The idea of using unfired earth bricks
for building homes in the UK is not
just pie in the sky. It is a method that
anyone could consider now!
Tom Morton explains...
The main benefits of earth
However, the technical devel-
construction (a healthy indoor
opment illustrated in foreign
environment and low environmen-
projects and an increasing
tal impact) have been increasingly
market for sustainable construc-
well documented over the last
tion have created conditions in
fifteen years, particularly in
the UK where earth construction
Germany where manufactur-
could break out of it s nurturing
ing of proprietary products,
niche into mainstream construc-
contractor training programmes
tion over the next 5-10 years.
and governmental approval of
In 2003, with funding from
industry standards have fostered
the DTIs Partners In Innovation
an increasing catalogue of high
project and Communities
quality examples of modern earth
Scotland, Arc Architects began a
construction.
detailed, 2-year study to assess
In the UK, for a variety of
the potential for the benefits of
historical, cultural and economic
earth to be realised in low cost
reasons, the development of
UK construction projects.
modern earth construction is
about ten years behind Germany.
The design, construction and
habitation of a new house in
Unfired earth brick building
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BFF Autumn 2005
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Perthshire was studied in detail
etary earth materials and those
aided by the local enterprise
over a period when mainstream
company.
construction has stagnated.
by a team including Dundee
imported from Germany are
and Robert Gordon Universities,
expensive. The manufacture of
Natural Building Technologies Ltd.
the Errol unfired bricks required
tion that require unfamiliar
and the Errol Brick Company Ltd.,
no new equipment, labour skills,
specialist processes, such as
Earth in a layered
construction
with a wide advisory group repre-
or methods of marketing and
rammed earth, and those that
The same practical consid-
senting the various parts of the
distribution for the manufactur-
used hand-made or untested
erations fed into the design and
thoroughly tested as part of a
ers. The brick company could
earth materials, such as in
construction of the building. The
BBA certification process and
therefore diversify into produc-
vernacular cob construction,
earth materials were intended to
were considerably cheaper than
ing more sustainable products
are limited to a niche market.
be suitable for use by standard
comparable products imported
for a relatively modest invest-
However, the mainstreaming
tradespeople without specialist
from the continent. The brick-
ment. While the brick industry is
of new sustainable materials
training, equipment or super-
works also supplied powdered
vulnerable to increasing energy
requires them to be simple to use
vision, ie in normal low-cost
clay and a lignosulphate (tree
costs and taxation, manufacture
and similar to ubiquitous conven-
construction circumstances. The
resin waste by-product of paper
of the unfired bricks needs only
tional materials, as the successful
house was therefore built without
pulping) additive for the mortar.
14% of the energy of their fired
marketing of sheep s wool insula-
the specialist input that is normal
equivalents.
tion has shown. An increasing
for earth projects.
Other forms of earth construc-
UK construction industry, as well
as earth experts from Germany,
the USA and Canada.
Low-cost earth house?
The house was designed to be
as eco-friendly as possible over
a broad range of criteria and
within the financial and physical
constraints of a low cost housing
grant scheme. The aim was not to
create the best earth house that
could be built, but to use earth
materials to achieve a range of
specific technical benefits at an
affordable cost within a holistic,
simple and efficient design. The
key to achieving this was to gain
multiple benefits from one easyto-use material.
Earth brick masonry was
specified for the inner leaf
of the external walls and for
internal partitions. The materials used were Errol eco-bricks ,
air-dried extruded bricks made
from a mixture of clay, sand
and sawdust. These massproduced materials had been
Earth bricks are easy
However, the Errol Brick
market for earth masonry should
The building reversed normal
The availability of these materials
Company did invest in new equip-
allow costs to reduce with a rising
timber frame construction. An
at low cost , compared to other
ment for the manufacture of
scale of production. This has
external timber frame, clad in
earth materials, sheds light on
clay mortars and carried out a
been demonstrated in Germany
local untreated larch, achieved
the development of the market
lot of testing in the development
over the last 5 years, where the
a quick and structurally efficient
for earth materials. At present
and certification process for the
earth construction sector has
weatherproof envelope. Inside
there is little demand for propri-
bricks, though this was grant
sustained significant growth
this the earth construction could
BFF Autumn 2005
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25
Plasterers needed to get used to the slower
drying rates of earth render and other working
qualities compared to gypsum
proceed unimpeded by the variable Scottish
climate. By separating the inner finish from
the structural frame, the frame could be sized
for optimal structural efficiency while allowing
cellulose insulation to be as thick as desired for
thermal insulation. Fully filling the cavity, the
installation of insulation to the walls and roof was
carried out in one day.
The location of the earth materials within the
building design was intended to have multiple
benefits:
•
to remove any risk of condensation from the
•
to give the building strategically located
wall construction
thermal mass
•
to regulate internal air relative humidity
•
to provide a degree of acoustic insulation
•
to achieve a perception of solidity to the
internal construction
The earth brickwork proved straightforward to
construct, with the bricklayers keen to use the
materials again. Problems did occur with the clay
plaster finish, relating to the difference of working
qualities between clay and gypsum plasters. In a
project with small rooms, the plasterers found it
frustratingly difficult to effectively programme
the drying time of the plaster. Their tendency
to overwork the topcoat, from years of polishing gypsum with steel floats, resulted in some
separation of the clay binders and fine sand,
causing some cracking and surface dust. These
relatively minor defects are simple to remedy, but
did demonstrate the need for training to achieve
consistent quality.
