What level of energy cost “penalty” am I likely to incur by going with a Dark Charcoal Blend Slate roof over a white color slate tile?
While color is an important factor in the thermal transfer of heat into the attic, it is not the only one. The thermal mass of a concrete roof tile slows heat transfer, the air space between the tile and the deck acts as an insulator, and the air permeable nature of individual tiles (air movement through the gaps between the tiles) all contribute to lowering attic temperature. Also, standard insulation of the attic space plus radiant barriers and attic ventilation contribute as well. The impact of color is not quantifiable specifically other than to say that white performs better than charcoal in heat transfer studies. To measure specifically, the other factors mentioned must be taken into account. The fact that current home construction involves generally up-to-date insulation does mitigate the effects of the color of the roof tile. The rule of thumb is to select the color most consistent with the architectural intent of the home.
