ventilation

Occupants spend a significant amount of time indoors where temperature and air quality has an important impact on their comfort, health and work performance. Understanding the role of airflow exchange between spaces is crucial to describe the processes of mixing and transport of substances driven by air motion and therefore essential for evaluating indoor air quality. This work presents the results of field measurements and laboratory experiments designed to characterise door operation and to quantify its influence on air volumes exchanged between rooms due to door motion.

The air tightness of ventilation ductwork was measured in two recently built low-energy houses and in two conventionally built houses in the summer of 2013. The ducts and components were metal in three houses and plastic in one house. The air tightness of the ductwork had been checked by an installation survey after construction. The measured leakage airflows corresponded to air tightness class A or lower, therefore did not satisfy the minimum requirement set for class B regarding the air tightness of ventilation ductwork.

The characterization of power-law coefficients of the airflow through ventilation system components and ductwork or building leaks should include corrections on the airflow rate measurement because of two phenomena: a) the temperature and pressure conditions at the flow measurement device may not be the same as those seen by the test object; b) the temperature and pressure conditions experienced by the object may differ from reference conditions. This paper gives the analytical expression of these corrections depending on the air viscosity, air density and flow exponent.

The paper investigates the possibility for using a traditional ventilation system with ceiling mounted diffusers to provide heating under winter time conditions in relatively cold climates – in buildings with low transmition losses such as “passive houses”. The analysis is done through a number of CFD simulations of a simplified office. It is shown that even small over-temperatures reduce the Air Change Efficiency substantially. On the other hand even very small internal heat sources increase the efficiency.

Mechanical positive input and extract ventilation are common strategies employed in English houses, generally because they provide adequate indoor air quality and specifically because they are effective at minimizing mould growth and its associated negative health consequences. Air is either exclusively supplied or extracted (never both) by a mechanical system at a prescribed airflow rate designed to ensure adequate indoor air quality.

The present study aims at investigating carbon dioxide (CO2) concentrations inside elementary schools’ classrooms and how students’ productivity is affected. Measurements were conducted in 9 naturally ventilated schools of Attica from April to May 2013. Monitoring lasted for 7 hours per day, for a period of one to five days per school. CO2 concentrations were monitored simultaneously in the inside and the outside environment of the classrooms. Indoor concentrations of CO2 in almost all schools were higher than the ASHRAE threshold limit values.

Reduction of energy consumption and green house gas emissions of buildings is a great challenge in Europe. In this context French energy performance regulation, RT2012, requires an improvement of the buildings' airtightness. In airtight buildings, ventilation must be perfectly controlled to ensure good indoor air quality.  However, many failures are observed when ventilation systems are inspected (Jobert, 2012). They are mainly due to bad conception, poor implementation and lack of maintenance.

To realize the concept of low-energy buildings, an increase in the thermal insulation performance of building parts, especially the openings that show poor insulation performance, is necessary. In addition, an adequate level of thermal comfort is also needed within residential buildings. We have developed window-applied dynamic insulation (DI), and verified thermal insulation performance in chamber and field tests.

The article describes the results of an experimental campaign carried out at ITC-CNR in outdoor test cells to evaluate the energy performance and the related comfort level achieved through a coupled system made up of a dynamic window and a heat recovery unit.

The mixing of a tracer gas with zonal air was compared between two zones in an unoccupied test building in both the horizontal and vertical direction. A constant injection of sulphur hexafluoride (SF6) tracer gas was released into each zone separately and its concentration was measured at different positions within the zone. Variations in concentration were observed for different horizontal positions in the southern zone indicating incomplete mixing.