So let's be clear about what condensation like that is about:

1. humid air

2. meets cool surface

3. that is below the dew point for the given temp/humidity level

The way you fix this type of issue is to address these points:

1. Why is the air so humid inside the house?

2. Can you eliminate cool surfaces (insulation on the AC in the attic, for example)

3. Below the dew point: this has to do with the temperature and moisture level of the air and the temp of the object it's in contact with.

The first thing you need to be sure is that there are no sources of moisture in the house. Fans in the bathroom are an obvious issue... but a house built on a slab without a vapor barrier can be a huge source of moisture in the house. Also, a leaking roof can do it.

The second issue is insulating the AC in the attic - along with the condensate line.

The dew point issue usually happens when the AC is not properly sized. When it is oversized, it can make things "cold" without having enough time to remove the humidity. That will increase the retaliative humidity in the house and cause water to condense when it hit a cooler object.

Since the AC was sized for the add-on I suspect, like others, that the AC is not properly sized but is too big. Have someone do a calculation on the heat/ac load. To get the best results, don't let them see what size of unit is installed now.

If you are on a slab, I would also try to get some definite answer about if a vapor barrier was installed.

IMO,if you have to figure this out with help on the net then tell the builder how to fix it,I wouldn't want his people working on it. The builder is supposed to use subs that know what they are doing to begin with. The builder is playing you like a violin until warranty expire's. Too much time has elapsed already and with every passing day the builder is getting more comfortable with leaving you holding the bag. If you have a paper trail starting a year ago,this is what I would do. Send builder a return receipt letter laying out the problem and demanding he resolve it within xx days. Do not try and tell him what you have been told might be the cause. Let him know if it isn't resolved within xx days,you intend hireing someone to do what is required then sue him for reimbursement. If he hasn't resolved it by xx days,I would have used the time while waiting to vet prospective contractors. In Texas,small claims is within the capability of average people but limited to $10k. I'm not optimistic $10k will cover this because I believe it is multi faceted involving more than hvac or ventilation. I wouldn't expect a contractor to research and prepare a proposal for free and I certainly would not ask builder to use the proposal as a guide. I also wouldn't try and have court to order builder to preform work,reimbusement instead. If the proposal exceed's small claims limit,hopfully an attorney will give you a 30 minute consultation.

We need to know the sized of your AC condensers. You should see a plate attached to the side or rear. Take a picture of it. The model number will indicate the size.

You say the builder is reputable which is great, but then you are worried he is not going to spend the money to fix the problem. Someone who wants to maintain their reputation will spend the money to fix the problem correctly.

Klem1 is right that the builder is trying to wear you down so you will go away. You are already bringing in other HVAC people who are giving you terrible advice. Adding insulation to cover metal surfaces so there will be less condensation is not the fix. The condensation is the symptom of a very humid house. This could develop into a long term mold issue. You need to get this fix this summer.

Klem isn't wrong. The longer this goes on the more comfortable the builder is with leaving you with the problem. It's fine to listen to us... but your builder has to fix this and you don't have to have to take on the responsibility of HVAC troubleshooting. You do have to take on the role of Owner and lay down clear expectations and deadlines.

One other thing crossed my mind that could contribute to this issue: The fan set to the wrong speed or otherwise miss-matched airflow could cause many of these symptoms.

If there isn't enough airflow over the coil, the temperature drop over the coil can be too great and you get cold air instead of dehumidified air. That would cause the condensation on the AC unit in the attic and the vents.

The temp difference between the air inlet and outlet should be between 15-20 degrees as a general ballpark. If it's more than that, there's a problem. That measurement isn't an exact science -- but it's a good place to start to look at what's going on.

Increasing airflow will increase the coil temp and reduce the temp difference over the coil.

All that said, I think you need a good HVAC person who can go in and assume nothing is correct: Meaning doing a load calc, checking delta -T over the coil, measuring airflow to see if it matches the coil's specs, make sure there are no restrictions, etc.

Here’s the unit info (like I mentioned, we have 2 units and the larger unit is for downstairs)

The condensation in the outside of the house can only be reduced ontwo ways, increased insulation or increased temp inside. It may or may not be a problem. I mostly I want to point out that you would likely be more comfortable at a significantly higher temp at 40% RH than at 60%. Start with data to define the problem.

We are going to purchase a humidity logger for sure. Our house is well built in many ways. The builder is a local one and is a great man with a great reputation, but the HVAC duct work obviously has issues and the subcontracted HVAC company has been less than prompt in getting it addressed.

