The door has three weaknesses, allowing the penetration of cold air. The first is the door groove, especially with the old ones, warped wings, and then a curved threshold and a letter slot, which often does not close tightly.
Sealing door seams.
If the wind is whistling in the gaps between the frame, and the wing of an old door, the most common cause of these noises is warping of the door leaf, which does not fit snugly against the frame groove in all places. Also, damaged seals allow cold air to enter the interior of the apartment. As with windows, self-adhesive or permanent seals can be a good remedy. In the case of a newer type of door, the old seal can be removed and replaced with a new one.
Draft with the newsletter. The letter slot in the door to an apartment or house is often the cause of heat loss. Flaps closed with a spring – especially in old systems – do not fit perfectly to the edge of the opening. A sealing brush can be an effective protection (available for purchase at hardware stores), which is screwed or glued to the edge of the hole.
The brush prevents drafts under the door. The gap between the door and the floor can be sealed with a special brush. DIY models are ideal for DIY enthusiasts, which can seal a crack even to 20 mm wide. The brush sticks to the floor thanks to a spring that presses it.