In recent years, natural ventilation systems have been attracting greater attention as an approach to reducing building energy consumption. As a result, naturally ventilated building designs have been increasingly applied, even for large office buildings. In Japan, mid-seasonal outdoor air has a wide temperature variation range. Therefore, determining the appropriate ventilation opening area for the introduction of natural ventilation is an important factor in achieving energy saving and comfortable indoor thermal environment. In this paper, we describe the influence of the natural-ventilation opening area on the energy-saving performance of the natural ventilation system. The influences are studied in three phases : 1) analysis of the load characteristics in mid-season, 2) proposal of pre-estimate method using ventilation opening area heat balance equation ; and 3) simulation analysis using The BEST program. We propose a method for predicting the required opening area from the adaptive room temperature range and for determining the mid-season load characteristic using the heat balance equation. In determining the required opening area, the analysis results indicate the importance of natural ventilation operating hours, load reduction, the indoor thermal environment, and the introduction of the outdoor air temperature. The BEST simulation results indicate that the total operating hours of the natural ventilation system range from 602 to 782 h. The natural-ventilation system heat-load removal rate is 35 to 85 MJ/m²a.

This paper constitutes Part 4 of a series of studies on a radiator combined with plastic pipes for air conditioning. We propose a design concept for a radiant cooling and heating system composed of a heat pump, radiators combined with plastic pipes, and a ventilation system with an air-liquid heat exchanger. First, we develop the air-liquid heat exchanger for air dehumidification and preheating of the ventilation air. In cooling mode, the rooms can be dehumidified. In warming mode, a suitable blown-air temperature from the exchanger can be maintained. These results show that the exchanger works well for residential use. Next, we propose the vertical air blowing of the ventilation system above the radiators. The proposed design contributes to the improvement of the indoor thermal environment.