The condensation on the metal vent is usually only present from around 1-2 pm and onward. And when we wake up in the morning, it is usually gone.

We do have 2x6 walls, a conditioned crawl space, and have had no other big issues with the home except the humidity/condensation one. During the late spring, summer and early fall is the only time we have issues with it. Once it cools off, the issue gets better.

We used to set our air conditioning lower at night to around 71-72 and when we mentioned we saw condensation on the outside of the windows downstairs each morning (never on the inside though), the HVAC company told us we were keeping the air setting too low (which I feel is ridiculous and I shouldn’t have to adjust my comfort to prevent these issues in the home). I’ve grown up and lived in this area (southeast coast) and we have never had to deal with this issue until now. Regardless, we stopped adjusted temps (day vs night) and keep it at a constant steady temp and raised the temp to 74 downstairs and 75 upstairs. But we can see that the issue remains.

We have plans to have another HVAC company come out too to inspect the whole system and hopefully they’ll have some answers.

You have 3 ton and a 2 ton systems. I think the units are over sized for new construction. It will be interesting to see the load calculation for each floor.

Running the AC at 71-72 will allow for longer run times which will help lower the humidity. Set the thermostat where it is comfortable for you. Condensation on the outside of windows is not an issue. I think the builder's HVAC contractor is clueless as to what is going on.

"I think the builder's HVAC contractor is clueless as to what is going on."

Patently, but the builder didn't have to pay him as much as contractors that do know what's going on.

Haha. Well, we have had the best experiences with every other subcontractor except HVAC. My concern is they DO know what’s going on and they just don’t want to fix it b/c it will be too costly.

If oversized units are contributing to this, is there a way to fix it?

On a related note, going through old emails last year, our builder did forward an email to us and a few other relevant subcontractors from a humidity specialist who recommended two things:

1) air sealing
2) additional insulation

Soon after that email was sent was when the subs and builder had a meeting at our home and all went through ideas and put wrap and additional insulation all around the return unit and handler.

I can tell you that based on what I looked up online for air sealing, that was not done.

I know y’all haven’t seen the house and all but do you think air sealing could make a difference?

Do you have any exposed walls in the basement? If so are they damp? How is the drainage around the house? Is the land sloped towards the house? Is the surrounding land constantly wet?

You may be experiencing excess moisture coming up from the foundation. The cause of this could be poor drainage. Have you asked your next door neighbors if they are having similar problems?

For me, the timing of the condensation problem argues against a general AC problem. Humidity generally increases at night with less call for cooling.

isn’ there an active thread right now about humid outdoor air entering through a bathroom vent duct? OP, do you know if your home is negative or positive pressure relative to outdoors? Check with the AHU blower running and not.

What’s the best way to test that?

ionized_gw: You may be on to something... but the argument on the other side of that is that mold was growing under the sink inside the vanity.

Now, if there was negative pressure inside the envelope and outside air was leaking in through the bathroom vents and possibly around the plumbing under the sink, this could happen....

OP: Does the wall that your son's bathroom sink is on back up to the attic space or otherwise have access to outside air?

Negative inside pressure would come from things that pull air from the inside of the house. Examples include: Range vent, bathroom vents, vented fireplace, clothes dryer, leaky supply vents in attic.

Most of those things are limited in duration (range vent, clothes dryer, bathroom vent) for example so seem unlikely.

Is is the system running heavily during all daytime hours or is it managed with a daytime set-back?

Good thought and question about the plumbing, Jake.

Negative pressures can be induced by the AHU in two different ways. If there are leaks in the outdoor supply ducts, the home will depressurize in general. Make up air will be drawn in somewhere. On the other hand, if return air flow is not adequate in some rooms, those rooms can become positive to the outside. That can cause air to be forced outside via small leaks. That will cause makeup air to be drawn in somewhere else just like leaks in supply ducts.

If that is the problem, you've got two choices, you can track down duct leaks and make sure room to room air flow is sufficient if you don't have returns in every room. Otherwise, a controlled intake of outdoor air to deliberately pressurize the home is possible. This is often done with an ERV or HRV. Sometimes in humid areas, a dehumidifier is incorporated instead.

The pressurization can be constant or only when the AHU is running. In the latter case, you are basically introducing a controlled "leak" into the air return path to deliberately draw air from the outside.

Smoke pencils may aid in locating air leaks and determining if an area is positive or negative to an adjacent area. They are a bit easier to use if you are on the negative side watching smoke being sucked into a leak compared to inside detecting air getting sucked in.

