English

This paper deals with techniques aiming at reducing noise entering into naturally ventilated buildings while reducing airflow path resistance.The description of the combined experimental and theoretical approach is made. A method is suggested to enable the acoustic and airflow performance of apertures for natural ventilation systems to be designed simultaneously.

Reported symptoms from 2000 workers in air-conditioned offices and from 500 workers in natural ventilated buildings have been analyzed using univariate and multiple logistic regression models.The conclusion of that study is that buildings with air conditioning have a higher prevalence of work related upper respiratory symptoms than buildings with natural ventilation though located in tropical country with high relative and absolute humidity rates all around the year.

The deposition rates of particles in a town-house with a forced air circulation and in-duct filters have been calculated for that study. It appears that the use of central forced-air fan along with in-duct filters allows the reduction of particle concentration. And it is more effective than reducing ventilation by closing windows or making homes more insulated.

The author describes how to improve the usual formula to calculate air flow rate through an opened hopper window.Improvements consist in better taking into account the geometry of such windows when estimating their opened area and also in adapting to this type of windows the model used to take into account the influence of wind and of thermal draught.Improved model gives a good comparison with on site measured data from the literature.

Indoor aerosol particles, their concentration and deposition in displacement, their movements in two ventilated rooms are compared numerically. For the simulation of particle tracks, the discrete trajectory model is adopted whereas the Eularian method is used for solving the continuous fluid flow.

This paper reports mainly on field studies were indoor overnight CO2 levels are monitored along with outdoor ventilation rates in bedrooms where room air conditioners are employed.The results of laboratory experiments using two typical RACs (room air conditioners) are also reported and discussed.

The principle of displacement ventilation involves air supply and distribution in a room by upwards displacement, i.e. as direct as possible through-flow in the occupied zone in order to achieve high ventilation efficiency. In addition, air distribution by displacement generally makes it possible to supply a larger quantity of air than for conventional mixing ventilation, which requires concentrated supply at high velocity.

For that study, the constant concentration dosing method and the decay method were used to test air changes performances in an office equiped with a VAV mechanical ventilation system and in a domestic apartment with natural ventilation . The measurement results from those two tracer gas methods are compared.

There is a resurgence of interest in naturally ventilated offices. Most of the time, cooling the buildings is possible with the opening of windows. Simulations with the softwere TAS were made and showed that window opening allow a sufficient day or night ventilation rate, even if wind characteristics are not favourable. The optimal size, shape and location of the window apertures to reach sufficient ventilation rates has been studied along with the impact of the wind orientation and the building degree of protection on these ventilation rates.

For that study, IAQ measurements were carried out in 3 residential Singapore dwellings. CO2 levels were higher in air-conditioned bedrooms than in naturally ventilated bedrooms. Another survey demonstrated that almost all occupants using air-conditioners while sleeping presented one or more SBS symptoms than when using natural ventilation.