[Greenbuilding] FW: Aerated Autoclaved Concrete

[Jan Fillinger]

Hello:

 

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
95-95 deg, summer RH of 15 to 35%) that will be mainly solar-heated.  We
have modeled the house with the Energy-Scheming software developed by
University of Oregon professor G.Z. Brown.  We know that the sun will
provide about 95% of the heat required to maintain comfort, as long as we
provide a sufficient amount of solar glazing, internal thermal mass, and
well insulated envelope.  The basic heating strategy is: solar heat gain
through large south facing glass (properly shaded against summer radiation,
of course), large surfaces of 4” thick thermal mass surfaces exposed to the
indoor air, and a tight well-insulated envelope.

 

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.

 

However, I recently met with several contractors who have been building
Aerated Autoclaved Concrete (AAC) block homes around Bend.  This product was
originally developed in Germany under the name of Hebel.  The closest mfrg
plant, for us, is in Phoenix AZ.  These individuals were literally
evangelical about this product.  They state, and provide all kinds of
supporting literature, that this product has provides both high thermal mass
and insulation and that it would be perfect for a climate such as Bend’s.
The stated R-value is 1.25 per inch, which adds up to only R-15 for a 12
inch think block wall (it must be said that there is no infiltration through
the wall, since it ends up being monolithic masonry).   Despite that, the
proponenets state that the “effective” is  R-value is much higher due to the
“Dynamic Benefit of Massive Systems” (see last link, below).  Additionally,
they have numerous studies (including Oak Ridge National Laboratory) and
reported tests that appear to support extraordinary qualities for this
masonry product.  

 

The AAC gets covered with stucco and/or plaster inside and out.  Because it
is basically only a two step assembly, this masonry system could offers
significant cost savings in both labor and materials when compared with the
stud and masonry veneer approach.  For it to be acceptable for our project,
it is critical, however, that it meet both the thermal mass and insulative
needs of our project. 

 

I have asked some people at the UO architecture dept, as well as a local
mechanical engineer to give us their feedback on this product.  I am hoping
that some of the researchers and designers on this greenbuilding list can
give us their opinion on this product and the submitted performance data.


 

Here are the links to the studies and reports:

 

Oak Ridge National Laboratory studies HYPERLINK
"http://www.safecrete.com/aac/products/techmanual/pdf/thermal.pdf"http://www
.safecrete.com/aac/products/techmanual/pdf/thermal.pdf

 

HYPERLINK
"http://www.safecrete.com/aac/products/techmanual/pdf/thermal_performance.pd
f"http://www.safecrete.com/aac/products/techmanual/pdf/thermal_performance.p
df

Here is a list of AAC standards and approvals

 

HYPERLINK
"http://www.e-crete.com/standards/index.htm"http://www.e-crete.com/standards
/index.htm

Here is a chart with DBMS and R-values for Eugene(and other locations)

 

HYPERLINK
"http://www.e-crete.com/pdf/rvalue.pdf"http://www.e-crete.com/pdf/rvalue.pdf

 

 

Thank you, 

 

Jan

 

Jan C. Fillinger, AIA, LEED

Principal

 

STUDIO-E Architecture, PC

2749 Friendly Street, Suite E

Eugene, OR 97405

Tel 541-338-7558

Fax 541-484-2319

HYPERLINK "mailto:janfillinger at clearwire.net"janfillinger at clearwire.net

 


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