This is the wall of the bathroom. It backs up against the other bathroom (looks like the other bathroom’s shower tub is against the wall shared with the vanity).

Not sure what you mean by daytime setback, but we keep our temp constant at all times (no changes from day vs night). We used to have temp lower at night (71 downstairs and 73 upstairs) and higher during the day (73-74 downstairs and 75 upstairs), but when we were going through the process of trying to figure out solutions for the humidity issue, they told us not to do. They also said it makes the units work harder. So, we now are set to a constant temp.

We do have another HVAC company coming out Friday to check it out. It’s unfortunate that we have to pay out-of-pocket but I feel like we need to have a thorough, unbiased Evan of the situation.

I’m sure they’ll check everything y’all mentioned. But do you think air sealing the attic would help with any of this?

That is unfinished living space in the attic? Is it air conditioned right now?

I'd be tempted to employ a more all-over building specialist rather than another air con company. As the saying goes, when you've only got a hammer, everything begins to look like a nail. If this were me, in my area, I'd call this outfit. I was introduced to them in a house purchase situation and was impressed. The inspector called one of their structural engineers over to look at something. After that, I called them back for an engineering consult. If you are lucky, maybe there is a similar company near you.

Building consultants

Don't believe the bologna about setbacks not saving energy and "causing the units to work harder". Setbacks will always save energy unless you have variable-output equipment. Even then, setbacks might still save energy. In the case of single speed equipment, the recovery time constant running is advantageous, less wear and tear on equipment, better dehumidification, less power used. Setbacks generally save, the only question. is how much?

The attic is above the bathroom. There’s an unfinished room (potential 5th bedroom) to the left that you can see part of. The bathroom would be an en suite to that bedroom should we ever finish it.

So, we need a “building consultant?”

I don't know for sure who would be best. The root cause here might or might not be the AC. The AC guys may or may not be broad thinkers. If not, they might not be able to suggest a reasonable solution. I don't know how common the the type of consultant I cited is either. An experienced energy rater might be able to offer a cause and solutions. They know how AC is supposed to work, are familiar with moisture problems and know how to look for air leaks, You might just call one or two, describe the problem and ask if they feel they can help you.

Is that finishable attic space actively air conditioned right now?

We did have a neighbor who owns his own HVAC company come by as a friend and look and he didn’t see anything grossly wrong with the setup. But he didn’t do any official testing. Just looked at the setup of the bathroom and the air handler and recommended adding extra insulation to the boot of the bathroom duct where condensation was forming the most (of course, now we are seeing condensation forming around 2 other bathrooms).

There is no heating and air in the attic or unfinished room.

I’m not sure if we have anyone here who does that kind of stuff. As I mentioned above, last year when this whole debacle started our builder did consult with a man who specializes in heating, air and insulation and forwarded an email to us that mentioned air sealing and insulation as the “only fix.” Soon afterwards every one came out, and the HVAC people said they didn’t see anything wrong with what they had done and the insulation guys spent an entire day in the attic adding more insulation and a moisture wrap all around the space surrounding the handler. Didn’t work obviously.

When are you getting the humidity gauges? Perhaps when the builder sees how high humidity readings are he will begin to understand how magnitude of the problem.

I don't think this is a HVAC problem. However the AC alone is not able to lower the humidity. You could install a whole house humidifier.

The question is why is the humidity so high in a new constructed house? My theory is the moisture is coming up from the ground.

The humidity logger arrives today. So, that’ll be a nice data tool.

We have a conditioned crawlspace and a recent 1 year inspection. It’s dry down there. Very low RH. I don’t have his report with me (maybe it was around 10%). But he said he doesn’t think we’ll ever have moisture issues down there. Is that what you mean by the ground?

I thought you house has a basement, but maybe I am confused. Are you saying there is a crawl space under the house and it is sealed?

What month was it done? Did the inspector measure the humidity? It is hard to believe it was only 10% relative humidity.

I could be off with that number. And I lied. It wasn’t the general home inspector who gave us that info, it was the termite inspector. That was done at the very end of May before our year mark June 1, and he said it was very low humidity down there and almost the same temp as inside the home (humidity was well below the concerning threshold), and said we would likely never have issues with it. It has spray foam insulation and a thick vapor barrier. But we do not have a basement. They called it a conditioned crawlspace. We had no vents. Never had them down there. It has its own HVAC duct going to it that supplies conditioned air inside.

