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Why did I come to specialize in designing and building with AAC 032524


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Title: Why did I come to specialize in designing and building with AAC 032524

How and why did I come to specialize in designing
and building with Autoclaved Aerated Concrete
  • Before delving into talking about AAC I feel I
    need to give a thumbnail sketch about my
    construction background to explain how and why I
    came to specialize in designing and building with
    Autoclaved Aerated Concrete designs (AAC).
  • I started in construction when I was 14 years old
    working for one of the finest master builders in
    the Atlanta Metro area. We built high end houses.
    The builder gave me the opportunity to work on
    the various crews from framing, plumbing,
    electrical to finish carpentry. I learned what
    all goes into building a house.
  • The next five years in the summers, after school
    and on weekends I worked for a millwork company
    making cabinets, custom furniture, doors,
    moldings, and other millwork. We took on a
    project working to restore an old farmhouse built
    before the American Civil War.
  • It was built in the Empire style of architecture.
    We worked on repairing and/or replacing cornices,
    railings, balustrades windows and doors. Many of
    the windows and doors were beyond repair so we
    carefully salvaged the wavy poured glass and made
    new windows and doors exactly like the original
    fixtures installing the original glass. We also
    restored the leadedetched and beveled glass for
    the great front entrance, which included
    repairing and replacing the lead glazing.
  • Furthermore, I learned from an old paint
    restoration specialist how to make restoration
    paint to be as exact as possible to the original
    paint that had preserved the exterior of this
    house for over a hundred years. I marveled at the
    detailsthat went into the work of building this
    grand house and of all the craftspeople who
    produced all its elements with the materials they
    had available to them on the building site with
    only hand tools, most of which were produced by
    the artisans themselves.
  • This project took us with power tools more than 6
    months to complete. I can only image what it took
    for the original craftspeople to construct this
    house. I gained an enormous appreciation for fine
    craftsmanship and their love of their trade. I
    began to learn what craftsmanship, materials and
    building practices go into building a house that
    last for centuries and serves the dwelling needs
    of many generations.
  • Another summer while in college I worked with an
    antique restoration specialist restoring fine
    antique furniture. He introduced me to epoxies
    for permanently bonding together joints and
    especially in chairs.
  • More than this I learned how to reproduce
    intricate details using casting rubber and
    filling those molds with color integrated epoxies
    to reproduce elements that were

missing on pieces we were restoring. Many of the
pieces we got to restore were little more than a
pile of lumber. To restore such pieces, we had to
be well versed in the styles and techniques of
the original periods when these pieces were
produced. Through this work in reproducing
intricate elements, we got a job working on a
Victorian house in which many of the original
plaster moldings had disintegrated. This often
happens when central air and heat are installed
in an old house which dries out the old horsehair
plaster moldings. We were able to produce rubber
molds from the surviving original plaster cast
moldings and permanently make exact reproductions
out of epoxy and install them into the places
where the originals had deteriorated. While in
graduate school I worked on the carpentry crew
specializing in repairing or replacing cornices,
corbels, windows, and doors on the old buildings
on campus. Later I started my own antique
restoration business working on all kinds of fine
antiquities from 1000-year-oldGrecian urns to
ChineseChippendalesofas and chairs. One of my
clients had spent years traveling around the
world purchasing precious antiques and shipping
them to her twohistorical mansions in the United
States. I spent a great deal of my time working
on these pieces. She introduced me to one of her
friends who was an interior designer for the
finest historical mansions in Louisville,
Kentucky, which she furnished in antiques and
exact antique reproductions. Among the projects I
did for her included producing exact period
reproductions. Through these relationships I was
asked to work as a consultant on the restoration
of the Governors Mansion in Frankfort, Kentucky.
My work included acquiringantiques throughout
Kentucky and restoring these period pieces to
furnish the mansion.I also served as an adviser
on how to restore the building itself. I have
carefully observed many antique buildings to
especially understand what materials,
craftsmanship and techniques the original
designers and builders employed with the
resources available to them to make these
structures durable and reliable for the many
generations who have dwelled in them. I have seen
what works and does not work over a long period
of time. What has impressed me the most is how
they have employed simple principles of thermal
dynamics to make these homes comfortable homes
for their occupants. I have observed in many old
houses built especially in the South with hot
humid summers turn the house to the prevailing
breezes and have a large central hall through the
width of the house with high ceilings where they
would spend their summer days enjoying the
constant cross through breezes. I have observed
houses that have utilized the simple principle of
convection air flow using tunnels or thick stone
earth bermed cellars as heat/cold closets and
cupolas at the apex of the house to create a
natural convection air flow drawing the cool air
from these tunnels or cellars through the house
to both heat and cool the houses.
  • Other houses as early as the mid-18th century
    have usedsolar thermal collectors to provide hot
    water and heating the house by placing lead or
    copper pipes on the roof with a fire in the
    basement and iron radiators throughout the house
    to heat the house in the winter. They used the
    principles of thermal dynamics and the direct
    energy of the sun. These systems used a closed
    loop of tubes filled with water to heat to a
    certain temperature and the hot water rises back
    to the top of the system and flows throughout the
    series of cast iron radiators.
  • One such house was in upstate Western New York
    just below the St. Lawrence Seaway where the
    winters can be quite harsh and some of the summer
    days just the same.
  • This estate was built around 1730. This house was
    built out of thatched hay between hewn logs for
    the structure and the joints plastered on both
    sides. This created a high thermal mass to keep
    heat in and prevent hot summer heat from
    radiating through the walls.
  • Later, the outside of the house was sided with
    clap board and porches were built around the
    perimeter of the house to both protect the
    windows and doors and utilize passive solar
    energy on the south face where most of the
    windows were placed. The original roof was made
    with thatched water grasses and later probably in
    the early 19th century a zinc standing seam
    metal roof was installed on which the solar
    collectors were placed.
