For a 12-m × 20-m one-story house located in San Francisco, CA, determine the cost-effectiveness of exterior walls retrofit to have SIS. The house has a BLC of 400 W/°C, wall height of 3.5 m, and WWR of 25 percent. The cost of wall SIS retrofit is estimated to $40/m² of opaque wall area. The opaque walls are initially insulated statically with RSI-3.5 and when retrofitted are operated with two-step control strategy. Assume the house is heated and cooled with a heat pump with COP_H = 2.7 for heating and COP_C = 4.2 for cooling. The analysis can be carried out 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.