10% (or thereabouts) could have been a soil or wood moisture measure rather than RH. Moisture content of wood has to be below 16% to never see mold.

The good news is that the crawlspace might be constructed properly for the climate. It is coupled to the living space, vapor barrier on the ground with no insulation, insulation at the perimeter?

proper crawl space

When we built this home, everyone told us how crawlspaces can be problematic with moisture so we went above and beyond to ensure it wouldn’t be as much an issue.

Oh the irony that we have it elsewhere.

I have never heard of sealing an attic but maybe that’s something we should ask them to do since the builder received that recommendation and it was never done.

Maybe insulation and sealing are the answer?

Hi OP:

We have thrown a lot of possibilities at you. It's time to stop guessing.

The humidity logger will be very helpful because it will give us actual data.

Yea. It was suppose to arrive today (ordered on amazon) so when I get home I’ll check.

In the hot, humid South, sealing the attic and insulating at the roof line can be useful, especially if there are ducts in the attic. If the ducts are within the living space envelope, the benefit is greatly reduced. The drawback is that you add lots of cubic feet of space to cool (increased surface area as well. You lose somewhat in an area that helps to dissipate heat.

This is often a good move with old homes that were retrofitted with AC and have leaky shells. One advantage, in addition to bringing ducts inside is that you eliminate all the air leaks between the living space and the attic. In older homes they are often riddled with holes from added wiring, can lights and more. More are added all the time because people doing work don't have to pay attention to sealing things up. If the building envelope is the roof, no one will dare punch a hole and not seal it because it will be noticed immediately the next time it rains. In older homes, knee walls between attic living space and exterior are notorious sources of heat loss and gain to the outside and air leaks. Presumably, you have this under control with a new home.

For serious entertainment value and some practice building advice, read Joe Listiburek's Top Ten Dumb ...

... Things to do in the South

This is what I found with my humidity monitor:

The meter is in Celsius so forgive me (I haven’t learned how to change that yet).

With the logger giving an outdoor temp of 24.7 C and outside humidity of 82.2% (temp is relatively low considering the recent rain and these readings were taken at 11 pm at night)

indoor A/C settings at 22.8 C downstairs and 23.3 C upstairs:

All rooms upstairs and down are between 21.9 and 23.5 C with humidity ranging from 53.9-55.8%.

Even the bathrooms upstairs and downstairs were comparable and fell within that range EXCEPT near the exhaust fans:
Right by the exhaust fans in the ceiling the Temps ranging 23.3-24.4 C and humidity of 72.9-81.3%.

The bathroom with the worst condensation and the influence behind this originally post had a temp of 23.3 C and humidity of 81.3% right under the exhaust vent.

I did also measure under the vanity in that same bathroom and the temp was 22.1 C and humidity was 65.2%.

The unfinished attic itself had a temp of 27 C and humidity of 85%.

Lots of numbers and again, this is all on a cool night. Humidity outside is usually this high most of the day and night but temp is usually MUCH higher especially during the day.

Should there be other places or ways I’m measuring?

If you bought an AcuRite monitor there should be a button on the back to switch the temperature to Fahrenheit.

I was confident your humidity would be above 70%, but to be over 80% is a serious problem. That is a lot of moisture.

Where does the bathroom vent end? Does it go out through the roof? I would expect some leakage from the outside, but that can't account for all the moisture.

If you can go into the crawl space I suggest you take some readings there.

I find this data the most interesting:

outdoor temp of 24.7 C and outside humidity of 82.2%

The unfinished attic itself had a temp of 27 C and humidity of 85%.

The attic has a higher temperature (which you would expect from solar gain and radiant heat) and a higher relative humidity (which you would not expect). If you take outside air and warm it up like you would do in the winter, then the relative humidity should go down. Here we see it goes up, which means there is more moisture in the attic than the outdoors. That could mean that moisture is being added from within the house. Your readings could be off, but the fact that the measurements are close to each other is disturbing.

All bathroom vents go outside to the sides of the home (vents with flaps that close when the fans are off).

We have a few folks coming out tomorrow from HVAC to see but I honestly am not certain this is an HVAC issue. It seems like it’s an insulation thing.

It makes sense to me to see condensation on ceiling vents when the cool air is coming out close to hotter, more humid air from a nearby ceiling exhaust fan, right?

All bathrooms have lower humidity when you are at a normal person height (55-58%) but when you go up towards the ceiling, that’s when it climbs. Especially near the exhaust fan.

