Roofing Tile

General Description

Roofing tiles can be ceramic (e.g., clay fired at a high temperature) or fabricated from cement concrete. Some of the lighter types use fibers (e.g., cellulose) added for strength. The color of a tile may be dispersed throughout, or it may be applied in the form of a coating. Perhaps the most venerable type of roof tile is the Spanish style red barrel tile made from fired clay. The modern version of this tile is sometimes a cement tile with a suitable coating. In either case, the red color is due to the ubiquitous iron oxide material, hematite.

Roofing tiles are available in a wide range of colors; more data on the solar reflectance properties is needed. A starting point for the estimation of the solar reflectance would be to use the reflectance of a paint coating of similar color.

Advantages of tile include fire safety, as they are non-combustible, and durability. Disadvantages include increased weight and cost compared with low-cost asphalt shingle roofs.

Tile roofs often have enhanced air circulation compared to other roofing types because ambient air can circulate below as well as above the tile. (Wood roofs also have provision for air circulation below the roof, to make sure they always remain dry.) This enhanced air circulation helps the roof shed solar heat more readily. The temperature rise figures in the table below are conservative in the sense that we have not attempted to account for this uncertain benefit of enhanced convection.

Table:  Solar Reflecting Characteristics of Roofing Tile
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   Product         |  Solar    |Infrared   |Temperature |Solar Reflectance| Reference
                   |Reflectance|Emittance  |   Rise     |     Index       | 
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red clay tile      |  0.33     |   0.9     |     58 F   |       36        | FSEC 1
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red concrete tile  |  0.18     |   0.91    |     71 F   |       17        | FSEC 1
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unpainted cement   |  0.25     |   0.9     |     65 F   |       25        | FSEC 1
tile               |           |           |            |                 |
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white concrete     |  0.73     |   0.9     |     21 F   |       90        | FSEC 1
tile               |           |           |            |                 |
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concrete tile,     |  0.63     |   0.9     |     30 F   |       76        | LBNL 4
light beige coating            |           |            |                 |
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concrete tile,     |  0.42     |   0.9     |     50 F   |       48        | LBNL 4
light brown coating            |           |            |                 |
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concrete tile,pale |  0.41     |   0.9     |     51 F   |       46        | LBNL 4
bluish purple (mauve)          |           |            |                 |
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concrete tile,     |  0.53     |   0.9     |     40 F   |       63        | LBNL 4
pink & gray coating|           |           |            |                 |
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concrete tile,     |  0.74     |   0.9     |     20 F   |       92        | LBNL 5
off-white coating  |           |           |            |                 |
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fiber cement,      |  0.26     |   0.9     |     64 F   |       27        | LBNL 5
earth brown color  |           |           |            |                 |
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fiber cement,      |  0.25     |   0.9     |     65 F   |       25        | LBNL 5
pewter gray color  |           |           |            |                 |
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