Panasonic ventilation fans are engineered for 100,000 hours of continuous use!  They are very quiet - Panasonic ventilation fans have a defect rate of less than 0.0006%! Many of the different models are energy star rated.  The warranty on these units are 3 years. Why do you need to ventilate? You can click here to find the answers.  The Home Ventilating Institute recommends that a bathroom exhaust fan be able to deliver eight air changes per hour. The simplest way to calculate what size fan you require is: Step 1: Calculate the cubic feet of your bathroom (length x width x height) Step 2: Divide by 60 (the number of minutes in an hour) Step 3: Multiply the result by 8 (the number of recommended air changes per hour) Click Here For R.E. Williams Bathroom Fan Calculator  (The result represents the minimum recommended cfm rating for your bathroom fan). You can view this link for a simplfied explanation of the recommendations of the Home Ventilating Institute for bathroom ventilation - Bathroom Ventilation Recommendations. Click Here For A More Technical method using a chart to properly size a bathroom fan. Remember, if you have a steam room, sauna, or hot tub, you will need to increase the size of the fan to compensate for additional moisture.  Find Answers to your Frequently Asked Questions - Follow This Link Here. General installation guidelines-Recommendations for installation of a Panasonic ventilation fan. R.E. Williams Guarantees Its Pricing On These Units. We Will Beat Any Advertised Price You Find. We strive to give you a higher level of service, satisfaction and an overall outstanding experience when ordering through our company. Online since 2001, incorporated 1979. Need help sizing your fan? Call M-F 7 am - 5 pm PST Toll Free 888-845-6597, or order online 24/7.