skip to main content

Bathroom Fan Question

14 years ago

Hello, I have a small bathroom 5X7 and there is a Broan 80 CFM fan currently installed but after a shower there is a lot of moisture on the walls etc. I am considering putting a fan that is 150 CFM rated just curious if I could really expect to see a noticable difference or am I really just wasting my time and energy? I just hate to spend the $200.00 bucks and a days labor on something that is not going to make much difference, appreciate any comments. Thanks!

Sort by:Oldest

Comments (3)

jake2007
14 years ago
Your bathroom is 280 CF if it has 8' ceilings. Your existing fan will completely change all of the air in 3.5 minutes.

Before changing the fan, I would check a few things first:

1. Is the bath fan venting properly? Do you see it pull the steam out? Is it possible that it's clogged, a flap not opening, etc?

2. Do you have a shower head that is breaking up the water too much? I installed a water saving shower head that generated much more steam than the standard head - in part because it broke up the water more and in part because I had to boost the water temp in order to feel the hot water.
I had to get rid of that water saving shower head - the extra steam was damaging my bathroom.
oneslip
Original Author
14 years ago
Thanks for the response, I went outside and I could feel the air pressure coming out the vent, I had taken the motor out and cleaned the fins a while back but it does not change all the air in 3.5 minutes. It takes about 20 mins. at least with the door open to clear out the bathroom. You said my bathroom is 280 CF, you mean I need a 280 CFM rated fan?
Related Discussions
two questions about a fan in my small 5 x 7 bathroom
Q
Comments (4)
A bathroom exhaust fan should be sized to provide a complete exchange of air in 15minutes (4 air exchanges per hour). To compute the fan size you begin by computing the total volume of the room, length x width x height. You stated your bathroom is 5x7 and assuming an 8ft ceiling we get 5x7= 35sq.ft x 8ft height equals a total volume of 280cu.ft. We want the fan to exchange the air four times per hour so we multiply the room volume by 4 to determine the total volume of air to be moved per hour. 280cu.ft x 4 = 1120cu.ft/hr. Now divide the total CFM/hr by 60min/hr to determine the required CFM of the fan. 1120Cu.ft per hour / 60min per hour = 18.66cfm. The purpose of the fan is to insure we remove any residual water vapor in the room after you finish your shower. For optimal performance you should have a fan switch that has a 15 minute delay on break. With this type of switch the fan will start as soon as you turn the switch on, but when your leaving the room you turn the switch off and it will continue to run the fan for another 15 minutes causing one more air exchange before turning the fan off, thus it will provide a maximum reduction of moisture in the air.
...See More
Bathroom fan placement question
Q
Comments (3)
If you are concerned about having adequate lighting, I would put in a fan without a light and install separate light fixtures (perhaps two 4-inch recessed lights in the shower).
...See More
Bathroom Fan CFM Question
Q
Comments (2)
I put a 150CFM Panasonic in my bathroom which is smaller than yours (5'X7'). I know that it moves more air than recommended, but I like that. It gets the moisture our quicker and completely removes smells before they have a chance to enter the rest of the house. The only downside is that it pulls out the "conditioned" (heated and cooled) air from your home, but you could regulate that by changing how long you keep the fan on for. Buy a good timer to control the fan so that it stays on for about 5-10 minutes after a shower and a "Number 2". Actually replacing the fan could be hard if you never did it before.
...See More
bathroom fan questions galore
Q
Comments (8)
With existing mold and the higher ceiling, I'd opt for a Panasonic 110cfm. Do not choke the duct down to 3". Run a 4" duct, then transition to an outlet that will fit the physical dimensions you need (3" height max) but will not limit the airflow. Meaning that your outlet will have a 4" round to accept the 4" duct from the fan, but the exit hole out of your house might be 3" tall by 5" wide. They do have outlets that are literally the size of a standard brick for just this purpose. I usually put fans on timer switches. I use ones by EFI. EFI has motion sensing switches. This one will turn the shower fan/light on when someone enters the area, and you can set it to stay on for up to 30 minutes after the person has left the room. The Panny Whisper fans are quiet. To maintain the quietness, use rigid 4" metal duct instead of the cheap flex duct, and have no abrupt turns in the duct within 2'-3' of the fan. Flex duct (unless just using a short section of it to isolate the fan from the duct) or turns in rigid duct too close to the fan will create the dreaded air turbulence noise and minimize air movement out of the bath. Mongo
...See More
homebound
14 years ago
Do you have a gap under the bathroom door? You need a gap so replacement air can get into the room.

Alternatively, with a bit of luck, there's a fan upgrade kit that might fit your housing. Pull down the cover, measure the dimensions and go from there. One caveat is that sometimes they still don't fit even with the same dimensions. When this was the case, I was able to swap the old fan mounting bracket to the new motor assembly to get it in there.

It sounds like a pain, but it was still better than opening the ceiling to replace the whole thing, since I didn't have access from above. But if you do have access above, definitely swap out the whole thing.

Related Stories

REMODELING GUIDES Survive Your Home Remodel: 11 Must-Ask Questions

By Mitchell Parker

Plan ahead to keep minor hassles from turning into major headaches during an extensive renovation

LIGHTING 5 Questions to Ask for the Best Room Lighting

By Karen LeBlanc Design TV Host & Writer/Blogger

Get your overhead, task and accent lighting right for decorative beauty, less eyestrain and a focus exactly where you want

DOORS 5 Questions to Ask Before Installing a Barn Door

By Apartment 46 for the Home

Find out whether that barn door you love is the right solution for your space

ORGANIZING Pre-Storage Checklist: 10 Questions to Ask Yourself Before You Store

By Laura Gaskill

Wait, stop. Do you really need to keep that item you’re about to put into storage?

4 Questions for Houzz Design Stars

By Annie Thornton

Help Houzz Readers Revamp Their Struggling Spaces

REMODELING GUIDES 9 Hard Questions to Ask When Shopping for Stone

By Ventana Construction LLC

Learn all about stone sizes, cracks, color issues and more so problems don't chip away at your design happiness later

5 Questions for Design Stars

By Annie Thornton

Share Your Suggestions for These Exteriors, Patios and Baths!

5 Questions for Houzz Design Stars

By Annie Thornton

Post Ideas for Updating an Exterior, Balancing an Off-Center Window and More

KITCHEN DESIGN 9 Questions to Ask When Planning a Kitchen Pantry

By Susan Redman

Avoid blunders and get the storage space and layout you need by asking these questions before you begin

REMODELING GUIDES Considering a Fixer-Upper? 15 Questions to Ask First

By Sarah Phipps Design

Learn about the hidden costs and treasures of older homes to avoid budget surprises and accidentally tossing valuable features

Sponsored

EK Interior Design

5 Reviews

TIMELESS INTERIOR DESIGN FOR ENDLESS MEMORIES

More Discussions

Calling all plumbers and contractors! Acrylic tubs you have known

7

overwhelmed! free standing faucet match champagne bronze delta

2

Separate shower head and hand-held shower controls

15

Changing shower fixtures

2

Shower faucet system

3