it sounds great and i love the aesthetics, but i wonder how green it really is considering concrete accounts for somewhere around 10% of our carbon emissions and has an extraordinarily high level of embodied energy when compared to virtually any other building material. yes, aerating it would cut the emissions in half when compared to standard concrete, but it's not going to work as a replacement for concrete in snowbelt foundations (blocks just don't work well with freeze-thaw cycles). it would replace whatever wall systems would normally be used which are often very resource efficient. could this really be more sustainable than local wood and cellulose or denim insulation in the northeast?
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R-value numbers I saw were order of magnitude higher than regular block with exterior shielding and insulation layer added. Very high in other words. You can download the pdf specs for details.

Frost penetration has been decreasing in the norther states over time due to climate shifts, and I expect that since the joint compound used is not plain masonry cement that frost resistance comparisons are not direct. Local building codes may have to be modified in accordance. Again, this depends on their published specs.

Finally, load bearing walls can be semi-interior and sheltered from precipitation, as between a garage and interior room or between a roofed porch and inside room.

i read the specs, and yes compared to regular block it is a good r-value and a simple system, but any contractor will tell you never to build a foundation in the snowbelt out of blocks of any kind. global warming isn't going to remove the freeze-thaw cycle before my foundation walls get cracked up. my point was that up here it is a replacement for wall systems most of which are actually less resource intensive and have much higher r-value.

i still wonder how they claim no pollutants and low-energy production. do they just leave the whole concrete production out of the equation? or do they use something other than concrete?

The stuff is very easy to carve. It cuts easily with any type of saw, can be sanded or chiseled or anything. It is easier to work with than wood. I know. I have built my own house with my own hands out of AAC, and I have built some of my own wooden furniture. And sculpting AAC is much easier than wood. Very easy stuff to work with.

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One of the best parts of TH is that the readers aren't pundits; they're real people with real answers. Thanks

I've been meaning to post a comment in this website for a while regarding wood house construction (and organic insulation added to wood homes). In my opinion, wood homes are NOT an environmentally friendly construction material. Here in southern Europe, where I live (Spain), nobody builds houses out of wood. In this part of the world, wooden houses are not considered houses. They are actually frowned upon by the vast majority of people. For the simple reason that wood houses are not houses that last. For one well built brick house, you many need to go through several wood houses. Just like one good CFL lasts the same as numerous incandescents. I have heard the argument that wood houses can last centuries - if properly maintained. And I am sure a few of them do. But most don't. Why? Fires, termites, floods, moisture, inadequate maintenance, excessive winds, etc., etc., etc. A wood house is not comparable to a brick house. And much less so for a house made of AAC. I'm sure many would disagree. But I think most wouldn't.

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Thanks to Houston for giving us his insights into the chuge cultural divide(s) between Europeans, Americans, and Japanese regarding what is considered resource efficient and what is not in living spaces. The idea of "product life extension" is critical to this common European view. A structure made with high resource burden, like brick or concrete, is maintained to last many generations, hence the "functional unit" of energy expended is "per generation". A brick building can last 5 to ten generations and later the bricks will be be used (re-incarnated) into another building. The Japanese tradition is the exact opposite, with paper and stick homes expected to last 20 or at most 30 years, after which the building is simply burned. THe US is in between these traditions, seemingly. As for the longevity of wood, old growth timber, now long exhausted, lasts hundreds of years of weathering. Plantation pine and composites simply do not last more than a generation or two.

i don't know if it's a matter of opinion houston. while the next generation of wood is growing, it is cleaning the air, providing habitat, erosion control and beauty. it can easily be milled on site and is renewable and biodegradable. that's reasonably cradle to cradle. nothing similar can be said for industrial concrete. how old is the oldest aac home you've seen? the r-values are too low for the snowbelt so additional framing or foam must be added. if you want to witness longevity of wood, travel around new england and note there's no shortage of wood homes and churches from the 18th and 19th centuries. or the hundreds of temples in japan from long before that.

mortar breaks down faster than you think. 25-50 years is normal. brick averages 100 years or more.

wood probably doesn't make practical sense in europe with it's limited forest resource and termites, but around here, forests have increased from 20% to 80% coverage in less than a century. quality timbers are often re-used in the same manner that used brick is only it actually fetches a higher price than new. the main difference being the high level of embodied energy of concrete and brick.

