Off-site construction (OSC) offers a promising means to improve the efficiency of construction projects. However, the lack of experience and knowledge regarding its use results in errors in design owing to conflicts and omissions of considerations for OSC projects. To mitigate these problems, the design for manufacturing and assembly (DfMA) is widely used to include the considerations in the OSC design process. Several studies concerning the DfMA application in OSC have been performed, but the comprehensive design process is not suggested for mitigating the aforementioned problems. This study proposes an OSC design process by integrating the fragmented DfMA considerations reported in previous studies. The considerations are identified through a systematic literature review and classified into structural and architectural types. To validate the proposed process, an OSC project design has been undertaken as a case study, wherein a significant portion of the building structure has been modified to comprise precast concrete (PC), instead of its reinforced counterpart, with a demonstrated reduction in the PC element design duration. The proposed process would guide and support the design process for reduction in the duration and errors incurred in the process. Moreover, the process can be considered a design guideline for the execution of future projects.

Modular construction, which involves factory-based modular unit manufacturing followed by installation at a construction site, has been recognized as one of the sustainable construction methods. Its advantages are known to be implemented through (1) standardized design, (2) standardized production method, and (3) large-scale development (mass production system). These three conditions are basic requirements for modular construction market expansion, but it is difficult to define that these conditions are a prerequisite for judging whether modular construction applied or not. Nevertheless, public development companies in regions or countries where modular construction has just begun thought that modular construction should meet all three conditions that are suitable for applying public construction projects. This is because it is difficult to compare conventional construction projects with similar conditions to modular construction projects. This paper analyzes the cost and duration data of three small-scale public construction rental housing (PCRH) projects involving modular construction in Korea. These cases presented herein include a public college student dormitory, public low-rise rental housing, and public mid-rise rental housing in small-scale development projects. Those were applied not standardized design (common design and regulation), but were reflected in each project’s demands (different design and regulation). To compare it, this paper analyzed 91 public housing provision projects’ construction data from 2011 to 2017 from one of the public rental housing provision companies in Korea. Among them, 19 small-scale public rental housing data were extracted for comparing with modular construction project data. The results show that, even if not standardized, the design and production process, and modular construction durations, were more effective—but costs were similar or expensive. Based on the conclusion drawn from three cases, this paper presents important considerations for the application of modular construction in other small-scale public construction rental housing projects from the perspective of public development companies.

Thermal bridges in building envelopes can cause significant heat loss and heat gain. In this study, the developed thermal bridge breaker was applied to an interior insulation finishing system in residential buildings to minimize the thermal bridges in building envelopes. To investigate the thermal and energy performance of the developed thermal bridge breaker, the surface temperatures and heat flow at the wall and floor junctions were predicted using Physibel. In addition, the heating and cooling energy consumption in a residential building was analyzed by EnergyPlus. As a result, the use of the thermal bridge breaker can minimize the effective thermal transmittance in the building envelope system. Moreover, when the building envelopes were equipped with the thermal bridge breaker, the heating and cooling load through the exterior walls was decreased by 15–27%. Thus, the thermal bridge breaker can play an important role in minimizing the heat loss and occurrence of condensation in building envelopes.

The public housing demand in Seoul has been continuously increasing, but the available land for housing is insufficient. To meet the demand, the Seoul government is planning to develop small-scale housing in urban areas through various methods. Construction activities for increasing housing capacity cause negative environmental impacts, and this inevitably leads to an increase in the number of civil complaints. The complaints can be mitigated by using offsite construction (OSC) for fabricating components. However, OSC remains underdeveloped in Korea owing to concerns over high project costs. To promote OSC, the government must develop a long-term plan to secure demand for OSC. For such a plan, the number and feasibility of applicable sites in Seoul must be estimated. This study suggests a two-stage research framework: (1) estimate the number of applicable sites in Seoul using GIS and (2) conduct feasibility analyses of these sites through architectural planning. The estimated number of sites was equal to the expected supply of small-scale housing units in Seoul for 8 years, and the selected case sites were identified to be feasible. Therefore, the use of OSC for developing small-scale housing units in Seoul is reasonable. This research differs from previous studies in that the previous use of qualitative studies to promote modular construction was replaced with a quantitative analysis that included the entire Seoul area. Using the research framework, the Seoul government can develop a specific long-term plan based on the quantitative research analysis. Furthermore, manufacturers can develop plans based on the government plan and deliver returns on the higher initial costs. The contractors can reduce the higher project cost and doing so is expected to mitigate the negative perception and to promote modular construction in Korea.

The NOx removal performance of photocatalytic construction materials is demonstrated using two experiments under indoor and outdoor environments: (1) A photoreactor test was conducted to assess the NO removal performance of construction materials (e.g., coatings, paints and shotcrete) using a modified ISO 22197-1 method; (2) A water washing test was conducted using two specimens enlarged to the size of actual building materials and artificially exposed to NOx in a laboratory to analyze NOx removal performance. For (1), the UV irradiation of the outdoor environment was analyzed and the experiment was conducted in an indoor laboratory under UV irradiation identical to that of the outdoor condition. Photoreactor tests were conducted on construction materials applied to actual buildings located in Seoul, South Korea. In (2), the enlarged specimen was used for a field experiment by applying a modified method from the ISO 22197-1 standard. On sunny days, the NOx removal performance (3.12–4.76 μmol/150 cm²·5 h) was twice as much as that of the ISO 22197-1 standard specification (2.03 μmol/150 cm²·5 h) in the real-world. The washing water test results indicated that general aqueous paint achieved a NOx removal of 3.88 μmol, whereas photocatalytic paint was superior to 14.13 μmol.

An external wall panel (EWP) as a novel alternative to provide spatial flexibility and improve the performance of external walls was developed. The purpose of this study was to analyze the thermal performance of this EWP. A simulation analysis was carried out to scrutinize whether it was vulnerable to condensation, considering South Korea’s weather conditions, and find countermeasures to prevent this. Results indicated that the indoor surface temperature with the measures of added insulation materials and an inserted thermal-breaker was over 16.5 °C and that these methods could prevent condensation. In addition, this study assessed unsteady-state thermal characteristics, linear thermal transmittance, and the effective thermal transmittance of EWP. Effective thermal transmittance was estimated in consideration of the heat transmittance of EWP and the linear thermal transmittance of its slabs and its connection parts. The thermal characteristics of the building envelope are needed to analyze effective thermal transmittance and linear thermal transmittance-associated thermal bridges.