Source: HempLifestyleMagazine.com
There are two types of hemp builders. On one side there are your
hemp advocates; those who already know hemp is a fantastic resource
for so many different aspects of our daily lives and would never
consider building with anything else. On the other side, there are
those who set out to build an environmentally responsible home and
quickly realise that hemp is one of the best alternative building
materials available.
Kirstie and Ben, who are currently building their house on the
Southern New South Wales coast of Australia, definitely fall into
the latter category. "I live in a mud brick house which is
beautiful to live in but building with mud brick is really hard and
heavy work", says Kirstie. Knowing that she wanted to build an
environmentally sustainable home led Kirstie into researching
natural building techniques such as rammed earth, light earth and
straw bale. It was an article in Owner Builder magazine that
alerted Kirstie about the benefits of hemp.
Kirstie recalls, "I looked into the light earth technique and saw
cases where the material had taken too long to dry out and the
straw started going mouldy. When I first read about hemp building I
dismissed it as something a bit new and untried, but eventually I
was attracted to it because the lime [used in the binder] is
naturally anti-mould. Plus as the lime dries out it continues to
cure regardless of the weather".
During her research Kirstie found that most natural building
materials either provide thermal mass, such as mud brick and rammed
earth or provide excellent insulation such as straw bale. In
contrast, hemp provides great insulation and thermal mass, which
for Kirstie who is building a passive solar house, was an important
factor in her decision. After taking part in a hemp building course
with Klara Marosszeky, Kirstie took the plunge and submitted her
plans to her local Council for approval.
Getting Council approval was not a straightforward process to start
off with. Any new build using traditional methods such as brick
veneer and weatherboard must comply with the Building Code of
Australia. As Kirstie was working with a non-standard building
method she needed to prove that it would meet certain requirements
including standards for weather proofing, fire safety and wind
resistance. Once she realised that she needed to find a suitably
qualified engineer who would be able to prove to Council that hemp
building did meet the requirements of the Building Code, and with
Klara's help, she obtained the necessary engineers report and
finally received approval.
Building a house that heats and cools itself
Kirstie's passive solar design uses the sun and the day/night
temperature to heat and cool the house, without the need for active
sources such as air conditioners and heaters. "I think that every
person who is building a house has an obligation to build the best
way they can. Rather than having a poorly oriented, poorly designed
house that you then have to pump a lot of electricity into to keep
it at a comfortable level, a better solution is to build a house
where the design of the house does these things itself".
The house is designed to capture as much winter sun as possible
which falls onto the concrete slab and acts as a thermal mass to
absorb, hold and re-radiate the heat during the cooler evenings. In
summer, the reverse happens; at night all the windows are opened to
let in the cool air, which is absorbed by the concrete slab and
keeps the house cool during the day.
The building process has presented some challenges. For example,
Kirstie chose to build using a prefabricated timber frame. "I had
specified stud [the upright pieces of wood in the frame] spacings
of 600mm but because of the location of windows and the extra
height of some of my walls it meant that we had to put in extra
studs. So in some spots we are packing hemp between quite closely
spaced timbers, which is more time consuming".
Another issue Kirstie found tricky is packing the hemp underneath
and around the noggings [the horizontal bracing piece used between
studs to give rigidity to the wall frames of a building]. While
they have figured out a way around this, Kirstie acknowledges that
next time she would work more closely with the framing company
about their designs, as using stronger or larger timbers would
reduce the need for so many of the studs.
Hemp building - it's girls work!
Having previously built a mud brick shed, Kirstie noted that hemp
building is something that can be easily done by women. "In
contrast to building with mud brick, where after a day of making
the bricks your shoulders and arms know about it, hemp is so light
for its volume. Even when you mix the hemp with the binder and sand
and when you're lifting the hemp and pouring it in, it's really not
heavy work".
Another aspect of hemp building that Kirstie found appealing is
that it is not a highly skilled task, which means that friends have
become willing helpers after being shown a couple of times how to
mix the hemp and binder and how to tamp the mix between the
formwork. Kirstie recalls the sense of camaraderie from having
friends involved in the building process. "On a few of the more
difficult sections, we had one person working from the inside and
one person working from the outside. It was just lovely working
together on it".
To minimise the environmental impact of the building process,
Kirstie tried to source the hemp and binder as close as possible to
the site. The hemp was supplied by EcoFibre Industries in the
Hunter Valley, about 5 hours away from Kirstie's location. While a
large proportion of the cost was due to transport fees, after
purchasing a semitrailer of hemp there should be enough material
available left over for Kirstie to build her house and either a
garage or shed as well. The binder, which is made and tested in
Australia, was purchased from the Australian Hemp Masonry Company.
At just 123 square metres the house is small by today's standards.
However, building a small house is probably one of the best ways to
reduce your carbon footprint as you need less materials and
generate less waste. What about the costs of hemp building compared
to traditional techniques such as brick veneer? Kirstie says "just
based on the cost of materials the price would be similar. The
problem then is that you have to pay a skilled brick layer, unless
you can lay bricks yourself, and then someone to gyprock the inside
of your house. So the real cost saving for us is that we are doing
the build ourselves".
As an owner builder who is also working part-time, Kirstie hopes
that the house will be completed within 12-18 months. Kirstie
advises that anyone interested in learning more about building with
hemp should do a workshop or work on someone else's build to gain
the confidence to build their own house. Kirstie's final piece of
advice to anyone interested in hemp building is "if you are looking
for an environmental building material, that doesn't have high
energy inputs and has a lower carbon footprint, hemp building
definitely ticks all of those boxes".
For more details in relation to Kirstie's build visit her blog at
Resources
The Owner Builder Magazine - www.theownerbuilder.com.au
Ecofibre Industries - www.ecofibre.com.au
Australian Hemp Masonry Company - www.hempmasonry.com
