Can a blocked air vent cause penetrating damp?

[Creamrevenge]

Hi

I moved house in May to a 1940's(ish) mid terrace cottage and all has been well until a few weeks ago when the rains/cold came.

In the corner of one room I have a damp/wet patch on a NE facing wall. It is not mold but I do have a little mold around the windows and in a different corner. I know mold can be caused by a lack of ventilation.

On the other side of the damp area is an air vent (Wire Mesh) but it is blocked on the inside.

I have been all round the roof and can't see a leak and see no wet areas in the loft.

I have removed a small section of the celing plaster and it looks damp/wet on the bottom(in the bedroom) but not on the top (in the loft).

Could this be caused by cold air coming in through the air vent and having nowhere to go?

Or is water penetrating somewhere and I can't find it?

Gutters are clear but the overhang of the tiles is not quite long enough but the exterior wall does feel dry.

There used to be a chimney in this area which my neighbour has told me was removed a few years back for this reason so i think the last owners may have been battling this for some time with no luck.

HELP!

Thanks.

 

[Creamrevenge]

Additional:
The old chimney has not been capped. Under the roof tiles there is just the chimney hole going straight down, this backs onto the damp area.

Could it be cold air coming down the chimney? or moisture? Should i "cap it" some how?

Thanks

 

[big-all]

a blocked vent cannot cause damp

to much moisture in the air condensing on cold surfaces can
an open vent can however help remove excess moisture from any source that gets into the room air

so in answer to your question a blocked up vent may allow damp to show up or get worse but will not be the cause
you should allow free air movement within a chimnie with a vent top and bottom

 

[Creamrevenge]

So could it be the old removed chimney? Could I cap it and/or stuff a roll of loft insualtion down it?

Or would I be better drilling a hole through the chimney on the inside and putting a vent in?

 

[big-all]

no you must leave it empty and ventilate top and bottom

 

[Creamrevenge]

So do you think it could be a lack of ventilation or penetratve damp?

How do i tell the difference?