1), virtual-targeted (existing Case 2), and simultaneous calibration (novel Case 3). Under the simultaneous errors, only Case 3 satisfied the reference accuracy for all sensors. Specifically, the average MAEs in Case 3 were improved by approximately 79.3%, 75.3%, 63.9%, and 87.5% for the target physical sensor, backup virtual sensor, virtualized sensor, and validation virtual sensor, respectively, compared to the accuracies before calibration. These results demonstrate the importance and effectiveness of simultaneous in-situ calibration of physical and virtual sensors in digital twin-enabled building operations. The proposed calibration can contribute to the synchronization of physical and virtual building systems, thus achieving reliable and informative virtual sensing-driven digital twins.

Experimental analysis of airtightness performance in high-rise residential buildings for improved code-compliant simulations

Recently, the government of Korea announced a green remodeling policy to improve building energy efficiency and achieve the zero energy goals by 2030. As a result, the insulation performance of residential buildings has been enhanced every 2–3 years for the past 10 years. However, the airtightness performance has been revised once only for windows and doors. Also, energy modelers in practice still use a predetermined and fixed infiltration value for code-compliant energy simulations in the design stage without any differences in air leakages. Currently, a few articles investigated measured data of air leakage rates for high-rise residential buildings in Korea. Thus, typical code-compliant models may not represent realistic airtightness performances, especially in retrofits that were built in different construction years (i.e., the 1990s to 2010s). In this study, we performed the experimental analysis of the airtightness in residential buildings in Korea. The blower door tests were conducted in twelve representative households in the capital area. The results were compared to the previous measurement studies, and specific metrics were calculated to confirm the characteristics of influential factors on airtightness in residential units. The measurement showed that the airtight performance of the recently built residential buildings has improved by about 3–4 times compared to the residential buildings built 30 years ago. The identified airtightness in this study will provide better knowledge for designers and engineers to develop more accurate residential energy models for code compliance.

Energy usage and cost analysis of passive thermal retrofits for low-rise residential buildings in Seoul

This study focuses on the energy performance of low-rise residential buildings and on the technological improvements required to improve their performance. As most low-rise residential buildings in Korea are old, they are being renovated to improve their energy efficiency. However, as renovations are expensive, the government intends to apply low-cost energy-efficient technologies that are currently in use as well as quantify their performances. To this end, low-rise residential buildings in villages were selected for the survey; among these, five buildings were evaluated for the application of energy-efficient technologies. Based on the survey, which included information on the actual energy consumption, the reliability of the simulation analysis was verified, and the effects of the technologies were evaluated. The survey focused, in particular, on the airtight performance of the implemented technologies, the efficiency of the heating equipment, and the insulation performance. Moreover, the performances were validated quantitatively by actual measurements. As a result, the energy saving for each technology were evaluated, and the corresponding annual savings were calculated. Finally, the payback period of the investment was evaluated using economic analysis.

Verification of Energy Usage Based on Standard Building Model Development of Low-Rise Residential Buildings in South Korea

The energy consumption of low-rise residential buildings in South Korea exceeds the targets set in national policies and the standards of other countries. Moreover, there are insufficient policies in place to improve the energy performance of existing low-rise residential buildings and no means to investigate the current status. A standard model enables cost-effective and fast load forecasting and can also be used to establish long-term policies through evaluation of energy saving in buildings before and after the application of energy policies. This study developed a standard model for predicting energy consumption by reflecting the characteristics of low-rise residential buildings in Korea. The standard model was developed based on reliable related standards, national statistical data, and national reports, and the energy variables applied were validated through a sensitivity analysis. Surveys and field measurements were conducted to investigate the energy usage of 70 households in low-rise residential buildings in Korea, and the developed model was validated through comparison with the actual energy usage data. Consequently, the total energy consumption error rate was 12.67% (R2 value: 0.8164), with a significance level higher than 80%, which indicated that the developed model was highly efficient and reliable.

