I moved into a newly build apartment in December 2001. In March 2003
(15 months after property was built \ moved into) a strange effect has
appeared on certain walls. The effect looks like someone has put
their fingers in grease and dabbed them sporadically over the walls.
There is no pattern to this and it has only happened on the inside
walls that are next to an outside wall, neither are the walls westerly
facing. No mould marks have appeared and the effect does not feel
damp to touch. I did have a picture frame on one of these walls and
the backside of it (i.e. facing the wall) was covered in mildew. I
brought the builders in to inspect it and they put it down to lack of
ventilation and the moisture in the room had attracted to the walls
causing this effect. They have suggested treating the wall with a
‘stain block’ product and re-painting (although they are
prepared to supply painters). So the questions I have got a

1. Is this correct what they are telling me i.e. lack of ventilation
causing moisture to attract to the walls?
2. What should I use to treat the walls so that this effect will not
show though when I re-paint?

Thanks,

James