This is a question I have been thinking about a lot lately and one I am curious about how others have taken advantage of the humidity inherent in a tropical climate.
A double-layer roof of a flat concrete slab with an open metal gabled roof over it was recently modeled for one of our projects located in the tropics with good results.
- Ventilation was supplied by louvered openings in the walls in line with the prevailing winds and vented out high clerestories.
- The concrete roof supplied mass for thermal stability and the metal roof supplied reflectance.
- The air space between the two encourages the ventilation.
Build a model before you commit to a design
Your suggestion of a concrete tile roof with a high emittance coating plus eave and ridge vents seems like a good idea. If you can, I'd have a mechanical engineer run some calcs on it. Even an engineer located elsewhere can do this if you don't have one locally, as data and degree days and humidity for the whole world seem to be available these days.
High humidity can reduce standard ventilation updraft, because sometimes the higher air is heavier, unlike a more dry climate, so the amount of humidity in your area plays a big role in what kind of ventilation will work best for you.
Consider the local vernacular architecture
If the jungle (I'm not sure of your location), is one that still has access to a traditional building culture, study the local wisdom.
- The long house of Southern Asia, for instance, is built on stilts, allowing air circulation below the living area. This allows for a downdraft instead of the updraft we often use in drier climates.
- The thatched circular huts traditional in many African countries, on the other hand, have a conical-shaped roof, sometimes with a vent located near the peak. This vent is made by separating the top of the cone from the rest of the roof, leaving a space between where air can escape.
Low-mass vs. high-mass structures
Also consider what the rest of the building is made of and how open it is. Some hot/humid climates may want a low-mass structure that won't stay heated when the sun goes down, while in others, a high-mass building is more appropriate.
Of course, if your jungle is in Africa, low-mass metal is expensive and wood is gobbled up by the voracious and huge African termite, who, by the way, is an expert at natural air conditioning. Because some species of termites cultivate fungal gardens in their mounds, temperature control is important for food as well as comfort. The column of hot air rising through the above-ground "chimneys" helps move the air circulation throughout the mounds.
But I digress.
For more information:
Read "Three Ways to Make Your Roof More Energy Efficient" for three tips that will helpgreen both your roof and your home.
Also, visit http://www.squidoo.com/passivecoolingcalcto get a sense of what might work for you.