Hello all,
First-time post, but have been a reader for years.
We finished adding a 2nd floor onto the house in the fall. We put a new laundry closet upstairs in basically the middle of the 2nd floor. The vent goes into the (cold) attic and out a side gable wall. The vent is long (~25ft) and has 4 90’s in it. I know that is long and twisty, but according to the dryer manual, we’re still within spec, even with the bends. The vent is rigid and insulated with fiberglass that is covered with plastic.
Problem is, the vented air is losing heat and condensing outside the vent. So, now the fiberglass is getting wet and the platic is holding the moisture in the insulation. I have no leaks, it’s just wet. I take the vent apart at the end every 2 months or so to clean the lint from the outlet grill, and when I do, water drips out of the insulation.
I’d like to get rid of this moisture. I’m thinking of three options:
1. Add insulation to the vent to minimize heat loss.
2. Add a booster blower to accelerate the vented air’s exit.
3. Shorten the effective vent length by venting to a closer location (an eave). This would be the most difficult, obviously.
Any opinions or other ideas? Unfortunately, the “chief” loves the laundry where it’s at, so moving the dryer would be a difficult political exercise. The attic is large and the vent easily accessible.
Chuck in Illini-land
Replies
is this rigid vent? 4"?
Shorten the vent would be a good thing.
In lieu of making the vent shorter a fan booster would
be a good thing. I don't know about the insulation
thing but maybe someone else can chime in for that.
he vent is long (~25ft) and has 4 90's in it. I know that is long and twisty, but according to the dryer manual, we're still within spec, even with the bends.
Are you sure about these specs from the manufacture?
Also would like to add Welcome to breaktime.
The vent is leaking air, not just heat. Losing heat into the insulation won't cause condensation. Losing moist air into the insulation will cause condensation. As long as it is leaking, none of your three options will do you much good. When you get the leaks fixed, none of them will be necessary, except maybe more insulation, and that would be only if you're seeing condensation inside the pipe.
Now that I think more about it - you're right. The cold air in the attic doesn't carry much humidity, so it can't be condensation from that air. Plus, if it were, the condensation would be on the outside of the insulation, which is currently dry.I don't think any of the joints are taped, so that's got to be it.Thanks a ton for your thoughts, Unc!Now, I can finally use some duct tape for what it's actually made for!Chuck
Chuck,
Duct tape is used for every thing but fixing ducts. Use some duct mastic.KK
The tape is a good idea, make sure it is the kind used for ducts, the type I am familiar with is the silver, almost like a tin foil, fits tightly to the pipe.
I think you might be having a condensation problem anyway, the duct is too long, more insulation and a booster blower could be part of the entire solution.
Chuck, never vent to an eave! If you have a ridge vent system your not really exhausting the moisture out of the attic, since the soffit vents will allow the moist air right back into the attic. If you don't have ridge vent system the typical air flow at the eaves will tend to push the air back into the duct.
You could vent thru the roof which would ,I assume , shorten the run significantly.
If you must maintain the long run , try to eliminate the 90's and elevate/pitch the duct toward the exterior. This will help prevent any standing water/ mold situation within the duct work. Good luck!
Geoff
Well, I did some debugging and found a couple things.First, I removed the insulation on the duct and discovered I was wrong - the joints are taped. The only joint not taped was the one I removed the tape on in order to clean the screen over the outlet hole. This gets clogged with lint that collects in it. So, the original duct is tight.Second, since I never retaped that joint (so I could easily clean the screen periodically), I ran a test with the dryer running. I found that particular untaped joint to be leaking huge amounts of hot, humid air. So, I think this was the source of the water. This single joint.Now my problem is how to set things up so I can clean the screen from the inside without needing to untape the joint every time. Our dryer's lint filter really stinks in that it lets a lot of lint get past it and into the ductwork.Thanks for all the replies. Oh, and Geoff, it is exhausted out a gable end, not under the eave. So I'm good location-wise.Chuck