Analysis of Passive cooling and heating potential in Vietnam using Graphical Method and Typical Meteorological Year weather file

This paper studies the potential to improve thermal comfort in Vietnam thanks to passive
strategies. First, a thermal comfort zone for the Vietnamese is proposed by using the PMV-PPD
heat balance model of Fanger and the effects of adaptive mechanism of the people living in
tropical hot humid region. Then, the comfort zone is enlarged using the algorithms proposed by
the authors to calculate the effects of the passive heating and cooling strategies. Typical
Meteorological Year (TMY) weather data are used for graphically printing of hourly
environmental parameters on the psychrometric chart and for climate analysis, subsequently. The
limitation and the scope of this method are also specified. Results of this study show that in all
climatic zones of Vietnam, natural ventilation is an efficient cooling solution, low-cost and easy to
apply. Thermal comfort improvement of natural ventilation strategy varies with the climatic zones,
increasing from 17.1% in Hanoi, 21% in Danang to 31.4% in Hochiminh city. Meanwhile, passive
solar heating is not really effective since winter in Vietnam is usually not too cold and the
capacity of the passive solar collector system is usually limited. Direct evaporative cooling also
has a great cooling effect compared with that of natural ventilation, but significant humidity
augmentation in the air in hot and humid conditions may be inappropriate. Seasonal analysis
reveals that natural ventilation gives higher performance than other methods and is particularly
effective in mild seasons. During 12 months in Hanoi, the analysis clearly shows significant
contribution of natural ventilation in the period from April to October during which comfort
period achieved might vary from 30% to 81%. The combination of all passive strategies
considerably improves thermal comfort: 22.6%, 31.7% and 47.6% of total time in Hanoi, Danang
and Hochiminh city, respectively. Finally, the findings of this study indicate that conventional
heating and cooling methods are also needed during extreme weather conditions in summer and
winter, especially in Hanoi.