A house located is Chicago, IL, is heated with a natural gas-fired furnace with an efficiency of 85 percent. The house has a BLC of 600 Btu/°F·hr with WWR of 30 percent. Using the data listed in Table 11.6 , estimate the annual heating energy use and cost savings when the windows are retrofitted with an automated and SIS operated using two-step controls. The cost of natural gas is $2/therm.

Table 11.6

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Location WWR Chicago Phoenix WWR = 15% WWR = 30% WWR = 50% WWR = 15% WWR = 30% WWR = 50% San Francisco WWR = 15% WWR = 30% WWR = 50% Annual Heating Energy Consumption (kWh/year) (Percentage Saving) Static 4,985 (0%) 5,155 (0%) 5,563 (0%) 0 (0%) 0 (0%) 0 (0%) 49 (0%) 18 (0%) 18. (0%) Switchable Static Switchable Static Switchable 4,147 1,332 912 2.22 2.08 (17%) (0%) (31%) (0%) 3,584 1,717 911 2.36 (47%) 910 (58%) (0%) 2,308 4.97 (30%) (0%) 3,107 2,160 (44%) 0 Annual Cooling Energy Consumption Electrical Peak (kWh/year) Demand (kW) (Percentage Saving) (Percentage Saving (-) 26 (47%) 8 (58%) 6 (68%) (0%) 2,899 (0%) (20%) 3,572 2,436 (0%) (32%) 4,383 2,592 (0%) (41%) 913 482 (0%) (47%) 1,259 455 (0%) (64%) 453 (73%) 1,653 (0%) (0%) 2.53 (0%) 5.49 (0%) 5.77 (0%) 2.18 (0%) 2.42 (0%) 2.63 (0%) (6.4%) 2.09 (11.5%) 2.11 (16.5%) 4.91 (1%) 5.41 (1.5%) 5.65 (2%) 2.07 (4.9%) 2.21 (8.5%) 2.31 (12.1%)