Thermal Bridges: Where They Form and How to Prevent Them

A thermal bridge is a spot where insulation is interrupted or the structure conducts heat more easily. Mould and condensation often start exactly there.

After the first winter in a freshly renovated room, a dark patch appears in the ceiling corner and a damp stain on the window reveal. The walls are insulated and the heating works, yet the problem keeps coming back in the same places. The cause is often a thermal bridge: a strip or point in the building envelope where heat escapes more easily than through the surrounding area.

What a thermal bridge is and why it matters

Heat always takes the path of least resistance. If most of a wall is insulated but a concrete column, a reinforced beam or the edge of a floor slab passes through it, heat flows out along those elements. The inner surface temperature there is lower than in the rest of the room.

A cold surface causes two problems. The first is extra energy loss: strips that look minor add up to something noticeable across a whole house. The second is condensation: water vapour in the room air turns to water on the cold surface, and the moisture creates good conditions for mould. Mould is not just a cosmetic issue; it damages finishes and is undesirable for health.

There are two kinds of thermal bridge. Structural bridges come from a difference in materials, such as a concrete element inside an insulated wall. Geometric bridges come from shape: at external corners the outside surface is larger than the inside surface, so the corner cools faster.

Typical locations

• Floor slab edges: if the slab cuts through the full wall thickness to the facade, every storey gets a long cold strip.
• Cantilevered balconies: a balcony slab that continues the internal slab acts like a cooling fin sticking out into cold air.
• Window and door reveals, when the window sits far from the insulation layer and the reveals are left uninsulated.
• Lintels above windows and cast-in-place ring beams.
• Columns within infill walls.
• The junction between foundation and wall, and the perimeter of the ground floor.
• The roof-to-wall junction and parapets.
• Metal brackets holding facade cladding or air conditioning units.

Solving them at the design stage

The cheapest and most reliable way to deal with thermal bridges is to design them out. The key principle is that the insulation layer wraps the whole building without interruption. If the designer can trace the insulation line on the sections without lifting the pencil, the construction is on the right track; every place where the line breaks needs its own solution.

Practical solutions include:

• covering slab edges and columns with the external insulation;
• separating the balcony slab from the internal slab with special load-bearing connectors of low conductivity, or setting the balcony on its own supports;
• placing the window close to the insulation plane and wrapping the reveals with insulation;
• using insulated lintels above openings;
• insulating the outer face of foundations and basement walls with moisture-resistant boards, and adding edge insulation around the ground-floor slab;
• putting isolating pads under facade brackets.

What can be done in an existing building

Eliminating bridges completely in a finished building is hard, but the situation can be improved. External facade insulation is the most effective step, since it covers slab edges and columns at the same time. When windows are replaced, reveal insulation and a properly layered installation joint can be addressed.

Where working from outside is not possible, as in an apartment, local insulation in the problem area and keeping furniture away from cold walls help raise the surface temperature. Lowering indoor humidity through regular ventilation also tackles the cause of condensation directly.

Simply painting over mould hides the problem without solving it. Damaged plaster and finishes should first be removed, the surface treated with an antiseptic product and dried thoroughly. If the finish is then reapplied without dealing with the cause of the bridge, the stain will return within a season or two.

How to tell where the problem is

The clearest signs are dark patches in corners and at the ceiling-wall junction, condensation around windows, a musty smell behind curtains or furniture, and wall strips that feel cold in winter. For an accurate map, a thermal imaging survey is carried out; it is most informative in cold weather, when the indoor-outdoor temperature difference is large.

Zaferoğlu İnşaat carries out construction and renovation according to the solutions set in the design, from excavation to the roof covering. Contact us to find the cause of damp and mould in your home, or to avoid thermal bridges in a new build.