Purpose / Context –The purpose of this study is to investigate indoor environment and energy saving performance of houses, which employ passive ventilation systems, built in mild climate region and hot humid region in Japan.

Methodology / Approach – In this study, investigation of passive ventilation systems, such as passive stack ventilation systems and solar heating panels, have been conducted by two steps. The first step is real measurement of indoor environment and heating energy in houses employing passive ventilation systems. The second is analysis of total primary energy consumption of heating, cooling and ventilation by using a computational program based on the extended heating degree method.

Results – From the measurement results, a passive ventilation system can be used in the regions from the viewpoint of the indoor environment. From the calculations results, a passive stack ventilation system with a self regulating damper yields less energy than typical mechanical ventilation systems. It is confirmed that a solar heating panel have a positive effect on heating energy reduction even in hot humid region.

Key Findings / Implications – In mild climate region, indoor environment of the house employing a passive stack ventilation system have almost met the reference values of the Act on Maintenance of Sanitation in Buildings in Japan. A solar heating panel works well as an assistant heating system on houses even in hot humid region. In mild climate region and hot humid region, a passive stack ventilation system which is generally adopted in cold climate regions can be used with less energy by employing a self regulating damper than typical mechanical ventilation systems.

Originality - In mild climate region and in hot humid region, where passive ventilation systems are generally not employed in housing, primary energy consumption and indoor environment of houses employing passive ventilation systems are evaluated by real measurement and computational calculations.

 Keywords - Passive Ventilation, Domestic Ventilation, Mild Climates, Hot Humid Climate, Primary Energy Consumption