Darker Stains on Ceiling

I have these darker stains (very faint though) on the ceiling of my kitchen and living room. The ceiling is not wet, my roof is only a year old. I just recently noticed these stains because they are faint. Went into the attic, took the moisture temp of the wooden beams, and nothing reads above 18, which is good.

What do you think these stains are? Cause for alarm, etc.?

Attached are some pics. These pictures really make the stains seem worse than they are.

 

They look like typical condensation stains (from the larger photo it looks like they track the ceiling joists). The solution will largely depend on where in the country you are, but assuming its NC the issue may be that in the winter you get frost in the attic due to poor air sealing. Alternatively if its humid in the attic and your living space is air conditioned that might be causing condensation to form. Nothing to really worry about at this point, just keep an eye out for mold and see what you can do to reduce the humidity in attic.

 

Could be that the ceiling was painted before the ceiling was dry, which can happen when the internal temp. is cool, and the contractor is in a hurry.

 

In the winter warm air will be attracted to cooler areas and leave dirt on the ceiling.
Sometimes you can see where every joist is, then more insulation is needed.

 

What can I do to reduce the humidity? And, what’s the likelihood of this developing into mold?

 

Assuming that its caused by excess humidity in the attic then as oldognewtrick was alluding to it may be a function of better ventilation. I don't know what is typical in your area, but if its just passive vents on the gable ends you may want a fan. Alternatively if its more a function of condensation caused by the warm air in the house touching the cooler surfaces in the attic (those joists become thermal bridges for the cold) it may be addressable with better insulation.

I guess the question is (and you may have mentioned and I missed it) when did this staining develop? Also as a separate note while mold is of course always a concern I don't think you have any major cause for such a concern here.

Also I come from a land where there are no textured walls/ceilings, so I don't know if those have any specific things you might want to look out for (such as the possibility that the stains are from dust/dirt. If you haven't already tried I would see if they wash off.)