Smart Series 150 CFM Ceiling Bathroom Exhaust Fan, ENERGY STAR

A:  I would not recommend a 4 inch vent. You would need an adapter, it wouldn't move the volume of air it's supposed to, and it would likely make more noise. It does move the air. I did the tissue test, and it held it in place with the suction.

A:  You can get an adapter to go from a 6 inch to a 4 inch pipe. That is what I did.

A:  Instructions do not specify other than 150 CFM

A:  The ceiling exhaust covers approximately 150 sq. ft.

A:  The fan is 150 CFM, and can handle a 120 sq.ft bathroom with 8ft ceiling. Make sure that 6in DIA pipe/duct is installed and there is 0.9" gap between the floor and the bottom of the door.

A:  150 cfm Say your bathroom is 8ft tall ceiling, 6ft wide, 10ft length(480cubic ft) It would take 3min10sec(480/150=3.2) to completely replace the air in your bathroom if you have no restrictions (air duct undersized, too small of a gap under your door...). Half of that rate is probably ok in terms of performance for that size. Each bathroom is different, you'd need to run the numbers You can also compare it to your old one

A:  neither the box nor the instructions specify square footage. However, both specify air movement of 150 cubic feet per minute which met my criteria.

A:  Yes, you can install this unit from below. Please review the assembly instructions on page 7 and 8 of the user manual for additional information (the linked user manual is not for SMT150, but the instructions are the same). http://www.deltabreez.com/Upload/SalesBinder/5_IM/1_Signature/SIG80_SIG80M_SIG80D_SIG110_SIG110H_SIG110D_IM_e.pdf

A:  I don't believe so. You have to run out the exhaust somewhere. The unit is designed to sit above ceiling and mount to a stud.

A:  No. I had to work in the attic to brace the unit, connect the ductwork and the electrical line,

A:  Yes, the unit can be installed without access from above but the installation will be time-consuming and difficult for some installers. If you do not have access from above I would recommend to purchase the fan which was designed to be installed from a bathroom.