Pumice
House
Bob Alexander, who owns and operates LX&R Design based in Chamita, New
Mexico is much happier these days.
After designing sustainable solar efficient homes for more than a
decade he says he has found the perfect material for the
owner-builder do-it-yourselfer.
"Pumice-crete casting is the best thing that
ever happened to sustainable housing." he says. "This
material is fire proof, rodent and insect proof, rot proof,
non-toxic and relatively cheap and easy to use. It doesn't cost
an arm and a leg to build a really nice home with it."
As for proof, Bob's friend, Ron Vanderzanden, recently built a pumice-crete casted home for his sister at a
cost of around $50.00 a square foot. This includes the cost of
the well, septic system and electric. And it was done using a
low-tech method and untrained labor.
"For years I have been interested in the wall casting idea
and I did a lot of research on it. Casting has several advantages
over many other forms of construction, but, many of the casting
materials I looked into had problems such as excessive shrinkage
which led to cracking and low R-value which results in higher
heat loss."
"Another big draw back is that these materials aren't well
known to the Construction Industries Division who issue building
permits here in New Mexico and they are reluctant to put their
stamp of approval on something they don't know much about."
"Pumice-crete, on the other hand, has been in use here since
at least the 1940's and, although it is still considered an
'alternative building material', getting a building permit for it
is pretty straight forward."
"It's not rocket science to build a really nice home with
it. Another big plus for me as a solar designer is
the fact that it has high mass, meaning that it will store solar
heat. And it doesn't use a lot of wood which is getting more
expensive."
"With the rising cost of heating fuel, it only makes sense
to use solar energy if you can, but, you don't build a good solar
house by simply adding a lot of glass. That creates a greenhouse
effect and the house will soon overheat. You need a fair amount
of mass to soak up that heat. At night that mass will release
its' heat back into the home keeping your heating bill down. The
reverse is true in summer. If you cool the house down at night it
will stay reasonably comfortable through most of the next
day."
"It still takes a good solar design to achieve high solar
efficiency, but the pumice-crete casting technique is something
almost anyone can do and it doesn't cost much to get going with
it."
"We used a paddle batcher which does a better job
than an cement mixer, but, you could mix it by hand in a
wheelbarrow. The forms were made out of ¾" plywood and a metal yoke
system,
which Ron designed, was used to hold them in place. The forms
were reused as the walls grew taller. This is referred to as
'slip forming'. Even the interior walls were casted, but,
full-height plywood forms were used there which required stronger
bracing."
"An old electric forklift was fitted with a platform which
would accommodate two wheel barrows making it easier to get the
mix into the forms at the higher levels. It can be done using 5
gallon buckets. In fact, that is how Ron and his wife built their
own house ten years ago, but, it
takes a bit more work."
"You can stop whenever you want to and start back on it when
you can. Doing a little work each day makes it easier on you and
your budget. You can even use the stuff as roof insulation, but,
it is heavy in the wet state, so strong roof bracing is
recommended."
"It is also possible to make building blocks out of the
stuff and stack them like adobes. If the building site is remote,
you could make them in your back yard on weekday evenings and put
them up on weekends once they are dry enough to handle."
"Pumice is a lightweight rock
available locally for around $14.00 a cubic yard. The only other
ingredients are water and Portland cement which is only 1/15th of
the mix by volume. Making a good casting mix requires a little
practice. You don't want to over mix the stuff since this will
cut down your R-value."
"Rons' sisters' house has 16" exterior
walls which were required to meet current energy codes. No
additional wall insulation is required. This home features arched
windows and doors and flared window and door openings resulting
in a nice smooth appearance."
"Our goal isn't to build homes for people. It's to show
people how they can build their own high-quality homes using
inexpensive materials and relatively low-tech methods. We have
started to write a booklet on this method and we may eventually
produce a video tape on it."
"Traditionally, people have had to take out a long-term
mortgage to get a high quality home. This cycle has gotten us to
where we are now. I would like to see this change, so people can
live within their means. It does take some 'sweat equity', but I
know it is possible."
For more information on pumice-crete casting and sustainable
solar home design, visit the LX&R Design website at www.lxrdesign.com or you can reach
LX&R by E-mail at lxr_design@yahoo.com.
Reprint from "The Sun News"
Vol.5 No.6
(June 2004)
See also: "A
Revolution in Architecture" & LX&R
Design Casting Page
