Should dryer exhaust duct attach to dryer roof vent?

[pb4uski]

Installation must be in accordance with the manufacturer’s instructions. You probably don’t have that available but dryerjack has a lot of info on their web site, including code requirements: https://dryerjack.com/dryer-termination-code.html

I’m sure they should be connected. Be careful to observe the code requirements not to use sheet metal screws or similar as they present an obstruction in the duct giving a place for lint to be caught. Screens are a no no as well.

SF Gate has a web page on this as well: https://homeguides.sfgate.com/install-rooftop-dryer-vents-21258.html

Thanks. On the first link I noted:

504.4 Exhaust installation. Dryer exhaust ducts for clothes dryers shall terminate on the outside of the building and shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination. Ducts shall not be connected or installed with sheet metal screws or other fasteners that will obstruct the exhaust flow. Clothes dryer exhaust ducts shall not be connected to a vent connector, vent or chimney. Clothes dryer exhaust ducts shall not extend into or through ducts or plenums.

Ours and Chuckanut's terminate inside the building by an inch or two.

 

[GalaxyBoy]

Don't you run the risk of a rodent getting in? As I said in an early post, I just re-connected mine to the Attic vent and there was definitely a fine mesh screen.

I’m no expert but look at the pictures on the dryerjack web page I linked. Somewhere they also mention that screens used to be common but the pictures illustrate why that’s no longer considered a good idea. Code requires a backdraft damper for the purpose now.

I should also mention that dryerjack referenced the model code. The code actually adopted in a jurisdiction obviously takes precedence. Also, legal requirements for existing buildings might differ.

Disclaimer: I used to be a professional engineer in fire protection but since retiring I let my license go and now specialize in relaxing and drinking homebrew. I might not know what I’m talking about.

 

[triangle]

I wonder if in the last building re-roof they weren't connected back up. Like maybe new vent housings that didn't have as long as a tail. Or there was a connector like Sunset mentions, and they just yanked off whatever came out with the old vent housing.

I also expect that is what happened. When I replaced the exhaust vents on my home last summer I noticed some variance between manufacturers on how long the vent cap pipe extended below the vent caps. And variation in lengths of female connectors that one would use to connect the vent cap to the longer section of pipe. So if the person overseeing the work was not very diligent then it could come up short or not fit together properly.

Fine mesh screens are a bad idea for a dryer vent cap as lint can build up and block the exit. They are a good idea for bathroom exhausts. But when there is no screen, critters can get in so not an ideal situation. For a wall exit putting the dryer vent cap inside a cage is a workable compromise for keeping larger critters out while not creating a blockage below the vent flapper.

 

[Jerry1]

For a wall exit putting the dryer vent cap inside a cage is a workable compromise for keeping larger critters out while not creating a blockage below the vent flapper.

Even when you do that, you have to keep it clean. Clearing the lint becomes an important maintenance activity. It's not a screen, but it still gets clogged up in time.

 

[triangle]

Even when you do that, you have to keep it clean. Clearing the lint becomes an important maintenance activity. It's not a screen, but it still gets clogged up in time.

Yes. Though does help make it more visible and therefore more likely that a homeowner does not overlook it for long periods of time. Also some chance that the wind or a driving rain will help flush out the lint, though not something to be counted upon since a wall vent cap should be protected under an eave.

Most homes setups do not have a secondary lint trap in the laundry room behind the dryer, but I recommend that. Cuts down on the frequency of needing to clean the vent pipe or vent cap. I installed one last year and was surprised how quickly lint built up in this secondary trap.

 

[Sunset]

It talked with the maintenance guy who is frequently in the attics for other reasons and he told me that they were all done that way (not connected that is).

Not a very proactive maintenance guy, hopefully there are not other issues that he knows about and ignores.

 

[Sunset]

I had my bathroom vent like that for years until I got around to fixing it. When the house was built, they just took a flex pipe up to a roof vent and nailed it to the sheathing....... My bathroom vent never caused any problem .....

Same here, I checked and my bathroom vent ends right under a roof vent, there is no damage (thankfully)
Our bathroom would have much less moisture production up the vent than a dryer.

 

[skipro33]

https://www.twincitiesfurnacecleaning.com/blog/hidden-danger-on-your-roof-dryer-vent-screeningI think it's built right and here's why. Dry vents can not have mesh or any sort of screening over the outlet. Reason being is that lint will build up and block air flow. The built up lint gets hot from the drier exhaust and could catch fire. So an air gap is installed to allow lint to fall out into the attic while venting the hot and humid air. The roof vent can now have wire mesh to keep out rats, birds, bats and such.

I almost learned this the hard way when my house was built. 2 months after moving in, the propane dryer would thermal off 5 minutes into the dry cycle. I trouble shot it and discovered there was little to no air flow out the vent. I traced the vent to a covered patio that is uninsulated. The vent cap had mesh on it all plugged with lint. I then checked with the building inspection department and it turns out that the screen should have been removed and the inspector should have caught it and required the contractor to fix this.

Here's a link explaining the situation;
https://www.twincitiesfurnacecleaning.com/blog/hidden-danger-on-your-roof-dryer-vent-screening

Exhaust ducts shall terminate on the outside of the building. Exhaust duct terminations shall be in accordance with the dryer manufacturer's installation instructions. If the manufacturer's instructions do not specify a termination location, the exhaust duct shall terminate not less than 3 feet (914 mm) in any direction from openings into buildings. Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination.

 

[zinger1457]

There is a lot of lint that gets past the dryer screen, found that out the hard way during my last dryer switch out. After removing the old dryer inspected the dryer vent connection in the wall and found the 90 degree piece connecting the wall plate with the vent pipe had separated at the bend, might have been that way since the house was built (20 years). Opened up the wall to fix it and filled a good size garbage bag with all the lint that was inside the wall.

 

[ERD50]

There is a lot of lint that gets past the dryer screen, found that out the hard way during my last dryer switch out. After removing the old dryer inspected the dryer vent connection in the wall and found the 90 degree piece connecting the wall plate with the vent pipe had separated at the bend, might have been that way since the house was built (20 years). Opened up the wall to fix it and filled a good size garbage bag with all the lint that was inside the wall.

That's also holding moisture, which could lead to damage and mold.

That's one of the reasons they say to *not* use the "leaf blower trick" to blow out a dryer duct, the air pressure can cause the joints to separate, then you have moist air/lint escaping.

Fortunately, I can see our vent , the whole run is routed through the rafters in the basement, out the wall. It's a tight bend from the wall down to the floor, but I was able to get the brush through it OK.

-ERD50