PART I: CLIMACTIC CONSIDERATIONS

If your home is situated in a hot, humid, tropical setting, picking out the right roof for your home entails a different set of considerations than you would need to think about had your home been located in a colder or more temperate region. While the heat is, and always will be, a major factor in your choice of roof, other factors must also be 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.

PART I: CLIMACTIC CONSIDERATIONS

The demands of a tropical climate dictate different considerations when choosing a roofing material for your home: Factors that may or may not play a significant role in roofing in a different climate can make a big difference in a tropical situation. Here are some things to consider when choosing a material for your roof:

SLATE

Slate is naturally fireproof, and its low (less than 0.4%) water absorption index makes it virtually waterproof. This also makes it a material that doesn’t favor the growth of algae. Choosing a light-colored or earth-toned slate increases your roof’s ability to reflect radiant light. Coupled with slate’s high thermal mass, this reduces the amount of heat absorbed into your home. Slate’s high durability and low maintenance requirements make it a good, high-end roofing material.

The main downside to slate, aside from the expense, is the weight: not all homes can support the weight of a slate roof.

CLAY AND TERRA COTTA

Clay and terra cotta are similar enough that considerations pertaining to one carry over to the other. Both materials have good thermal mass. When combined with modern “cool” paint colors they are very good at keeping a home cool by reflecting back radiant heat.

PART II: MATERIAL CONSIDERATIONS

One important consideration when choosing clay or terra cotta tiles is their shape: the half-barrel or “S” shape tile allows both water and air to flow freely below the tiles. The free passage of air beneath the arch of the tiles prevents heat capture and keeps the area below (i.e., your home) cooler.

As with slate, the main disadvantage to clay and terra cotta tile is the weight: the tiles are heavy and require a solid foundation on which they can be installed.

CONCRETE

Concrete is generally less expensive than slate or clay, and comes with many of the same considerations. It is heavy and requires a solid foundation. Its high thermal mass, when combined with a cool color, gives it good reflectivity and makes it an effective cool roofing option. The main difference is that, while concrete is available in tile form, it is also available as poured concrete. Such concrete slab roofing is a common, low-cost option in many developing countries, providing good protection from both pests and bad weather.

PART II: MATERIAL CONSIDERATIONS

METAL ROOFING

Metal roofing’s main advantages are its durability and low maintenance. It is also generally lighter than any of the different tile materials, which may make it an attractive option in situations where the house cannot otherwise support a tile roof.

As an option in tropical areas, one must consider that metal heats up very quickly, however. It absorbs heat much faster than tile: even painted white, it reflects much less heat than a similarly white-painted clay or concrete roof. Proper installation is also a consideration: if the roof is not properly constructed with considerations for the slope and glare, no matter how reflective the material is, it will reflect heat and light on nearby residents.

PART II: MATERIAL CONSIDERATIONS

While older, proven materials can be made to work in a tropical climate, in recent years certain innovations have been shown to provide interesting new approaches to roofing in a tropical setting. These innovations serve to address one or more of the factors particular to living in a tropical environment.

EPDM

EPDM, short for ethylene propylene diene monomer, is a strong, weather-resistant thermoplastic similar to a synthetic rubber. EPDM comes in single-ply rolls or sheets that can be used to cover large areas quickly; it is also available in thermoset form, as a pre-molded or “set” material.

It may seem counter-intuitive to use a rubber roof in a warm climate, but in this case, it is surprisingly effective. EPDM, colored white, serves as a cool roofing option with a good amount of thermal reflectivity. Whether as thermoset or in its sheet form, EPDM is weatherproof and durable. The non-thermoset form is ideal for use on a sloped surface.

Because EPDM can be applied almost seamlessly to any surface, it makes for an exceptional waterproof barrier, protecting the surface underneath from water penetration. This is a particularly important consideration in tropical areas.

PART III: ADVANCED ROOFING MATERIAL OPTIONS

GREEN ROOFS

One of the more radical options for roofing in a tropical climate is the so-called green roof. Green roofs, also called living roofs, are so called because they incorporate living vegetation into the roof itself.

Green roofs offset the urban heat island effect in many ways. Instead of painting the roof white or some other reflective color, the radiant light is instead used to fuel the growth of plants on the very roof itself. By incorporating a waterproof membrane (such as a rubber roof ), green roofs cool the area naturally via the temperature of the soil and the growth of greenery. Additionally, the incorporation of living plants into the roof allows them to release oxygen into the air, reducing atmospheric toxicity. Water runoff from a green roof serves to cool the building underneath, and the entirety of the green roof system serves to protect the actual roof of the building, making the roof last longer.

PART III: ADVANCED ROOFING MATERIAL OPTIONS

Arry’s Roofing Services, Inc.

401 East Spruce Street, Tarpon Springs, FL 34689

Phone: (727) 938-9565

www.ArrysRoofing.com