French doors are often used to enhance the appearance of the exterior or interior of a home, but like any door, can allow drafts which will prevent you from maintaining a comfortable room temperature. Of course, escaping heat and air conditioning will also increase your utility expenses. If you indeed have a draft coming from your French doors, you can take several actions to seal and weatherize the doors.
Attach a bristle sweep to each of the French doors. Drill and screw to the bottom of each door. The sweeps prevent air from coming in or leaving and still allow you to open and close the doors. Obtain bristle sweeps at any hardware or home improvement store.
Install a drip edge to the outside bottom of the French doors to prevent drafts and water from getting inside the room during inclement weather. Using a plane, shave off a layer or two of the door to ensure you have room for the drip edge. Paint the wood to seal it after shaving it down, then secure the drip edge with a drill, using the screws included with in the kit.
Observe the door for any cracks and fill with caulking adhesive or wood filler. Pay special attention to areas around glass, since French doors feature many window panels. The seal securing the glass in place may have worn down over time. Fill in around glass using a waterproof adhesive.
Install weatherstripping around the French doors to prevent drafts from coming through the frame. Cut the strips with tin snips, then screw into place around the frame with a drill.