Measurements of ventilation airflow from pivot and side hung opened windows

¹ Building Services, Lund University, Box 118, 221 00 Lund, Sweden
² Energy and Building Design, Lund University, Box 118, 221 00 Lund, Sweden
³ Building Physics, Lund University, Box 118, 221 00 Lund, Sweden

^* Corresponding author: dennis.johansson@hvac.lth.se

Abstract

HVAC systems have the purpose of improving indoor air quality in buildings to enhance appropriate occupants’ comfort, health and good productivity. Window airing may be one measure to consider in the absence of occupant control of the ventilation and by that, we mean occupants opening windows and doors. Approximating the volume of air exchanged during window airing is important in understanding the necessary durations needed for adequate airing and minimizing heat loss during the heating season as the need to reduce heat losses in buildings becomes more acute. There is theory describing ventilation airflow caused by wall openings, but they usually refer to holes or simply hung windows, and do not cover pivot hung windows. This paper aims to investigate and present ways to quantify the amount of air that comes into a room when a modern Swedish pivot hung window is opened during the airing, comparing it with a side hung window with or without an open door adjacent to the window. Using elevated temperature sensors, and CO₂ tracer gas, measurements were conducted in two different study rooms and settings. The room air was proliferated with CO₂ gas to 4 000 PPM and room air heated to temperature differences of between 16 °C and 25 °C relative to the outdoor air temperature. The window was then opened, and CO2 decay were monitored. Results show that there, as expected, are significant differences in volumes of air exchange between room and outdoors occur with window opening angles going from 10° to 30° while continuing to 90° doesn’t increase the airflow as much as expected. The rate of air exchange is also increased when the door into the room is opened. It is also evident that a side hang window allows for more air exchange volumes compared to pivot hung window at low opening angles. The obtained airflow is finally compared with the common theory. It can be seen that for a pivot hung window, the airflow increases rather linearly to half the opening angle, while for a side hung window the airflow increases fast in the beginning of the opening and much less happens at high angles.