5 Answers

Check for yourself.

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Yes it is true... Kiltz at one time only made primers... Today they produce paints of all types. Be sure to read the can and buy the correct product.... They person who services the paint counter will know just what to use. 

Never heard it being a vapor barrier. Your problem is not coming from inside the house. Make certain the soffit's have no obstruction and air is permitted to circulate thru the space above the ceiling.

yes it is Kilz is a good product, also

Benthere - you are the 2nd person to agree by using Kilz primer paint, it will stop the black blemishes appearing where the trusses meet the sheet rock.  I was told this is due to lack of insulation at the point of contact. 

Are you a building or a general contractor?