This paper investigates how significantly the error in prescribed parameters affects identified results supposing that thermal properties in a massive concrete are identified. Error sensitivity equation which represents sensitivity of the identified results with respect to error in prescribed parameter is derived in order to make analytical evaluation of the error effect. By using the sensitivity equation, we pointed out importance of selecting proper record length used for this identification, as change in the record length produces change in the identified results. Furthermore, we examined which prescribed parameter values need to be assigned accurately in order to make accurate estimates. Monte Carlo simulation is employed to verify the results obtained from the sensitivity equation.