  • Probably about the same time two cupolas were
    placed at the top of the roof. These cupolas had
    light weight louvers made of zinc which would
    remain closed until the temperature reached
    approximately 96 degrees. The thermal pressure
    would cause the louvers to slightly open and
    create a draft which would draw the cool air out
    of the basement and vent out the hot air at the
    top of the building.
  • The basement was deep, approximately 12 and the
    walls were made of thick stone collected from the
    property and was covered with earth on all sides
    except a small section where there was a large
    walk-out door.
  • During the winter they cut slabs of ice from the
    near by lake and stored them in the basement
    insulating the slabs with hay. This would last
    them through the summer, fall and spring.Needless
    to say, thisgreatly improved the cooling effect
    in the house throughout the summer. This house
    remains between 58-68 degrees throughout the year
    no matter what the winter or summer extremes may
  • This is just one example of many I could share
    where the designer/builders resourcefulness and
    understanding their environment and the simple
    principles of thermal dynamicswas employed to
    make their houses as comfortable a home as
    possible for its inhabitants over many
  • Thesimple principles they employed
  • Prevailing breezes.
  • Passive and direct solar energy.

  • Hot air or water rises and coolair or water
  • The constant cycle of convection air flow.
  • High thermal mass slows the transfer of hot or
    cool air.
  • These principles, though simple, always work. In
    our modern age of advanced technology and
    automation there is,it seems, a certain kind of
    arrogance and ignorance of the things that have
    proven reliable for centuries. I for one choose
    not to be arrogant or ignorant in designing and
    building houses that will prove reliable,
    durable, and highly energy efficiency to serve
    the dwelling needs of many generations.
  • So for me the simple principles I have enumerated
    above are of first course of action in my
    designing process. That does not mean that I do
    not keep abreast of latest technology or of the
    current resources available to utilize in my
    plans, but for me first course is to be observant
    of the resources available on the site and to
    work with the sun rather than against it and to
    intentionally work as much as possible in a
    synergistic relationship with the environment.
  • In 1990 I returned to Atlanta, Georgia which is
    my home. I started out repairing and replacing
    outside wooden decks and creating a formula to
    preserve them from the effects of the sun and
    weather. This led to repairing rotten door
    frames, windows sills and other exterior elements
    on houses.
  • My aim was to provide as much as possible
    permanent solutions to my clients house
    maintenance issues. I utilized my knowledge of
    epoxies to repair many of the more minor
    deterioration issues and built porches to cover
    entrances and soffits and gutters to repair and
    prevent damage to bay windows.
  • I also utilized polyurethane moldings and as Poly
    Viny Carbonate(PVC) building materialsbecame
    available in sheets, I built windows and door
    frames with these materials as permanent
    solutions. I have been in the business long
    enough to have seen almost all the materials that
    construction manufacturers have made grand
    promises as to their usability and durability all
    fail miserably and costinghomeowners small
    fortunes in costly repairs.
  • Admittedly many of these failures were a result
    of improper use and poor workmanship, but
    nonetheless these manufacturers over promised
    their products and in the end the cost was
    absorbed by unwitting homeowners. A couple of
    products among numerous others were hardboard
    (same as the material used to make cardboard so I
    often refer to it as cardboard siding) siding and
    OverlaidStrand Board (OSB) siding.
  • Here in the Southern United States one of the
    most disastrous building materials was the use of
    Exterior Insulated Finishing System (EIFS). This
    is a system where 1-3 of 2 lb. density
    polystyrene foam is applied to the outside of a
    framed structure and is finished using synthetic
    stucco made of plastics.
  • Sounds like a good idea, right? 2 lb. density
    polystyrene foam has a heat resistance rating of
    R-4 per inch of thickness, which is a great
    thermal mass where 2 of this

sheathing is R-8 and this added to 4 of
fiberglass insulation between the 2x4 studs makes
for a R-21 wall. It seemed like this was a good
way to improve the energy efficiency of a
standard framed wall. This system works just fine
in climates where the relative humidity is low,
but in the South where the relative humidity is
high throughout the year this system proved to be
disastrous. This is because this system developed
an airtight envelope as well as a watertight
envelope. The results were that condensation
moisture got trapped between the EFIS and wood
frame walls and had no place to go causing rot,
black mold, and insect infestation in the wood
structure. Here, especially in the South, a house
needs to have breathability to allow moisture and
other vapors to escape. What exacerbated this
problem with EFIS coatings over wood is that our
framing materials come from other regions whose
climate is significantly different. Most of our
wood framing materials come from the Northwest,
Canada, Finland and Norway where the relative
humidity is low. This timber is much lower
density and porous than Southern Yellow Pine and
thus cannot tolerate the moisture we always have
in this region, so it is subject to rot, molds
and insect infestation. Furthermore, trees have a
natural adaptation to its environment and the
indigenous insects. To give you an example, I
worked on restoring a church building that was
built just after the American Revolution in
Kentucky. I am sure that when they built the
building it was outside the flood zone of the
nearby river, but over the years the seasonal
floods gradually encroached upon this building
and now the building was flooded every spring.
This had washed out the stack stone piers the
buildings structural timbers rested upon. Now
these beams were mostly sitting in mud. We had
assumed that we were likely going to have to
replace these beams, because of rot and termite
damage. I had asked the local craftspeople 6
months before we had scheduled restoration of
this church building to cut down local pine trees
20 in diameter and larger to be prepared to
start drying out so we could bring in a mobile
sawmill to cut lumber we would need to restore
this building. The task before us was to jack
this building up high enough to get it above the
flood level and replace and salvage the stone
from these piers with cast concrete and then used
the salvaged stone to cover the piers. The
timbers under this building were enormous and ran
the entire length of the building. They, no doubt
were cut from the nearby virgin forest. To my
surprise these timbers were mostly sound. The
only damage was to the outside sap edge of these
virgin pine timbers where rot and termites had
tunneled but had not touched the heart wood at
the core. So all we had to do was strip off this
outside layer of these beams.
