Sol Power Tile: Integrating PV into Clay Roofing

Used for thousands of years, clay roofing tiles are common in Europe, particularly in Mediterranean countries; in the U.S. they are found primarily on high-end, Mission-style buildings in Florida, California, and the Southwest. Clay tiles are expensive but have a number of positive environmental attributes: they’re made from readily available raw materials, won’t burn or rot, are insect-resistant, and are highly durable—often outlasting the roof decking on which they sit. Curved clay tiles have small air gaps at the roof edge and overlaps, allowing air to circulate under them and escape at the ridge, helping to cool the roof. U.S. Tile’s Mission-style tiles also have a solar reflective index (SRI) as high as 61—well above the Energy Star criterion of 25 for steep-sloped roofs and LEED’s requirement of 29.

Incorporating PV into a clay roof has, until now, been a challenge. Clay tiles are installed on roofs with steep slopes—typically a 4:12 pitch (a 4" rise for every 12" run or 10 cm for every 30 cm)—and the tiles are breakable, so walking on these roofs to install PV panels is treacherous. Mounting standard flat PV panels into the rafters or trusses risks damaging the tiles and requires careful flashing details to prevent moisture penetration.