Although wood expands and contracts with varying temperature, these dimensional changes are small compared with shrinkage and swelling caused by varying moisture content. In most cases, such temperature-related expansion and contraction are negligible and without practical importance. Only temperatures below 0 °C (32 °F) have the potential to cause surface checks; in living trees, unequal contraction of outer and inner layers may result in frost cracks. Wood exhibits a low thermal conductivity (high heat-insulating capacity) compared with materials such as metals, marble, glass, and concrete. Thermal conductivity is highest in the axial direction and increases with density and moisture content; ...(100 of 12879 words)