A household unit of an existing apartment in which residents lived was selected, and the indoor air quality in each space of the unit was measured for analysis. Analysis of the measurement data indicated that the concentration of carbon dioxide (CO2) constantly increased beyond 1000 ppm when a resident stayed indoors for an hour or more. Specifically, the concentration of CO2 increased when the resident was asleep to a level wherein negative impacts on health were observed. Moreover, the inflow of particulate matter (PM) was mainly caused by natural ventilation from the outside rather than the behavior of indoor residents, which generated an insignificant amount of PM. This study proposes a new ventilation system for solving the above-described problems. According to the system, when a window is closed, the window cavity created between a new frame and the existing frame is utilized as an air path for ventilation. The application of this system ensures a stable amount of ventilation through forced ventilation and prevents the inflow of external PM. Moreover, this system was designed to recover indoor heat through the window cavity and facilitate the pre-heating of outdoor air through heat collection based on solar radiation during the day.

The objective of this study is to establish boundary conditions to evaluate the cooling capacity of the Cooling Radiant Ceiling Panel (CRCP) considering the environment of a room equipped with the CRCP. The current study investigated the boundary conditions and derivation techniques from previous studies. Based on the results of the analysis, a heat transfer model was derived for a room fitted with CRCP. In addition, the heat transfer model was used to derive the factors affecting the cooling capacity of the CRCP and each factor was simulated and verified through this model. The effects of these factors on the capacity of the CRCP was established by using various boundary conditions. To verify the validity of the simulation model, the experimental results were compared with the cooling capacity for a specific case. As a result, it was established that even for the same panel, there was a variance in the cooling capacity of the CRCP based on the boundary conditions and that the influence of the surface exposed to the outdoors had more implications. Consequently, this study presents the influence factors to be considered when designing CRCP.

In order to expand the zero-energy building, it is necessary to evaluate the economic feasibility of the passive and active elements applied to achieve the zero-energy building. The purpose of this study is to verify the final energy consumption and investment cost of a building according to the change of passive and active elements. In this study, the final energy consumption was calculated by region for the passive element S/V ratio (surface-to-volume ratio), the building’s orientation, and the active element (building-integrated photovoltaic) for the Department of Energy reference building type using simulations. In addition, the change in investment cost according to changes in energy consumption and production was calculated. As a result of the study, it was reasonable to invest in passive elements rather than active elements in the central region of Korea, and it was confirmed that investment in active elements was highly economical in the southern region of Korea. It is expected that the results of this study can be used as a guideline to enable the economic analysis of design elements in the design of zero-energy buildings.

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The thermally activated building system (TABS) can reduce the peak load by integrating with the ground heat exchangers. When integrated, the cost of groundwork and stability of the ground temperature would counteract because the weather conditions would influence the ground temperature in shallow depth. However, previous studies on TABS assumed constant ground temperatures such as average outdoor air temperature. In this study, ground temperatures in different depths are simulated for their detailed investigations, and simulated results of ground temperature were applied to building energy simulations for observing the load-handled ratio (LHR), representing the peak load reduction by TABS evaluated in various weather conditions. Simulation results of ground temperatures from 1 m to 39 m depths show that the temperature stabilized at 2 m to 11 m depths depending on the characteristics of the outdoor air temperature. LHR increased as the ground depth increased because the ground temperature at shallow depths increased during peak hours. Ground depths of 8 m were found ideal for maintaining consistent LHR for all weather conditions. Detailed observation of ground temperature and its effect on LHR in various weather conditions can help system engineers design and operate the TABS with the ground system.