I have not seen any of these EFIS sided buildings
over wood frame in my region of the South that
were not subject to rot, mold, and termites. I
cannot tell how many of these houses I have
stripped all the EFIS siding and replaced
destroyed wall, floor and even roof structure
piece by piece. You can only imagine what that
cost the homeowners. I got so when I came to
inspect these houses I went first up to the attic
to see if termites had encroached up to this
space and in many cases found them. I always told
the owners in this case that it was in their best
interest to have their house pulled down with an
excavator and hauled off, because the cost of
restoring their house was way more than building
a new house. I have even seen EFIS walls
installed on wood frame below grade. These
ghastly misapplications of this product has cost
homeowners millions of dollars which they will
never recover. I fault building material
scientists for this misjudgment. Just because a
product may perform well in one region does not
mean it is appropriate in others. This short-
sightedness continues and building material
manufacturers continue to make high promises of
their materials durability, reliability, and
suitability for use everywhere. The demand for
wood framing materials greatly exceeds the
availability of the supply of locally grown
timber. I have seen this same mentality with
Leadership in Energy and Environmental
Design(LEED) which is the official measure of so
calledleading green construction. I personally
give little credence to their certification. I in
fact have come back behind these LEED certified
builders to repair and replace materials and
workmanship that has failed and costing
homeowners dearly. This systematic ignorance of
regional differences serves the material
manufacturers and their products more than the
homeowners who will live with the short-sighted
results. I know we have filled landfills with
these sidings and the resultant deterioration of
these wood structures. After synthetic stucco
failed, then many builders decided to use real
stucco directly over Overlaid Stran Board (OSB)
and called this green construction because they
are using recycled wood in OSB. Masonry stucco
has been used as a classical finish for centuries
but was never intended to be used over stick
frame construction but for over solid inert
structures such as concrete, brick or stone. Wood
is an organic material and is in constant flux
depending upon its environment. This expansion
and contraction cause cracks in cement stucco
over a wood frame and subsequently moisture
incursion. Cement based stucco is not waterproof
nor should it be because especially here the
structure needs breathability. Synthetic or
real stucco are not suitable for a wood framed
structure especially here in the South.
The largest infestation of black mold I have ever
seen is under this masonry-based stucco where the
food for this mold has been the delaminating OSB
subbase for this stucco. Now every house and
buildingis covered from sub walls, roof decking
to subfloors and even as the backing of laminate
flooring with OSB and then covered with plastic
wrap. To say the least this traps the innate
formaldehydein this product to preserve it. This
is a toxic environment for an indeterminate
amount of time. I have asthma and when I enter
one of these new green structures I begin to
experiencewheezing and shortness of breath. We
have done many bathroom remodels and invariably
when gutting out the existing showers we have
found rotted out subfloors and often floor joists
and in some cases side wall structure. In two
cases the existing shower had fallen through to
the first floor necessitating the homeowner to
have to remodel their bathrooms. Besides finding
rotting wood structure I almost always found
faulty plumbing and wiring. In one house that was
just 4 years old I found when tearing out the
shower walls that one Pex pipe connection had
never been cinched and had been leaking since day
one. It was a part that then only cost .75 yet
the restoration and remolding cost the
homeownersthousands of dollars. At least a dozen
times I have found live electrical wires just
hanging in the walls without being housed in a
box or capped with wire nuts. I do not have to
say how dangerous that is. In two cases these
live wires were in a metal electrical box
uncapped. We have also done numerous kitchen
remodels, building the cabinets on site to make
them an exact fit for the space and maximizing
cabinet space. The same has been true when we
have gutted out kitchens to remodel, we have
almost always found fundamental flaws inside the
walls and the floors. In one case the dishwasher
was dumping its water and waste directly into the
crawl space. After crawling under the house, we
discovered that this moisture had caused black
mold to grow on the floor joists and subfloor.Of
course, we had to tear out the sub- floor to
expose the joists and replace them. This was a
costly repair over and above the cost of the
kitchen remodel. After a while Igot so I would
anticipate typical kinds of problems and tell the
owners ahead of time that I would put these
costs into my proposals and estimates. When I
found problems behind walls and floors,I always
showed the owners and explained how we needed to
fix these problems and what it would cost. On one
house we were called upon to build custom
cabinets, window seats and shelves for a bedroom
on the third floor. When I was about finished
with all these fixtures,I sent one of my men up
to cut back the carpet for where we would be
installing these built ins.
After he returned, he had a grim look on his face
and he simply said, you are going to have to
take a look at this before we do anything
else. I went up and pulled back the carpet and
the OSB subfloor was black and rotten, so much so
that I could stick my fingers through it. I
immediately went down to the basement and found
that the floor ledger and the top wall plate on
which all the structure of the house sits was
nothing but mushroom compost. I felt sick. I went
up on the roof and found where the rainwater had
been pouring into the wall on the third floor.
This is one of those houses that has real
stucco siding. Besides a faulty roof design that
I see all the time the builder or his workers
assumed that this stucco was waterproof and had
left out any the flashing where this wall met
with the roof. The roof design was funneling
water directly against this wall. The result of
course was this water ran down inside the wall
all the way to the basement. Then I discovered
that at this corner of the house the floor ledger
and foundation wall plate was directly below the
ground and the house sits on a negative elevation
from the street and this run off was running
against this wall and the basement. I cannot tell
you how badly I felt showing and telling the
homeowners the problem they had and how costly
this repair was going to be. We had to tear out
sheetrock on walls and ceilings on all three
stories to expose the damage.All the OSB sub-wall
was eaten up with black mold and the structure
both walls and floor joists were infested with
termites. We actually had to jack up the house to
replace the floor plate and floor joists and then
regrade the front yard to overcome the effects of
negative elevation. This was just the beginning
of extensive repairs we needed to do to this
house because of poor design, failed materials
and shotty workmanship. This was just supposed to
be a 2000.00 cabinet job that turned into 10s
of thousands to repair fundamental problems on
this house. To say the least it is extremely
important to have carefully prepared detailed
house plans that even the general laborers
understand, and each plan requires carefully
prepared alterations to accommodate the unique
features of a specific lot. Professional builders
should know intimately every factor in all phases
of construction to understand and expect the
eventualities throughout the process and provide
careful supervision. I personally do not think
you can do this if you are building 10 or 100
houses at the same time. Owning a house is for
most people their single greatest financial
investment and should be able to rely on their
house being built by competent professional
builders whose greatest responsibility is looking
for the long-term best interest of those who will
dwell in the house they build whether it be 1 or
10 generationsthat will inhabit that space.
