[Greenbuilding] [BULK] FW: Aerated Autoclaved Concrete

[Corwyn]

On Feb 05, 2008, at 10:59, Jeannie Babb Taylor wrote:
> AAC is not only a thermal mass system.  It has insulating properties as
> well.

Yes, this is a key point.

> It's a "hard sell" in the US because Americans have no
> conscience about cutting trees and producing high-energy, high-waste,  
> toxic
> building products.

Well I don't think concrete classifies as green.

> In Europe, it's a different story.  Something like 60% of residential
> construction is AAC.  Why would it be so popular for 80 years if it  
> didn't
> work?

Why would it be so unpopular here for 80 years if it did work?

I really hate the 'they do it in europe, it must be great' card.  I  
hate even more the 'it's popular therefore it must be great' card.

On Feb 05, 2008, at 10:14, Lawrence Lile wrote:

>> Despite that, the proponents state that the "effective" is  R-value  
>> is much higher due
>>  to the "Dynamic Benefit of Massive Systems
>
> This drivel has been promulgated for years by people who come up with
> poorly insulated materials that are massive and can't figure any other
> way to market them.  Log home dealers are also notorious for using this
> line. If it could dip below zero for an hour and then climb back up to
> 70F, massive materials would be OK, but it never does that.  When it is
> sub-zero outside for several days, any effect due to mass is over with,
> and you are going to miss your insulation and your house won't retain
> heat very well.  Insulate your wall and forget about this stuff.   
> People
> evangelize about stuff because it needs a hard sell, if it was really  
> so
> great they wouldn't need to work so hard.

And the 'it needs hard sell, means it doesn't work' card.  And the  
'since unscrupulous people use the concept, the concept must be flawed'  
card.  sigh.

Here is a study done by  Oak Ridge National Labs judge for yourself.
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/dyn_perf/ 
index.html

(Note that building location and wall construction type play a large  
factor in the benefit.)

On Feb 04, 2008, at 15:09, Jan Fillinger wrote:

> I am designing an off-grid house in the Bend area of Oregon (high  
> desert
> climate, 340+ days of sun, winter lows around 20-30 deg, summer highs
> around...

> Originally, the thought was to use staggered 2x4 @ 12" oc staggered on  
> a
> 2 x 6 plate, so as to eliminate direct thermal bridging through the  
> studs,
> and all cavities filled with closed-cell polyurethane foam which  
> eliminates
> any infiltration. In order to meet the thermal mass heat storage needs  
> as
> defined by the computer program, in addition to a 5" slab (fully
> insulated with rigid insulation underneath and around the perimeter),  
> we were
> planning to add 4" brick or concrete block veneer on the inside of the  
> open
> public spaces receiving the majority of solar heat gain.

If you are going to go to all the trouble of a double 2x4 wall, why not  
make it thicker than 5.5 inches.  For the cost of mostly only more  
insulation, you could have a R-40 or greater.  This would significantly  
reduce the required thermal mass.  For that much insulation, you might  
not want it all to be poly foam.

  The recommended insulation value for your area (unencumbered by  
construction type) is around R-50.  Even if the AAC will get you the 2+  
DBMS benefit claimed, the wall will still only be around R-24.


Thank You Kindly,

Corwyn


-- 
Corwyn
Kermit didn't know the half of it...
http://www.greenfret.com/
corwyn at greenfret.com