Bath Fan Venting - General DIY Discussions - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > DIY Forum > General DIY Discussions


Thread Tools Display Modes
Old 07-08-2009, 10:59 AM   #1
Join Date: Jul 2009
Posts: 3
Rewards Points: 10

Bath fan venting

Hello fellow DYI's,
I'm contemplating installing a 110 CFM Fan/Light combo in a kids bathroom were 15-20 minute showers occur atleast once a day. The fan would go in place of a ceiling mounted light fixture. Is 15ft too long a distance to vent outside? I thought of venting through my soffet which would be a shorter distance but was advised that condensation could be drawn back into the attic through the slotted openings in my soffet when my thermatically- controlled attic fan runs only during Summer months. Any input would be greatly appreciated.
Thank You.


BillPa is offline   Reply With Quote
Old 07-08-2009, 01:58 PM   #2
Registered User
Join Date: Mar 2009
Posts: 11,730
Rewards Points: 526

There are all sizes of fans available. It should do at least 5 room air changes per hour IRC 303.3
Backdraft damper required
Duct termination min. 3 ft. from bldg. openings or property line
Fan must vent to exterior

The best install would be up through the roof as hot air rises naturally. Run for 15 minutes minimum after shower.

The roof mount exhaust is 5-10% more efficient at removing warm, moist air (hot air rises) than a side mount one. Roof terminal should have a pipe neck attached for a positive connection. Use straight pipe (metal or PVC) whenever possible, wrapped with insulation. Corrugated, flex, pipe creates turbulence and has almost double the surface area for water exhausted in baths to collect on. Use as few bends as possible, and 45s* instead of 90s*. Tape metal joints with silver tape, not duct tape (4 year life). Use hose clamps or similar, and a screw on topside of metal joints. Use HVAC black tape for plastic covered insulation. Insulate the whole pipe and the fan box. Use caulk to seal the small gaps at the fan to wallboard joint. Let no heated moist air into the attic which would cause mold, mildew, wet other insulation (defeating its purpose), and even make frost in your attic.

Used some of my tips from elsewhere. Wade through it and pick out what pertains. Be safe, G


Gary in WA is offline   Reply With Quote
Old 07-10-2009, 03:22 PM   #3
Roofing Contractor
Leftyho's Avatar
Join Date: Apr 2009
Location: Coplay, Pa
Posts: 83
Rewards Points: 75


Vent it through the roof.
Leftyho is offline   Reply With Quote
Old 07-11-2009, 02:40 PM   #4
Household Handyman
Join Date: Feb 2009
Location: Albany, Ga.
Posts: 2,478
Rewards Points: 1,408

I also had to put up with the long showers when the boys were still here and I had to remind them many times to leave the fan running when they left the bath and shower area. NOW, I am installing bath vent fans as part of my business and have found something I wish I had twenty years ago. This is not an advertisement, just advice! Mark-Time now has a timer switch for the bath vent fan that looks like a regular toggle switch, except it has a built in timer for the vent fan. You turn on the light and fan combo, then when you turn off the light the fan continues to run for the pre-set amount of time to clear out the moisture. When I run across a customer with teenagers and can talk them into this switch they love it. Thanks, David
Thurman is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Soffit venting vs. DCI Smart Vent JDPII Roofing/Siding 1 02-28-2009 08:42 PM
Switching the Plugs in Bath Fan/Light MrBill_DIY Electrical 3 12-01-2008 06:45 PM
bath fan venting ponch37300 Remodeling 8 09-14-2008 08:14 AM
Venting question. Bcoleman6 Plumbing 7 03-21-2008 03:41 PM
Complex challenge with bath exhaust fan - need help with solution! Honest Bill Electrical 6 11-02-2007 02:52 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1