The exhaust pipe is 4" the same as the outlet size, has only one slight U bend to accommodate a PVC pipe (<20degrees) and the fan assembly still vibrates the joists when the exhaust pipe is disconnected. I ran out of canned air but I'm going to give it a good squirt and see if it got concrete dust in the open box when I was cutting up the floor, maybe it is dirty?
10/11: Bought the perfect house;
11/12: 10k & 200 hours,08/13: 30k & 400 hours into the perfect house, 12/13: 35k & 500 hours
02/14: 37k & 550 hours, 08/14: 38k & 650 hours
05/15: 40k & 700 hours and I think it's done, Home appraised +40k!!! 1 to 1 ratio achieved!