We expect no less from our doctor or attorney and
so should be our trust in builders. I could write
volumes on the ghastly problems I have found and
repaired in modern homes especially in mass
produced houses of which most subdivisions are. I
certainly hope and pray youare among the happy
and carefree homeowners who have not fallen
victim to the costly maintenance and repairs of
the few examples I have described or
others. However, if you are among those who have
had costly repairs and wondered what elseis
around the corner and wondered if there are
alternatives to conventional mass-producedhouses,
then you especially should read on. By the mid
1990s I had become so tired of making my living
at the heartbreak and expense of my clients. I
had become truly cynical of conventional building
materials and general building practices and what
galls me the most is the audacity to call these
materials and methods green construction. I
hate that term especially when it means nothing
and all it benefits in the end are material
manufactures and large construction
companies. First of all how can we call stick
frame construction green or especially
sustainable construction? We cannot continue
clearing land and forest to build temporary
structures that likely will be mowed down in 20
years to build more temporary structures that
appeal to the latest trend or fashion. This may
be great for capitalism and financially
sustainable to those I have mentioned above and
others, but it is murder on our environment and
cannot go on, because our forestsare so critical
to our survival on the earth. We cannot continue
building low thermal mass houses that consume so
much energy to heat and cool. It is really a
whole lot like thinking we can heat and cool the
outdoors. I made it my mission to design and
build houses for my clients that are truly
sustainable by being low cost to maintain, highly
energy efficient and designed and built as
durable, reliable structures that will serve the
dwelling needs of many generations. This meant I
would be able to find building materials and
methods of construction that overcome the typical
issues I was facing in remediation of modern
houses and would be energy efficient enough to be
able to justify the initial costs of heating and
cooling systems which truly utilize sustainable
renewable energy. My aim was not to find a
cheaper way of construction but to look at long
term cost in energy and maintenance for houses to
last at least a hundred years. This is not only
good for the environment, but more the people who
will inhabit these houses that they make their
home. I hate short sightednessand I was
determined not to be so or ignorant especially of
alternatives to the status quo.
I had learned enough from my historical
restoration experiences to take into account
using simple principles of thermal dynamics and
especially of utilizing the direct and passive
energy of the sun and to take advantage of
natural convection air flow. Furthermore, simple
things like designing houses with covered porches
and deep eaves and soffits to reduce the effects
of the sun upon windows and doors and building
structures and to provide shading to reduce solar
gain and decrease cooling costs and to orient
houses to the sun to take advantage of passive
solar energy in the winter to reduce heating
loads. Not only do porches provide practical
purposes for reducing energy consumption, but
they are welcome spaces for outdoor living. I am
also an avid advocate for using Evacuated Tube
Solar thermal collectors for domestic hot water
and water source heating and cooling. They are
relatively inexpensive as compared to solar
voltaic collectors. When you design and build for
high thermal mass and not working against nature
and its principles it only makes sense to utilize
sustainable renewable energy systems that are
initially more expensive to install than
conventional HVAC, but the long-term energy
savings are incomparable. My next objective was
to find building materials that stand up to the
test of time, do not rot or become subject to
insect infestation, will not burn, and can
effectively stand up to harsh conditions like
high winds floods and even earthquakes. I knew I
was looking for a whole building system and not
just a particular building material. I knew that
a composition building system like conventional
frame construction could not stand up to high
winds, floods,and earthquakes because it is not a
monolithic system that can move together under
such conditions, much like a ship on the sea.
Instead,it is only as strong as its weakest
link. When a part of the system is imposed to
high winds for example it moves and pulls against
the rest of the structure unevenly and
consequently pulls itself apart and the whole
system fails. From my experience with historical
buildings,I knew that the best system would be a
solid form of construction. I had seen solid
brick and stone structures that have remained
reliable for hundreds of years. I also was
familiar with tabby-builthouses and hay bale
houses that have long stood the test of time and
the weather it has endured over centuries. I have
also had experience in designing and consulting
on construction of rammed earth structures. There
are adobe houses that are over 400 years old and
do well in a certain kind of environment but not
suitable to a variety of regions. I was looking
for something that would perform in very diverse
conditions and regions. I am familiar with all
kind of masonry construction and they all do
better than stick frame construction. They have
two major drawbacks. They are put together with
thick bed sand and cement base mortar and the
joints can become weak and under extreme
conditions collapse. The other drawback is these
systems do not have a very high thermal mass
relative to their thickness. I did extensive
research looking for the right material and
building systems that met with my criteria. As
you might have already gathered, I am skeptical
of the high claims building manufacturers have
made about their products and have seen them
fail. I was looking for a material that had
alreadyproved itself over a long period of
time. I was pretty sure that such a thing was not
available in the United States and began to think
I would have to create a niche in construction
making houses out of such things as post-consumer
waste like old tires, glass and plastic bottles
and cans and knew I could do it, but it was a
market for just a few people and not financially
sustainable for me. I also considered designing
and building rammed earth structures, but here in
Georgia where I live our heavy dense red clay and
our climate are not well suited for this form of
construction. So, I started exploring materials
and building systems in Europe where forests are
already depleted and framed construction is
frowned upon. Solid construction is the norm in
most of Europe and I felt there had to be a solid
material and building system that was both
monolithic and proved over a long period of
timein diverse climates and could meet the
criteria of being fireproof, water resistant and
not compromised by moisture. It also had to be
insect proof especially to our termites and have
highthermal mass.Secondarily I was looking for a