There is still a musty smell in that upstairs bathroom though. Just smells weird, and I’m sure it has to deal with the same issue. Not sure how to fix this but maybe if we present the numbers, they’ll know what to do.

I’ll check the crawlspace later when I am back at home.

Also, should indoor humidity be that high in the 50’s? I read online that it should stay somewhere between 30-50% for comfort, and anything above 60% puts you at risk for mold. Under the sink inside the vanity cabinet is where mold was found last summer and it happens to have a humidity in the 60’s but I tested another vanity that never had mold issues and it was about the same.

The general guideline is to keep humidity below 60% in order to avoid mold problems. For comfort the humidity should be below 50%, and ideally in the 40-45% range. New construction with a properly sized AC should be able to be below 50% even on hot humid days.

Adding insulation will not reduce the humidity. Making the house tighter will reduce the amount of outside humid air from entering. You stated you have 2X6 wall construction. That would imply at least an R-19 insulation. It is not heat transfer that's the problem, it is humid air infiltration.

It is hard to believe a new house would have such poor air infiltration. I think all the exterior penetrations through the exterior walls and the attic floor have to be examined closely as possible air sources. I think the readings from the crawl space may give another clue as to what is going on.

I will definitely be checking the crawlspace. How do you make a home tighter?

You can start by replacing the windows. Do you know what windows you have?

You could hire someone to do a door blower test. A big fan is installed at your front door so that the air leakage of the house can be measured. Once the house is pressurized the tester can use a smoke emitter to visually see where is entering and exiting.

Looks like YKK something

But I these are suppose to be good windows. We have a ton of windows in the home and most are very large. I don’t foresee our builder agreeing to replacing every single window.

30-50% for comfort and health. For the health of the building, I'd say on the low side of that if possible. Maintaining humidity in the hot, humid South below 50% is difficult with single speed equipment and difficult even with more sophisticated variable speed blowers and compressors. It is not hard to hit in daytime in summer months, with large solar radiance loads but at night and in the shoulder seasons, more of a challenge. What you have to settle for is a good average with no long excursions above 50%.

If I had to guess at a percentage of the residential fan dampers that work as intended, I'd say it is a shockingly, to most, low number. Someone has some statistics somewhere. Motorized and pneumatic dampers work better but are a lot more expensive to install .

These two, obviously related, reports are a little dated so there might be more up to date publications. They represent the kind of thing you can look for when boning up on humidity control in humid environments. One take home message for me is that nothing short of a dehumidifier will work 100% of the time. I was also surprised at how poorly the variable-speed cooling equipment performs:

Supplemental

Dehumidification

in Warm-Humid Climates

Building America Report - 1310

July 2013

Armin Rudd

Residential

Dehumidification Systems

Research for Hot-Humid

Climates

Building America Report - 0505

Feb-2005

Armin Rudd, Joseph Lstiburek, P.Eng., and Kohta Ueno

I think that your biosensors, your nose and your perception of humidity near the ceiling (whether that be by the feeling of less drying in your nose and mouth, or your skin) is telling you something important. Of course you have to be careful because you are not exactly coming into the situation with no bias. Do check out the dampers on your exhaust fans to see if they are working properly.

Take an experimental, hypothesis-testing approach. Put your hygrometer(s) in the areas that you have symptoms and then put a fan in there to see if the problem dissipates. (I once regularly put a common box fan in a conveniently-sized laundry basket to blow air vertically.) That will work for the cabinets, but maybe better to see if vent backdrafting is a the problem, seal off the bathroom vents with some plastic wrap or cut up plastic bags and tape or some other way that won't damage your paint. (Taking off the cover and reinstalling it in a way to hold the plastic in place might not be difficult.)

See what happens with the simple tests, but a blower door test is not a bad thing to start thinking about. Energy raters do that every day. You will see if your windows and doors are installed properly and they can also check duct leakage in the same trip. They should be able to advise you on whether your home is positive or negative pressure relative to the outside and if there are excessive room to room pressure differences.

Your windows are fine if they were installed properly. I was just giving an example as to where air infiltration can occur. The installation would have to be really bad to achieve the humidity levels you are seeing. There has to be other humidity sources that are not obvious.

Fast forward to present time: we have had multiple things done in attempts to fix this issue. We’ve had our builder work with an energy inspector who determined the unit upstairs was too large and so...

1) they changed the upstairs unit to a 1.5 ton unit from a 2 ton unit.

2) they insulted AND added HVAC units to the “unfinished” bonus room off of the upstairs hall/bathroom. So now the bonus room has conditioned air blowing into it.

