Patio doors are an excellent home feature that allow you to enjoy the view and let in natural light. In winter they may be a source of cold drafts which are annoying, uncomfortable and result in you spending more on your heating bills. Drafts can come from different areas of patio doors. In general, you can stop the cause of the draft, or at least reduce it, without the expense of getting your windows replaced.
Locate where the air is coming from by holding a lit match or candle and slowly moving it around your doors. Watch the movement of the flame to locate the source of the draft. There may be more than one area that drafts are coming from.
Place a draft excluder, also known as a draft stopper or draft dodger, against the bottom of your door if the draft is coming from the bottom of its frame. You can buy one or make your own. In the short-term, use a rolled-up towel or rug pushed snugly up against your door to stop the draft.
Seal with a silicone sealer if drafts are getting in where the door frame meets the wall of the house. This can be done internally and externally using a tube of silicone sealer in a caulk gun. Follow the instructions on the tube. Wipe away any excess with a damp sponge before it has time to set.
Stop drafts from between the glass and the frame of the patio door with silicon sealer. This is most likely to occur in older doors with many small window panes where some of the old putty may have perished and broken away. If this is a big problem you might have to consider a full replacement.
Seal the top of any fixed door with silicone sealer, and use weather stripping to seal the top and sides of an opening or sliding door. Remove any old weather-stripping first before cutting the new weather-stripping according to the manufacturer’s instructions. It has a peel-off sticky side to attach it firmly to the door
Tighten any latches or handles that are letting air leak in. Use washers if they are loose. Sometimes a significant amount or air can come through a keyhole and the simplest solution is to place a piece of sellotape over it during the winter.
Install window treatments if drafts appear to be from convection currents generated by cold air outside your door's windows. Heavy curtains can also lessen the effects of a draft, as can honeycomb insulating blinds and window quilts.
Use a flame to test where drafts are coming from to prevent wasting effort on sealing something that wasn’t necessary.