How does Autoclaved Aerated Concrete(AAC) compare in R-value to Faswall and normal stick build?

Asked by Denise
O Fallon, MO

Foundation / Framing options


Elizabeth DiSalvo

Answered by Elizabeth DiSalvo

Ridgefield , CT

Trillium Architects

July 16, 2012

Autoclaved Aerated Concrete (AAC) has been used in Europe for decades and is currently the most commonly used construction material for residential houses there. It is more recently becoming used in the United States. 

Most people are unaware of it but like many building products, that does not mean it is bad. In fact, since Europe and parts of Asia are so far advanced in many technologies, and they typically try to work at the cutting edge of technological advancement, that if a product has been used there for decades, I feel confident that it's probably one of the best out there.

Features of AAC

Missouri is actually a great place to be considering using AAC. Most of the manufacturing and distributing of this material seems to be happening in the south, Florida and Georgia are producing AAC regularly. It is a great product for down south as concrete naturally keeps things cool.

But it is a great product for any climate because it has so many great features.

  • It can be cut with a regular saw blade and easily drilled.
  • Its blocks are solid and relatively lightweight.
  • They have high “R” values for superior insulation.
  • One can nail or screw into an AAC block at any point to hang something – no blocking required.
  • It is has great acoustical qualities
  • It is fire resistant
  • It won’t grow mold because there is no organic material (food) for mold to eat
  • It is not highly priced.

Higher R values

Studies have shown that an AAC wall performs at about 10% higher R value than an equal thickness wood frame wall and about 20% better than a Concrete Block wall.

  • Because of the way it is formed and built it also naturally kills thermal bridging and air infiltration – both of which reduce R-value significantly in stick frame construction.
  • The construction is simple and cost effective.

You get a lot of bang for your buck with a wall like this.

Passive House

AAC performs so well that people building Passive House homes are using it. (Passive House ratings require the most energy efficient construction available).

This I think is the highest recommendation of all. If I were building a new home I would strongly consider using AAC.

Good luck!


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