[Greenbuilding] [BULK] FW: Aerated Autoclaved Concrete

Tue Feb 5 09:59:11 CST 2008

I live in an AAC home (walls only 8 inches thick) and my heating/cooling
bills are significantly lower than my neighbors' with smaller homes, in
spite of my high ceilings and large windows.  Call it "drivel" if you want,
but you wouldn't think so if you were the one paying the electric bill.  ;-)

AAC is not only a thermal mass system.  It has insulating properties as
well.

I am in Georgia but there are AAC homes all over the US, including a good
number in Oregon.  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.  Most people (especially spec builders) just want to
purchase the cheapest home possible.  If they aren't the one paying the
heating/cooling cost, what do they care about performance?  Nor do they care
how well the structure will hold up over the next 30 years.  

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?

Many architects are exciting about AAC, not just for its thermal properties
but because it has the highest fire rating on the market, is more green than
most building products, does not off-gas, saves on jobsite waste, etc.

For full disclosure, I have interest in the lumber and AAC industries. I
spend most of my days selling lumber, but if I were going to build another
house, it would without a doubt be AAC.

Jeannie

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Lawrence Lile
Sent: Tuesday, February 05, 2008 10:15 AM
To: Jan Fillinger; greenbuilding at listserv.repp.org
Subject: Re: [Greenbuilding] [BULK] FW: Aerated Autoclaved Concrete

>Despite that, the
proponenets 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.  

I could see using a material like this in a climate like New Mexico,
where it gets cool at night but always warms up in the day.  One night
you might be able to use the mass to some effect.  But a conventional
wall and some masonry inside will buy you the same thing.  

Lawrence Lile, PE, LEED AP
Project Solutions Engineering

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Jan
Fillinger
Sent: Monday, February 04, 2008 2:09 PM
To: greenbuilding at listserv.repp.org
Cc: 'Mark Piepkorn'
Subject: [BULK] [Greenbuilding] FW: Aerated Autoclaved Concrete
Importance: Low

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.  

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