This article appeared in Western Roofing magazine January/February 2007.
Cool Clay Tile
Clay Tile Roof: Steeped in Tradition – Engineered for the Future
by Lyla Lawry, Marketing Coordinator, MCA
With a growing awareness of the benefits of “cool” roofing, and the much sought-after traditional beauty of an Old World look, one clay roof tile is enjoying a revival in today’s market. Long known for its classic appeal and durability, clay roof tile has stood the test of time. But all tiles are not created equal. With an increasing demand for environmentally-friendly and energy-efficient products, MCA’s clay roof tile, in an array of colors, has earned a Cool Roof rating by the Cool Roof Rating Council (CRRC).
Because of the inherent thermal properties and durability of clay, people have been using this natural material for more than 5,000 years. Clay tiles have been traced back as far as 3,000 B.C. in China and the Middle East. Clay roofing was also used in Greece, Egypt, and Rome and made its way to America with the first English settlers. Spanish padres used clay tile roofing in the constructions of the missions of California and Texas, now so famous for their beauty. However, clay roofing tiles are not just about the past; modern manufacturing techniques developed by MCA offer architects both contemporary and traditional design in a modern “cool roof” tile product.
Maruhachi Ceramics of America (MCA) is one of several industrial partners who participated in a California Energy Commission Public Interest Research (PIER) project that made cool-colored roofing products a market reality. Clay tiles contain complex inorganic color pigments that boost their reflectance in the infrared spectrum. A matte glazed process is used to add color to the surface of a clay tile. Once matte glazed, the clay is kiln-fired. The firing temperature, the atmosphere, and the pigments affect the final color and solar reflectance , which can be further increased with the help of new “cool roof” colors. The color is permanent and does not fade over time. In a report prepared by the Oak Ridge National Laboratory (ORNL) for the U.S Department of Energy, Dr. William Miller’s research concluded that certain clay tiles exceed in solar reflectance. Tests also showed that after three years of exposure the clay roof tiles still met, or exceeded, California’s Title 24 Cool Roof standard of 40% solar reflectance and thermal emittance requirement. MCA offers 33 colors rated by the Cool Roof Rating Council that meet or exceed the 40% requirement.
Dr. Miller’s research also tested the energy efficiency and performance of a roof system by measuring the amount of ventilation between the roof deck and the roofing material. In cooling season field tests conducted at ORNL, MCA’s clay S-Mission tiles were nailed directly to the roof deck. Dr. Miller’s research shows the clay tiles had low heat flux through the deck. This natural ventilation translates into cooler attic temperatures in the summer and warmer temperatures in the winter. According to Dr. Miller, “The clay roof tile showed up to 70% heat reduction entering the house as compared to roofs with asphalt shingles. Thermal mass, along with solar reflectance and recyclable properties, make clay roof tile an environmentally-friendly product. After a long and useful life, clay roof tiles are harmless to the environment and can be recycled for new applications.”
One of the oldest roofing products in the world, clay roof tile meets the highest ASTM standard, ASTM Grade 1, while maintaining an “old world” look. Roosevelt High School, located in Corona, Calif., is an excellent example of this blending of traditional good looks with contemporary cool-roofing, energy-saving technology. Designed by Glenn Ueda and WLC Architects of Rancho Cucamonga, Calif., Roosevelt High School is an impressive school that looks more like a college campus than a high school. Working in conjunction with Letner Roofing, Orange , Calif. , MCA created an energy-efficient custom blend for the 1400-square project. With a solar reflectance of over 42% and an thermal emittance of nearly 85%, MCA’s custom blend of Old Mission Blend and Santa Fe Brown gave the new campus an authentic traditional design while making use of modern cool-roof technology.
Frank Hughes of Letner Roofing liked the combination of an energy-efficient tile and the aesthetics of the “Hacienda” style. “We have used MCA’s Energy Star and cool roof tile on numerous projects and have always met with success,” he said. “We installed MCA’s Old Mission Blend on several projects including the Hyatt Regency in Huntington Beach, a cool roof with 43% solar reflectance and 86% thermal emittance.”
Helping to maintain livable interior temperatures and lower energy costs has prompted Northern California’s Pacific Gas and Electric (PG&E) to offer Cool Roof rebates to its customers. Only roofing materials rated by CRRC are eligible. Peter Turnbull, vice chair of the Cool Roof Rating Counsel and program manager with PG&E, notes, “Cool roofs save air conditioning energy when utilities need it most, on hot summer afternoons. We’re excited about the benefits customers will receive by installing cool roofs.”
The 2008 update to California’s Title 24 is expected to prescribe new design criteria to reduce energy consumption, with residential cool roofs being one of the options. According to Bob Hale, sales manager at MCA, “While other roofing product manufacturers may scramble to meet the conditions, MCA clay roof tiles, recognized by CRRC, LEED’s qualifying, and Energy Star approved, already satisfy the requirement.” Rich in history and recognized all over the world for its renowned beauty, clay roof tile is at the forefront in energy efficiency in an environmentally conscious modern world. •••