Natural ventilation with a supply air window and motorized skylight: a field study

Fenestration systems that allow air to circulate between window panes, also called ventilated or airflow windows, can be a simple and efficient way to provide or remove air in a building. This contribution presents modelled and experimental results from a field study where a triple-glazed supply air window is installed in the bedroom of a small, airtight house. A motorized skylight in the living room completes this natural ventilation system. Simulations of the ventilated cavity following ISO 15099 reveal an effective U-value 12-26% lower and a heat recovery efficiency of 58-38% when under a natural ventilation regime and a constant airflow of 14.4 m3/s. The temperature and CO2 levels in the bedroom and living room and window air outlet velocity were measured during 2 nights of single occupancy and 2 nights of double occupancy. Experimental data reveal a dynamic airflow through the ventilated window where local wind conditions have a large influence on the airflow. Effective average room ventilation flow rate between 27 and 42 m3/s were calculated with the transient mass method. This ventilation system is simple, silent and provided satisfactory indoor air quality in the building.