A daylighting system using dimming controls is being considered for a five-story office building located in Denver, Colorado. A typical floor is 200 ft × 50 ft with perimeter offices extending 12 ft from the vertical windows. The electrical lighting has a density of 1.2 W/ft2 and is operated (without daylighting controls) 5,500 hours/year. The cost of the daylighting system is estimated at $40,000. The energy cost is $0.08/kWh.

i. Assess the cost-effectiveness of the daylighting system using a 20-year cycle and 5 percent discount rate if double clear glazing is used. Consider three WWR values: 10, 20, and 30 percent.

ii. Repeat (i) for double reflective tinted glazing.