The current temperature specification is determined by intuition or experience rather than by systematic derivation. This investigation proposes to evaluate the specification of temperature points using the eigenvalue decomposition to the governing matrix. A connection was established between the eigenvalues and the condition number of the matrix that describes the posedness of the problem. The effects of the number and locations of temperature points on the inverse solution were analyzed based on a three-dimensional ventilation enclosure. The results showed that the proposed inverse model provides accurate solutions with appropriately specified temperature points.