I have to vent a dryer straight up through a low slope rowhouse roof, and I’m not finding any really good vent solutions for this application, so I’m hoping someone can point me in the right direction with this…. First, there are roof caps like the Fantech RC:
I worry that with a low slope roof, this type of vent would be vulnerable water intrusion with the occasional snow or heavy rain, since it would be near horizontal when mounted. Also, from what I understand, venting a dryer through the roof isn’t usually a good idea because you’ll get moisture condensing on the vent cap and running back down into the house. Being this is simply a sheet metal cap, I can definitely imagine this happening…
My next idea would be to use B-vent pipe for dryer venting, running it out the roof 8 or 12″, then topping it with a shuttlecock vent cap like this one:
The double wall B-vent would hopefully prevent condensation within the exposed portion of the pipe, and the cap doesn’t have a screen or anything that would be easily plugged with lint.
I simply don’t have a good place to vent the dryer horizontally that wouldn’t be 30 ft off the ground and 30 ft away from dryer location (smack dab in the middle of the house). My archy said to simply run PVC for the vent through the roof and put an elbow on top, but the IRC is unclear about PVC being appropriate for the application and after getting
shocked out of me by static buildup in a PVC pipe in my homemade insulation vacuum, I really don’t think it wise.
Am I totally over thinking this?
Z
Replies
I had the same problem with roof vent for bath fan, that is, heavy rain reflecting off the roof and coming into the duct. If you installed the cover (your picture) directly on the roof, you will have water problem. How about building a box 2' high? The cover can go on top of box and can be flashed using the cover flashing. The box will have to be flashed to the roof with appropriate material. If you are not sure, check this site-Eternabond.com. I had success with this flashing tape and I can recommend this with confidence.
So you're saying to mount it vertically on a box I would built out of my roof? or would simply increasing it's angle be enough to keep the damper from opening with wind driven rain? I'm thinking maybe a wedge shaped curb.Thanks,
Z
The vent cap could be on the top and you could add sheetmetal around and over the vent door so the wind driven or splatter would not go back into the vent. This is what I did with mine. Or the vent could come out on the side of the box as well, I think this might be better protection from the wind. The roof of the box could be removable for maintenance. Hope this helps.
on a coin op laundry install in a shopping center i had... they vented all the dryers thru the roof... all they did was elbow em over... so they came up and out of the roof then did a 180 blow'n down... picture an upside down J...
for bath fans that went thru a flat roof i just use the mushroom looking alum moisture vents... all have worked so far
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Ponytl, somethink like this?:
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Do you install an inline damper then as well?
Thanks,
Z
Just my .02, I know the dryers have a limit on length of run, and it drops a lot with two 90 degree bends. If you already have the dryer it'll be in the manual.I seem to recall the run amount dropped if going vertical vice horizontal but I don't swear by that.
I can't find anything about the line length being restricted in a vertical run, but since I'm only going up 9ft, I don't think it would matter too much. The line on my gf's dryer probably goes up 25 ft from her basement apartment then turns and runs another 20ft or so to the outside wall. It doesn't dry worth a damn.Thanks,
Z
no it looks like a mushroom ... we call them "moisture vents" on built up roofs... round spun alum about 12" tall with a mushroom looking cap... i mostly use them for bathroom fan vents on flat roofs.... for the dryer i'd come up and over with an elbow...
p
Ponytl-
Perhaps something more like this??
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Should I worry that something like this doesn't have a damper on it?
Thanks,
Z
yep looks like that except it's spun alum ie: one piece flange & stack (no joint no leaks there) then the mushroom cap sits on top...
while i was looking for something today i saw a standard vent cap ... see no reason that wouldn't work... and no i really wouldn't worry about a damper on the roof... on the side of a house where birds wasps ect might nest yes... but i don't see that as a real issue on the roof...
p
PVC is against Code for dryer venting here in NY, and have never seen a dryer vented thru the roof in a residential application. Gotta make a mess.
Yeah, I don't think that I'd ever run a dryer vent with PVC... Like I said, I've personally been subject to the amount of static electricity that build up in a PVC pipe.As for making a mess, the roof is easily accessible for me, so keeping it clean wouldn't be a problem. If I had to vent it out a wall, the vent would be nowhere that I could easily access it, and vent pipe run would be far more complicated... So I guess it's a tradeoff, but one that I'm okay with assuming I can find a vent cap that actually works.Thanks,
Z
I would stick with a more typical roof jack with damper, but get a decent one, not one carried by big box stores. We have used ones from Grainger, who you can order from online. They cost more but they have all different sizes and are heavier built than others I've seen. There is less for any lint to catch on with these.
I was actually looking at Grainger, especially since they just opened up a branch 3 blocks from my house ;) But it looks like they only carry Broan roof jacks in the 4" size, and unless they're complete different from the Broan roof vent at the Homey D, they're cheaply made.So if I want a vent with a damper I'll go with something like the Broan roof vent and put it on an angled curb to help prevent water intrusion. I'll have to rip the bird screen off, but at least if I do have problem, it's easily accessible for cleaning. If I do a simple U vent, Pontyl, is there a specific type of pipe for this? The IRC simply says "metal", but if I'm running out the roof, I assume there is vent pipe rated for exposure...Z
Bosch makes a condensing dryer unit, no vent needed. Adds about $300 to the price. We like ours just fine.
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http://www.copperlab.com
You can vent through the roof, several options for vent caps people have posted will work.
My comment is that you will have a lint problem. Pipe will get clogged at the elbow out of the dryer eventually and the roof will get lint on it.
"My comment is that you will have a lint problem. Pipe will get clogged at the elbow out of the dryer eventually and the roof will get lint on it."
Exactly. And if there's a screen on the vent to keep the critters out, it will keep the lint in, making the problem worse and requiring regular trips to the roof for cleaning.
Mike HennessyPittsburgh, PA
Bottom line, it's called maintenance, and no different than a second floor laundry vented out a wall 15' above ground. Sometimes you have no choice, especially if the laundry is centrally located in the floor plan and down isn't an option. Most times there is an elbow at the dryer regardless unless back of dryer is right against the exterior wall. We have used the dryerbox installation so you can do a flex connection with a longer sweep to go up.
Yep. Maintenance. Just thought the OP should remember the fact that such maintenance WOULD be required, and this should be pointed out the the HO to avoid issues down the line.
Mike HennessyPittsburgh, PA
Your right.
It seems like after all these years someone would have invented a system that:
1. traps ALL the lint at the machine.2. Utilizes a heat exchanger, switchable for cold periods to keep heat in the house.3. Still exhaust the actual air outside, while doing the above.Maybe they already have and I just don't know about it!
Or maybe they already have, but it costs more than the washer and the dryer put together. ;-)
Mike HennessyPittsburgh, PA
Try looking at a condensing dryer. No vent, no lint problems (other than having to wash off the removable coil once in awhile), and more energy efficient to boot.Z
Mike-
You're totally correct on that point, and as I've pointed out one of the reasons for going roof top is that it would be easier to maintain as a wall vent would be a PITA to get to anywhere I could locate it. Besides the location, I've seen more wall vents clogged with lint than I care to remember, especially common when they've installed one of those crappy plastic deflecto vents with the birdcage on it. Ugh.Z