When a space needs serious airflow, this 20-inch shutter exhaust fan delivers up to 4499 CFM to clear out stale air, dust, heat, and odors from attics, garages, barns, and workshops. Its AC motor runs at 1500 RPM on 127W, pushing air at up to 10 m/s, and stepless variable speed control lets you adjust output from a light breeze to a powerful blast depending on the job. Steel housing gives it the rigidity to resist deformation and handle damp conditions and rain better than a plastic build would hold up over time. The louvers open automatically past a 50-degree angle once the fan is powered on, then close when it shuts off to help keep rain and debris out. At 22.4 x 22.4 x 9.5 inches and 20.86 pounds, it runs at 70 dB or quieter and wall-mounts for year-round ventilation in larger sheds, barns, and workshops.