11-25. It is desired to determine the most economical thickness of insulation for a large cold-storage room. Insulation is expected to cost $150 per 1,000 square feet of wall area per inch of thickness installed, and to require annual property taxes and insurance of 5% of the capital investment. It is expected to have $0 market value after a 20-year life. The following are estimates of the heat loss per 1,000 square feet of wall area for several thicknesses:

Insulation, in. Heat loss, Btu per hr 3 4,400 4 3,400 5 2,800 6 2,400 7 2,000 8 1,800 The cost of heat removal (loss) is estimated at $0.04 per 1,000 Btu. The MARR is 20% per year. Assuming continuous operation throughout the year, develop a spreadsheet to analyze the sensitivity of the optimal thickness to errors in estimating the cost of heat removal.

Use the AW technique. (11.3)