ventilation effectiveness

These Guidelines recommend the ventilation required to obtain a desired indoor air quality in a space. The first step is to decide the air quality aimed for in the ventilated space. A certain air quality is prescribed to avoid adverse health effects while a decision is required on the level of perceived air quality aimed for in the ventilated space. Three different comfort levels are suggested. The next step is to determine the pollution load on the air caused by pollution sources in the space.

Mixing and displacement ventilation are common systems in commercial buildings, while mixing ventilation is used in residential buildings. Displacement ventilation provides fresh air to the occupied zone in a more efficient way than mixing ventilation but it is important to know how well it works with a floor system for heating or cooling. Can, for example, a floor heating system warm up the supply air too fast and destroy the displacement effect?

The aim of that guidebook (74 pp), published by REHVA is to provide a clear analysis of the definitions of ventilation effectiveness and to present case study examples

The ordinary displacement ventilation system (DV) needs large installation spaces for large supplydiffusers with lower supply air velocity to avoid the draft discomfort at the foot level, and large supply airvolume to control allowable vertical temperature gradient within the occupied zone. Furthermore, theDV is difficult to heat without other warming means in the winter. The swirling induction type HVACsystem (SWIT) was developed as utilizing a compact air diffuser increasing the induction function bymeans of swirling air jets.

In this paper, the indoor environmental quality for the commuter train space was analyzed for assumingthe load factor of seat capacity to be a parameter of analysis. Especially flow fields, temperature and airquality distributions in vehicle space were analyzed by using CFD technique. Furthermore, it reports onthe result of examining the controllability of indoor climate in the vehicle when the displacementventilation system was applied in it.

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.

Investigations in six car parks were carried out. Measurements of carbon monoxide levels were made during the peak hours to compare the performance of the different types of ventilation systems : the performance is better with a combined supply and exhaust system than the exhaust only system though more energy is consumed.

In experimental chambers, the ventilation effectiveness and thermal comfort of a task ventilation system has been investigated. The method and results of the experiment are presented in this paper. The conclusion of that thermal comfort survey is that task ventilation systems maintain the occupants thermally comfortable while saving energy.

For that study, 60 person have been tested to compare their response to personalized ventilation and mixing ventilation. The benefits presented in human response were obtained with the personalized ventilation system. The results could be improved with a further development of ventilation effectiveness.

In this study, serial environmental measurements in 12 large buildings in Taiwan have been made to control the air exchange efficiency on the indoor microbial contamination. High levels of airborne microbes seem to be more easily observed in buildings equipped with fan coil unit system than with air handling unit system.
Adequate filtration of fresh air intake should be imperative to control effectively microbial contaminations of outdoor origin.