"Architects rely on sustainable and climate-neutral material:
Straw is cheap, insulates well and grows back quickly - it could become the
building material of the future.
For Christoph Harney, straw is one of the building materials
of the future. "It is a by-product of grain cultivation, grows very
quickly compared to other sustainable building materials and is available in
large quantities," explains the architect. 20 million tons of straw are
harvested in Germany every year. “Around 20 percent of this, and therefore four
million tons, is not needed and is simply left over.” Harney is currently
installing part of it in an apartment building in Kassel.
The walls of the building's penthouse are insulated with
straw bales. 250 pieces have been pressed into the compartment.
The outer walls
are plastered with lime, the inner walls with clay.
Wall heating is also
integrated. Harney can allay worries about moisture or pest infestation.
"If it's installed properly, the straw won't rot and won't be infested by
rodents and vermin," he explains. It also has very good fire protection
properties.
Straw as a climate-friendly building material
The finished assembly systems made of wood and straw were
supplied by a company from Taucha in Saxony. A company from Göttingen tested
and certified the construction straw for moisture and compression, among other
things. "The straw is untreated, we even have organic quality here,"
says Harney.
Straw bale construction is particularly good for the
climate: "The straw stores carbon dioxide during growth and for the life
of the house," explains Harney. The production of the bales resulted in
minimal carbon dioxide emissions compared to other thermal insulation
materials. In addition, straw bale houses have a very good insulation value.
"The bales are a good heat store and help to save on heating costs,"
explains Harney.
"The construction sector is conservative"
"If we really want to be climate-neutral in a few
years, we have to rely on renewable building materials," says Holger
Zimmer from the Hessen Chamber of Architects and Urban Planners. Straw bales
are an important component. Manufacturing a straw bale house saves so much
energy that it can heat a house for 70 years.
In addition, Keller sees savings
potential for the builders, because with straw bale construction, with a little
knowledge and guidance, you can do some things yourself and save money.
His
conclusion: "The construction method is wrongly completely
underestimated."
The architect attributes this primarily to a lack of
awareness of ecological building materials. "We have been introduced to
synthetic industrial building materials far too much over the years." You
could just as easily build a house with straw, "but the construction
sector is conservative". A rethink is urgently needed. "In order to
conserve resources and make ourselves independent of imported materials, we
have to rely on renewable raw materials," explains Zimmer.
"Straw is an important part of the construction
revolution," agrees Adina Lange from the German straw bale construction
association. It is estimated that there are currently more than 1,000 straw
houses in Germany. About 50 are added every year. "Straw bale construction
is picking up speed," says the construction engineer and carpenter. She
would like more knowledge to be conveyed about this type of construction.
Straw bale construction as a possibility for affordable
housing
"More education is needed about the irrevocable
advantages of straw bale construction and more further training," agrees
Holger Zimmer. The architect is confident that straw will continue to gain
popularity as a building material. “On the one hand, sustainable building will
be more strongly promoted by law in the future. On the other hand, everyone
will be thinking about how they can save energy costs at the latest when the
next bill is issued.”
The architects Susanne Körner and Tilman Schäberle from Bad
König in the Odenwald district are pioneers of straw bale construction in
Hesse. In 2005, they erected the first office building in Darmstadt made of
straw bales. In 2008 the first residential building followed in Bad König,
which they live in themselves.
Around 750 pressed straw bales from the region
were used for the complete thermal insulation of the 260 square meter house.
More than ten years later, Körner is still enthusiastic.
“Straw bales are the most sustainable insulating material. They are
climate-neutral, available locally, offer good thermal insulation in summer and
good insulation values for the outer wall in winter,” she explains. In
addition, unlike conventional insulating materials such as Styrofoam, straw can
be disposed of in the compost after dismantling without any problems.
Unfortunately, sustainable construction techniques have been neglected for a
long time, says Körner. Luckily, interest is now growing.
The straw bales were also convincing in Kassel. In the first
of three construction phases, he added the bales only tested in the attic,
reports Christoph Harney. "We have had good experiences with this and are
therefore planning to build the other two construction phases entirely with
straw bales."
In straw bale construction he sees an opportunity to create
more affordable and climate-friendly apartments.
On average, ten tons of straw
are needed to insulate a residential unit.
"With four million tons of
straw left over as a by-product, that makes 400,000 residential units," he
calculates. "Enough for the 400,000 apartments that the federal government
wants to build every year."
Straw bale walls were first erected by North American
settlers in timber-poor Nebraska in the 1900s. At the time there was a strong
need for housing, but scarcely available building materials. Straw, on the
other hand, was available regionally. In Nebraska, the bales were initially
used like bricks to build walls.
Post-and-beam construction with wooden posts
later developed in the USA."
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