Aircrete Guide: Everything You Need To Know
Concrete is one of the most widely used, human-made materials on the planet. Some estimates state that we have made enough concrete to cover the earth's entire land surface in a thin coat of cement. Concrete is a durable and robust building material; however, it comes with a sizeable carbon footprint. The Royal Society of Chemistry estimates that between 5 and 7 percent of all carbon dioxide emissions result from concrete manufacturing. Thus, anything we can do to make concrete less strenuous on the planet is a critical step in the right direction. Aircrete is one "green cement" alternative that offers numerous advantages, which we will explain below.
What is Aircrete?
Aircrete is simply concrete with bubbles. Regular concrete that we use for our roads, basements, and foundations traditionally made from Portland cement. This combination hardens into a highly dense material with impressive compressive strength. The addition of iron rebar adds additional structural integrity.
Aircrete reduces or eliminates the traditionally used aggregate. Instead of including gravel or other coarse aggregate types, aircrete relies on incorporating premade foam pieces that essentially add bubbles of airspace within the concrete mix. Instead of foam, another option is mixing certain types of reactive substances into the wet cement mix. The chemical reaction creates gas bubbles within the cement and water slurry to harden with empty cavities.
GaiaDome is one company that specializes in making aircrete domes. According to its website, "aircrete is a lightweight cementitious material that contains stable air cells uniformly distributed throughout the mixture. It is a concrete that utilizes a stable air cell rather than a traditional aggregate. It is also called cellular concrete, foam concrete, lightweight concrete, aerated concrete, etc."
There is no set recipe for aircrete, as the exact amount of foam or air bubbles depends on how the aircrete will be used. Generally, aircrete with higher proportions of foam or air bubbles will offer less compressive strength but higher insulation capacities. Builders and homeowners might decide to use some traditional aggregate like gravel in aircrete applications requiring structural strength.
The Benefits of Building with Aircrete
Aircrete offers many of the traditional concrete benefits with added properties that can enhance sustainable and energy-efficient homes. If you have ever been inside a cement and cinder block home that was not adequately sealed, the chances are that it will feel cold and damp. Aircrete, on the other hand, offers superior insulation properties due to the foam and air bubbles built into the concrete itself.
As with regular concrete, aircrete can be formed into blocks for easy application or poured into forms for walls and other interior and exterior purposes. In one sense, aircrete is similar to insulated concrete forms (ICFs). It increases the insulation capacity of traditional concrete. Unlike ICFs, however, aircrete doesn't require separate polystyrene foam blocks or other rigid insulation that is subsequently connected with space in between for pouring a concrete wall.
Other benefits of aircrete for the sustainable home include:
- Relatively inexpensive
- DIY friendly for innovative homeowners and home builders.
- Good compressive strength
- Self-leveling
- Improved acoustic properties
- Better thermal performance
What are the Disadvantages of Aircrete?
Aircrete is an innovative approach to "greening up" traditional concrete. However, in some cases, the use of aircrete can lead to certain disadvantages. When high densities of foam are included, aircrete can become brittle, and chipping can occur. This type of aircrete will have limited compressive strength and could not be load-bearing.
Homeowners should understand that aircrete and concrete are fundamentally different construction materials with different uses. Concrete that incorporates natural aggregate has different performance characteristics. Concrete is a great alternative wherever high levels of compressive strength are needed. Where increased insulation is a concern; however, aircrete offers superior advantages.
What is the R-Value of Aircrete?
As we mentioned above, aircrete drastically improves upon the insulation properties of regular concrete. According to one analysis, aircrete might be able to offer insulation values of R-6 per inch. Blown cellulose, for comparison's sake, only offers R-values of 3.70 per inch. A home built with aircrete blocks that are 6-inches thick could potentially achieve an R-value of 36. That value is significantly higher than the R-13 to R-23 insulation values that are recommended for walls.
Similarly, an 8-inch poured aircrete form could be used for ceilings, attics, and foundations. The resulting R-48 insulation value would offer more than significant insulation capacity, especially when combined with sound building envelopes.
Is Aircrete Safe and Non-Toxic?
Homeowners could decide to save money by purchasing the cheapest plywood on the market for their home renovation. However, that plywood would most likely come imbued with formaldehyde and other VOCs that could poison your indoor air quality. However, with a little research and extra investment, homeowners could purchase healthier and more sustainable bamboo plywood made without any synthetic resins.
As with any building product, there are several different ways to manufacture and produce aircrete. Foam products have long been associated with VOCs and other harmful chemicals. However, some companies provide aircrete with limited synthetic residues. Airkrete® GREENsulation™ is one alternative that goes the extra mile to reduce reliance on synthetic foams. According to their website, their product is made from "mineral-based inorganic chemistry (not plastic) with desirable characteristics such as 100% fireproof, no toxic fumes, no CFCs, HCFCs, asbestos, or formaldehyde."
Is Aircrete Water Resistant and Fire Resistant?
Aircrete is also water-resistant and fire-resistant. The Portland cement in aircrete offers necessary water resistance. The foam or air bubbles provide an added layer of protection against moisture. Like all cement structures, specific vapor barriers can also help reduce condensation penetrating your home. For homes located in areas where wildfires are an increasing threat, aircrete exteriors can diminish vulnerability and increase overall resiliency.
What Can Aircrete be Used for?
Aircrete is most often used for exterior and interior walls. However, aircrete can also be used for several other home applications, such as precast blocks and panels and concrete slabs for an insulated flooring system. Some contractors also use aircrete for poured roofs, which increases the insulation capacity of ceilings and attics where heat tends to escape from homes. For households located in cold areas, aircrete can even insulate underground pipes.
How Much does Aircrete Cost?
The cost of building with aircrete will depend on several factors, including the thickness of application, the cost of Portland cement in your area, how much foam aggregate you include, etc. In general, however, aircrete will be much less expensive than building with regular concrete. According to one estimate, a 1000 square foot dome built 4-inches thick would cost about $4000. Another builder estimates that aircrete structures come out to about $9 per square foot.
Article by:
Tobias Roberts
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.