More than a week since this was all done, it STILL smells musty and there is still a small amount of mold grows in the vanity and on the bathroom ceiling. To make matters worse, we just noticed it in a new place: the loft built-in desk (see pics) which is at the opposite end of the hall from the bonus room and bathroom (door seen at the end of the hallway in the pic is to the bonus area). It wasn’t there before.

They have done a lot in attempts to fix this issue. Yet we are still seeing (and smelling) the issues. What else can be done? Is there anyone we can contact ourselves to get to the bottom of this?

I think it's also worth mentioning that a big reason condensation tends to form on vents/air diffusers is because so many of them are typically made from metal. Choosing a product that isn't made from metal prevents the issue from happening in the first place instead of forcing you to try and fix it down the line to no avail. Here is a blog post that explains in more detail: https://blog.inviair.com/blog/diffuser-condensation-is-a-serious-problem.-heres-what-you-can-do-to-avoid-it

Did you ever figure out the reason why you’ve been having condensation. I’m having similar issues and none of the AC techs have been able to figure out the root cause. I already have molds behind walls where I have ducts running. it is my first summer in my house which I bought last October and my issues started mid July and still ongoing. I am beyond frustrated and not sure what to do.

Seble, we have had multiple things done which helped with it and it seems to have gotten better. They switched out our HVAC unit to a smaller one (turns out our upstairs unit was 1 ton too large so it was short cycling and not removing enough humidity inside). They also insulated an unfinished bonus room upstairs that connected to the hall bathroom where our biggest issue was. And they also foam insulated around outlets, bathroom vent fans, etc.

It sounds like you have a bigger issue since your mold is behind the walls and ours was surface mold only.

We have a slight smell still up in the loft where we have the built-in desk/bookshelves, but they came out and did some more insulating a few weeks ago. So, I’m hoping that that’ll resolve the issue permanently. This is our 3rd summer in the house and so, we’ve dealt with many troubleshooting session with the builder and his various subcontractors. We had a structural engineer come out and do a full inspection too. You might have to do the same. It’s very frustrating, and I’m not even sure we are 100% out of the issue. Just praying we are. It seems like it is a multi-factorial issue and every change has made some improvements, but there wasn’t a single fix.

"They switched out our HVAC unit to a smaller one (turns out our upstairs unit was 1 ton too large so it was short cycling and not removing enough humidity inside)."

So sad that contractors don't do load calculations any more. It's highly unusual for a company to admit they oversized a unit that's causing problems like yours. You were quite fortunate.

They actually did a load calculation but the owner of the HVAC company had a stroke around the time the order for the units was placed, and apparently they had put down original “guesses” before the load calc was done. Because of his stroke, the order was never adjusted to the correct sized units and the order was placed with the guesses. So, it was bad timing. But they were nice enough to correct it (very nice in my opinion). However, we still have a smell upstairs but no obvious source of mold. I cannot tell if it’s a moldy smell or a smell coming from the unfinished room off the hall (that has HVAC ducts and insulation but no drywall etc). The structural engineer that came out to do his assessment said that that room is a weird oddity. Like a “hybrid” room since it is connected to the HVAC and has insulation but is otherwise unfinished. Maybe finishing off the room will get rid of the smell...but we had our priced out earlier this year and because of hurricane Florence, many companies had increased the price of drywall and installation so much that it would have been $5-6,000 just to drywall and mud a room less than 300 sq ft.

I know im late to thos but did you ever get this resolved? We are dealing with a similar issue and its frustrating

@Matt S we think we did. They eventually came out, made sure all the areas where condensation was occurring were properly insulated and the HVAC units were changed (both units were oversized and short cycling which led to higher humidity levels in the home). We seemed to fix the issue but then had to move last summer. To us, it appeared fixed but we have no contact with the new owners. So, I guess there’s a possibility that it came back. But it was a frustration like no other in a new construction. Good luck with your issue!

So nice of you jcwright to keep everyone up to date and explain all the remedies so thoroughly.

We are third summer into antique home with total gut renovation near Cape Cod. Last year in late summer when noticed the same issue and we did several of the things you did. Only thing different is the paint is peeling around the tiled and glass doored shower. I always suspected it is the bathroom is over a crawl space and we did put down a vapor barrier. Fast forward to this year and problem exists. I think since one AC unit covers the master bathroom and bedroom and the other the rest of the first floor we probably have too much AC and need a smaller unit as you did.

Thanks again...