My wife is Finnish. Comes from a forest country. The main industry if forest. Everything is built of wood. The houses are all made of wood. Correction. They were until a Finn discovered AAC. Wood is no longer the main construction material. It is now a minority material and becoming more so every year. This isn't a coincidence coming from a wood country.

i don't deny that it is a very practical and brilliantly simple system for for the builder but adoption by the masses doesn't make it green, it usually means that it is economical. i'd like to see real stats and lifespan data. my question is still how they claim it is a green material considering concrete's extraordinarily high embodied energy and carbon emmissions.

This becomes a less attractive material when you factor in all the energy consumed to make the stuff.

In addition to the energy and carbon consumed in making the concrete, the blocks are usually autoclaved at high temperatures after being "foamed" with a chemical additive.

There is a much more eco friendly alternative that supplies many of the benefits - plus the added benefit of being form-castable: fibrous concrete. Typically, recycled paper fiber is mixed with concrete and poured into molds or formwork. The fibers shrink as the concrete absorbs moisture, cures, and dries, leaving tiny voids similar to the air-entrained concrete. In addition, the fibers add workability and tensile strength. Physical and insulation properties can be varied by adding sand and other materials to the mix.

Water repellency and flame resistance are insured by mixing in sand and/or commercial "crystal polymer" sealant.

For more info:
www.livinginpaper.com

AAC does not "contain" concrete. AAC consists mostly of silica (sand, reclaimed fly ash, reclaimed copper mine tailings, volcanic ash, etc.) It does contain cement -- about 4% of the finished product.

As for the foaming, the objector here misunderstands that, too. The "foaming" is a process not a chemical. AAC does not contain EPS or other types of "foam" -- only air bubbles!

The autoclaving is not very energy-intensive, either. At our plant in Ringgold, Georgia, we create the steam by burning lumber waste rather than fossil fuels. We use the very same boiler and indeed the very same steam used to kiln-dry our lumber! Thus it sounds funny to me, hearing someone use the steam to claim that AAC is less "green" than lumber.

Lumber is a great product for many applications, but please recognize that the lumber you use to build a house is not fresh from the forest. It must be sawmilled, trucked to a lumber company, sorted, cut to size, planed, kiln-dried, sometimes pressure-treated, and often kiln-dried again, before it is trucked to the hardware store. All of these processes require energy.

Jeannie Babb Taylor
http://www.SafeCrete.com

A comment from inside the industry: AAC does not "contain" concrete. AAC consists mostly of silica (sand, reclaimed fly ash, reclaimed copper mine tailings, volcanic ash, etc.) It does contain cement -- about 4% of the finished product.

As for the foaming, the objector here misunderstands that, too. The "foaming" is a process not a chemical. AAC does not contain EPS or other types of "foam" -- only air bubbles!

The autoclaving is not very energy-intensive, either. At our plant in Ringgold, Georgia, we create the steam by burning lumber waste rather than fossil fuels. We use the very same boiler and indeed the very same steam used to kiln-dry our lumber! Thus it sounds funny to me, hearing someone use the steam to claim that AAC is less "green" than lumber.

Lumber is a great product for many applications, but please recognize that the lumber you use to build a house is not fresh from the forest. It must be sawmilled, trucked to a lumber company, sorted, cut to size, planed, kiln-dried, sometimes pressure-treated, and often kiln-dried again, before it is trucked to the hardware store. All of these processes require energy.

Jeannie Babb Taylor

The embodies energy is actually lower compared to other concrete products.

What makes the product " green " ?

- Excess material can be recirculated in production.
- Low energy consumption during production.
- High thermal insulating properties. Means, saving on additional insulation what should be estimated into the energy consumption of the complete building during and after refection,

The flaws the product might contain are rather to find in the type of material you can ore can’t get on the market.

Conclusively, it is a environmentally sustainable material.

And, as it is “soft “ on the “ harvesting “ of its raw materials and the raw materials are to be found in almost any place in the world, it is rather the material of choice for less developed countries
which otherwise would have to use “ hard core “ industrial produced materials.

The center of concern is not about whether selected customers with rather deep pockets are able to have a “ green “ home built. They can, and will do it anyway.

Centering point is to provide a environmentally sustainable product which can be used on industrial standard.

http://www.aeratedconcrete.info

As concrete contributing to 10% of the worlds carbon emissions throughout its manufacture and entire lifetime.

Plantation timber that requires 1000s of hectares of native bush flattened to grow usually an imported species which requires processing and chemical treatment before it can be used to build anything not forgetting the large amount of energy used to get the trees processed and transported and in the store before it is shipped to the building site which in my opinion can be compared to mining.

Steel seems to be a viable answer.

In Australia our steel is produced from 80% recycled material and can last well past a lifetime. It is lightweight cutting down on heavy vehicle transport and in the end is 100% recyclable.