I have two double size air brick vents at floor level in my lounge which make the room very cold in winter, these were fitted for a coal fire when the house was built and are no longer needed. What is the best way to Seal them up, Can I chop them out of the outside wall and put in a house a brick in and what insulation can I use and plaster inside the room? Could someone talk it through for me getting a bit confused thank you Tully