Bathroom exhaust fan venting outside via soffit?

[MiamiCuse]

I have 4 bathrooms where the bath exhaust fan were connected to 4" sheet metal ducts, when I remodeled the bathrooms I chased the ducts and none of them actually vent outside, they just vent into the attic.

I was able to connect one exhaust fan to an abandoned vent through the roof, the vent was originally intended for a kiln which I removed. Now I have three bathroom exhaust to deal with, all 4" ducts.

I am trying to avoid punching holes through the roof so looking for an alternative. The house's roof has an overhang about 5 feet wide, and the soffit is made of wood panels. My idea is to vent through the soffit.

What I am thinking of doing is to cut a 4" diameter hole from the underside of the soffit panel. Once this is done, then I will take a 90 degree 4" duct elbow, connect it to a flex coiled aluminum duct with stainless steel clamps, and push the elbow from inside the attic towards the hole (I cannot crawl too close to the hole, as the space is real tight in the overhang area) once I am near the hole I can go back outside, and crab the elbow and pull may be about half an inch of that elbow to the outside.

Now here is where I am not sure what to do. Is there some sort of collar or vent cover that I can clamp on glue onto that duct hole which is now facing down? Something that would normally be closed but will only open when there is positive pressure from the fan? This would have to be something that is spring loaded right? I don't want to just leave a 4" wide hole there as critters would just go in. I guess I can cover it with a fine mesh of some sort.

My question is - will this work? To have a exhaust vent outlet that face down instead of up? If so, is there any sort of special vent cover designed for this situation?

Thanks,

MC

[aemeijers]

Not an ideal solution, but it will work. But you need to start from the other end- attach the hose to a spring-loaded vent cap that screws to soffit, and stuff it in from the outside of house. A dryer vent cap should work. You can tape the loose end to a straightened coat hanger or something, and use that to steer the hose to the taller part of the attic, or maybe attach a tennis ball to six feet of twine tied to the end of the hose, and reach up through the hole and pitch it the right direction so you can pull the hose that way. It is really a lot easier with 2 people, especially if you can draft a skinny 10 year old to help. The person in the attic can use a stick with a hook on the end to snag the ball and twine if the opening to soffit is too narrow to throw through.

Note that code may require X number of feet between fan outlet and window, if there is one. Make sure not to have low spots in hose where condensation can collect- go UP from fan, and then a smooth arc to outlet, hanging hose from rafters as needed, in a manner that won't collapse the hose.

-- aem sends....

[RBM]

I recently looked at a job where I had a similar situation. I didn't wind up doing the job, but here is the soffit vent fitting I came up with. I think I only came up with one other soffit mounted fitting, which I can't find now. I like your idea though. Make sure you drill the hole larger than 4". I think 4.5" will be a comfortable fit. I would piece together the elbow and a

5' section of vent pipe for the attic section, then attach a damper and flex. At the opening you can cut and flair the elbow, then screw the flaired sections to the soffit. HD sells a sort of bird cage fitting that could be screwed over the opening, or you can just use this fitting: >

[Limp Arbor]

Most exaust fans have an internal flapper. All you should need is a bug/bird screen for the end of the run.

[MiamiCuse]

RBM, if I do it from the other end, I am not going to be able to push 5' of pipe into the hole with the soffit being so shallow at that spot. I guess I will just have to try it. The vent cover link is a good choice, I am going to order it.

Thanks,

MC

[MiamiCuse]

RBM, I found this one that may be an alternative.

[RBM]

The Lambro is even nicer. Don't buy your hole saw until you see what the diameter of the collar is. The hole has to be big enough for the collar, the duct, and whatever attachment device you use to connect the duct

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[RBM]

On another note, I hate that flexible aluminum duct. I've used several brands, and found all of it to be miserable to work with. It dents and rips so easily especially when you have blind areas, like soffits that you have to drag it through. It's also hard to clamp it onto duct and collars. The best stuff I've worked with is a type of plastic or vinyl, that looks metallic, but isn't, and of course I buy stuff from so many sources, I can't remember where I get that.

[bob haller]

Install a central main blower, when any fans are activated the main one in the attic will turn on and vent thru the existing vent if its large enough.........

way quieter too

[Nate Nagel]

I found some heavier aluminum duct from the Despot of all places. Used it for my dryer vent, and it's soooo much nicer than the usual dryer vent stuff. Instead of bending it around the corners I used two elbows and just used the flex for the run between the elbow at the dryer and the elbow at the vent hood.

For a bath fan, I believe a short length of flex close to the fan is desirable at least for vibration isolation, but in an ideal world you'd use rigid for the rest of it.

nate

[trader4]

It's easier to install, but how long will it last? And if it starts falling apart, in many cases it isn't easy to replace.

[RBM]

It's easier to install, but how long will it last? And if it starts falling apart, in many cases it isn't easy to replace.

I don't know how long the aluminum stuff lasts either, and my bigger concern is how many holes and rips I got with the aluminum, in the installation process, that I don't know about. The metal also has a tendency to buckel when trying to make tight 90 degree bends. Airconditioning companies use an insulated plastic duct, that seems to hold up just fine

[Don Young]

A piece of heavy copper ground wire is bendable but stiff enough to permit fishing 10 feet or more easily. If necessary have two people with two pieces of hooked end wire working from opposite ends. You can also tie a cord to a fishing pole and push it to where you want it, untie the cord thru the hole and retrieve the pole.

You can also get pretty far under eaves if you lay a piece of plywood across the ceiling joists and lie flat between the rafters. You would need to be really careful of any nails sticking down thru the roof decking. As an extreme measure, you can even brace the ceiling and slide on the top of the ceiling between the joists.

Don Young

[MiamiCuse]

Any reason I cannot just use 3" PVC DWV pipes, for most of the run, and only switch to aluminum ducts when it's near the van and near the soffit, this way even if I am doing stuff in the attic there is a very little chance of someome just stepped on the duct and flattens it.

One of the bathrooms vent pipe was totally flattened because the only had the AC handler in the attic replaced, and whoever did it left the old blower in the attic, and it sat on top of a 4" duct from an exhaust fan, and that duct was totally crumbled.

MC

[Tony Hwang]

Hi, First, if you live in cold winter climate zone, duct has to be insulated to deal with codensation.

[RBM]

I have no idea what building codes say, regarding that, but for the reasons you describe, and the fact that smooth pipe will allow better air flow,I used 4" ABS pipe for the straight runs in my house.

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[HerHusband]

MC,

Around here (Washington State), it's hard to find vents made for soffits. Most are made for wall installations. But if you can find the vents, they should work fine. The one issue you have to watch for is not mounting the exhaust vent near the eave vents for the attic. Otherwise the moisture can get pulled right back into the attic.

At my in-laws house, I ran a line across the top of the ceiling joists and out through a side wall. They have a hip roof, but had extra high walls above the ceilings, so it worked great. Otherwise, you could vent out a gable end wall (if it's not a hip roof).

I used 4" PVC DWV for the straight runs in our house and only used the aluminum ducting to make the connections at each end. Making the transition is the difficult part, the 4" PVC is just a bit too big to fit inside the flexible duct. I don't know if 4" DRAIN line would work better, you might measure the two pipes at the store and see if the outside diameter is smaller with the drain pipe.

If you need to make bends in the PVC pipe, try to use 45 elbows instead of

90's to maximize air flow.

When you install the vent, try to slope the majority of the run towards the outside vent. That way any condensation that builds up in the duct can run off outside instead of back into the fan.

Anthony

[RBM]

The ABS that I used is thinner and lighter than PVC. The tapered ends of 4" vent pipe fit snugly inside the pipe