Its 64 sq ft. From what i understand thats supposed to be able to heat 640 sq ft for a window . I have mine on a angle Usin this calculator
Solar Angle Calculator | Solar Panel Angle Calculator
43 degrees on january
And 51 degrees for Febuary
I put it at 48 degree slope Figured that sun moves 8 degrees a month.
So 124 cfm fan should be just fine Im guessin.
The hardest part was crawlin under the house and runnin a vent.