Cost assessment model for sustainable health and safety management of high-rise residential buildings in Korea

ABSTRACT The accident rate in the Korean construction industry is much higher compared to the one in other industries. One of the main reasons for this problem is the health and safety management cost (HSC) estimation method which does not reflect the project features at construction sites. In Korea, health and safety management cost is estimated by applying a legally designated ratio in proportion to construction cost without reflecting construction features, such as the building’s shape, number of floors, and construction period. However, such a method does not fulfill the cost for the gradually strengthening safety management of high-rise residential buildings. Therefore, the objective of this paper is to develop a cost assessment model for sustainable health and safety management of high-rise residential buildings. For this purpose, actual data of 23 completed projects were collected and analyzed to identify problems and influence factors of HSC assessment and to establish a regression model. By applying the model established for five new sites as a case, its validation was verified. The results of this study will be utilized as reference data for the HSC estimation method and its relevant policy establishment.

Statistical Methodology for the Definition of Standard Model for Energy Analysis of Residential Buildings in Korea

This study was conducted to propose an optimal methodology for deriving a standard model from existing residential buildings. To strategically improve existing residential buildings, it is necessary to identify standard models that can be used as quantitative standards. In this study, a total of six methods were established for different algorithms in the dimensionality reduction and clustering stage of the data preprocessing stage. In addition, a total of 22,342 households’ data were analyzed, and a total of 26 variables were used to perform cluster analysis. The process of method 6 (data pre-processing, principal components analysis, clustering [K-medoids], verification) was proposed as a way to derive the standard model from the existing Korean housing. The method proposed in this study is capable of deriving a number of standard models considering all variables (n) in a single analysis. The representative building derived in this study contains a lot of building data, so it can be effectively used for planning and research related to buildings on a regional and national scale. In addition, this process can be applied to various buildings to derive representative buildings.

Seismic Fragility of Ordinary Reinforced Concrete Shear Walls with Coupling Beams Designed Using a Performance-Based Procedure

The seismic performance of ordinary reinforced concrete shear walls, that are commonly used in high-rise residential buildings in Korea (h < 60 m), but are prohibited for tall buildings (h ≥ 60 m), is evaluated in this research project within the framework of collapse probability. Three bidimensional analytical models comprised of both coupled and uncoupled shear walls exceeding 60 m in height were designed using nonlinear dynamic analysis in accordance with Korean performance-based seismic design guidelines. Seismic design based on nonlinear dynamic analysis was performed using different shear force amplification factors in order to determine an appropriate factor. Then, an incremental dynamic analysis was performed to evaluate collapse fragility in accordance with the (Federal Emergency Management Agency) FEMA P695 procedure. Four engineering demand parameters including inter-story drift, plastic hinge rotation angle, concrete compressive strain and shear force were introduced to investigate the collapse probability of the designed analytical models. For all analytical models, flexural failure was the primary failure mode but shear force amplification factors played an important role in order to meet the requirement on collapse probability. High-rise ordinary reinforced concrete shear walls designed using seven pairs of ground motion components and a shear force amplification factor ≥ 1.2 were adequate to satisfy the criteria on collapse probability and the collapse margin ratio prescribed in FEMA P695.

Evaluating recycling potential of demolition waste considering building structure types: A study in South Korea

