This works in 3 ways:
As the travel distance for the transport of the key materials is
much reduced, less pollution and energy consumption results from
sourcing the main building material from the fields.
The use of straw is seen as a method of carbon storage, as the
carbon absorbed in the growing process is then trapped inside the
walls for hundreds of years. So it’s as good as planting trees.
The internal environmental health and air quality inside the
building will be enhanced by the breathability of the materials
and the lack of chemicals which can cause health problems when we
are forced into contact with them over long sustained periods.
A typical cross-section of a wall with lime render exterior on a
clay skin on a bale thick wall with another skin of clay and
lime-wash equates to a u-value of around 0.13W/m2·K. The latest
Irish Building Regulations 2011 are to achieve a u-value of 0.21W/m2·K
which would require the use of insulation and other potentially
expensive materials to achieve the same. Unless the materials
science moves on in leaps and bounds it will be hard to achieve
u-values of 0.13 without recourse to expensive measures.
Also thanks to the “breathable” nature of the wall make-up it is
easier to regulate internal temperature of the buildings during
hot and cold periods, making a low grade heating system or
PassivHaus design more feasible. I spent a week last October with
Bee Rowan of Strawbuild on her course at
The Centre for
Alternative Technology and I came away feeling
good and empowered to build my own straw bale buildings. As it’s a
low tech building technique, a motivated individual could start
building having completed a short course.
I’m watching the green shoots of barley straw pushing up through
the dry Meath clay loam on our farm and thinking “That’s my house
growing in those stalks”. When you look at it like that, how could
you not build with straw? The clay for the plaster is another
local material and we could even quarry and slake the lime, as
would have been done a hundred years ago in our beautiful lime
kiln in the farmyard. But I think we’ll leave that for another
Good fire and sound protection
Straw bale walls have a very good fire rating: 1 hour for clay
plastered walls, 2 hours for lime rendered walls. Whereas a
typical timber frame dry-walled structure would have a 30 minute
rating. Straw bale walls provide excellent sound insulation and have a
positive effect on interior acoustics.