product that would lend itself well to all kinds
of architectural styles and lastly be user
friendly so I could teach American workers on how
to build with this product and construction
system. I discovered a product that was invented
and patented by a Swedish architect in 1924. His
name was Dr. Johan Axel Eriksson who was working
with Professor Henrik Kreuger at the Royal
Institute of Technology in Sweden. They called it
cellar concrete. By 1929 a factory was built in
the town of Yxhult and the name of the
manufacturer is Ytong. In 1939 another production
company, named Siporex heighten the popularity of
this material and it began being used widely
throughout Europe. Soon they had operations in 35
locations worldwide.Autoclaved Aerated Concrete
(AAC) is made under several names Autoclaved
Cellular Concrete, Aircrete, Thermalite and
Hebel. So what is Autoclaved Aerated Concrete
(AAC)? It is made with completely inorganic,
sustainable materials and there is no waste
byproduct in its production. Unlike conventional
formed concrete blocks (CMU) whichis made with
cement and course fine aggregate it is made with
sand, lime a special kind of white clay and
It is mixed with water in large square forms and
aluminum oxide is added to the slurry and this
causes a chemical reaction to occur. This
reaction causes thousands of tiny hydrogen
bubbles to rise in the mix and the slurry rises
like yeast in bread dough. The result is millions
of tiny air pockets are trapped in the concrete
as it begins to cure. It is then placed in
autoclaves to provide heat and pressure to cure
it to its intended compression strength. Though
it requires a certain amount of energy in this
process it is still less than half the energy
that is consumed in the production of bricks and
concrete blocks or even in kiln drying wood. When
it is completely cured it is wire cut into
dimensionally accurate blocks unlike CMU blocks
which are not dimensional accurate and thus
require being put together with thick bed mortar
which can deteriorate and weaken the
structure. All the shavings from cutting the
block are captured and used to make thinset
mortar for putting the blocks together and to
also make lightweightstucco which is an ideal
finish for the exterior or a lightweight plaster
for the interior walls. In this process it is
completely sustainable with no waste by-products
since everything is recycled. I became very
fascinated with this product and yet skeptical as
usual, andso I continued to research the product
looking for performance reports. I read about a
chemical factory in Germany made of AAC, which
had a fire, and the fire was so intense the
firefighters had to stand back and watch it burn
for 4 days straight. It was assumed that the
exterior structure made of AAC was compromised so
engineers checked it out and took core samples
and it was as sound as the day it was completed
even though the steel internal structure was
vaporized. In 8 weeks,the factory was back in
business. I have seen what happens to CMU block
structures when exposed to such intense heat. It
just crumbles under this kind of stress. I found
another article and saw pictures of a house that
survived a wildfire. The picture showed hundreds
of slabs and basements all around except for this
one house made of AAC and had a clay tile roof
was the only thing still standing. I also found
an article and pictures of two AAC houses that
were the only structures still standing aftera
massive flood had swept all the other structures
away. Later I read about an AAC house in
Indonesia that survived a class 4 cyclone. The
pictured showed a vast expanseof vacant slabs and
rubble and this one house standing unscathed. It
had not only survived the high winds, but also
the storm surge of water. It is often the case
that a house may survive the high winds of a
hurricane/cyclone and even the objects that fly
around and hit the structure during the storm,
but when the seas recede, they finish off the
houses already impacted. This AAC house had
survived all these harsh elements that had
destroyed all the other neighboring homes.
I was truly impressed and began to wonder if this
material was available in the United States. I
had read that one of the manufacturers, Hebel had
plans for production of their AAC blocks in
America and that they already had a factory in
Monterey, Mexico and shipped their products
worldwide. I decided to make a call to Hebel in
Germany to learn as much as I could. I learned
they were building a manufacturing plant in Adel,
Georgia, which is about a 4 ½ hour trip from
Atlanta. I asked for all the literature they have
on their products and asked the engineer who I
was speaking to me to let me know when they would
start production in Adel. I learned all I could
about building with AAC and decided I would
design and build a house for my own family using
this product.Twelve weeks later I got a call from
the German engineer whom I had spoken with
earlier. He told me that he was in Adel, Georgia
and theywere startingproduction of their blocks.I
made an appointment to meet him down there.In the
meantime,I came up with at least a hundred
questions I jotted down that I wanted to ask
while I was there. I took my house plans down
with me and spent 2 ½ days there. I got a tour of
the plant and watched a slurry being made and the
chemical reaction when they introduced the
aluminum to the mix. It was a marvel to behold,
seeing the batch rise. They had a two-day class
for me to attend, which included building a small
room with Hebel blocks and mortar. This was a
great hands-on experience, seeing how easy it was
putting the blocks together and sawing the block
with a basic hand saw. I spent at least half a
day going over my building plans and learning
what alterations I needed to make and the
reinforcement necessary to make this house a
strong solid monolithic structure. I got a
certification as a Hebelapproved builder. I was
convinced enough to make the investment of my
time and financial resources to build my first
AAC house for my own home for my family. I had
known even before I had finished my research that
I would be building a house different and
superior to conventional stick framed
construction and that I would have to find a lot
that stood alone outside a typical subdivision. I
knew that my house would be appraised like all
the other houses in such a subdivision. We had
found a 5-acrelot in an estate lot subdivision
with lots of 2 ½ to 20 acres and all the lots had
custom built homes. I had picked out a site on
the lot and staked it out for grading with the
front of the house to be facing solar south. I
began designing the house for this site and it
seemed like we went through endless revisions as
my wife and I had differing visions of what we
wanted for our floor plan. I had decided to
design and build our house out of Insulated
Concrete Form construction, though I had still
had certain misgivings about building the entire
house out of this system. I still wanted to
utilize this material for my basement even after
I had
discovered AAC. I knew after seeing and working
with AAC that it would not be suitable for a
basement mostly below grade especially given our
heavy red clay and the enormous hydraulic loads
upon the foundation when the ground is saturated.
