Aluminium entrance groups: six junctions that decide whether there will be condensation

When a new aluminium entrance collects water on the inside in its first winter, the profile system is blamed first. The system is rarely the cause. A thermally broken profile from any serious manufacturer performs as declared. Condensation appears where the frame meets something else — and those junctions are designed, or not designed, by people on the project.

Condensation forms on any surface that is colder than the dew point of the room air. In a restaurant with a kitchen, a full hall and a door that opens constantly, the air is warm and humid, so even a small cold bridge becomes visible. Here are six places to look at.

1. The threshold

The threshold sits on the coldest part of the building — the slab edge — and is often the only part of the frame without continuous insulation beneath it. A warm threshold profile helps only if there is insulation under it and the screed inside does not bypass the thermal break.

2. The frame-to-wall joint

The frame must stand in line with the insulation layer of the wall, or be connected to it. A frame set deep in a cold masonry reveal is surrounded by cold on three sides, whatever the profile. The joint needs three functions: vapour control inside, insulation in the middle, weather protection outside.

3. The head and the lintel

Steel lintels and canopy brackets above an entrance are classic cold bridges. If a canopy is fixed through the facade above the door, the fixing detail belongs in the same drawing as the door.

4. Mullion and transom joints

In a glazed entrance group the profiles meet at many nodes. Each one has gaskets and sealing pieces that must be continuous. A missing corner seal does not show on the day of installation; it shows as a wet line in January.

5. The glass edge

The spacer inside an insulating glass unit conducts heat. A warm-edge spacer raises the temperature at the perimeter of the glass, which is exactly where condensation starts. It is a small line in a specification with a visible effect.

6. The door leaf itself

A door is the only part that moves. Its seals wear, its closer has to pull it fully shut against wind pressure, and its drop over time opens gaps at the top corner. Hardware sized for the real weight and traffic keeps the seals working.

And one thing that is not a junction

No frame can compensate for a room without ventilation. If humid air is not removed, water will find the coldest surface, however well the entrance is built. The ventilation of the hall and the heat source near the door — an air curtain or a radiator — are part of the same conversation.

Before the frame is ordered

• Is there insulation under the threshold, and is it continuous with the floor insulation?
• Where does the frame stand relative to the wall insulation?
• What penetrates the facade above the door?
• Who is responsible for sealing the perimeter joint — the installer or the builder?
• Is a warm-edge spacer specified?
• Are hinges and closers rated for the real leaf weight and frequency of use?

Six questions, one drawing. It is far cheaper than investigating a wet floor in February.