I replaced a bathroom ceiling fan today, and to do so I crawled up into our house’s attic for the first time since we moved in 2 years ago. After clearing away all the blown-in insulation, I was able to install the new fan without any trouble. However, when it came time to connect the old 4" vent pipe to the new fan, it occured to me that the pipe seemed pretty wobbly. I thought there might be a loose joint somewhere, so I traced it as it ran horizontally toward the closest exterior wall. It ran out through a batt of insulation, past the exterior wall, and stopped over the soffit vent. The roof on our house has about an 18" overhang with a continuous soffit vent of perforated metal that’s a foot or so wide. Puzzled by this, I realized that I couldn’t see a vent pipe for the toilet, either, so I dug around a bit and found a 2" toilet vent running parallel to the fan vent. It also poked out over the soffit vent, open-ended, one roof truss over from the fan vent. The area around the end of the vents was sort of boxed in with insulation batts, so the vents weren’t blowing freely into the attic. I squirmed my way over to the opposite end of the house and noticed that the other bathroom is vented the same way - into the space above the soffit vent.
Is this an accepted method of venting for a ceiling fan and a toilet vent pipe? I guess that I expected a vertical pipe or pair of pipes running to a roof vent. I didn’t see any rot or anything in the little wedge of space around the end of the vent pipe, but it seems like this setup would trap a lot of moisture in one spot under the roof.
In a related question, there is blown-in insulation in the attic, with fiberglass batts positioned vertically between the roof trusses over the external walls. I suppose that this keeps the blown-in stuff from covering the soffit vents. However, the batts go all the way up to the roof sheathing, so it seems as though there would be little air movement through the soffit vent into the attic space. Is this a potential problem? I’ve seen shallow tray-like things that can be tacked under the roof sheathing to keep an air channel open over the insulation; how would I know if I needed something like this?
That still seems odd to me. If it where MY house, I’d have someone come and move them so they actually vent outside (I can do most around the house work, but I don’t like putting holes in exterior walls or roofs). As for the vent, that just seems like a bad idea, you could wind up with noxious gas up in your attic and seeping down into your house. If I saw those things, I’d be atleast slightly uncomfortable. Do you have a roof vent? If you do and it’s always running you could run the bathroom vents up to that, and probably even the traps.
According to the current building codes, those are both unacceptable methods of venting, especially the plumbing stack. However these methods may have been acceptable when the house was built in your area. If your house is 20 or more years old and you live in a rural area this is very likely.
Plumbing stacks are normally run up through the roof and may or may not be covered with a rain cap. The plumbing vent is to allow excess methane out and provides for more efficient flow of the wastewater from your house. What you’ve described is somewhat concerning because in it’s current condition “sewer gas” can be escaping into your attic. While methane is flammable the situation you describe is more of a hygienic issue, as in your attic may stink if you have plumbing or sewer issues. You sound pretty handy so you may want to consider running that pipes straight up through the roof.
Until very recently it was ok to run bathroom vent vans just up into the attic. My first house was like this and I ran flexible vent pipe over to the large gable vent to prevent moisture build up. Originally it was assumed that there was enough air circulation in the attic to handle the air and moisture vented from the bathroom. More recently it’s been found that is not true and the extra moisture in the attic can lead to mold. What you describe should be fine since you didn’t seem to notice any mold and the pipe is venting to a soffit vent. In the current code bathroom vent fans are run to soffit or side of the house where they vent through a louvered opening. You may want to consider adding a right angle pipe that is wired to the soffit venting if your concerned.
Lastly what you describe in about the insulation sounds very odd. But then you didn’t describe the roof type. As a rule there should be a considerable amount of airflow in an attic. This prevents condensation in the winter and aids in cooling in the summer. You may want to have that issue looked at by an insulation contractor.
We discovered that one of the bathrooms in our house was vented into the attic, not to the outside. We discovered this because we had a perpetual waterfall in the central hallway whenever we ran the air conditioner. Mr. SCL got some flexable duct and routed the vent to the end vent in the attic. We have found that my late father-in-laws tendency to pay idiots to do things is costing us in the long run. Fortunately we have caught this stuff before permanent damage was done.
I went back up there to do a more thorough inspection this morning, and found that I was wrong on one point. The toilet stack does not vent into the soffit space as I had at first thought. It appears that the vent stacks for the toilet, shower, sinks, and bathtub are all piped together and run to a vertical pipe that goes through the roof - about 20’ from where I expected it to! So I don’t think that I have a potential methane buildup problem.
However, both bathroom vents *do *dump into the soffit space, although they both have a right-angle at the end that pokes down toward the existing perforated metal soffit. I choose to believe that the dude that put up the soffit panels forgot to cut a hole and connect the vent pipe to a true output vent like this. Not terribly attractive, but I like the flapper valves to help keep pests out.
At any rate, I’ll be hunting for a couple of these things; with any luck I’ll be able to do most of the work from the outside of the house. I will definitely not be going back up into the attic during daylight hours until the temperature here drops about twenty degrees…
I suppose that some of the exhausted air could get drawn back up into the attic space, but I think that it would be pretty well mixed with outside air. There is a lot of surface area of perforated soffit vent, and it seems like the ‘draw’ through any particular section (like the 2-4 feet on either side of a thru-soffit exhaust vent) would be pretty low. My main concerns are that the heat from air vented into the attic can cause melting of snow on the overlying roof and contribute to ice dams, and that the moisture in the vented air may condense on the inside of the roof or on the insulation. It seems to me that if you can ‘condition’ the exhaust with a lot of outside air, it should eliminate the heating/condensation problem. Still, it’s an open question as to how much heat/moisture could make it back into the attic space - but I know that it’ll be less than the current setup.
Is there any way (read, would it be ugly) to bring the pipe through the soffit and then out so that it’s atleast flush with the edge of the eve (then put some type of louvered cover on it)?
