A cold front door is almost always the gap around it rather than the door itself. Before you price a replacement, run the back of your hand around the closed door at the hinge side, the lock side, the head and the threshold. Where you feel air moving is where the heat is going, and most of those places are a cheap fix.
Close the door on a windy day and work round it with the back of your hand, which is more sensitive to moving air than your palm. Go slowly along the hinge side, up over the head, down the lock side and along the threshold.
A lit candle or an incense stick shows it better if the hand test is inconclusive. Hold it a few centimetres from the gap and watch the smoke rather than the flame.
Note where it is, because the location tells you the cause. Draught along one whole side points at the door sitting wrong. Draught in one short section points at the seal. Draught at the bottom points at the threshold. Draught in the middle of the door is the letterplate.
The rubber seal around the frame hardens and shrinks with age, and after ten to fifteen years it stops recovering when the door opens. That is the commonest single cause of a draughty door and the cheapest to put right.
Check it by closing the door on a sheet of paper and pulling. Firm resistance means the seal is compressing. If the paper slides out freely, the seal at that point has gone.
Replacement seal comes on a roll or in lengths, it pushes into the groove in the frame, and it takes ten minutes for a whole door. Take a short offcut of the old one with you to match the profile, because the shapes are not interchangeable.
A letterplate is a rectangular hole in your front door, and on most doors it is the single biggest opening in the whole thing. A cheap letterplate has a sprung flap on the outside and nothing else.
A brush-and-flap letterplate seal fits on the inside face and closes the hole with bristles and a second flap. It costs less than a takeaway, it fits with two screws, and on a door with a bare letterplate it makes more difference than any seal you can buy.
Worth knowing while you are there: a letterplate is also the route a burglar uses to reach a key or a handle. A seal with a deep brush restricts that as a side effect.
An old timber threshold wears hollow in the middle where feet land, and once it does, no seal above it will close the gap. Put a straight edge across it and look underneath.
A brush strip or a weather bar screwed to the bottom of the door closes a small gap. A worn threshold that has dropped needs replacing, which on a doorset means the frame.
Check the drainage at the same time. A threshold that holds water rather than shedding it is a threshold that will rot, and that is a bigger problem than the draught.
A door hanging out of square presses hard against the seal on one side and barely touches it on the other. The symptom is a draught down one edge with the other edge sealing fine.
That is an adjustment rather than a replacement. On uPVC and composite the hinges adjust with an Allen key. On timber the fix is at the hinge screws or the keep.
Two kinds work and one does not.
Compression seals in the frame groove are the proper answer, because they are what the door was designed to close against. Replace like with like.
Brush strips on the bottom of the door work for a threshold gap and cost very little.
Self-adhesive foam tape stuck round the frame is the one to skip. It compresses permanently within a season, it holds moisture against the frame, and on a door with a working seal it stops the door closing properly, which causes the problem it was bought to solve.
Condensation is not a leak. It is moisture already in the air, meeting a surface cold enough to make it turn back into water, and a front door is often the coldest surface in a hallway.
Three things reduce it. Ventilation, because air that can carry moisture away does. Heat in the hallway, because a warmer surface stays above the dew point. And insulation, because a door that is not cold on the inside face has nothing for the moisture to form on.
If the water is running down the inside of the glass on cold mornings and clearing by mid-morning, that is normal condensation and it is a humidity question. If it appears between the panes, the sealed unit has failed and the glass needs replacing.
Sometimes the gap is fine and the door is the weak point. Two cases account for most of it: single glazing in a glazed panel, and an old solid door with no insulating core.
Every door we make has double glazing as standard, with triple glazing available across the range, and inside and outside faces you can specify separately.
The one that seals properly, whatever it is made of. A well fitted door with intact seals and a sealed letterplate loses less heat than a technically better door hung badly, and the gap between the two is larger than the gap between materials.
Once the fit is right, the glass matters more than the frame material, because it is the largest area. Triple glazing in a glazed door does more than any change of frame.
