Although there is a lot of interest in green finish materials, they don’t tend to come up often in the context of building energy performance. However, they do have the potential to influence energy performance in the following ways.The color and reflectivity of interior surfaces affect the amount of lighting power needed for indoor tasks; waste heat from lighting then contributes to cooling loads. There is an excellent discussion of these relationships in The Integrative Design Guide to Green Building, by 7Group and Bill Reed.The color and reflectivity of exterior surfaces can affect the amount of solar radiation absorbed and subsequently converted to heat inside the building; in hot climates, “cool roofs” can be particularly important. (See Richard Defendorf’s July 30 blog post on this.)Sheetrock and hard floorings (e.g., concrete, stone, tile) provide thermal mass—the capacity of a material to store heat—which can help modulate interior temperatures. Climates that see large diurnal temperature swings benefit the most from thermal mass; during the day, it absorbs heat, which is then reradiated at night when the house cools down.Lime and earthen plasters may help ease cooling loads by reducing humidity. These materials can attract and hold moisture vapor from humid air and then rerelease it to the air in dryer periods. While scientific proof has yet to be produced, according to natural building expert and GBA advisor Bruce King, anecdotal evidence is too strong to disregard.