Not isotropic; having different physical properties in different directions.
Used for materials where the thermal conductivity varies depending on the direction of heat flow; for example timber has an approximately 2.2 times higher thermal conductivity, when the heat flow is in line with the grain, than when it is perpendicular to the grain. End grain boards used as flooring will thus have a significantly lower thermal resistance than for example plywood boards, even when exactly the same timber is used. While most building materials can be viewed as isotropic, i.e. having a thermal conductivity not depending on direction, building materials other than wood may behave anisotropic as well, for example vertical coring lightweight bricks, or certain forms of reinforced concrete. When a material is not uniform, or extensively structured, anisotropy is likely.