The Whole Building Design Guide (WBDG) from the National Institute of Building Sciences offers a series of calculators that can help insulation contractors, plant managers and maintenance managers determine the right amount of insulation for a variety of situations.
Say you want to minimize the temperature change in fluid passing through a pipe. The Design Guide has a Temperature Drop Calculator that helps estimate the extent that measurable temperature changes in flowing water can determine the optimal amount of pipe insulation required to meet the objective.
Or you may want to accurately estimate the performance of an insulated flat surface given the operating temperature, the ambient temperature and other details about a given system. For this, you have the Energy Calculator for Equipment.