Thermal bridges and energy efficiency.
What is a thermal bridge?
Thermal bridges account for between 5% and 10% of a building’s heat loss.
At Icazar Architects, we are aware that in order to significantly reduce the number of thermal bridges in buildings, a good design and planning is necessary, paying special attention to the architectural details and their execution during the construction work.
A thermal bridge is a point or a line in the building shell where cold or heat flows more easily than in the surrounding area due to an irregularity in the thermal resistance. It is a place where the insulating surface is broken due to a change in the geometry of the shell or to a change of materials or thermal resistance.
That is why any architectural solution takes into account a possible thermal insulation irregularity so as to prevent the temperature inside the building to be affected by the building shell materials.
An example is windows where an aluminium frame is used. Insulating glass has lower conductivity than the aluminium frame, which is why the heat can be lost through the frame. In winter, it is common to see small drops of water condensation on the frame, while no such condensation occurs on the glass. By breaking the thermal bridge, we manage to avoid this heat loss, which consists in preventing the inner and outer sides of the frame from the contact with each other, including double-glazed windows with a non-conductive material between both sides of the frame, thus avoiding thermal flow between the outer and inner environment.
By breaking the thermal bridge, we will achieve:
– To save energy and, as a consequence, economic savings and also a reduction in the CO2 emissions.
– The interior space of the house will have a higher temperature than the exterior, thus avoiding water condensation on the frames or glass. The possibility of having two-colour frames, different inside or outside the building.
– Compliance with the Kyoto Protocol and also with the Technical Building Code, which requires the aluminium frames to be thermally insulated.
The places where we find thermal bridges are:
– Windows: for years now, windows have been thermally insulated, as a non-conductive material is used between the inside and outside of the window. But if the same windows have been used for a long time, it is likely that they aren’t thermally insulated and the heat is lost. In addition, if the window is not double-glazed, a thermal bridge is created that will affect the temperature inside the house and produce higher energy consumption.
– Pillars: in old buildings, it is common to find pillars embedded in a wall in contact with the outside, cutting the insulation of the facade if there is any.
– Frameworks: in the same way as with the pillars, it is common to find frameworks with edges located almost on the outside of the facade, cutting the insulation.
How can thermal bridges be detected?
There are three methods for locating thermal bridges: visual examination, by means of thermography or with numerical calculations.
This method is not very reliable, but in many cases it is sufficient. Especially, in the case of windows, where simply by placing a hand on the windows or by observing the presence of condensation, a thermal bridge is detected.
This system allows locating the most sensitive points of a building’s shell without having to perform special tests on the construction quality.
The examination is carried out with thermographic cameras that will provide a series of images that will clearly show where the building loses heat.
This system is also perfect for energy reconstruction or rehabilitation, since by making a thermographic examination before and after the work, the energy savings can be easily measured.
If the purpose is to have a building with almost no consumption or a passive one, rather than a thermography, certain calculation programs must be applied that will give much more reliable results.
Thanks to programs, such as LIDER, CYPECAD MEP or ECODESIGNER STAR, together with the BIM technology, it is possible to calculate the overall thermal behaviour of the building shell.
The best way to avoid thermal bridges is to know how the construction of each element of the building should be carried out. For this reason, the Technical Building Code provides a series of construction details that give an exact instruction on how to proceed in each case.