[jimluke]

I have a downstairs half bath in the middle of the house. In the summer when the AC is going there is tremendous condensation in this room. The ceiling beads up and the walls sweat. There are no exterior walls but there is an HVAC return behind one wall. No one seems to know what is going on.

[smoothy]

Does it have a recirculating vent or does it actually vent outside.

I'm willing to guess it recirculates.

You have a sink and a toilet in there... both are moisture sources, all you need is a cold wall or ceiling and you have condensation.

[jimluke]

How would I answer the question about ventelation? I looked in the attic and there is a white pvc pipe coming from the area of this bathroom that goes to the roof.

[ballengerb1]

That PVC is your drain vent and I think Smoothy is talking about a HVAC vents supplying air or return air. This room is likely a bit coledr than the rest of the home when the AC is running. It needs more air circulation. If you have a return behind one wall you may be able to cut in a return vent for the bath. Is there a supply air vent to this room?

[smoothy]

I used the wrong terminology actually.

I should have said Exhaust fan. Many houses have only those that move the air around in the room a little and make a lot of noise, and don't vent outside. It does little to get rid of odors or moisture in the room. Most have moisture issues in bathrooms as a result. But what ballengerb1 mentioned will go a long way to helping the problem long term by increasing air circulation where air might become stagnant. Half baths and closets both can suffer from this.

[ma0641]

You are reaching the dew point in the room when the relative humidity exceeds the water carrying capacity of the air. You need to get air circulation in the room. This is typical of a bath, lots of water sources and usually little air removal.