Want to make some rough calculations on potential savings and benefits gained from thermal insulation? The Department of Energy has some tables of calculations that can help. The first set of tables aids in identifying the rate of heat loss from an uninsulated surface, — specifically from horizontal pipes and from either horizontal or vertical flat surfaces.
The second set of tables estimates the insulation thicknesses required to obtain surface temperatures below 125F with zero wind. From these it is possible to make a rough calculation of the savings in the rate of heat loss and an estimated time to pay back the investment, given some assumptions about fuel costs, hours of operation, depreciation rates and the initial costs.