A: Energy savings are different for light commercial vs. large commercial buildings and obviously depend upon the initial duct leakage level. The Aeroseal Energy Savings Excel spreadsheet can be used to estimate the savings for both types of buildings. For ducts above an insulated ceiling in a light commercial building, energy savings should be 10–30% of HVAC energy use, and peak electricity-demand reduction is generally a higher percentage. In a large commercial office building with a VAV system, energy savings and demand reduction should be 20–40% of fan-system energy use and 5–10% of cooling energy use. As a rough estimate, excluding any of the non-energy benefits of duct sealing, simple payback times typically range from 1 to 4 years, and return on investment between 30% and 70%