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As the globe continues warming, regions across the world are experiencing more and more severe weather events and prolonged periods of above-average heat. In hot climates like these, homes bear the brunt of the punishing weather, and roofs — where the sun beats down all day long — get it worst of all.
But roofs do a lot more than keep the sun off your back. A poorly made roof degrades in the heat, cracking and breaking down over time. It also transfers heat from the sun directly through the surface and into the home. That process, in turn, drives up energy costs from home cooling, making certain materials a lot less energy-efficient than others.
On the flip side, certain roof types not only stand up to the brutal heat with aplomb, but also provide much-needed ventilation and airflow between the roofing material and the decking, meaning that homes stay cooler than they would with asphalt shingles. Some materials make thermal transfer much more difficult or reflect sunlight off the roof, keeping homes cool as a cucumber. Different hot-weather materials all have their pros and their cons, of course. To help you weigh the different aspects, we present to you a guide of the most popular hot-climate roofing materials.
Terra-Cotta Tiles and Ceramic Roofs
There’s a reason this roofing material is so popular throughout the Southwest, and it has nothing to do with its appearance; although, terra-cotta does make an excellent choice for those hoping to capture a bit of Spanish colonial style. The words terra-cotta literally translate to “cooked earth” in Italian, and it’s that baking process — in a kiln at high temperatures — that gives these tiles their weather-resistant properties. In fact, clay tiles have been known to stand up to the heat for centuries, regularly lasting as long as 50 years or more.
The curved shape of the tiles makes a difference, as well, allowing air to circulate below the surface, which keeps roofs and interiors cooler. The only drawbacks for this stylish energy-efficient choice are the weight of the tiles and the material costs. Clay tiles weigh somewhere between two to four times as much as conventional asphalt roofs, so many homeowners find they need their roofs reinforced before they can install terra-cotta on their homes. Furthermore, they’re also one of the most expensive materials because they run around $700 to $1,000 per square (that’s 100 square feet if you’re not up on your roofing lingo). Still, considering their long lifespan, they may just make back your initial investment.
Concrete Tiles and Slab Roofs
Concrete makes a great option for those who like the thermal properties of terra-cotta but not the price. The thickness of this material means it takes longer to heat in the sun — and hence longer to absorb that heat back into your home. Slab concrete is a cheap — although heavy — solution for hot-weather roofs.
However, roofing vendors also manufacture more aesthetically pleasing concrete tiles that are dyed to give them a little hint of color. Of these options, S-tiles stand as one of the more energy-efficient models of the bunch. Like many terra-cotta tiles, they’re fashioned into a wave pattern, which improves airflow between the decking and the roof surface. And that has the ultimate effect of reducing heat transfer and cooling costs in return.
EPDM Roofing Membranes
Often referred to as rubber roofing, EPDM membranes aren’t really rubber at all but a synthetic rubber-like substance known in longhand as ethylene propylene diene monomer. EPDM’s composition makes it exceptionally sturdy in extreme conditions. In field tests, it has been shown to resist UV radiation without cracking and breakdown. And it’s often praised on life-cycle analysis for its low energy overhead during manufacturing. The material is particularly effective at heat reduction when it’s coated with titanium dioxide, which gives the EPDM a lighter color.
This color reflects light and heat from the roof surface back into the atmosphere. However, homeowners should be careful when using these kinds of “cool roof” techniques to reduce energy consumption. Studies have found that this method may have potentially dangerous side effects for the environment at large. For instance, Arizona State University researchers who modeled the long-term effects of cool roofs showed a 4 percent decrease in local rainfall. That’s worth thinking about before you go this route.
Metal Roofs
Metal roofs are the material of choice these days in stylish warm-climate cities like Austin and Los Angeles. The story of metal roofing is one of peaks and valleys. Used since as far back as Ancient Rome, metal got a bad rap in the ’80s and ’90s, when it was seen as a cheap, tacky material suitable mainly for farms and barns. However, the past few years have witnessed a virtual renaissance for this versatile and durable material. A construction analysis from 2016 indicated that metal now makes up 11 percent of the market share in the roofing industry, second only to asphalt in popularity. Part of that shift can be contributed to its perception as a sustainable material.
Aluminum, steel and copper roofing products are frequently manufactured from recycled materials; in fact, aluminum roofing systems often contain recycled soda cans, which has a natural appeal for environmental-thinking homeowners. There’s more to it than that, however. In hot climates, where cooling expenses form the bulk of homeowners’ energy bills, energy-efficient aluminum roofing systems include an integral airspace between the metal panels and the decking. This “dead” space acts as a thermal barrier, blocking heat transference from the roof to the interiors below. In some cases, this innovation has reportedly reduced cooling costs by as much as 20 percent — not too shabby for some repurposed soda cans!
Green or “Living” Roofs
A rooftop covered in moss and plants sounds like something straight out of The Hobbit, but oddly enough, it has a lot of practical value beyond its charm. Green roofs, which literally consist of plant life suspended over a waterproof membrane, have the benefit of both reducing heat loss and heat absorption, making them a suitable choice for both hot and cold climates. Additionally, they reduce what the scientific community refers to as the heat island effect: the temperature increase in urban areas resulting from the sun baking on asphalt and metal surfaces.
Likewise, they add necessary oxygen back into the environment, which makes them a vital asset for populated, congested areas. While certainly not the most popular roofing material, the idea is gaining ground among environmentally minded homeowners in hot-weather cities, so don’t be surprised if one day you see neighbors out weeding their roofs. When it comes to protecting your home and keeping it cool, any material is fair game!
All images via Modernize unless otherwise stated
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