Batt insulation causing stains on ceilings?

Did an older home yesterday. The batt insulation had a very thick, non-porous, vapor barrier (it was not Kraft paper) against the ceiling. On top of that, they added another layer of batt insulation with the vapor barrier face up.

The ceilings had yellow streaks throughout the house. There were no signs of leaks. The attic was not well ventilated (only 2 gable vents.) Below is what I said in the report. Does this sound reasonable? Could there be any other cause for streaks? (Sorry, a photo in the living area does not show the ceiling stains well.)

“The thick, non-porous, vapor barrier in the attic traps the rising moisture next to the ceiling. The result is condensation and subsequent moisture stains on the ceilings below. We can elaborate, but we suggest that you have an insulation specialist comment on the current installation method and consider complete removal and re-insulating the attic.”

“The attic is insulated with multiple rolls of batt insulation. The multiple vapor barriers trap moisture next to the ceiling and may result in condensation and subsequent ceiling stains. We can elaborate, but we suggest that you have an insulation specialist comment on the current installation method and consider complete removal and re-insulating the attic.”

Photo 2 shows the vapor barrier which was against the ceiling. Photo 3 shows stains on the attic side of the ceiling.

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You might have the right idea, condensation. Photo #3 looks like pooling of water, and all the photos appear to have a very dirty attic.

The insulation layer looks ‘thin’ so the walls could be getting very cold in the wintertime, and getting a layer of moisture. That allows dust, smoke, etc to stick to the walls and discolor it. The idea about insulation and it’s associated moisture barrier is to prevent penetration of moisture into it. Once inside,ventulation should allow for easy escape. It looks like there is moisture barrier on the ‘exit’/attic side. That barrier should be removed to prevent moisture from becoming trapped in the insulation.

IMHO, defer to an insulation/energy expert, since the attic might need to be fixed, and added to.



Sounds like “ghosting” streaks from the thermal bridging where the insulation allowed for themal differentials to exist.

Good one Doug.

Joe, any stains on the roof sheathing indcating leakage? Sounds like the lower layer of insulation was installed correctly, with the membrane toward the warm side. The upper layer would have been installed incorrectly with the membrane toward the cold side. Condensation would have had to competely soak both layers of insulation before reaching and soaking through the ceiling to discolor the ceiling interior.

Seems like the thermal differential theory would require a long time and big differentials to cause that, and seems like stains should be brown rather than yellow. Have you seen this on other homes in South Carolina?


No stains on the roof sheathing–no roof leaks. I’m thinking that since the vapor barrier membrane was non-porous, that the moist warm air that naturally rises through the ceilings gets trapped unde the vapor barrier and soaks the ceiling. The stains on the ceiling in the attic seemed to indicate that. The ceiling stains were not just where the ceiling joists were. They had no regular patten and were scattered throughout.

I’m of the opinion now that no vapor barrier is best for an attic. Think about it…blown insulation doesn’t have a vapor barrier in most cases.

The color of the stains can be debated. They were definitely water stains, however.

The attic had very poor ventilation, as I stated. I thought that may contribute to the conditoin.

Thanks for everyone’s comments.

I think you already mentioned that the real problem is the lack of sufficient ventilation in the attic area. Cold moist air on a warm surface will create condensation. Mother Nature hasn’t changed the recipe.


Here is some info on air, and vapour barriers.

Looks like water penetration to me (Roof leak?) The only place I find condensation issue stains are around the perimeter walls as the water condences on the roof decking then run down to the lowest point,… but anything is possible. Call it out to be further investigated.

Other way around…warm moist air on a cold surface creates condensation. Cold air hold less moisture. As the temperature drops, vapor turns back into liquid.

Mice, rat, squirrel urine. Doug

Yep, don’t totally discount that possibility.