Tropical Cooling Systems


Tropical hut 1 

Every three months, foreigners have to leave Honduras to renew their visa. I took the opportunity to visit Rio Dulce, Guatemala, experiencing, first hand, the natural ventilation of the palm-covered wooden bungalows typical to the area.   I have to say that I was impressed.

These lightly-built houses are typical to tropical areas. Similar structures are found as far away as Asia.  

Their cooling strategy begins with the large screened windows permanently open under the roof at both gable ends.  The screens are a modern improvement to prevent mosquitos, which can be dangerous in the tropics. 
  
The bungalow, itself, is oriented in the direction of the prevailing wind. My bungalow pointed toward the river, which had at least a 10  knot
ventilation
Wind Scoop at Ceiling.
wind blowing in the day, and at night, just a breath of air. In addition, these buildings are constructed above the jungle floor on wooden piles, which help catch the more frequent, higher breezes.   (The other purpose is to keep out the flooding during the rainy season.) As backup, for days without wind, each bungalow also had the ubiquitous and effective ceiling fan above the bed.

The house's structure consists of the wooden piles, as the foundation, pressure treated joists and planks for the floor and logs for the roof structure.  From this frame, they hang wooden panels, as an enclosure.  The roof system is fabricated from 6-12" of native palm leaves, attached to the structural log rafters.

This light wood construction allows for the entire building to breath. The short-coming is that enclosing the building tightly is very difficult,  allowing openings for mosquitos, the vectors of dengue and malaria. The solution in my bungalow was netting over the bed.  That being said, during my stay in the bungalow,  I had no problems with insects.

hut-structure
The Bungalow on Stilts
to Catch Breezes
and to Avoid Floods
The advantage of this building type is that it does not absorb heat during the day, as do the concrete block homes, or the traditional adobe structures. The adobe construction, developed in hot, dry areas, is not necessarily ideal for hot, humid climates.  I distinctly noticed the contrast between my concrete block room in Copan, which becomes intolerably hot around 3:00 PM and the comfortable feel of the bungalow.

The real secret of this building is the thick palm leaf roof, which acts as insulation against the tropical sun.  In combination with the gentle breeze blowing through the building, it provides a very pleasant environment even in temperatures 80 - 85 degrees F. and higher.

One problem with the roof system is that it could become a habitat for many dangerous pests. To avoid this danger, the house must be kept clean, and may even need an occasional fumigation.   In my bungalow, the roof palms were well-maintained and free of any apparent pests.

In conclusion, the lessons of  the river bungalow, with implications for sustainable design in the tropics and the U.S., are:

1.  Cross-ventilation of the entire building.
2.  Orientation of building to prevailing winds and 
     construction high above the ground surface  to enhance 
     exposure to winds.
3.  Use  of light materials, which don't absorb the heat.
4.  Long overhangs at the gables and eaves to shade against the sun
     and prevent rain penetration.
5.  Roof insulation.  

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