The advantages of building with Autoclaved Aerated Concrete or AAC
Autoclaved Aerated Concrete (AAC) was introduced in the United States in the 1980s, primarily as a lightweight, energy-efficient alternative to traditional concrete masonry or CME. The technology originated in Sweden in the 1920s and gained popularity in Europe before making its way to the U.S. market. It is made from a mixture of cement, lime, water, and a small amount of aluminum powder. The aluminum reacts with the other ingredients to create tiny air pockets, resulting in a porous structure that gives AAC its lightweight and insulating properties.
In the U.S., AAC has been promoted for its energy-efficient properties, fire resistance, and ease of use. Its adoption has been gradual, with growing interest from engineers and builders looking for sustainable construction materials. Despite its advantages, AAC has faced challenges, such as a lack of familiarity among contractors and builders, as well as competition from more traditional materials. As of October 2024 there are approximately a dozen manufacturers of AAC in the United States.
Photo courtesy of NorthwestAAC
As for the percentage of residential homes built with AAC blocks in the U.S., it remains relatively low. Estimates suggest that AAC accounts for less than 5% of new residential construction. However, this number may vary by region, with some areas seeing more extensive use due to local building codes and sustainability initiatives.
The market for AAC is expanding as awareness of its benefits grows, and it is increasingly being considered in eco-friendly building practices, as well as a healthier alternative to concrete.
Photo courtesy of AerCon
Advantages of Autoclaved Aerated Concrete (AAC)
Design Flexibility: AAC Block is made of a unique combination of materials making it lightweight, easy to cut, be drilled or shaped on site. This gives architects and designers more flexibility compared to traditional building materials like masonry, concrete or brick. AAC come in multiple shapes for any commercial and residential project. It is used as cladding, sub-flooring, roof and fence panels or be molded into various shapes, sizes and finishes. It can be easily painted or coated allowing a wide-range of aesthetic finishes from modern to textured to rustic.
Photo courtesy of AerCon AAC
Energy Efficient:
AAC Block has high thermal mass, which can absorb and store heat, helping regulate indoor temperatures and reduce energy consumption. This feature allows architects and designers to create energy-efficient buildings with a range of design options, including large windows and open spaces, without compromising energy efficiency.
Photo courtesy of Northwest AAC
Better Acoustics : AAC Blocks offer superior sound insulation due to its high surface mass and porous structure. Coupled with AAC Wall panels, noise and sound is drastically reduced compared to other common building materials. Noise control inside buildings is of great significance for the health and wellbeing of occupants.
photo courtesy of MegAACrete
Environmentally Friendly : AAC is made from natural raw materials making it a sustainable, renewable resource. The primary ingredients of most AAC is made from cement, lime, water and a rising agent. They are processed thus creating air pores. At AERCON in Haynes City, FL, their production process emits no toxic or environmentally hazardous by-products. The trimmings are returned to the initial mixture during the trimming process, eliminating the loss of raw materials. AERCON saves energy during the curing process, where the hot steam used in the autoclaves is reclaimed for reuse. This technically advanced process conserves precious energy resources. The steam curing production method helps conserve energy since steam curing is carried out at relatively low temperatures, and thermal energy is recovered for maximum efficiency. And because AAC is so lightweight, the energy costs of delivering and installing the AAC is reduced (i.e. less manpower and fueled-driven equipment).
Photo Courtesy of LiteCon
Speed of Construction: Because AAC Blocks are larger and lightweight, they are easier to transport compared to traditional concrete blocks. Blocks are pre-cast or pre-drilled making it easier and faster to install at the building site. On average, AAC blocks weigh 50% less than standard concrete block and AAC panels weigh 30% than standard ones. Lightweight AAC creates an easier and happier work environment. The project is completed in a shorter amount of time keeping costs lower and homeowners happy, too!
Pest, Fire and Mold Resistant: AAC is made up of non-combustable materials giving it a Class A (4 Hr) Fire Rating and meets all building codes. It is a safe material for commercial or residential projects of all sizes. The alkaline pH of AAC make it highly resistant to water and moisture and inhibits the growth and spread of mold and bacteria. Pests, such as termites and rodents, are deterred due to the ingredients and chemistry if AAC.
Photo Courtesy of AerBloc - CO residence
*Note: Some AAC manufactures use fly-ash, an unhealthy and toxic byproduct of coal combustion in power plants. AERCON’s AAC is a non-toxic and hypoallergenic material that does not emit dangerous chemicals, making it a safe and healthy indoor choice. It has no toxic chemicals like formaldehyde or volatile organic compounds (VOCs), which sets it apart from other AAC manufacturers. By following eco-friendly and sustainable ingredients and procedures, Aercon is one of the “greenest”: A quote from their website - “this contributes to a family's health and enhances the air quality within the house”.
AAC Block Manufacturers in the US
AerCon - Haines City, Florida
AAC-West - Cheyanne, Wyoming
America’s Best Block* - Beverly, West Virginia
MegAACrete in Kerryville, Texas
NorthWest AAC - Bend, OR
*AAC contains Fly-Ash a toxic byproduct of burning Coal
The concrete industry, including lobbyists and trade associations, has historically promoted traditional concrete products, often viewing alternatives like Aerated Autoclaved Concrete (AAC) as competition. While there may not be a coordinated effort specifically targeting AAC, the concrete industry's lobbying activities can influence building codes, regulations, and standards that affect the adoption of AAC. While direct opposition from concrete lobbyists specifically targeting AAC isn't well-documented, the broader dynamics of the construction materials market can impact AAC's growth and acceptance. To benefit the climate and the wellbeing of human health, architects, engineers, builders, designers and contractors must educate themselves and consider using AAC in a future project.
Further research at AAC-Worldwide describes the future of new opportunities for AAC industries in North America.
8 Disadvantages of using traditional Concrete Masonry (CMU)
High Carbon Footprint: 8% of the worlds carbon emissions is from concrete production. The process of making cement is the most carbon-intensive part of concrete production. Cement is made by heating limestone and clay in a kiln to over 1,400 °C using fossil fuels. This process releases carbon dioxide through the energy used to heat the materials and from a chemical reaction that occurs when the mixture is heated.
Thermal Insulation: Concrete blocks have low insulating properties compared to other materials, which can lead to higher energy costs for heating and cooling unless additional insulation is added.
Weight: Concrete blocks are heavy, making them more labor-intensive to handle and requiring stronger foundations.
Cost: While concrete blocks can be cost-effective, the overall expense can increase due to additional insulation, finishing, and labor.
Moisture Absorption: Concrete blocks can absorb moisture, which may lead to mold or mildew issues if not properly sealed or if drainage is inadequate.
Aesthetic Limitations: The appearance of raw concrete blocks can be unappealing, often requiring additional finishing, such as stucco or paint, to achieve a desired look.
Cracking & Erosion: Concrete can be prone to cracking due to settling or temperature changes, which may require repairs. Salt air can cause erosion and pitting.
Sound Transmission: Concrete blocks can transmit sound, which may be a concern in residential settings, requiring additional soundproofing measures.
