metal and ceramic roofing materials

If you are re-roofing your home, or if you are building a new home, bet on cool roofing materials, namely some white metal roofs and white or light clay and cement tile. That will be an excellent way to reduce your air-conditioning bills and to contribute to a better environment. The results will be exceptional in hot and temperate climates.

Solar Reflectance

Good reflective materials should both reflect solar heat and release the absorbed heat. The SRI index (Solar Reflectance Index) gives a good rating of roofing materials, namely of their reflectance.

In 0-100 scale, white asphalt shingles have an SRI around 20-25 when new (and significantly less over time), while dark asphalt shingles have a SRI of just 1 (obviously, the higher the SRI the better).

White metal roofs have excellent SRIs: 70-80, while new galvanized steel or aluminum also rates well (around 70). These materials, and some white clay tile are the best in the market to improve roof reflectivity and get lower energy costs.

Metal Roof Advantages

Many metal roofs are durable and have a clear energy-efficiency advantage over asphalt shingles and other common roof materials.

In sunny climates, metal roofs may provide energy cooling savings up to 20% relatively to asphalt shingle roofs. Besides, metal roofs are fire retardant and have a low maintenance cost.

White metal (with an SRI of more than 80) or new aluminum metal (around 70) have excellent performances as roofing materials.

Metal roof Coatings

Bare metal roofs and metallic coatings have a relatively low emissivity - they trap and block too much solar radiation, instead of reflecting it - and aren’t excellent cool roof materials. Bare galvanized steel, for instance, is far from being as effective as white metal: it has a SRI in the 40s while metal has a SRI of 80 or more.

To attain excellent cooling performance, metal roofs should contain a coating able to offset the relatively low emissivity of the bare metal. These coatings – often a polymeric - are very similar to paint and may be factory-applied.

Ceramic roofing Tiles

Ceramic and concrete tiles can also be an excellent roof cooling solution, namely white clay tiles.

Ordinary red-barrel tiles made from clay are a natural and environmental product, with a reasonable energy performance, but the best roofing tiles are other modern versions, namely white tile with energy-efficient coatings. The solar reflectance (SRI) for some traditional types of ceramic tiles are often between 20 and 50, while the best white concrete tiles provide a SRI of 90...