https://doi.org/10.6110/KJACR.2026.38.9.481

Min Kyu Bang ; Chan Kyu Kim ; Hyusan Jang ; Yong Min Song ; Seung Hyo Baek ; Myoung Souk Yeo

Recent studies have explored the use of low-temperature water supply heating in district heating systems. However, research on low-temperature water supply heating using condensing boilers in individual heating systems remains limited, despite approximately 52.4% of residential buildings in Korea relying on such systems. This study assesses the suitability of low-temperature water supply for individual heating through comparative experiments conducted in an 84 m² experimental house in Sejong City, evaluating both low- and high-temperature water supply. Performance was measured based on boiler efficiency and the ability to maintain indoor temperatures. The average boiler efficiency for the low-temperature case was 84.4%, surpassing the 78.4% efficiency observed for high-temperature supply, largely due to the condensing zone operating for 96.3% of the total time. Furthermore, the duration of thermal comfort was longer under low-temperature conditions (56.1 hours) compared to high-temperature conditions (43.4 hours). While neither scenario experienced underheating, the high-temperature conditions resulted in greater temperature overshooting, leading to deviations from the comfort range.

https://doi.org/10.6110/KJACR.2026.38.9.489

Jihoo Lee ; Min Su Jeon ; Hee Gang Kim ; Myoung Souk Yeo

Bathroom ventilation has typically prioritized humidity removal and air exchange rates, often overlooking pollutant exposure. This study reassesses bathroom ventilation performance in relation to feces-derived pollutants using a well-mixed model and CFD simulations based on the geometry of an actual apartment bathroom. The findings reveal that the nominal ventilation rate of 80 CMH is inadequate for removing hydrogen sulfide (H2S) in airtight conditions; reduced effective ventilation hinders pollutant removal, leading to a rapid buildup of concentrations that exceed hygiene limits within minutes of use. In contrast, ammonia (NH3) levels remain below guideline thresholds under conditions of fecal-origin emissions. CFD analyses further illustrate that ceiling-mounted exhaust systems, along with buoyancy-driven thermal plumes from occupants, can transport toilet-generated pollutants into the breathing zone, resulting in concentrations up to 40.6% higher than the room average. These results suggest that evaluating bathroom ventilation performance should consider not only nominal ventilation rates but also effective ventilation in airtight conditions and exposure to pollutants in the breathing zone.

https://doi.org/10.6110/KJACR.2026.38.9.499

Jeeyoon Lee ; Sungmin Yoon ; Doosam Song

This study quantifies the impact of climate change on heating and cooling demands across South Korea and explores its implications for envelope U-value standards. Daily mean air temperatures from the Korea Meteorological Administration were transformed into spatially continuous gridded fields using inverse distance weighting. Heating degree days (HDD) and cooling degree days (CDD) were calculated consistently for a baseline period as well as for future periods under Shared Socioeconomic Pathway scenarios. These values were then aggregated to administrative districts to obtain district-level means and projected changes. The results indicate a nationwide decline in heating degree days and an increase in cooling degree days, with more pronounced shifts occurring under higher emissions scenarios and over longer time horizons. This trend pushes many districts toward warmer climate classifications, particularly near current zone boundaries. To address these changes, a framework for revising envelope U-values is proposed. This framework recalculates target U-values based on district-level changes in HDD and CDD to stabilize conductive loads in future climates. A composite indicator that combines HDD and CDD prevents the relaxation of standards based solely on declining HDD, while also accounting for the increasing CDD. The trends of decreasing HDD and increasing CDD remain consistent from the 10th to the 90th percentile.

https://doi.org/10.6110/KJACR.2026.38.9.509

Byeongjun Jang ; Jeyoon Lee ; Sungmin Yoon

As global demand for carbon neutrality rises, fault detection and diagnosis (FDD) in building HVAC systems has become crucial for energy-efficient operation. However, traditional FDD models are often built with manually tuned parameters and do not adequately capture the unique operational characteristics of individual buildings. This study addresses these limitations by proposing a novel method that combines an in-situ modeling approach with a performance evaluation process for fault detection. In this method, fault detection models are automatically generated using site-specific operational data and are continuously calibrated and updated throughout the building's life cycle within a digital twin framework. To validate the effectiveness of this approach, comparative experiments were conducted between models generated by our proposed method and traditional parameter-based models across various fault scenarios. The results show that the models produced by our method consistently demonstrated superior detection performance in all scenarios. These findings indicate that our proposed method not only improves fault detection performance but also supports more adaptive and energy-efficient building operations over time.

https://doi.org/10.6110/KJACR.2026.38.9.523

Jaedeok Ko ; Ji Hwan Jeong

This study examines both domestic and international cases of water-source heat pumps, assessing their effects on energy consumption and greenhouse gas emissions. The findings indicate that these systems significantly reduce energy demand for space heating, cooling, and domestic hot water in the building sector. However, the analysis was hindered by a lack of detailed information on equipment capacity, system configurations, refrigerant types, and annual performance metrics. Additionally, the concentration on specific sectors limited the ability to generalize results. The insufficient verification of long-term performance and maintenance costs underscores the need for more comprehensive data. To enhance policy effectiveness, it is essential to share operational performance information more broadly and implement continuous monitoring. This approach will facilitate the development of reliable, data-driven policies that promote the expansion and improvement of water-source heat pump systems. Such initiatives are vital for reducing carbon emissions in the building sector and achieving national carbon neutrality goals.