This study investigates the recycling potential of demolition waste (DW) according to building structure, while considering environmental and economic aspects For that, this study surveyed 1,034 residential buildings in Korea immediately before demolition to collect reliable information on demolition waste generation rates (DWGRs). This study classified the removal stages of buildings into the demolition, collection and sorting, transportation, and disposal stages. This study suggested a method for carbon emissions calculation for each stage and carried out an inventory analysis. The economic value of recycled DW materials was also calculated. Furthermore, the recycling potential was calculated based on the economic value and the environmental load for the current scenario, i.e., the current waste recycling rate in Korea, and the maximum scenario, i.e., the maximum theoretical recycling rate. Regarding building structures, the recycling potential of wooden structures was the highest in both the scenarios. However, masonry-block structures showed improved recycling potential in the maximum scenario. Regarding DW types, the recycling potential of plastics was the highest, with plastics from reinforced concrete (RC) structures showing 6.6 times higher recycling potential than those from wooden structures. And the possibility of improving the recycling potential was higher for glass and plastics than aggregates, timber, and metals. Through the above research, this paper devised an approach that can be used to plan a detailed construction and demolition waste management strategy, considering building structures and DW types, and this method can also be applied to other regions and countries.

Field measurement on the particle concentrations and exposures in five residential buildings in Korea

This study measured five apartments in the Daejeon. There is higher fluctuation for ambient air particle conditions. The average PN (particle number) concentrations was 5.2x108/m3. There are differences between five sites because of fluctuation for ambient air conditions. Particle concentration has different each occupant schedule. I/O ratios were different by occupancy schedules. Indoor particles exceeded 0.7 μm was significant emitted indoor activities. This result comes from two reasons. 1) Penetration by envelopes. 2) Indoor sources by occupants’ activities. PN decay rate (a+k) were 0.49-4.29 h−1 during indoor peak events. Total emitted particles (σ) was 0.0136.15 x 1013 particles per events. The cooking generated PN were wide range because of different event conditions. The ventilation rate is not enough to remove particles.

Exploring residential experiences of female immigrants in Korea

ABSTRACTDespite the rapid growth of multicultural families, few studies have been undertaken about the residential experiences of foreign-born residents. As examining the residential experiences of migrants allows better understanding the assimilation processes of foreign-born residents, this study examines housing satisfaction and factors affecting residential location choices of female immigrants and their families. By interviewing 25 female immigrants living around Ansan, an ethnically diverse city in Korea, this study finds that there was a large gap between current housing status and preferred housing, thereby leading to low levels of housing satisfaction among female immigrants. Regarding, residential location choices, proximity to co-ethnics, neighborhood ethnic composition, services for multicultural families, job opportunities, and availability of low-cost housing were related to residential location choices of female immigrants. Additionally, given finding that female immigrants preferred living in an apartment (i.e., a housing complex with high-rise residential buildings in Korea) and in an integrated neighborhood, this study predicts that boundaries between where foreign-born residents are concentrated will shift toward where native Korean residents are concentrated.

Analysis of Heating and Cooling Loads of Electrochromic Glazing in High-Rise Residential Buildings in South Korea

This study compares the impact of the recently developed electrochromic glazing technology on load reduction by comparing it with the double-glazing and shading devices that are sold commercially for high-rise residential buildings in Korea. These buildings are similar to large office buildings in terms of their high window-to-wall ratio. The energy consumption of such buildings was simulated using an analytical model of a high-rise residential building. The patterns between the heating and cooling loads were found to be similar to that of office buildings, in that the cooling load was considerably higher than the heating load. This study hypothesizes that the load reduction performance of electrochromic glazing with variable solar control and high solar radiation rejection is superior to that of existing double-glazing products and shading devices. This hypothesis was tested by analyzing the cooling and heating loads of buildings with different types of double glazings. Bleached electrochromic glazing exhibited lower transmittance than colored glass double glazing, low-e double glazing, and double glazing with a shading device, and is thus not effective in reducing heating load. Colored electrochromic glazing provided higher solar radiation rejection than colored glass double glazing and low-e double glazing, and thus is effective in reducing cooling load.

