View Full Version : Any tinner/hvac guys on here.. bathroom vent question

11-22-2009, 09:17 AM
have a few questions about the proper way to vent my bathroom fans with stacked bathrooms.

11-22-2009, 10:46 AM
typically in remodel work if on the 1st floor out the wall 2nd mount vent pipe close to a roof vent

11-22-2009, 11:59 AM
Vent each fan seprate. Like ezra said 1st floor out wall. I like to put seprate roof vent for 2nd floor or vent out wall. Many city codes do not allow to vent in attic near roof vent must be vented out it own vent.

11-22-2009, 12:25 PM

1st floor out the wall, second floor out into the soffit or gable end if applicable. Just make sure it gets to the soffit horizontally and under the blown-in insulation. If you run a vent into the "free air" space of the attic by going vertically to a roof vent, the warm, moist air will surely condensate and freeze on its way up, thus creating ice and melting back down the pipe and ruining the drywall ceiling.

This is why there is a code for it.

Best of luck!


11-22-2009, 02:29 PM
well if you want to get technical the 2008 WI standard for energy star homes ASHRAE62.2 states that bath fans run constant at 30 cfm and be hooked to a motion sensor and the kick to 80cfm when some one enters room and run for 20 min after someone exits room.

11-22-2009, 05:56 PM

That code was created for newer homes that are built very tight and receive no "fresh air" naturally because windows and doors are gasgetted much tighter than they used to be. The interesting part of this code is that while they speak of "fresh air" for the home, they speak nothing of a make up air system to feed the air transfer. You cannot take air from a known space without replacing the air you're removing. That is called negatively pressurizing a known airspace. A perfect example of this is when you pull the door open to a restaurant and it's either hard to pull open or makes the "whistling" sound when you do. You'll find this commonly practiced at greasy "picture menu" restaurants that operate on a tight budget. The range hood needs a make-up air system to combat negative pressurization.

Unless I understood redrev incorrectly, he just wants to know how to vent two fart fans. No more, no less. Besides, that code has been modified from commercial to residential for no other reason than to be a revenue generator.

Common sense should always override a lobbyist with a hidden agenda.


11-22-2009, 06:55 PM
I know they did the same thing in MN.it is a joke but what are you going to do.I'm MN it is only if you are trying to build a energy star home so kinda more a if you want the ratting code.we do all remod in the west burbs of TC metro.have never been called on just using 4in insulated flex next to a vent.in summer we go out the top or side in winter if not a hip.but then inspections have become a joke also.I think the last kid that came out was no more than 21yrs old and was going off a check list he had on his clipboard

11-22-2009, 07:41 PM
In Illinois we vented first floor out the wall and second floor connected to flex and to a round diffuser in the sofit. No longer can just get the flex close to vent, need to connect directly to outside, kinda like a dryer vent. The purpose is to eliminate the moisture entering the attic area and vent it directly out. Round diffusers look good and are fairly cheap, for sure no moisture in attic

11-22-2009, 07:56 PM
Like lenny said http://www.johndee.com/discuss/clipart/happy.gif


11-22-2009, 08:19 PM
oh the joys of buying a used house. lets just say i bought my house from a do it all maintenance guy...looked great at first but then after living in it for a while you see things you dont like. right now the fans are goin to the attic &#40;i know it is bad news&#41; i think he said they are tied together. the top bath can be put out a gable end or terminte through the roof but the lower bath im not sure. i think the lower one is surrounded by concrete wall in basement. i could beat this guy for cobbling <font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font> together.

11-22-2009, 08:21 PM
Vent it to your Teenagers Bedroom - revenge - GOD they can be mouthy!

11-23-2009, 12:39 AM
Forget City Code &#40;Permit$&#41; on Owner DIY remodel stuff. If I done my research and feel comfortable and confident with my work, I do it. You can too. And I aint talkin Beverly Hillbilly fixes.
On my bath fan, I ran it vertical 4 ft direct to an outside roof vent, sealed both ends and used insulated tape from a roll, plastic and couple strips of fiberglass batts . Other than the Jet Engine fan I knew I was buying, Im good. No drips or moisture in fan or ceiling.
1st floor only option is thru an outside wall.
2nd floor thru outside wall or attic roof.

What was the question?