The World Health Organization (WHO) announced that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may spread through aerosols, so-called airborne transmission, especially in a poorly ventilated indoor environment. Ventilation protects the occupants against airborne transmission. Various studies have been performed on the importance of sufficient ventilation for diluting the concentration of virus and lowering any subsequent dose inhaled by the occupants. However, the ventilation situation can be problematic in public buildings and other shared spaces, such as shops, offices, schools, and restaurants. If ventilation is provided by opening windows, the outdoor airflow rate depends strongly on the specific local conditions (opening sizes, relative positions, climatic and weather conditions). This study uses field measurements to analyze the natural ventilation performance in a school building according to the window opening rates, positions, and weather conditions. The ventilation rates were calculated by the tracer gas decay method, and the infection risk was assessed using the Wells-Riley equation. Under cross-ventilation conditions, the average ventilation rates were measured at 6.51 h -1 for 15% window opening, and 11.20 h -1 for 30% window opening. For single-sided ventilation, the ventilation rates were reduced to about 30% of the values from the cross-ventilation cases. The infection probability is less than 1% in all cases when a mask is worn and more than 15% of the windows are open with cross-ventilation. With single-sided ventilation, if the exposure time is less than one hour, the infection probability can be kept less than 1% with a mask. However, the infection probability exceeds 1% in all cases where exposure time is greater than two hours, regardless of whether or not a mask is worn. Also, when the air conditioner was operated with a window opening ratio of 15%, power consumption increased by 10.2%.

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Many fuel poverty support programs have been implemented in the world. Energy-efficient retrofitting in low-income households is a main aspect of support programs in the context of energy saving, reduction of greenhouse gas emissions, and improvement of the thermal comfort and health of residents. This study analyzed the effects of an energy efficiency program for fuel poverty in Korea on the thermal comfort of residents. A total of 330 households were investigated wherein energy retrofits had been conducted. Indoor temperatures in the main bedroom and in the living room were recorded twice. The results showed that the average indoor air temperature in the surveyed households was 15.1 ± 3.7 °C, indicating that 95.2% of main bedrooms and 80.0% of living rooms did not meet the recommendations of the World Health Organization regarding temperature. These results indicated that the surveyed households did not use energy for heating their rooms, and an energy-saving effect due to the retrofits was difficult to expect. Accordingly, retrofit building or energy policies addressing fuel poverty are shown to be ineffective in the context of energy saving and thermal comfort in Korea. This article highlights issues that need to be analyzed to evaluate how effective the welfare program is. The results of this study alert policymaker to the need to improve the welfare policy; the methods proposed in this article will help them in their decisions.

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