I have a wierd situation and could really use some advice
An addition was built on a house that already had a small concrete walled room in a basement, this added room surrounds the small room in the basement in an L shape. The only access to it is a 26" x 18" hole in the wall, it is a sand filled crawl space and the room above it is cold because there is only insulation stuffed between the joists. there are 2 holes in the exterior walls I assumme are for ventilation, Should I put a vapour barrier on the ceiling of this room and seal the holes leading outside?
I hope I have explained this well enough...
If your plan is to install a vapor retrder on the bottom of the floor joists, then that is a bad idea. Warm moist air from the inside of the living space will migrate to the vapor retarder where the moisture will condense at the bottoms of the joists. The vapor retarder needs to be as close as possible to the warm in winter space. You could place a plastic vapor retarder on the dirt floor of the crawl space to slow moisture from emanating from the ground. As far as the ventilation, that needs to remain open or you could find some condensation issues inside the ring joists. A better option is to upgrade the insulation between the floor joists with a vapor retarder up against the underside of the warm floor.
Another solution would be to insulate the wall that faces outside to the weather! Place a vapor barrier on the inside and on the dirt floor!
Close off the ventilation and install a heating duct from the furnace.
Does the addition have a crawl space also?