Environment Temperature found in the details of the Static Structural object in the Mechanical tree is the temperature of the bodies unless this temperature is explicitly specified by a thermal condition or an imported temperature. Now, if a thermal condition or imported temperature is specified, the environment temperature becomes the reference temperature in the thermal strain equation given by α *(T-TREF), where α is the coefficient of thermal expansion. Reference Temperature, which is found in the details of the individual bodies under the Geometry branch of the Mechanical Tree is the thermal strain-free temperature of a body and again thermal strains are given by α *(T-TREF), where α is the coefficient of thermal expansion. Note that reference temperature defaults to By Environment hence using the temperature specified in Environment Temperature. By changing it to By Body, one can override the specification to differ for that particular body, while defaulting remaining bodies to By Environment, etc. Please note that Reference Temperature that is found in engineering data under the secant coefficient of thermal expansion is NOT used for setting the strain free temperature. Please also see solutions 2038325 and 2045884 for added explanation and details.