Though AAC is a very strong system as compared to
framed construction it is not as strong as poured
concrete.However, especially nowpoured concrete
is more expensive than AAC and AAC has a higher
thermal massrelative to its widththan ICF
construction. Unfortunately, I was not going to
be able to get ICF forms from Georgia in time for
our construction schedule. The closest forms were
in Oregon, and I would have to wait for them to
be shipped and pay that expenseto use for our
foundation.Also, I had a very good friend whom I
have known for over 15 years who had been in the
business of pouring concrete and waterproofing
for longer than I can remember. Since then, I
became acquainted with a manufacturer/distributor
for American Polysteel Forms here in Georgia and
subsequently planned and built basements using
their product and were pleased with the
results. I knew that my site would need a full
basement where three sides would be mostly
underground, and I planned to utilize the
insulating value of the earth to make the
basement a heat/cool closetto integrate into our
heating cooling system. We formed and poured
asteel reinforced monolithic slab installing
vertical rods 16 on center for the subsequent
reinforcement of the foundation walls. We waited
28 days for the concrete to cure to its strongest
strength which you can imagine is a very
important thing to do when you are building an
all-concrete house.Afterwards we poured a full
surround 10 thick concrete wall and waited
another 20 days beforebeginning AAC
construction. We set engineered wood web style
floor joists for the first floor. I knew this was
not the best option, since wood and concrete are
not particularly compatible. If I had had a
choice,I would have used 8 thick engineered
floor panels from Hebel, but panels were not yet
in production in Adel. In fact, I received some
of the very first blocks produced by the Hebel
plant in Adel, Georgia. Since then, I have
always specified in my plans the use of floor
panels for floors and when possible,for roof
panels. In fact, they make panels up to 20 long
which can give you a clear span width up to 19
8 and as long as you want. Our walls were built
with standard 8x 8 x 24 blocks which are the
minimum for a load bearing wall. For residential
construction they also make 8 x 12 x 24 blocks
and for interior walls they have 4 and 6
blocks. Thes blocks are less than 1/5 the weight
of standard concrete blocks. An 8x8x24 block
weighs approximately 40 lbs. Why are they so
light? It is because of the millions of small
pockets of air trapped in the concrete in the
chemical reaction
process. This also is the reason for its high
thermal mass and the reason it is fireproof. The
blocks are 60-80 air. It is approximately R-4
per inch of thickness. So an 8 thick block
finished with light weight stucco and plaster has
a thermal resistance of R-32. To give you a point
of reference,a standard wood 2x4 stick framed
wall with fiberglass insulation between the studs
has a heat resistance of R-13. To get anywhere
near the same thermal resistance using stick
framing you would have to use 2 x 8 studs and
1 of 2 lb density polystyrene double kraft faced
aluminum thermal sheathing for the outside and 8
of fiberglass insulation between the
studs Especially now with the high cost of wood
framing materials, thermal sheathing, and
fiberglass insulation you would at least be
spending 2 ½ times more than using Autoclaved
Aerated Concrete. Evenif you decided to build
that way you will have created a new problem by
making your structure so airtight. You would be
trapping in toxic vapors inside the house such as
the gassing off offormaldehydethat is present in
sheetrock, carpet and other building material
such as OSB and what about carbon monoxide from
your gas fired furnace, gas water heater and gas
stove? A house needs to breathe especially in
climates that have a high relative humidity. The
fact that AAC is porous, giving it its high
thermal mass but it also allows the walls to
release gases. Many people, including me are
allergic to fiberglass insulation and it has been
proven to cause many people to develop
respiratory diseases over time. You may have
gathered earlier in my comments above that it is
not a good idea to apply polystyrene foam thermal
sheathing against a wood framed structure,
because it traps condensation moisture between
the foam sheathing and the wood frame, which for
obvious reasons is not a good combination. Further
more, building primarily with wood is not
sustainable.This is already the issue with
non-regional lumber being used in climates that
are not suitable. Here in the U.S we are already
importing most of our lumber from places like
Canada, Finland, and Norway to keep up with our
demand for framing materials. Has it even
occurred to you what kind of carbon footprintthis
is making on our planet? If you are convinced
that wood framing is your only option for
construction for whatever reason, then use lumber
that is grown,harvested, and milled in your state
or at least in your region. Now just a note here.
