AH-HAH … I found a gun and it’s still smoking … the problem isn’t your condo, A/C or duct work … the problem is the DC climate …
I’m looking at the dew points posted for Reagan Municipal Airport and they’re running in the high 60’s and low 70’s … so the air you’re bringing into your home and cooling down to 70 is reaching 100% humidity often enough … whereas only cooling it to 72 this saturation point isn’t reached as often … 74 may eliminate the problem altogether …
If you can endure the 74 setting, you could save enough money to take a two week vacation in Hawai’i come this January !!!
ETA: It’s of critical important with fiberglass insulation to NEVER compress it … it works best if the fiberglass is loose and fluffy … don’t stuff into tight places, cut the fiberglass to fit … so this material is fine just “resting” against the duct work …
What are the rules for your Association in this case? Isn’t it the case that with a condo, you need to proceed with caution when working outside the walls of your unit?
I’m not certain here, but maybe what you really need to do is replace the ducting and use the stuff that already has insulation on it.
If I understand the rules right, the ductwork is considered within my walls, therefore my responsibility.
Replacing the ductwork sounds like a huge and hugely expensive job and I’m going to try and exhaust every other possible option before going that route.
I know it’s likely the most obvious solution but have you changed the air filter recently?
If so, have you recently replaced the type you use to be the kind that removes more/smaller particles and therefore restricts more airflow?
I did this in the past thinking I was being clever by improving the quality of air in the house but it ended up decreasing airflow and causing more condensation on the coil and duct work. Like you, we like to run the A/C to a pretty low temp (68-70F).
Just the opposite actually – my filter was probably a bit overdue to be replaced, and so I replaced it yesterday in case this was contributing to the problem. I haven’t yet tested to see if this has fixed the problem.
In case anyone’s curious about how I’m “testing” various setups – right now I have a fan blowing directly into the open space (hole in the drywall of about 2-3 square feet), which seems to keep it dry no matter what. Yesterday was my first “test” – I kept the system at 72 and turned the portable fan off. And the test failed – there was condensation after several hours. Not as much as before, but still some condensation.
My plan is to use various methods – the spray, wrapped insulation cut to size, different temperatures, etc. while the hole is still open, since I can very easily detect condensation, to find out what the limits are. Hopefully the dew point will stay relatively constant to make the testing more consistent and useful.
It’s not clear how long you’ve lived in this condo. Is this your first summer? If not, what do you think has changed with your system or living environment from previous summers to this summer? (Assuming it’s not simply a clogged air filter.)
I live in NoVA as well and these are hardly the hottest days we’ve had this summer. Strange that it’s doing this now with the temps ‘only’ in the high 80’s as opposed to the high 90’s and worse that we’re usually into.
Another variable worth considering is whether your upstairs neighbours have turned down their A/C and therefore the additional ambient heat is affecting your ceiling ducts as a consequence.
We moved in in 2012. The HVAC system was very old and we replaced it in 2014-2015 (don’t recall exactly). We’ve had no problems with the HVAC system since then. In 2012-2013 we had a very similar problem in another part of the condo which we resolved with an expensive process of taking down the ceiling drywall and having someone wrap all the ductwork with insulation. This worked, and I’m confident it would work here, but since it’s been several years without the problem recurring I’m hopeful it isn’t so severe in this case and I’m hopeful we’ll be able to resolve it cheaply.
One other possible variable: two weeks ago my wife was out of town for the week, and since I like it a lot colder than she does I turned the system down to 69 for almost a whole week. I turned it back up when she got back. The wet spot on the ceiling occurred shortly after that.
If that’s the case, then did I start some sort of runaway effect? We normally had it on 70-71, so 69 wasn’t that out of the ballpark. Or was there always probably some condensation, but it wasn’t so much that it permeated through all the drywall until I made it that cold ?
It’s possible it reached a tipping point at 69F. Condensation always being there but not enough to drip and soak through the drywall. Once the drywall got saturated enough to show up as a water stain, it remained even with the temp turned back up above the threshold.
Most likely you simply reached a point where the amount of condensation dripping into the drywall would no longer evaporate on its own quickly enough to avoid damage.
I live in Florida, and we usually have our AC set to 76/77. But long ago - when I didn’t have a house or an electric bill - I would set everything to 72. That was in a college-targeted townhouse and the system started freezing up once or twice a week, so I eventually had to get used to higher settings. I adapted quite fast.
Thanks to everyone for all the advice and help. It’s much appreciated!
Does anyone recommend against my current plan (test various combinations of temperature settings and insulation while the hole is still open), since I’m trying to solve this as cheaply as possible?
It depends on how long your trial-and-error system takes. I’d be a bit worried about mold growth even with the hole, though perhaps it isn’t the issue in the DC area that it is here.
That may be a part of the problem. Doors are opened more often than windows, and let in a lot more hot, humid air. Are you going out onto the patio very often?
Also check to see if that patio door is airtight. (I’m not sure how to do that, though.) You might try adding weatherstripping around the door, maybe the foam strips that won’t bind the movement of the door.
I had a similar problem years ago after the installation of a new furnace intake.
Because I had limited space to work with I used foil-covered bubble wrap, which has done the job quite nicely.
So I went shopping and wrapped the exposed ductwork that was within reach (which is the only section that was sweating) with some adhesive foam insulation (already foil-wrapped), using foil tape along the edges and seams. I’m starting my first “experiment” – leaving the system at 72, but turning off the fan blowing at the open drywall hole, for about 4 hours or so to see if there’s any more condensation.
There’s a bit of condensation at a few of the “seams” and edges of the insulation and tape. I’m having a hard time keeping the edges sealed – after a few hours I’ll check again and it will be loose again in a couple of places. I’m going to see how much it drips overnight without the fan running to keep it dry.
