New Roof Soon - Bath fans out the roof or vented Soffit? (New Hampshire)

Hi All,

This has been racking my brain, searched the forum and the internet and I hear 50/50 for both Soffit/Roof Vent argument. I've tried searching for an answer but couldn't get enough info to satisfy my question.

Current Situation:

Both 2nd floor bathroom exhaust fans go over to the soffit for venting. My current roof has a full length ridge vent and full length soffit vents. There is no mold or any signs of damage to the plywood inside the attic where the two fans exhaust. (House is 22 years old)

Question: Since I live in New Hampshire and I am getting a new roof installed in a few weeks (Due to age - not leaks or ice dam damage) do I get two Roof vents installed or continue to goto Soffit?

Concern: I am concerned with the Snow build up around the roof vents during heavy snow winters (like this past winter)

Thanks!

 

I would vent the bathrooms through the soffit if possible. Like you mentioned there is no concern over them being blocked by snow and it's less holes in your roof which in general is a good thing. The only thing I have against baths venting through the soffit is dirt and mildew can sometimes collect around the outlet. Being on the soffit it can be visible but cleaning every few years should take care of it.

 

Thanks for the reply

I have gotten a 50/50 mix from the roofing contractors I have talked to... The contractor I am going to use would rather not install the roof vents.

Considering that there is not any mold/moisture issues around the area where the bath fans are currently vented I think I am just going to stick to the soffit venting.

 

Difficult choice given you've had no apparent problem so far. But now is the best time if you ever wanted to move them to the roof.

The correct answer would normally be the roof, as exiting the soffit runs the risk of warm moist air being drawn back into the attic, just where we don't want it. How much of a concern depends somewhat upon how much overhang there is and how that exhaust duct terminates in the soffit. When a contractor gets really lazy and just lays the end of the duct in the soffit area there is a greater risk of a problem. When an actual soffit mounted vent is used, at least the moist air makes it to the outside before it is temped to head back into the attic.

Roof slope, location on the roof, and history of snow and ice all play a role, but my vote would be for installing it through the roof. Properly installed, there should be almost zero risk of a future leak.

Another concern is when you sell, future inspectors may not like the soffit termination.

One added caution for the through the roof is to insulate the to avoid condensation dripping back in the direction of the fan.

Use a "delayed off timer" on your fan switch to remove more moisture and to dry out the duct before the fan turns off.

Bud

 

I'll have to pitch my hat in with the NO vote. If the soffit venting is working for the fans, it ain't broke. Why punch two holes in a perfectly non leaking roof when your method is working presently?

 

I'm with Bud on this one.
https://www.googleX.com/search?q=sof...2F%3B300%3B225

 

Bud gave you the right answer. Out the soffit is the WRONG way to do it. You probably have mixed results from your roofing contractors because half of them don't want to be bothered to do the extra work, or don't know the difference. Exhaust vents should go out the roof, or out the gable end walls.

 

Never out the roof if there is an alternative way of doing it. Gee, why chance the leaks, snow back up, icing, etc??? Soffit exit may not be ideal, but if it is working without problem, why fix it? Gable wall ends are better, provided the run is not too long and feasible.

 

In my opinion, it don't matter if there is one roof penetration, or 100 of them. As long as they are done right, there will never be an issue with them.

 

So CrazySteve, your choices still haven't been conclusively made for you. Still split somewhat. You'll just have to choose the best of the suggestions and run with it.

 

Steve, I went through the same thing a few years back when we did our roof. A hip roof ranch, so no gables, and for 30 years our bathroom vents went through the soffits, but I knew that was "wrong", so decided they were going through the roof. But, even though I fully understand the air flow issues, and generally recommend going through the roof, or definitely gables if that is an option, ours are still through the soffits. First off, I inspected the underside of the sheathing and the insulation very carefully, and found absolutely no harm done from those 30 years of venting through the soffits. Secondly, we don't get the heavy wet snows that whip up the east coast like perhaps you do, but we're in Michigan, and do get snow. It is not uncommon to have 6" or more of snow on the roof for 4 months or more, and that's 4 months or so that those vents would be blocked. Last winter, it was more like a foot or more for closer to 5 months. So clean it off! Yeah, that might sound practical south of the Mason Dixon, but not here. It's bad enough to clear what you can once in a while to get the weight off and to dig the vents out so that the waste lines don't back up. Yup, I understand and agree with the issues, but, when it came time, I went with my gut, and did not put any more holes in the roof.

 

Out the soffit 'can' work without issues, but that does not change the fact that it is wrong wrong wrong. There is really nothing else to say on the subject. Read any building science article about exhust vents in the soffit and they all will tell you no.

 

Building Science is cute, but it, by no means, encompasses every aspect of installation, every climate into which such will be installed, and uses generalities way too much. Practicality must prevail rather than a consortium of generalists. They say it is "wrong". Wrong for whom? Location? Reasoning? Not comprehensive enough to me.

 

So not sure what to do.. because as "Aka Pedro" Says 30 years no issues with bath fans out the soffit.

