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efficient cross ventilation. This envelope design approaches can increase ventilation
rates, distribute the air stream well in occupancy zones and consequently reduce the use
of electrical equipment such as fans, resulting in an energy-efficient home solution.
Even when natural ventilation can be used as a passive strategy just for a short number
of hours during the whole year, the natural ventilation rule of thumb must being
considered as a main variable during the house design decision-making process. It is
crucial for taking important decisions and adopting simple architectural strategies such
as orienting the house according to the predominant wind direction, using short distance
between inlet and outlet opening, large opening, using an open plan layout or spreading
the program layout organization. The natural cross ventilation efficiency is rigorously a
function of the wind characteristics, especially in hot and humid climates or tropical
weather in general. However, as the wind is a variable parameter but openings have
noisy environment as a drawback, a flexible ventilation system should be considered.
The potential of the upward-airflow ventilation system applied to a naturally cross
ventilated tropical house is discussed and two architectural components are analysed:
a) Sawtooth roof geometry and b) On-floor air diffusers by a naturally pressurized
plenum. Analysing both architectural components is interesting due to their implicit
aesthetical and functional potential in the house design. But, more than their aesthetical
appeal, both components have a considerable function in the upward natural cross
ventilation efficiency.
The leeward sawtooth roof geometry is fundamental for increasing the pressure gradient
along the building surfaces (Gandemer & Barnaud 1989). The sawtooth roof geometries
analyzed here are similar to the designed by the Brazilian Architect João Filgueiras
Lima, “Lelé”, and analyzed previously by (Perén 2006). More details about these leeward
sawtooth roof geometries are given in section 2.
Moderately pitched roof is characteristic of the tropical building style which also includes
wooden construction with wide roof overhangs, screened verandas, and screened
fenestration. For the current study, a typical tropical house was selected. The two-storey
house with sloped roof, large eaves and elevated on piles is a typical tropical house as
those built at the Quarry Heights military reservation near Balboa, Panama, Republic of
Panama (the former Panama Canal Zone). The selected building is an excellent
example of the architectural style designed, constructed and employed by the Isthmian
Canal Commission (ICC) during the construction period 1904-1914 (Enscore et al.
1996). The main architectural characteristics of this tropical house are shown in figures
1- 4.
The square two-story house with a full-height wraparound veranda along the front façade
has wide, overhanging eaves, screened porches, and strategic ventilation openings
suited to the warm tropical climate. The original roof is a turquoise-color galvanized
corrugated iron, moderately pitched (rising 15.24cm for every 30.48cm of horizontal
length) (Enscore et al. 1996).
Our main goal is to describe the potential of the upward-airflow ventilation system and to
highlight the relevance of the leeward sawtooth roof geometry for increasing natural
ventilation efficiency, which is part of the authors´ ongoing research concerning the
impact of the building geometry on ventilation (Perén et al. 2011). Illustrating this
ventilation system by an application case in a typical tropical house of the former
Panama Canal Zone is also important for recovering interesting features of this
traditional architecture for tropical weather.
