Thread: Bath fan venting and Dryer venting

Good afternoon,

I have been following this forum for a month or two now just for general curiosity and knowledge.

I have two questions I have found differing opinions on. I am hoping to get some good recommendations.

Bath fan venting:

I recently installed an 80 CFM bath fan in my bathroom (5' x 8' x 8'). The previous fan was vented to the gable end vent (about 20' away) using the cheap 4" flexible ducting. I have the following options to install the new vent: straight up and through the roof, through the brick siding in the gable end (20' away), or through the soffit with a termination that has a backdraft preventer. I am interested in the best approach regardless of the work involved. I intend to do things right the first time and want the job to last.


Dryer vent:

I also have a gas dyer that needs to be vented properly. The previous owners of the house vented the dryer into the crawl space. Because of HVAC ducting in the crawl space, the best options for venting the dryer are straight through the roof, using an approved cap, or through the gable end wall (20' away). Again what is the best option here? Each would require use of a ladder to check operaiton, and I have no issue with going on the roof once or twice a year to check things.


Thank you in advance for your help.

Similar Threads:

• Bath Fans Exhaust Venting to Exterior
• Electric dryer venting
• Dryer venting
• Dryer duct venting
• Venting a dryer indoors

In general, the shortest distance with the least amount of bends. I never liked roof vents for two reasons: 1 - Another hole in the roof, 2 - SNOW.

If you exhaust out a soffit that is vented it is recommended you close off 2'-0" of soffit to each side to avoid the exhaust going back into the attic through the vented part of the soffit. Kind of like blowing smoke into the wind blowing at your face.

Bath fan - shortest route is best - any of your options if properly installed should be fine.

Dryers are a bit more tricky due to lint build-up and need for cleaning. I'd go with the option that leaves the largest part of the duct accessible and/or straightest run possible for future cleaning considerations.

Roof vent directly above the bathroom for the exhaust vent.

Dryer vent, better to go horizontal. Blowing lint up hill doesn't work very well, and the roof vent gives you lint on the roof, unsightly, or a big wad of lint caught in a screen up there where nobody goes. You want a straight, smooth run. I'd drop down below the heating ducts or around them to the nearest wall.

Originally Posted by John Kogel

Roof vent directly above the bathroom for the exhaust vent.

Dryer vent, better to go horizontal. Blowing lint up hill doesn't work very well, and the roof vent gives you lint on the roof, unsightly, or a big wad of lint caught in a screen up there where nobody goes. You want a straight, smooth run. I'd drop down below the heating ducts or around them to the nearest wall.

Agree on both. Fewer turns for dryer vent is best. Turns catch lint.

Originally Posted by Lon Henderson

Agree on both. Fewer turns for dryer vent is best. Turns catch lint.

Be mindful of the life of the dryer blower motor... the longer the run the harder the blower has to work due to friction loss...particularly on vertical installation be mindfull of lint buildup increasing the need to clean the vent at regular intervals, again to save labor for the fan motor. Best advice is go horizontal and shortest distance possible.

Folks, check that dryer pipe in your crawlspace (or attic) now and then.

Originally Posted by John Kogel

Folks, check that dryer pipe in your crawlspace (or attic) now and then.

John, that looks like a property I bought. I filled a large garbage bag with just lint. Must have been that way for 20 years or more.
I run it to the outside.

Originally Posted by John Kogel

... roof vent gives you lint on the roof, unsightly, or a big wad of lint caught in a screen up there where nobody goes.

I know you know John but just so everyone else gets it, screens on a dryer termination is a big no, no.

Originally Posted by Loren Sanders Sr.

Be mindful of the life of the dryer blower motor... the longer the run the harder the blower has to work due to friction loss...particularly on vertical installation be mindfull of lint buildup increasing the need to clean the vent at regular intervals, again to save labor for the fan motor. Best advice is go horizontal and shortest distance possible.

Note: ONE LAST BIT OF INFO

If your dryer has a lint filter on top of the machine, remove the lint filter while the dryer is running and place a cleannex or other light weight piece of paper over the opening, be sure to keep a good grip in the paper, but if your vent is clogged, the paper will not be sucked down into the machine.

This does not mean that your dryer vent is totally clear but only helps you to understand if it is clogged. But all dryer vents need an occasional cleaning. The longer the run and vertical runs need cleaning more often. Do yourself a favor and take care of this normal maintenance chore. You will save money and extend the life of your expensive dryer. Unfortunately for me our new dryer has the vent filter inside the dryer and this does not work for those dryers.

