How to Heat an Upstairs Room From a Room Below With a Hole in the Ceiling

Use an electronic stud finder to locate the floor joists in the upstairs room. Pass the stud finder over the floor until it indicates the location of a stud by beeping or turning on its indicator lights. Mark the location of the joists with a pencil.

Turn off the electricity to any ceiling fixtures in the lower room to avoid an electric shock if you cut an electric wire.

Mark off the outline of the hole using a pencil and ruler. Situate the vent hole between the floor joists. This will help maintain the structural integrity of the floor because you won't be cutting the joists that support the second floor of the dwelling. Determine the correct size of the hole according to the size of the upstairs room in which it is located. For a 10-by-12-foot room, make the hole 10-by-12 inches.

Drill a hole in each corner of the marked off hole. Use a drill bit long enough to go through both the hardwood floorboards and the boards of the sub floor beneath them.

Cut the hole out with a rotary saw. Insert the blade into one of the corner holes you drilled earlier. Cut through the hardwood floorboards first, then insert the saw deeper into the space and cut through the boards of the sub floor. Finish the corners by cutting around the hole you drilled with a handsaw to create sharp, square corners. Remove the cutout portion and discard.

Drill a starter hole in all four corners of the hole on the top of the lathe and plaster or drywall ceiling of the room below. Make the holes large enough to insert the blade of the keyhole saw.

Cut a hole through the lathe and plaster or drywall that comprises the ceiling of the room below. Insert the blade of the keyhole saw into one of the starter holes. Cut a hole the same size as the hole you just cut into the floor.

Enclose the sides of the hole between the floor above and the ceiling below with lengths of boards the same dimensions as the floor joists. If the floor joists are made of 2-by-8-inch lumber, cut lengths of lumber the same dimension as the floorboards to the length of all four sides of the hole to block off the rest of the cavity between the floor joists. Blocking off this space will keep dust and debris from the floor/ceiling cavity from falling through to the floor below. Toenail the boards together by hammering nails at an angle to connect one board to the other.

Install a metal grate or mesh screen to the vent hole on the surface of the floor in the upstairs room and on the surface of the ceiling in the downstairs room. Purchase a metal grate that is 3/4-inch smaller than the hole it will cover up. The frame of the grate has a lip that will cover the gap and it will sit on the surface of the hardwood floor on the second floor. A metal grate works best on the floor surface, as it will withstand people walking on it. Metal mesh screening material is adequate to use to cover the hole on the ceiling of the first floor if a second metal vent is not available.

Frame the mesh screening, if used on the first floor ceiling, with stock wood molding. Miter the corners to 45 degrees and use finish nails to attach the molding to the ceiling.