The concept of an environmentally damage free material presupposes that:-
- no extractive processes are required to secure the base materials
- the material is renewable
- the material is applied to building construction with low energy
- the completed building system has good comfort and aesthetic
- at the end of the building's life the material can be returned to
the environment without residual damage, or can be recycled
to be used again in another new building development.
In the real world
Working in the real world within existing available building systems, materials
choices may be made where very few of the above attributes are secured directly,
or other pragmatic priorities possibly with environmental consequences might
be added to the list.
Whether these are realistic priorities, or rationalisations, each reviewer will
have to decide for themselves.
This practice uses a substantial amount of steel in some projects, including this
architect's own home.
Normally such a material derived from extractive mining, with high energy inputs
to form the material and further form useable products from the material and its
fabrication requirements would be judged environment unfriendly.
However the driving priorities favouring steel in a pro-environment context
Such materials are readily available, well understood by industry and regulatory
authorities; and approvals are achievable; although advocacy is needed for
these less usual applications of materials made by this practice (notably the use
of light industrial steel sections for residential structures).
- that the building could be substantially pre-fabricated and erected
on-site initially with only hand tools,
- erected on-site from within the final building 'footprint' with
minimal damage to the surrounding site
- erected with minimal support machinery until the renewable energy
system is operating on the building which then powers the support
machinery rather a generator.
Assumed to be 'environmental'
The practice also uses materials usually asociated with favourable environmental
performance: recycled timbers, stone salvaged from on-site, stabilised rammed
earth using site excavated material to bench the building, mud brick and aerated
Some regulatory authorities have little experience with some of these, and
it is not unusual for advocacy to be needed on individual concerns raised by
These concerns include: the structural capacity of recycled or
handmade materials, waterproofing of surfaces and materials, guarantees
as to definition of colour of surfaces of material embodying natural materials
in the completed building.
None of these concerns has a real basis in real world experience; it is
usually only the unfamiliarity with the material and its applications by the
Fully renewable material
An example of an emergent ecological material is straw bale construction.
There are few local examples of this construction; expertise, prior examples,
draft building codes and so on are all sourced from overseas.
As a result local building industry and authorities are perplexed by proposals
embodying these materials. Approvals are obtainable by energetic
advocacy including the ESD merits and the local application of precedent,
technology and experience from elsewhere.
Why devote effort to such building construction?
This building system embodies most of the desirable ecological material
- the material is sourced from waste in the normal agricultural
process, being the remnant stalk usually burnt or turned into
- new material is generated in the farm cycle each year
- the material is biological, with no extraction processes
- the material achieves R6 insulation characteristics
- at the end of the building life, the material is returned
to the environment by mulching
Technology, existing buildings, and draft building codes information
is centred in the US.
The most commonly asked questions about straw bale construction
material relate to :-
- 'three little pigs'
- 1. - is a children's fable; and none of the purported characteristics
- of any of the building materials claimed are found in the real world.
- 2. - The complete building system includes the straw in a pressed
- and bound bale with fire retardent applied as for cellulose insulation,
- (boric acid) and an external fire resistant render skin.
- The building system as a whole does not support combustion.
- 3. - Vermin find the hollow cellulose structure of the straw bale
- unpalatable due to the low cellulose density and regular air pockets
- in the matrix of the material. Vermin is also excluded by damp proof
- course and render envelope which are part of the building system.
- 4. - The rendered envelope and damp proof membranes built in as for
- other masonry systems means that the system is not subject to water
- ingress or logging.
Similar to other masonry systems, the material can be erected as infill
to a framed building, or as load bearing masonry.
In either system the system is internally reinforced with pins between
bale layers, and externally reinforced with mesh in the render envelope.
There is substantial local experience with 'Dri-bond' walls where loose
stacked hollow concrete blocks form the core and a glass reinforced
render envelope provides structural rigidity.
In load bearing construction for straw bale, the external reinforcing
and render fulfills the same role; additionally full height tie rods
and a wall plate bond beam is integral to the straw bale system of
construction as for autoclave concrete walls.
Thus all of the characteristics of straw bale construction are as found
in other conventional masonry systems.
There is some settlement in wall height during construction of load
bearing straw walls, and the tiedown and bond beam design allows for this.
There is nothing alien or technically difficult in the building system.
Successful application depends on design understanding the system
features, and construction practice allowing for these issues.
Traditional construction systems, notably kiln fired masonry situated on
reactive soil sites, have a long history of problems in use;
including substantial cracking prejudicing structural integrity, but
this hasn't stopped their use.