I wonder why there isn't more discussion on AAC blocks or panels as an efficient building system?

http://www.globalmodularconcepts.com/Aerated%20Autoclaved%20Concrete.htm

Like you, I have been researching various building systems including AAC. I posted a question regarding using AAC floor panels with an ICF shell in the ICF subforum but got only 1 reply.

http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/4/postid/34350/view/topic/Default.aspx

I think there just aren't that many people that have experience with it. But it looks like a very sensible material to me. Where I'll be building I wouldn't even need to add additional insulation. So wall structure and insulation would be finished in one step.

Jelly;

 

I used ACC floor panels on a masonry foundation, ACC floor panels, 4" steel SIPs walls and then 8" steel SIPs roof

it was a job built in to the side of a hill in Dade City, Fl. it was mostly over crawl space and a 3 car garage

yes, you will need a crane or big lull, the 2ft. x 13 ft. x 8" panels were 800lbs. after set each joint has a key way for a #3 re-bar to be imbeded in grout and tied back to perimeter tie beam. Before any finish flooring can be installed you will need to "top" the entire floor to get it smooth enough for flooring.
Not a cheap way to go but makes for a solid fire resistant system (4 hours)

Chris, who supplied the AAC? I know of manufacturers in Georgia and Texas (Mexico actually).

I'm looking at blocks rather than panels, and for the walls rather than floor. Should make a tight envelope with SIPS roof. Where I am now I can go and pick up a block about the size of CMU at the home improvement center - feels like somewhere between concrete and balsa wood! Not so easy to find in the States I reckon. The whole idea of concrete light enough to saw and rout for electrical runs is very exciting.

Aercon

http://www.aerconaac.com/

In most cases I don't think they are cost effective yet

They say "low heat transfer rate" but don't give any specifics.  Does anyone know how low?

Larry

Larry;

I have personally put my hand immediately on an ACC block after a torch was on it and it was barely warm.

the poroisity of the material disipates heat quickly

Chris,

Wouldn't that equate to a high heat transfer rate?

Larry

Larry;

I think if it was retaining heat then it could be transfered via thermal conductivity but since there heat build up the block stays cool

There is a whole lot of information and links to the largest manufacturers here:

http://www.aacpa.org/

Thanks Jelly. 

The only one that I saw in a quick read suggested a thermal rating of R-11.  So it's an interesting technology, but not as interesting if I want a high efficiency home.

Very respectfully,
Larry

For the climate in the Southeast, I would recommend that 1" of Styrofoam be added to the outside of the AAC walls, and then stucco or brick.  Several years ago, I discussed this idea with Hebel personnel.  I was told that is the way that some companies build in Europe.

The advantage of AAC panels are that they are soft and easy to cut

the dis-advsntage is that they are soft, will not hold unchors well and will spalls easily.

In removing a bad bamboo floor job the adhesive was stuck well enough that we were taking up large chunks right down to the re-bars

There is a whole can of worms that could be opened up regarding concrete and estimated versus measured R-values.

Jelly,

One of the techniques that seems an attractive alternative is
the concrete-foam-concrete panel such as at
http://www.tridipanel.com/
The down side doesn't seem to be the concrete but the
steel rods conecting the two panel grids.  So your comment on
concrete is of interest.  My understanding is that the concrete
has virtually no insulating value, but does add thermal mass to
both sides of the insulating panel. 

Sooo . . .  Concrete in general, such as in ICFs, or concrete
specifically in ACCs? 

Can you free the worms?

Very respectfully,
Larry

Jelly & Larry,

I have used the Tridipanel system when it was called In-Steel.  I would be happy to share my experience with this system.  You might want to look at a system called T-Mass that avoids thermal paths through the foam to the concrete.

Alton,

Being nearly totaly ignorant in concrete construction, I liked the In-Steel fabric in both wythes:  It looked like it would reduce problems with surface and through cracking.  And it was available with several different foam thicknesses.  But the steel links between wythes bridged the insulating foam, and it wasn't clear what R value would result.  So, I'd  *really*  like to hear your experience with the In-Steel system.

Thank you for the cite to T-Mass; I'd not come across that before.  It seems more similar to the SolarCrete system than In-Steel.  Have you built with it, also?

R values are pretty straight forward, and I think that I understand the basics of how thermal mass would work to moderate temperature swings during mild seasons.  But it's not clear why the mass would be a net advantage during either the winter or summer extremes when even the best outside temperature is well outside what you'd want to maintain inside.  And I wish I understood how insulation and thermal mass worked together.  By any chance do you know of any studies comparing concrete-insulation-concrete systems, SIPs, and stick built structures in moderate climates such as Virginia or North Carolina?

All of the concrete-foam-concrete systems would seem to offer very good isolation from outside sound, but I've not seen any discussion on their reflection of inside sounds.

Very respectfully,
Larry

Larry, as you've probably seen in the other forums, the ICF guys and the SIPS guys tend to go for each other's throats when the topic of concrete's thermal mass is raised and how it applies to insulation and R values. That's what I meant about the can of worms - I didn't want to seem like I was starting in on that mess if you know what I mean! :)

But when it comes to AAC, it has the thermal mass properties of concrete but also superior thermal transfer qualities (or lack of thermal transfer, or insulation in other words) due to the millions of tiny air bubbles trapped in the aerated concrete. The synergistic effect of this combination means that there is more to an AAC wall regarding efficiency than just "R-11". I'll leave it to you if you want to research that idea more, but AAC has been put to use in extremely high efficiency homes for more than 70 years in Europe.

My personal roadblock regarding any building system, whether T-mass, Tridipanel, or various SIPS type systems, and ICF, is that they are either proprietary or require some degree of specialized labor. There is almost no chance in that case to construct any cheaper than you could if you were to just build with wood.

So I need something green that I can buy relatively inexpensively and do it myself if I can afford to do it at all. Whatever green building method you can think of - take that price per square foot and cut it in half. The figure you get is still too expensive for me. So as much research as I've done, I keep ending up back at square one, and that is stacking CMU and cladding it with foamboard on the exterior. AAC comes close to that, depending on the unit cost and how much foam I can get rid of. Being able to simply rout utility chases into it make it very appealing, too.

Call me stubborn, but green building should be cheaper than inefficient building. Until it is, I doubt it will ever become the norm.