IECC Part 2 (Commercial) addresses energy efficiency in commercial buildings. Building envelope requirements include wall insulation, roof insulation, window U-factors, and air leakage limits. Mechanical systems must use high-efficiency equipment with SEER ratings for cooling and AFUE ratings for heating. Lighting systems must use efficient fixtures with occupancy sensors and daylighting controls in perimeter areas. Building automation systems monitor and optimize energy use. Renewable energy systems including solar panels and wind turbines are encouraged with incentives in some jurisdictions. Commissioning of building systems verifies that equipment operates as designed.