Good morning all, I’ve got a question for you all. I’m aware that a vent of anysort that passes through an attic on it’s path to outside may collect condensation which will flow to the lowest point. I can’t change the path of the vent, which is straight up to the roof of an interior townhome unit. And the vent is insulated. Does anyone have any ideas about how to deal with the condensation? The vent is aluminum flex.
To prevent moisture buildup and improve performance, install a continuous air barrier—such as drywall or specialized membranes—under tongue-and-groove boards or other interior wall paneling.
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Replies
You will get better flow (more cubic feet and faster) in a duct with less frictional losses. Aluminium flex has all those little ridges which really hurt. Rigid straight pipe is much better. Rigid one size up (5" instead of 4") is even better*. Minimize bends - two 45's to offset is better than two 90's, etc.
That it is insulated is good.
What kind of screen, flapper valve, etc at the end of the run? That can be a big restriction to air flow.
*If you currently have 3", there's the problem right there.
Reminds me of my father-in-law's rule of dryer vents: 4 turns is equivelant to a block ...
Bill.
I like that. Like electric conduit. Sure, five 90s are allowed, but can you pull the wire?David Thomas Overlooking Cook Inlet in Kenai, Alaska
there was a corralary ... after his 4th move, looking at the condition of his furniture, he said 4 moves equals a fire ...
Okay, now that you guys have got me grinning, my next question is that if I can increase the velocity of the airflow I "should" be able to reduce my condensation problems? BTW I only have one 90. This goes straight up with a little flex.
That's one of the reasons I'm concerned. This water just sits there at the dryer or can back up into the dryer...
Have you considered venting indoors in the winter? I just put in one of those little boxes that you mount in line with the dryer vent - it has a lever you can throw - in one position, it vents normally, in the other, it blows the (filtered) warm moist air into the room. It is heating and humidifying our house very nicely.
This would make your condensation problem moot, since you wouldn't be venting through the cold attic. In the summer, switch over to normal venting, with no condensation concern.
Just a thought ... Bill.
Yea. Then you'd be looking at the possibility of creating a condensation (read mold) problem inside the house... I think the guys talking about the velocity (or lack of) in the pipe are on the right track. Possibly check the insulation job too, as well as whatever screen is on the outlet - could be clogged or growing a birds nest. Warm moist air gives off liquid moisture when it cools. He needs to get the air out of the stack before it cools. Maybe it's just that the flex pipe right out of the back of the dryer is too kinked.
The *heavy* stiff foil-metal flex pipe is OK. That plastic flex is cr@q and the floppy foil is only a step better. Hard pipe is the ticket. http://hartshearth.com/chimney/dryer/dryervent.htm
I had one of those plastic boxes on my dryer vent - about 20 years ago... probably worked OK in conjunction with the wood stove.
I understand the concerns with direct venting indoors - wouldn't have done it in my last house, which was super tight ... sadly, this one isn't as tight, so I get enough air changes that it's not a problem. I was running a humidifier in the winter already, which is no longer needed.
I put it in a month ago and am watching it closely - the house really is much more comfortable, but doesn't feel 'damp' - I don't think mold will be a problem.
In any case, I just put it out there for consideration (and because otherwise I don't have a solution for the original question!)
Bill.
I agree that venting a dryer inside can be viable in cold climate where the alternative to chapped lips and hands is running a humidifier. You'd want to exhaust outside in summer, and in the summer the condensation problem wouldn't be an issue.
Obviously only a consideration with an electric dryer. Not a gas dryer!!!!David Thomas Overlooking Cook Inlet in Kenai, Alaska
Good point about the air changes. When I had one 20 years ago the house was 35 yrs old (back then). Quite drafty, and we had a wood stove. I think it was an electric dryer, but really can't even remember for sure...Matt
That was a great website thanks.
Greg
"The *heavy* stiff foil-metal flex pipe is OK. "
It still adds a lot of resistance to air flow.
You should not make a long run of it. Just enough to get around a bad obstruction or just at the dryer.
I agree. I don't dislike the aluminium flex for being filmsy. I want people to minimize their use of it because of frictional resistance to higher air flow.
Also: If you need to transition from one size to another, get the smoothest, gentlest transition you can find. An abrupt transtion (think tophat) is worse than a 90. A gentle one (think ice cream cone) is much better than a 90.David Thomas Overlooking Cook Inlet in Kenai, Alaska
>>Have you considered venting indoors in the winter? I just put in one of those little boxes that you mount in line with the dryer vent - it has a lever you can throw - in one position, it vents normally, in the other, it blows the (filtered) warm moist air into the room. It is heating and humidifying our house very nicely.
As noted:
DO NOT DO THIS WITH A GAS DRYER.. EVER!!!
Not real smart with electric either, in my opinion.
Condenstion. lint ....
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Do not vent to interior. Only rigid pipe should be concealed. Roof is best, in many minds, to vent dryer. I personally do not like holes in roofs. Soffit venting is second best. Possibly a 90 at the ceiling joists with a slope toward the soffit. Termination at exterior soffit would have to ensure no water damage potential. You may experience significant lint build up in the vent given the present condition. Longer drying times and other potential safety hazards may exist. Gas dryers pose a greater risk.
Made water damage repairs for a client that experienced your problem. Cleaned tons of lint from solid 4 inch vent. Added 90 degree to vent at ceiling sheet rock in attic and ran flex on top of sheetrock and below attic insulation to soffit. Vented to exterior away from soffit vents to ensure dryer moist air would not be pulled directly back into attic.
Why can't all laudry rooms be on exterior walls? Short run and no condensation!
>> Soffit venting is second best. <<
Assuming the soffit is not vented. If it is vented moist air will go right into the attic. :^(Matt
Read the whole message. I wouldn't install a dryer vent next to a soffit vent. I'd take it through the wall if I could. He can't. I also wouldn't put it near my AC compressor. How often do we see this?
Good Morning (or evening depending), thanks for your hard work through the evening. So I'm clear on this, the best move next is to check the vent on the roof for our feathered friends or other blockage, try stiff piping of 4" or 5" dia. Otherwise as a last resort vent to the interior with a lint catcher. The dryer is electric so we can do that.
Off to work now. Thanks again.
erc.