Plenum airflow distribution and its influence on the performance of a diffuse ceiling ventilation

Abstract

Implementation of diffuse ceiling ventilation (DCV) is slowly gaining momentum and applications in building ventilation have taken off with countries like Denmark, Finland and Netherlands taking the lead in Europe. However, DCV is yet to gain a foothold in Sweden and so not many installations are known, and their performance in relation to Swedish building practice is not yet established. A school in southern Sweden was subsequently renovated and two classrooms were equipped with a sound-absorbent suspended ceiling compatible with DCV. DCV has possible benefits for educational environments including improved thermal comfort as well as lower costs and noise levels. However, it is currently still unknown how supply conditions in the plenum affect the diffusion of air and resulting conditions within the room. To assess airflow characteristics and whether these influence flow conditions in the classroom, we investigated and compared the performance of DCV with two different supply conditions in the plenum. Air speeds and temperature distribution measurements in the plenum and classroom were performed with constant temperature anemometers and thermocouples respectively. The general observation from this study and the system setup herein is that airflow and temperature characteristics in the classroom were independent of the airflow conditions in the plenum. Further investigations in a controlled climate chamber are recommended to investigate and optimise system performance in accordance with Swedish building practice.

On the Performance of Diffuse Ceiling Ventilation in Classrooms: A Pre-Occupancy Study at a School in Southern Sweden

“…No structural beams were present, only exhaust ventilation service ducts, as seen in in Figure 1B, and wiring cables for electrical installations (sensors and ceiling lights). These had no influence on airflow distribution in the classroom [41].…”

“…Other countries have adopted or implemented the systems in commercial buildings with research and case studies in Denmark, Finland, and the Netherlands [24,28]. The advantages for the use of diffuse ceiling ventilation in Sweden may include low cost of installation (reduced ductwork), low risk of draft (airflow diffuses through the ceiling into the occupied zone) and ability to use low supply plenum temperatures (low outdoor temperatures in Sweden can be used) [3,18,24,[28][29][30][31][32]34,41]. These stipulated benefits underpin the need to investigate DCV application in Sweden.…”