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Not ecological? Autoclaved aerated concrete fact-checked

For many, autoclaved aerated concrete, or short AAC, does not seem like an ecological building material at first glance. Why is that? After all, it has a good ecological balance – among other things due to its excellent heat-insulating properties. A fact check on AAC in terms of ecologic properties and environmental protection.

08 February, 2022

"AAC is not natural."
AAC is made from natural and mineral raw materials. Quartz sand, quicklime, water, and small amounts of a blowing agent are needed for production. The mineral building material is free of pollutants, durable and environmentally friendly.

"Building with AAC is expensive."
As a high-quality building material, AAC is more costly than some other building materials. But the larger the AAC-modules are, the more economical they are: The large-format construction method is faster and more efficient than other construction methods, saving costs and time.

"AAC does not have a good eco-balance."
In fact, autoclaved aerated concrete has an excellent life cycle assessment due to its durable and energy-efficient properties. In the long term, the building material can save heating and thermal energy during the building use phase. Moreover, an additional thermal insulation composite system can be dispensed with, which also has a positive effect on the CO₂ balance. Building with masonry therefore has a similar or in some cases better life cycle assessment than building with wood, for example. (Source: Pohl, 2016, study by LCEE).

"Building with AAC is complicated."
The system is simple and resembles toy building blocks: Industrially prefabricated for an exact fit, the components only need to be dry-assembled in place. The panels have tongue-and-groove joints and are simply put together. The interior walls can be painted directly after assembly.

"AAC elements are inflexible."
AAC as a building material is just as suitable for offices as it is for shopping centers, production buildings or logistics and storage halls. A modular system with components in different lengths and thicknesses that can be applied throughout the building. This modularity, which starts at the planning stage, guarantees a flexible solution for individual building projects.

"AAC is harmful to health."
Autoclaved aerated concrete is completely free of pollutants and therefore cannot emit any emissions that are harmful to health. Even in the event of fire or exposure to water, no harmful substances are produced. The building material meets the criteria of the international standard ISO 14025, and this independent certification confirms that it is free of harmful substances.

"AAC cannot be recycled."
Our AAC has been Cradle-to-Cradle® (C2C) certified since 2011 - the first building material ever to be so. C2C is a design concept that takes nature as its model. It means that products are designed according to the principle of a closed and potentially infinite circular economy – with no waste generation. Learn more here

"Demolition residues from AAC cannot be reused."
Through good pre-sorting, AAC residues can be reintroduced into the production process – without any loss of product quality. In addition, autoclaved aerated concrete residues can also be fed into completely new recycling routes. For example, as animal bedding, as loose insulating material or as granules for technical applications, for example in the automotive industry.

"AAC production is very energy-intensive."
AAC is manufactured in a closed cycle, so less energy is used here than for building materials with comparable properties. The autoclaved aerated concrete elements are hardened in so-called autoclaves for between five and twelve hours at around 190 °C. The water vapor produced in the process is recycled in a closed system and 85% is reused. The wastewater recovery rate for building materials in our production method is around 51%.

"AAC is not fire-resistant."
Walls made of autoclaved aerated concrete already meet the requirements for fire walls from a thickness of 175 mm. The assembly components are not combustible, do not drip when burning and do not develop smoke or gases. As a result, cellular concrete as a building material prevents the spread of fire for more than 360 minutes - far longer than required by current standards. That is six hours to fight a fire in a targeted manner.

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