A Study on Potential of Engineered Wood for 9-story Office Buildings

The need for eco-friendly building materials such as engineered wood has increased to reduce carbon emissions. Although the range and height of engineered wood buildings are gradually increasing in North America and Europe, engineered wood is mainly used for low-rise residential buildings in Korea. In order to reduce carbon emissions more, therefore, it needs to expand the use of engineered wood by applying it to various buildings with different uses or more stories. With this background, the aim of this study is to investigate the applicability of engineered wood for 9-story office buildings. Since a 9-story building with engineered wood only is not allowed in KBC, an example building has RC ordinary shear walls as the lateral force resisting system while engineered wood is only used for gravity load resisting moment frames. Another example building is also used for comparison where both lateral and gravity load resisting systems are designed by RC. The applicability of engineered wood is investigated by comparing the seismic performance and the amount of carbon emission of both buildings. The result shows that the seismic performance of both buildings was not significantly different while the amount of carbon emission of the engineered wood building was much less then the RC building. Based on this result, engineered wood is sufficiently applicable to 9-story office buildings even though it still needs to pay attention to the shear design of reinforce concrete walls.

A Study on CO<sub>2</sub> Emissions in End-of-Life Phase of Residential Buildings in Korea: Demolition, Transportation and Disposal of Building Materials

Architecture and building industry have been made diversified efforts to create a construction environment that promotes resource recycling. Many studies have been done to better understand and reduce energy consumption and CO2 emissions throughout a building’s lifecycle. However, to promote sustainable development and a construction environment that facilitates resource recycling, more understanding and research is needed on energy consumption and CO2 emissions during the stage of dismantling a building. Noting that, this research investigates CO2 emissions in a building’s End-Of-Life (EOL) phase that includes dismantling of a building, transport and disposal of the waste generated in the course of dismantling residential buildings in Korea. According to the results of this study, CO2 emissions in a building’s EOL phase was 3,561kg CO2/100m2 for apartments, 3,184 kgCO2/100m2 for brick houses and 1,137 kg CO2/100m2 for wooden houses. The results showed that transport and disposal process of demolition waste accounts for 90% of all CO2 emissions in a building’s EOL phase. From this finding, it is necessary to have a proper, effective strategy for transport and disposal of demolition waste from dismantled buildings’ in order to reduce CO2 emissions during a building’s EOL phase.

Levels and sources of neighbour noise in heavyweight residential buildings in Korea

Indoor noise level is a significant factor for occupants’ health, comfort, and psychological well-being in residential buildings; hence the World Health Organization (WHO) recommends guidelines for residential buildings based on the 24-h sound levels. However, only few studies have examined 24-h noise levels and sources from neighbours. Consequently, 24-h noise measurement is necessary for understanding noise level and acoustic comfort in homes. Field measurements were performed in 26 residential apartments in Korea to investigate levels and types of noise from neighbours. Noise recordings were carried out at each residence in unoccupied conditions. The recordings were analysed at 1min intervals in terms of the A-weighted equivalent (LAeq) and maximum sound pressure levels (LAFmax) for three different time periods during the day. It was found that 20 apartments met the recommended WHO guidelines during the daytime (07:00–23:00). However, at night (23:00–07:00), eight apartments were in excess of the WHO guideline value in terms of LAeq while LAFmax exceeded the WHO limit level in 22 apartments during the night. Human footsteps, movement of furniture, and dropping of small items were found to be major sources accounting for approximately 80% of all the noise events. LAFmax of children’s jumping and dropping small items were greater than others. Adults’ walking showed larger variation of noise levels than other sources. Moreover, it was found that indoor noise levels were not affected by slab thickness and major noise sources.

