Thin And Highly Insulating Walls Lower Heating Costs

Better thermal insulation means lower heating costs – but this should not be at the expense of exciting architecture. A new type of brick filled with aerogel could make thin and highly insulating walls possible in the future – without any additional insulation layer.

The calculation is simple: the better a building is insulated, the less heat is lost in winter – and the less energy is needed to achieve a comfortable room temperature. No wonder, then, that the Swiss Federal Office of Energy (SFOE) regularly raises the requirements for building insulation.

In order to achieve the same insulation values as a 165 mm thick wall of aerobricks, a wall of perlite bricks must be 263 mm thick – and a wall of non-insulating bricks even more than one meter!

Traditionally, the insulating layers are applied to the finished walls. Increasingly, however, self-insulating bricks are being used – saving both work steps and costs and opening up new architectural possibilities. Insulating bricks offer a workable compromise between mechanical and thermal properties and are also suited for multi-storey buildings. They are already available on the market in numerous models: some have multiple air-filled chambers, others have larger cavities filled with insulating materials such as pearlite, mineral wool or polystyrene. Their thermal conductivity values differ depending on the structure and filling material. In order to reach the insulation values of walls with seperate insulating layers, the insulating bricks are usually considerably thicker than normal bricks.

Empa researchers have now replaced Perlite in insulating bricks with Aerogel: a highly porous solid with very high thermal insulation properties that can withstand temperatures of up to 300°C (see box). It is not a novel material for the researchers: they have already used it to develop a high-performance insulating plaster which, among other things, allows historical buildings to be renovated energetically without affecting their appearance.

Together with his colleagues, Empa researcher Jannis Wernery from the research department «Building Energy Materials and Components» has developed a paste-like mixture of aerogel particles to be used as filler material for the brick. «The material can easily be filled into the cavities and then joins with the clay of the bricks», says Wernery. «The aerogel stays in the bricks – you can work with them as usual.» The «Aerobrick» was born.