Timer frame building in reverse
- frame and timber cladding on
outside and heavy masonry as
interior skin.
All photos courtesy of Arc
Architects.
Monitoring proved earth s
performance
of asthma among young people
moisture performance was
and the link between r.h. and
monitored in multiple locations
asthma is well established, most
every 15 minutes for a year. The
clearly laid out in a recent book
detailed picture this provided
by Stirling Howieson, Asthma &
confirmed that the earth
Housing . CIBSE has recognised
masonry achieved its intended
this link in their guidance on good
performance, with the regulation
practice and there are moves to
of internal air relative humidity
incorporate indoor air r.h. targets
the most important attribute
within building standards.
The relationships between
BFF Autumn 2005
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has the world s highest rates
The building s thermal and
highlighted in the study.
26
ingly well understood. Scotland
The ability of unfired clays to
absorb and desorb atmospheric
indoor relative humidity (r.h.)
moisture is the key attribute that
and occupant health is increas-
also makes them effective in a
Unfired earth brick building
wide range of building applica-
the brickworks for re-cycling was
tions, such as the control of
more expensive than their value,
£650m was estimated to be the
arc-architects.co.uk. Arc are
mould spores and the creation
the waste off-cuts from bricks
conventional main contractor
currently writing a book, Earth
of stable environmental condi-
was naturally biodegraded into
procurement equivelant, calcu-
Masonry Design & Construction
tions for museum artefacts and
the site soil. The bricks create
lating out the special factors
Guidelines, which is scheduled to
acoustic musical instruments.
no waste during their manufac-
relating to the procurement of
be published by BRE Publications
ture and even the clay extraction
this house. This is a 2003 figure
early next year.
is ecologically beneficial, with
and £750m2 is probably more
worked out clay pits being
realistic today.
In this house the key target of
regulating internal air r.h. to 40
‒ 60% was generally achieved, but
the strength of clay s perform-
flooded to become biodiverse
ance exceeded expectations.
SSSI s.
Tests in the bathroom showed
A detailed audit found that the
A construction cost of
able from Arc s website www.
2
The future for earth construction in the UK is uncertain.
The house owner/occupiers
Unfired clay s fundamental
are very pleased with the house,
properties as a flexible, healthy,
despite the minor defects and
low-energy binder give it great
that there was no statistical
earth masonry had an embodied
the restrictions that earth materi-
potential in an evolving sustain-
difference in the rates of decay
energy of 123.5 KWh/tonne and
als place in internal decoration.
able construction industry. This
of atmospheric moisture after
22kg CO2/tonne at the factory
The house performs quite differ-
example of earth masonry
showers, whether the extract fan
gate. Accurate comparable
ently from their previous cold and
construction could help establish
was running or not. The ability
figures are difficult to obtain, but
drafty stone cottage and they
a basic mass-market for earth
of the clay surfaces to passively
this amounts to about 14% of the
have adapted their occupancy
materials in the mainstream
absorb excess air moisture was
embodied energy and carbon of
patterns as they get used to its
sector, which could foster more
thereby demonstrated to outper-
common fired bricks. The esti-
thermal response.
exciting research and devel-
form and render unnecessary
mated saving in this building is
the standard electro-mechanical
24.9 MWh and 7036 kg CO2 over
this house to that on other types
composite materials and sprayed
device.
common bricks, and 14.5 MWh
of housing, it is apparent that
applications. The commercial
reality is that while some major
Another strong result was
Comparing the results from
opment into prefabricated
and 4104 kg CO2 over lightweight
there is a value in the thermal
the low level of waste produced.
concrete blocks. This calculation
mass and slow response of the
brick producers are making
After it was established that the
does not take into account the
heating system. Evidence from
noises of interest in producing
cost of returning the waste to
plaster.
tightly designed lightweight
earth bricks, the kind of invest-
construction projects, which
ment that is needed for really
rely on controlled ventilation
progressive development is still a
and heat recovery, show that
long way off.
in reality people s uncontrol-
The increasing growth and
lable occupancy patterns, in
diversity of interest in earth
particular their desire for natural
construction from professional
ventilation and ability to manage
designers, materials suppliers,
heating systems, often under-
academics and the conservation
mine the theoretical efficiency of
community merits the estab-
such designs.
lishment of a UK Earth Building
In contrast, while the occu-
Society to promote the develop-
pants of this house created
ment and conservation of earth
ventilation rates far in excess of
building in Britain. Acting as a
what was necessary, the thermal
forum for debate, such an organi-
and moisture regulation achieved
sation could foster significant
through the mass of the earth
progress by establishing working
masonry did much to regulate
relationships with its European
the impact of this on comfort
counterparts and UK governmen-
and cost.
tal and industry organisations.
Tom Morton - Arc Architects
The future for UK earth
building
The full final report on the
project, together with a four
page summary and an interim
design guidance leaflet are avail-
Arc Architects interest in earth construction has developed through the
conservation of UK vernacular earth
buildings, the study of earth building
techniques abroad, the development of
new proprietary unfired clay products
and the design of new buildings.
Errol Brick Co: www.errolbrick.co.uk
NBT: www.natural-building.co.uk
Arc Architects: www.arc-architects.co.uk
BFF Autumn 2005
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