ANSYS was used to supplement analytical methods in the design of a new Guarded Hot Plate apparatus to measure the thermal conductivity of thermal insulation. The finite element simulations enabled designers to determine whether heater and coolant tube layouts would generate a uniform temperature profile on surfaces facing the specimen. Analysis also assured designers that one-dimensional heat transfer would be present in the meter section of the specimen. The use of ANSYS has provided greater insight into the physics of the apparatus and will enable NIST to make measurements with greater accuracy.