Most of the stock plans found on my website are
specified for primarily steel framed
construction, because I know it is hard to find a
builder that knows about any alternative
construction method other than conventional
framed construction and even fewer are willing to
change or ask their crews to change to a new
Framing with light gauge steel construction is
not much of a threshold of learning to overcome
and many commercial framing crews do use light
gauge steel construction.I have aimed in these
plans to provide as high of thermal mass as
possible using a standard 2x4 frame system and
solid 2 lb density foam thermal sheathing and
sprayed in foam insulation between the
studs. This gives a thermal rating of R-22 as
compared to the standard R-13. This type of
application is completely appropriate for light
gauge steel construction. I specify the roofs to
be R-24- R-40.Well, you ask, is this not
basically an airtight system? The answer is no
because in every plannatural convection air flow
is integrated into the over all heating and
cooling system allowing the system to
breathe Furthermore, I integrate the use of
Evacuated Tube Solar Thermal collectors(ETSTC)
for domestic hot water and quiet and clean water
source heating and cooling. It was a challenge at
first to find construction workers that were
willing to learn how to build with AAC and this
included skilled contractors in plumbing,
electrical and HVAC. I promised these specialists
that I would guide them through the whole process
and pay them on a cost-plus basis since they had
no idea how to estimate the cost of their
application to the system. I had the hardest time
with the HVAC engineer. I calculated all the
heating and cooling loads for him and confirmed
these calculations through the Hebel engineers
with whom I was working. For the size of 3040
square feet of conditioned space and our high
cubic feet of air with our high ceilings and
cathedral ceilings on the second floor that rose
to 14 feet he was baffled with the load
calculations I provided. He specified a 3 -ton AC
unit for each floor and I had to fight him to put
in a single 3 ton unit for both floors. Then I
told him I wanted to use a very energy efficient
heat pumpwater heater to provide endless domestic
hot water and to run hot water coils inside the
air handler to heat the house. Since I was using
the basement as a heat/cold closetdrawing fresh
air intake for the HVAC system from the basement
which always stayed between 64-68 degrees this
made the energy thresholdto heat or cool very
low. I insisted on using the heat pump water
heater for this purpose because the heat pump
would dry the humid air out of the basement and
not transfer humid air into the primary living
space. He told me repeatedly that the initial
cost of this system would never pay for itself
and that I should use a gas fired furnace
instead. I had the good fortune of hiring a young
Mexican man to help me with building the AAC
walls. It took a while for us to get to
understand one another since I knew very little
Spanish and he equally so in English. I worked
with him and observed how he worked. I soon began
to see he had an innate understanding of solid
construction. One day I ask one of my Hispanic
friends who
isaffluent in Spanish and English to come over so
I could have a more in- depthconversation with my
Mexican worker. I learned that in Mexico solid
construction is more the norm than composition
construction as in framed construction. He said
in fact he could not understand why gringos are
so enamored with building our houses out of
sticks and he especially could not get why we
build our fireplaces out of wood. Thats loco,
he said. I smiled and nodded. I learned that in
Mexico he was a master mason, building with
adobe, concrete blocks and had in fact worked on
a house made of AAC. I cannot tell you how
thrilled I was. I asked him if he knew others
that lived in the Atlantaarea who had his
experience. His grin was as wide as his face. Si
Tomas. I have 11 brothers and 3 sisters. Over
the years I have employed some and all of them on
my various projects and trained them through
every stage of construction short of electrical
and heating and air. They were invaluable to me
and they became like family to me and I to
them. I heard in reading other posts that one of
the biggest cons to AAC construction and for that
matter solid construction in general is finding
workers who know how to work with these
materials. I have good news. There are many
Hispanic workers in the construction job market
who have firsthand knowledge of solid
construction and are easily taught how to work
with AAC and not only are they easily taught but
they are more than happy to learn. If you find a
builder who is willing to build your plans out of
ICF and AAC, I have more than 20 years of
hands-onexperience designing and building with
theseforms of solid construction and can
certainly train a crew and advisespecialty
contractors in doing their work on these kinds of
structures. All our plans can be altered to be
constructed with Autoclaved Aerated
Concrete. While I was building my house in
Canton, Georgia one of mysoon to be neighbors
came to visit our jobsite. He also was a builder
and was constructing his own house for his
familys home in eyesight of my home. He was
building a stick framed house with real
cement-based stucco siding. What the hell are
you building here, a fortress? I stopped to chat
with him a bit and shared briefly what we were
building. His response was basically this is
going to cost you a fortune and is completely
unnecessary. Like a trout rises to a fly, I bit.
I said, I tell you what, I will share with you
my utility bills for you to examine if you will
show me yours. He responded immediately, Youre
on. I smiled and nodded. His house was slightly
bigger than mine,but I figured when it came down
to total cubic feet of air to heat and cool they
were nearly identical.We
exchanged utility bills for about 6 months. My
bills were less than a third of his, both in
summer and winter. I made note after that of
crews coming and going from his house doing
repairs. In the 20 years we lived there he had to
have large sections of his stucco siding torn off
and the OSB sub wall removed,and the stucco
replaced. I know that this was at least 4
times. When a severe storm came through with high
sustained winds and hail the size of baseballs,
all my neighbors had to have their roofs replaced
and even sections of siding, but our
architectural standing metal roof and house went
unscathed. We had no maintenance to do on our
house other than now and then pressure washing
the walls. Even when a tree fell in our back yard
hitting our house the only damage that was done
was a corner of our back porch roof had to be
replaced and a small chunk of block was broken
out which I easily repaired using color
integrated lightweight stucco I had left over
from building the house. Other than that, there
was no damage to our structure. The tree that
fell was no small tree. I may not have mentioned
itearlier but what makes AAC so strong and
resilient is that when built according to
engineering standards for this type of material
it is a monolithic structureunlike other concrete
block structures. The weak part of other masonry
block structures is that the weakest part of the
wall is the sand and cement based mortar joints
which decay over time and when impacted like in
being hit by a tree the wall gives way mostly at
the joints. Also, as in poured concrete, which is
very strong, it is also very rigid and when there
is a significant impact that impact is
transferred through the entire system and cracks
occur, which are in some cases impossible to
repair. What makes AAC different? The difference
is that AAC blocks are dimensionally accurate, so
they do not need to be put together with thick
bed mortar. Instead, they are put together with
thinset mortar made from recycled byproduct of
the production of the blocks. When this mortar is
applied it literally sucks the blocks together
and this bond cannot be broken no matter what you
do. These joints are 1/16-1/8 thick.Also because
of the nature of the blocks they tend to absorb
the impact rather than transferring this impact
through the whole system. I know firsthand that
this is true. Several years ago, I was called
upon to inspect an AAC house that went through a
tornado. A 6 diameter tree branch impelled one
of the walls and knocked out about a 16 chunk
out of the wall. This kind of impact would have
brought down a stick framed wall. I carefully
checked throughout the entire wall and all the
exterior walls, especially the corners and there
was no damage.
  • To repair this wall all I had to do isdrill
    four-1 diameter holes with a spade bit just
    below the top bond beam and down below where this
    chunk of concrete was knocked out.
  • Then with a 12 long reciprocating saw blade in a
    reciprocating saw, I cut a nice true square out
    of the wall.
  • After this it was a matter of installing new AAC
    blocks and finishing it out by replacing the
    color integrated lightweight stucco of the
    original to match the existing wall. The
    lightweight stucco is also made from recycled AAC
    shavings from cutting blocks in production. This
    is a perfect monolithic bond to the block because
    it is the same as the block.