A niece sent me this on Facebook. I tried it out and sure enough, my vent screen was clogged.

INFO ABOUT CLOTHES DRYERS (I do this all the time) The heating unit went out on my dryer! The gentleman that fixes things around the house for us told us that he wanted to show us something and he went over to the dryer and pulled out the l...int filter. It was clean. (I always clean the lint from the filter after every load clothes.) He told us that he wanted to show us something; he took the filter over to the sink and ran hot water over it. The lint filter is made of a mesh material. I'm sure you know what your dryer's lint filter looks like. Well...the hot water just sat on top of the mesh! It didn't go through it at all! He told us that dryer sheets cause a film over that mesh and that's what burns out the heating unit. You can't SEE the film, but it's there. It's what is in the dryer sheets to make your clothes soft and static free. That nice fragrance too. You know how they can feel waxy when you take them out of the box...well this stuff builds up on your clothes and on your lint screen. This is also what causes dryer units to potentially burn your house down with it! He said the best way to keep your dryer working for a very longtime (and to keep your electric bill lower) is to take that filter out and wash it with hot soapy water and an old toothbrush (or other brush) at least every six months. He said that makes the life of the dryer at least twice as long! How about that!?! Learn something new every day! I certainly didn't know dryer sheets would do that. So, I thought I'd share! Note: I went to my dryer and tested my screen by running water on it. The water ran through a little bit but mostly collected all the water in the mesh screen. I washed it with warm soapy water and a nylon brush and I had it done in 30 seconds. Then when I rinsed it, the water ran right thru the screen! There wasn't any puddling at all! That repairman knew what he was talking about!
Mama-A

Originally Posted by Marshall Eckert

A niece sent me this on Facebook. I tried it out and sure enough, my vent screen was clogged.

INFO ABOUT CLOTHES DRYERS (I do this all the time) The heating unit went out on my dryer! The gentleman that fixes things around the house for us told us that he wanted to show us something and he went over to the dryer and pulled out the l...int filter. It was clean. (I always clean the lint from the filter after every load clothes.) He told us that he wanted to show us something; he took the filter over to the sink and ran hot water over it. The lint filter is made of a mesh material. I'm sure you know what your dryer's lint filter looks like. Well...the hot water just sat on top of the mesh! It didn't go through it at all! He told us that dryer sheets cause a film over that mesh and that's what burns out the heating unit. You can't SEE the film, but it's there. It's what is in the dryer sheets to make your clothes soft and static free. That nice fragrance too. You know how they can feel waxy when you take them out of the box...well this stuff builds up on your clothes and on your lint screen. This is also what causes dryer units to potentially burn your house down with it! He said the best way to keep your dryer working for a very longtime (and to keep your electric bill lower) is to take that filter out and wash it with hot soapy water and an old toothbrush (or other brush) at least every six months. He said that makes the life of the dryer at least twice as long! How about that!?! Learn something new every day! I certainly didn't know dryer sheets would do that. So, I thought I'd share! Note: I went to my dryer and tested my screen by running water on it. The water ran through a little bit but mostly collected all the water in the mesh screen. I washed it with warm soapy water and a nylon brush and I had it done in 30 seconds. Then when I rinsed it, the water ran right thru the screen! There wasn't any puddling at all! That repairman knew what he was talking about!
Mama-A

Not disputing the above post but I tried the water test and the water did go through. However I took a tooth brush and scrubbed my current Maytag Dryer's screen has smaller openings than a screen door screen, there was a film on it that came off with plain hot water and a tooth brush, also the water would bead up and block it from draining through the screen, but when I blew on it, it would clear out. So this post is just saying that yes, there is a film on it and depending on the size of the screen openings you are creating a strain on the dryer motor if you don't clean off the dryer sheet residue with a tooth brush or other soft brush. Kudos to the Original Poster for the enlightening message.

I would check the manufactures recomendations for maximun vent run. In most cases, maximum run is 20 feet of straight venting. Subtract 5 feet for every 90 deg turn. This may help along with the other replys in figuring the best way to vent the dryer.

Bath venting should be vented thru the siding with a back draft damper NOT thru the rafter venting
Dryer to be rigid smooth walled pipe with no penetrating fasteners to catch the lint There is a high temp foil tape for this application. I would never vent a dryer exhaust thru the roof even if allowed Vent exhaust never to crawl area must be vented to outside