[GSBN] Looking for experiences with AAC and Rastra

[Derek Roff]

I've worked with Rastra a few times.  I don't like it.  I don't believe 
their insulation figures, even after they have scaled them back. 
Working with Rastra gives me a powerful reminder of some negative 
aspects of concrete and styrene, the component parts.  Cutting and 
shaping is possible, but it produces a lot of dust.  The dust is awful 
to be around.  I don't know if it is fair to say that the material is 
fragile, but it certainly surprised us multiple times with sudden 
breaks.  Working with ten-foot long, 150 pound blocks carries a 
significant injury risk to a small, amateur crew.

I've worked with two different kinds of Autoclaved Aerated Concrete 
(AAC) blocks.  They are more pleasant to work with than Rastra, for me. 
The ones that I used were very consistent in size and shape, with crisp 
edges and corners, which could be chipped in handling.  A few blocks 
cracked when dropped, but they seemed fairly strong.  I have concerns 
about the embodied energy, the need for two different kinds of massive 
kilns to make them, and their insulation claims.  It seems like every 
company talks about the amazing properties of their 2 pounds per cubic 
foot blocks, but the ones they actually sell have a higher density, 
which they often don't list.  The ones that I have used are still 
pretty light, but very different from what the industry keeps 
promising.

AAC blocks have a very rectilinear, industrial feel, which is the 
antithesis of the organic houses that I like.  But is seems reasonable 
to me to consider this option for foundation/stemwalls.

Derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu


--On Wednesday, December 22, 2010 10:41 AM -0500 Chris Magwood 
<chris at chrismagwood.ca> wrote:

> Hey all!
>
> I'm wondering if anyone out there has much or any experience working
> with Autoclaved Aerated Concrete (AAC) blocks and/or Rastra blocks
> for foundations?
>
> Neither product is readily available here in Canada, but I'm
> preparing some info on insulated foundation options and would like to
> include something about these products if I can get some info. I've
> obviously web-researched both, but I'm looking for actual
> experience... did they meet your cost expectations, were there
> peculiarities about the install process, how would you rate them
> environmentally, etc?
>
> Feel free to respond to me off-list, as I know this isn't exactly SB
> stuff. However, I'm hoping that among the vast experience included on
> this list would be some hands-on stories about these materials.
>
> Happy holidays!
>
> Chris