We have a problem with a draft from our teak front door which has a double glazed side half panel. Door is north facing and at this time of year the wind whistles from the base and around the edges of the front door into an adjoining room and up the chimney.Front door is not warped or twisted, and closes OK. It would seem that the seals ( which are nearly 20 years old) are not stopping the wind coming into the house. Should I replace these seals and/or put draft excluders on both the front door and the internal door ends and edges? Also should I place a seal on the attic trap door at the top of the stairs as air seems to flow down the stairs? Where's the best place to get these seals/draft excluders? Would the new seals interfere with the doors closing properly?