My house is 22 years old and both bath fans have gone out the soffit. Granted - only our 3/4 bath really gets steamy enough to be concerned (full bath is for the kids). I am heavily leaning towards continuing to use soffit vents and call it a day...

So let me throw this into the mix... One bathroom is at the top of the stairs which is the centerline of the colonial style house and is about a 12 foot run to the gable end. The other is in a 3/4 bath which is only a 8 foot run to the gable end.

So do I consider duct work with an in-line boost fan and vent to gable end?

 

The reason it is wrong has already been clearly defined. A statement such as 'building science is cute' just shows ignorance on the subject. Virtually all codes are derived from building science tests and historical evidence.

Essentially what you are saying is that because it works some of the time it is acceptable. Tiling over 5/8" osb with over spanned joists will work some of the time to, but you would never recommend that someone does it.

 

Crazy Steve, if it is working in your situation, it is honestly unlikey you will have issues if you continue to do it that way (presuming your current roof venting is maintained).

Having said that, you came here asking which way was the right way to do it. Out the roof or a wall is the right way to do it. Anyone that tells you different does not understand why it is wrong to go out the soffit.

 

Those horizontal runs to the gable ends don't sound too long for me, they are an option.

Although Pedro's has apparently worked it is short sighted to use a single example as evidence that something (anything) is acceptable. In defense of "science" it is at least a source where they have tested and reviewed the results over a large number of homes. I would expect that their testing resulted in many homes not having a problem, but that either more homes did or the consequences of the resulting problems were significant enough to avoid the potential failure.

IMO, it is the potential for having a mold problem in the future that would have me going through the roof. A leak, if it happened is easy to fix. Mold, on the other hand is a stigma that a house never overcomes and it is expensive.

Bud

 

I have to agree with Keith on this subject. If you are concerned about snow blocking the vent then instal a chimney instead of a flat roofjack. Stainless steel would stand the weather for years.

 

Thank you for the compliment. I have been doing this stuff in the South for over 20 years. We have a different climate than that averaged by studies. What works for us may not work for Winnepeg or Minneapolis. What is required by them is redundant and overkill for us. Florida is another example of extremes. Another example is sealing of crawlspaces. For some areas it is the best solution. Here, we are still required to install foundation venting all around. It works for us.

I appreciate your thoughts and I appreciate studies done in the name of keeping us all safe from ourselves. For the OP what you are suggesting is probably best, but putting it all in one basket is irresponsible.

 

Chandler, I appreciate your experiance, but moisture control is important in all climates. It is probably the single biggest factor in much of home design. Maybe it is less of an issue certain areas, but it is still an issue, and it should be dealt with the right way. However, the OP is not in a southern climate, he is in the same climate as myself, where moisture comtrol in an attic is of absolute importance. I have also been in the industry for almost 20 years, and am red seal certified in my field and am confident with my knowledge that I can stand behind my statement that out the soffit is the wrong place for any vent that exhausts moisture from a home. I also do home inspections and if I seen this, I would flag it as an issue.

At an absolute bare minimum, if you insist on running an exhaust vent out the soffit, the soffit 2 feet either side should be blocked off solid.

 

Well everyone - This turned out to be a great question with good results. Alot of good points have been made and I appreciate that.

I have at least decided that I am NOT going out the soffits anymore. I am going to call an HVAC guy to see what it would take to vent to Gable end as I am still weary about adding penetrations to the roof...

Furd made a great suggestion to use a chimney stack as opposed to the standard Broan 636 roof jack which is low profile and more susceptible to be covered with snow. Also that portion of the roof faces South East so it does benefit from alot of exposure to the Sun.

 

Gable end venting is ideal. You can vent up to 22 feet without the need to add a booster or increase the fan size. Just be sure the vent pipe is insulated it's entire length.

 

So if I did vent out the Gable - I gather, I'd want the pipe to go up and then slope down towards the Gable end exit. How much slope should I have on the pipe over to the Gable end?

 

Yes, it should slope towards the gable. it only needs to slope enough so anything that might condense in it will run outside and not stay in the pipe, or run back in the house. This is where the pipe insulation is critical. The better it is insulated, the less chance of condensation problems.

 

If you go with the flex insulated duct, provide a woof support the full length so that there are no dips to collect moisture. Although I don't care for the flex, when fully supported most of the concerns go away. Some I have seen look like a roller coaster ride and those dips will fill with water. I've seen gallons dumped out of them.

Also, in your climate, adding more insulation around and over the duct is a good idea.

Bud

 

Hello Gang!

Sorry for not checking in sooner - Life has been busy!

I had a new Certainteed Roof system installed at the end of May. I supplied the roofing contractor with 2 of these dampered roof vents. He was quite impressed with the quality (and said he will probably start using them as his preferred supplier)

Copper Roof Vents and Steel Roof Caps for Exhaust by Luxury Metals

He installed them 6 feet up the roof (just past the 2 courses of Ice and water).

For now I just hooked up the exisiting fans with flexible 4" duct hose. When I install the new fans in the fall I will go with rigid duct pipe.

Thanks again for all of the insight and knowledge!