A 10-m × 15-m ranch house is located in Golden, CO, with an overall BLC of 0.3 kW/°C. The walls have a height of 3 m and the window-to-wall ratio (WWR) is 20 percent. Determine the breakeven retrofit cost (expressed in $/m² of wall area) when the walls initially insulated statically with RSI-3.5 are converted to a SIS operated with a two-step control strategy. Assume the ranch house is heated and cooled with a heat pump with COP_H = 2.5 for heating and COP_C = 4.0 for cooling. The analysis can be carried using the LCC approach with a lifetime of 30 years and a discount rate of 5 percent. Assume that the electricity price is 0.12/kWh.