If your home is situated in a hot, humid, tropical setting, choosing the right roof for your home requires a different set of considerations than a cold climate does. While the heat is a major factor in your choice of a roof, other factors must also taken into account.
Radiant energy and the “urban heat island” effect
It is an established fact that dark colors will cause a material to absorb more heat quickly; a roof painted in dark colors will absorb and retain more heat than the same roof painted in cooler colors that reflect more radiant light. Concentrations of dark asphalt roofs, parking lots, and roadways in densely populated areas, such as large cities, create an “urban heat island” effect. Heat soaks into the area and is retained all throughout the day; it is not uncommon to feel heat still radiating from the roads hours after the sun has set.
A dark-colored roof not only contributes to the urban heat island effect, but also increases the amount of air-conditioning required in your house to make it comfortable. The simple act of painting your roof white, or some other “cool” color, can reduce your cooling expenditures by up to 15%. Built-up roofing is also an option, providing multiple roofing layers as a way to reduce radiant heat penetration. It is also possible to install a radiant barrier, such as a layer of aluminum in the attic or between the roof and the interior, designed to reflect radiant light back out and reduce heat buildup.
Heat, humidity, and algae growth
One unfortunate side effect of the year-round heat and humidity in a tropical climate is that it encourages the growth of algae. Roofs made of wood, concrete, tile, and standard “composition” shingles are vulnerable to infestations of algae, as well as moss and lichen. While these do not pose a health hazard – unlike mold and mildew – over time they will negatively impact the structural integrity of your roof. This can be avoided by roofing your home with metal, or by using special algae-proof shingles.
Stay tuned for Part II, coming soon, which will discuss the advantages and disadvantages of the more traditional roofing materials in a tropical climate.