To predict the thermal and indoor air quality performance of vertical displacement ventilation systems using two-zone modeling, it is necessary to account for the different nature of the air flow due to thermal and contaminant mixing within these zones. Two zone modeling of vertical displacement ventilation was performed assuming piston flow in the clean zone, uniform mixing in the dirty zone, and no recirculation between the zones except via heat source plumes.
The role of ventilation in the housing stack is to provide fresh air and to dilute internally-generated pollutants in order to assure adequate indoor air quality. Providing this ventilation service requires energy either directly for moving the air or indirectly for conditioning the outdoor air for thermal comfort. Different kinds of ventilation systems have different energy requirements. Existing dwellings in the United States are ventilated primatiy through leaks in the building shell (i.e., infiltration) rather than by mechanical ventilation systems.
The major objective of the IEA task XIII project is to design and construct low energy dwellings which should be technically and economically realistic in the period 2000-2010. The design criteria for the Belgian dwelling are the following: - low energy demand for heating purposes; - good thermal comfort conditions, as well in winter as in summer with attention to the problem of overheating; - very good airtightness (n50 <= 1 h^-1); - good indoor air quality conditions; - attractive design for majority of potential clients; - only use of realistic technical solutions.
The importance of natural ventilation, typically restricted to residential buildings application, is rapidly increasing also within the commercial buildings. This is mainly due to the energy savings expected from a reduction of the use of the forced ventilation. Moreover, the remote control of the indoors, provided by means of the intelligent buildings features, allows an easier management of the environmental quality. Furthermore, the indoor air quality is also directly affected by the air exchanges obtained by natural ventilation.
Under-estimating the ventilation flow rate results in increased sanitary risks and damage to the existing building structure. Over-estimating ventilation flow leads to energy waste. In this context, a number of approaches have been designed to determine indoor air quality indicators. The aim of these is to compare comfort and sanitary quality in different atmospheres. This document presents four air quality indicators developed by three French teams and one Danish team.We examine the strengths and weaknesses of each design, plus their specific areas of use.
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