Natural ventilation and thermal comfort in public buildings

Indoor air quality and building’s thermal comfort depend very much on a ventilation system. At the same time they have an influence on health and well- being of users of buildings. The users prefer the natural ventilated spaces. The running costs of naturally ventilated buildings are smaller than the running costs of mechanically ventilated buildings. However, the construction costs of the naturally ventilated buildings could be bigger. Public buildings could be ventilated naturally,

but the natural ventilation has its limits. The main rule for designing the natural ventilated spaces is to minimize the heats gains and indoor air pollution, and to expose the hygroscopic building’s components and the components with the high thermal capacity.

The temperature and the other air quality components would be more variable in naturally ventilated buildings than in air conditioned buildings. This is the reason, why the natural ventilation rather cannot be used in the buildings and the buildings parts, where the indoor climate parameters have to be constant. The thermal comfort in the naturally ventilated buildings should be assessed by the adaptive comfort model. The adaptive comfort model, relates indoor climate parameters to the outdoor conditions, and take into account the adaptation capacity of the users. The ventilation systems in the buildings located in moderate climates has to work at least in three scenarios: spring-autumn, winter and summer. The natural ventilation systems the best work in spring-autumn scenario. Winter scenario has to take into account the heat losses caused by the intake air. In summer, it could be difficult to maintain the continuity of the natural ventilation and to preserve the building from overheating. The night cooling could be used in periods of the occurring of the high outside temperatures. The effectiveness of the night cooling depends on the limitation of the heat loads, the building’s thermal mass and the night air temperature.

The natural ventilation systems require integrated planning. From the very beginning, architects, structure engineers, HVAC designers and the other specialists should work together on the design of the naturally ventilated building. This requirement, the limitations of the natural ventilation and the higher construction costs are the reasons why investors oft prefer the air condition or mixed mode systems.