When talking about energy efficiency in buildings, it is inevitable to mention thermal insulation. We rarely see it in a finished building and, even in the technical drawings, the insulating layer appears as a thin hatch. But this is an element that is of vital importance, as it acts as a barrier to the flow of heat, hindering the exchange of energy between the interior and the exterior, reducing the amount of heat that escapes in winter and the thermal energy that enters in the summer. In a building with good thermal insulation, there is less need for mechanical means and energy waste to keep the house at a pleasant temperature, also reducing its carbon footprint. Currently, there are many countries that require a minimum level of thermal insulation for buildings, with increasingly strict parameters. But how should this issue be dealt with in the near future, with the worrying climate crisis forecast?