[GSBN] Looking for experiences with AAC and Rastra

Thu Dec 23 23:50:05 UTC 2010

Cheers!  May all you Mass be Merry!

John

On Thu, Dec 23, 2010 at 2:41 PM, Graeme North <graeme at ecodesign.co.nz>wrote:

> Sorry sorry John - whoopsie
>
> I get it now -  I though you that you were implying that the mass is best
> placed on the exterior of the building and insulation on the interior - I
> was trying to say that the (thermal) mass needs to be available to the
> interior of the building and not insulated from it - as I think you were
> too-
>
> its Xmas eve - have a very merry xmas everyone  -  I'll have another wine -
>  at least we get Xmas here before anyone else so we get Santa's best
> presents,
>
>
>
> cheers
>
>
>
>  Graeme
> Graeme North Architects
> 49 Matthew Road
> RD1
> Warkworth
> tel/fax +64 (0)9 4259305
>
> graeme at ecodesign.co.nz
> www.ecodesign.co.nz
>
>
> On 24/12/2010, at 11:21 AM, Graeme North wrote:
>
> Hi  John - I miss your point -  the mass should be *inside* the insulation
> to give thermal mass effects for moderating swings of both heat and "coolth"
>
>
>
>  Graeme
> Graeme North Architects
> 49 Matthew Road
> RD1
> Warkworth
> tel/fax +64 (0)9 4259305
>
> graeme at ecodesign.co.nz
> www.ecodesign.co.nz
>
>
> On 24/12/2010, at 6:01 AM, John Swearingen wrote:
>
> I worked as a volunteer on a project with Rastra, a temple with high walls.
>  As Derek says, it's difficult to love--the dust is awful and the blocks
> are, well, grungy blocks.   This was probably one of the few applications
> where the massive concrete gridwork inside the forms made any sense, but the
> mass is all *inside* the insulation, and so doesn't do that much good
> otherwise.
>
> It's amazing how Rastra persists as a popular choice--I think it's because
> at first look it seems like Legos.  I've had to deliver my rap on it several
> times to clients who were initially enamored with it.  I wouldn't build with
> it.
>
> John "RastraRap" Swearingen
>
> On Wed, Dec 22, 2010 at 9:09 AM, Derek Roff <derek at unm.edu> wrote:
>
>> 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
>>>
>>
>>
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>
>
>
> --
> John Swearingen
> Skillful Means Design & Construction
> 2550 9th Street   Suite 209A
> Berkeley, CA   94710
> 510.849.1800 phone
> 510.849.1900 fax
>
> Web Site:  http://www.skillful-means.com
> Blog:         https://skillfulmeansdesign.wordpress.com
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-- 
John Swearingen
Skillful Means Design & Construction
2550 9th Street   Suite 209A
Berkeley, CA   94710
510.849.1800 phone
510.849.1900 fax

Web Site:  http://www.skillful-means.com
Blog:         https://skillfulmeansdesign.wordpress.com
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