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Thermal bridges in cavities

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Thermal bridges are motorways on which the heat can escape at a higher speed.

A thermal bridge is defined as the part of a building where the floors, walls or roofs insulating capacity change significantly due to:

a) Complete or partial disruptions in the building wall, materials with different insulating characteristics;

b) A change in the thickness of the wall;

c) Joints between walls, floors or ceilings.

These changes in the level of thermal insulation have a negative effect in the energy efficiency of the building, increasing energy consumption. It is estimated that between 5 and 15% of heat is lost through the windows. Furthermore, theses heat highways form condensations and damps which can create fungi and mould in the winter season (Even so, we have some advices to prevent them). Therefore, we must be aware of the importance of thermal bridges which affect our doors and windows.

Within the thermal bridges integrated into façades, we are going to study the ones which are directly related with the voids. As for the frames and glasses, we have an article which tells all the truth about Thermal Breaks.

In these joints, where an element finishes and the other one starts the solutions must be appropriate. Thus we must pay special attention during the execution of the works. Likewise, foreseeing accurately these joints in the project estate is fundamental.  First of all and as a general rule, we will always try to provide continuity to the insulation.

For example, we are going to study the case of a window jamb aligned to the outside. Let’s say that the wall has 5 cm of insulation, but the joint with the window is being interrupted, creating a weak point. If the carpentry were made of aluminium with Thermal Break, what would happen with that joint?

Figure2. Window jamb on façade wall.


 As seen in figure 3, the temperatures jump when they touch the thermal insulation and the carpentry. However, in the discontinuity area of the insulation the temperatures are distributed in a more evenly way, making that the window jamb had a temperature of 12ºC. In the other hand, we can see that the carpentry is at 8ºC on the inside due to the Thermal Bridge. Without any doubt this is an example of using in a wrong way a good carpentry.


Figure3.Temperatures diagrams (THERM).


In the next article we will show you how to identify these Thermal Bridges in doors and windows and how to solve them from the project and in the realisation.
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