Seismic performance of a 10-story RC box-type wall building structure

The purpose of this study is to evaluate the seismic performance of high-rise reinforced concrete (RC) box-type wall structures commonly used for most residential buildings in Korea. For this purpose, an analytical model was calibrated with the results of the earthquake simulation tests on a 1:5 scale 10-story distorted model. This calibrated model was then transformed to a true model. The performance of the true model in terms of the stiffness, strength, and damage distribution through inelastic energy dissipation was observed with reference to the earthquake simulation test results. The model showed high overstrength factors ranging from 3 to 4. The existence of slab in this box-type wall system changed the main resistance mode in the wall from bending moment to tension/compression coupled moment through membrane actions, and increased the overall resistance capacity by about 25~35%, in comparison with the common design practice of neglecting the slab´s existence. The flexibility of foundation, which is also commonly neglected in the engineering design, contributes to 30~50% of the roof drift in the stiff direction containing many walls. The possibility of concrete spalling and reinforcement buckling and fracture under the maximum considered earthquake (MCE) in Korea appears to be very low when compared with the case of the 2010 Concepcion, Chile earthquake.

Field measurements of infiltration rate in high rise residential buildings using the constant concentration method

It is very important to identify and measure the amount of infiltration in a building because the infiltration affects indoor air quality and heating and cooling load in buildings. However, no information is available on infiltration in high rise residential buildings in Korea. Therefore, the infiltration rates of 45 units of Korean residential buildings were measured using the constant concentration method with tracer gas. The purpose of this study is to examine the infiltration rate of residential buildings according to the area of the unit, level of the unit, the seasonal conditions, and presence of exterior windows to balconies. The measurements were simultaneously conducted at the low, middle, and high level unit in the same building over 24 h. The infiltration rate was measured by season and the average infiltration rate was about 0.2 ACH during the summer and autumn and 0.6 ACH during the winter. The infiltration rate according to the level shows that the infiltration rate tends to be higher in low level units during autumn and winter. Infiltration rates increase as the difference in indoor and outdoor temperatures increases. During winter in Korea, the difference in indoor and outdoor temperatures is approximately 20–30 °C and the infiltration rate varies from 0.3 to 1.2 h−1, which is much higher than in other seasons.

공동주택에서의 플러쉬아웃 현황 및 개선방향을 위한 연구

Volatile organic compounds in buildings from finishing materials, adhesives, built-in furniture, etc. can cause headaches, atopic dermatitis, etc. for occupants in the buildings. To mitigate this, the Korean government has obligated to flush out the buildings after new construction and before occupancy since 2011. In this study, the current status of performing flush-out in multi-family residential buildings in Korea were analyzed, and its improvement would be proposed. At first, a questionnaire survey was conducted to figure out the current status of flush-out performances targeting a number of construction companies who have already constructed multi-family residential buildings with compliance of the obligation. Through the analysis of this survey, several conditions that need to be improved for flush-out were identified. Secondly, the identified conditions were evaluated in varying conditions using a simulation program to figure out an effective way of performing flush-out rather than as it is. As a result, a flush-out performance period with an appropriate supply air volume, and indoor temperature and humidity were identified to be improved through the survey, and it revealed through the simulation that the flush-out should be performed at least 14 days to reduce the indoor air pollution more than a half.

제로카본 그린홈의 실내 열환경 및 난방에너지 사용량 평가

In total 80% of new residential buildings in Korea are multi-residential buildings. Compared with Europe, where most residential buildings are low-rise, there are a lot more households that live in these high-rise buildings in Korea. In this research, energy consumption rates were measured for 15 households in an eight-story apartment tower, named Zero Carbon Green Home (ZCGH). Three types of experimental conditions were considered in this research regarding the ZCGH: 1) households with controlled heat but with no residents, 2) household with residents, and 3) vacant household. Temperatures measured in the living room and the bedroom of each unit were compared and analyzed with the aim to understand the effect of occupancy within the households. In order to observe the change in indoor temperature in an unheated condition, the experiments were carried out without the boiler operation. With the use of energy consumption data recorded within the energy monitoring system, different energy consumption pattern was observed based on the size and location of each household. In considerance with the amount of wood pellets used for the boiler, the heating energy consumption amount in ZCGH was compared with the conventional apartment. The analysis results derived from this experiment will provide fundamental data to design high-rise apartments with the appropriate passive strategies and to distribute zero-carbon homes in the future.