  • After living in this house for a year I had
    observed that there was never more than a 6-
    degreetransfer in temperature over a
    12-hourperiod of time even on the hottest days of
    summer or the coldest days of winter.
  • So, I programmed our thermostat to only come on
    after 1100 at night. Our electric provider drops
    its rates during this period. Our living
    environment was never uncomfortable.
  • When our electricity went out, we would set a
    fire in our controlled draft, catalytic low
    emission woodstove insert. This heated the whole
    houseand after a while I needed to open a window
    upstairs to draft out some of the heat.
  • The other thing we noticed while living in this
    house was how quiet it is. We could not hear when
    the air handler turned on. We also could not hear
    when delivery trucks or service trucks came and
    sometimes, we could not hear our four watch dogs
    who always announced the arrival of any visitors.
  • If you were planning on visiting us, you needed
    to call ahead of time. AAC makes for a quiet
    house because it has such great sound isolating
    properties. I know of a sound recording studio on
    a college campus that is built not much more than
    30 from an active train track that is built with
    12 thick AAC block and 12 thick floor panels.
    The noise of the train never interrupts their
    sound recording.
  • The other thing we noticed living in the house
    over 20 years was we never saw insects of any
    kind inside our house.
  • So to summarize why I chose to specialize in
    designing and building withAutoclaved Aerated
    Concrete Houses
  • It truly is a sustainable building material and
    because of its high thermal mass making it highly
    energy efficient and because of this it makes
    sense to pay the higher initial cost ofdesigning
    and implementing alternativesustainable renewable
    energy systems.
  • It has proven itself as a very durable and
    reliable material in widely diverse climates all
    over the world now for 100 years.
  • It is a very low maintenance house.

  • It will not rot or otherwise deteriorate.
  • It is fireproof. Its official 4 hour fire rating
    is for sustained temperatures of 2000 degrees.
  • It is completely insect proof.
  • It is highly resistant to severe conditions such
    as high winds, floods and even earthquakes.
  • It is moisture resistant and cannot grow molds or
    other organisms like organic building materials.
  • It is a breathable material and puts off no VOC
    and that makes for a healthy house.
  • It is a user-friendly material that can be cut,
    drilled,and shaped with regular
  • woodworking tools and can even take course
    threaded screws or cut nails.
  • Because of its high sound isolation properties,
    it makes for a quiet house shutting out noise
  • There is no organic or inert waste at the end of
  • I have read and heard of the so-called cons of
    building with AAC as compared to building a wood
    stick framed house,which is like the futile
    exercise of trying to compare apples to oranges
    or ants to elephants.
  • They are not the same. The question I get most
    often is it more expensive than 2x4 wood framed
    construction? Remember you are talking about a
    wall at best is R-13 compared to a standard 8
    AAC wall which is R-30.
  • The answer is that it is more expensive. After
    having designed and worked hands on with this
    material for over 20 years I can tell you that
    the cost difference averages about 15 more than
    a standard 2x4 framed wall system.However, having
    recently looked at the inflated price for wood
    framing materials and the latest price list of
    AAC materials this difference is probably closer
    to 8.
  • If you are really serious about sustainability
    and your own personal impact on our environment
    then, you should really give designing and
    building with AAC serious consideration.

We also are happy to work with you in designing a
custom plan for your lot and providing
consultation to you and your builder. In case
you are wondering if Autoclaved Aerated Concrete
is available in the United States here is a
list Hebels primary manufacturing Plant in
North America is in Nuevo Leon, Mexico and its
primary distribution center in the United States
is in San Antoinio, Texas with other distribution
centersin Chicago, New Mexico, Texas, Wyoming,
and Oregon. Megacrete a completely owned and
operated Americancompany has centers in
Monterrey, Mexico, Bennettsville, SC, Haines
City, Fla, and Kerrville, Texas. I am the most
acquainted withAercon in Haines City, Florida.
My first AAC House and our home for 20 years.
Completed in 1996 in Canton, Georgia
This is our AAC house under construction. The
gable ends are being constructed. This is the
front face of the house.
This is an AAC house we are putting in roof end
corbels for the installation of AAC Roof Panels.
We cut our own U-blocks for window and door
lintels and top of the wall bond beams. These
U-blocks serve as permanent forms. After being
installed rebar reinforcement will be placed
inside ready to be filled with 4000 psi grout
that we will make and pour on site.
This shows the use of U-blocks for a wide opening
in the wall and the rebar placed for
reinforcement. This is the center of the house
where the stairwell is to be placed and these
walls will extend to the top of the clerestory
which is the highest point in the house. The
green pipes you see are 6 diameter pipes that
will extend to the top of the clerestory. These
are part of 160 of pipe loop buried an average
of 8 underground which provide a continuous flow
of air averaging 62-66 degrees all year round and
this ground cooled air is drawn through the house
by way of the clerestory through natural
convection air flow as well as fresh air intake
on the central air handler.
This shows the stacks of floor panels which are
being lifted by a crane to be placed at the top
of the first-floor walls.
Here we are setting the factory engineered with
integral reinforcement floor panels in place.
These are 8" thick floor panels.
This mountain house has four floors. The two
bottom floors at the front is mostly underground.
These two lower floors are 12' tall and were made
with permanent Insulated Concrete Forms (ICF)
which are American Polysteel Forms. The top two
stories above grade are built with AAC. All the
floors have factory reinforced AAC floor panels.
AAC is a very user-friendly material which can be
cut, shaped, and drilled with basic woodworking
tools. This picture shows fluted and chamfered
corner quoins and basic window details all of
which were shaped by a router on site and
installed. These elements have been finished
using color integrated lightweight stucco, which
is made from recycled by-products of the
manufacturing process. If you look closely the
walls are plastered with a pale-yellow stucco and
the detail elements are finished white with a
fine sand finish.
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