Aerated concrete: AaC homes and walls
Autoclaved Aerated Concrete (AAC) is a relatively cheap and durable wall construction material with some energy efficient advantages over masonry and other concrete wall building materials.
The high thermal mass of AAC walls and homes makes them a very energy-efficient solution in climates with large daily differences of temperatures, namely sunny climates with hot days and cold nights.
AAC walls and homes are also highly resistant to fire, moisture or pests. But they aren't so energy-efficient as some newer alternatives like ICF construction (see: ICF forms: Insulated Concrete Forms)..
See: AAC Advantages
What is Autoclaved Aerated exactly?
Autoclaved Aerated Concrete are blocks and panels for wall construction, invented in Sweden, in the mid-twenties.
They are made of natural raw materials – a mixture of cement, lime, sand and water, expanded through aluminum powder.
Climate
Although a popular building material in the cold Northern Europe, and only recently introduced in other climate zones, AAC is particularly beneficial in climates with large differences of temperatures over the 24-hours period of the day, namely sunny climates with long periods of hot days and cold nights.
And that because of the high thermal mass of AAC walls: aerated makes the walls behave like a sponge during the sunnier and hotter hours, before releasing the heat slowly, in the colder hours.
See: Thermal Mass Walls and Floors
AAC walls Costs
AAC wall costs are comparable to common concrete masonry units (CMU) walls, that is, something between $2 and $3 per square foot. These prices are lower than the much praised new methods of wall construction: ICF forms or SIP panels.
Aerated limitations and alternatives
The energy efficiency of AAC homes and walls is just reasonable in most climates.
In cold climates, with high insulation needs, or in super-insulated home strategies, there are better alternatives to get comfort and energy-savings (see: Rigid foam insulation or Sprayed-on foam materials for wall insulation).
For those who want high energy efficient walls, there are now new good alternatives to AAC home construction, namely the ICF forms or the SIP Panels.
Insulation performance
The insulation performance (R-Value) provided by Aerated Concrete can be ten times higher than that of common cement blocks. That’s excellent. But… wall materials like SIP panels and ICF forms can easily double that performance (in terms of R-value: R-20 to approximately R-10 in 8’’ thickness)…
In other words: when compared with common block and porous concrete, Aerated Autoclaved Concrete is an energy-efficient choice for wall construction, though not as performing as materials like SIP Panels and ICF Forms...
Codes
It's easy to to get official compliance to Aerated Concrete, but many state building codes still do not comprise them (in USA, where Aerated Concrete is a relatively new and a little used material, you should submit the project and the related architectural plans to ICC-ES).
Aerated Concrete vs. Concrete Block or Poured Concrete
Aerated Concrete may easily outperform the common concrete blocks or poured concrete construction. Its durability, and thermal, fire and accoustical properties are far superior to many other concrete-based materials and typical wood and cement framed walls without good insulation. But the quality depends also on its density.
Finishings
Aerated Concrete demands exterior (and eventually interior finishings). The open cells of Aerated Concrete, when exposed, can easily be damaged (physically or by debris and water).
See: AAC Disadvantages
Aerated Concrete Installation
See also: