We have a very small downstairs toilet, which is located partly under the stairs. The house is a 1920's property and I am pretty certain it used to be the pantry. There is a small window in there and above this an air brick. We are currently updating the room and wondering about filling the air brick. It's always freezing in there and I am not sure how much ventilation this adds to the rest of the house as the door is always closed. Does anyone know if it is a total no no?