Civil Engineering Reference
In-Depth Information
strawbale house stores latent heat, because
it has high thermal mass even though it
is not masonry. This means there are no
sudden changes in temperature if you open
the windows or doors occasionally, as can
happen in houses that have only insulation
but low thermal mass.
the field. The walls of a three-bedroomed,
two-storey house can be built with 350
bales. Also, because the building method is
so straightforward, people without previous
building experience can participate in the
design and construction, thereby saving on
labour costs.
The most significant saving on strawbale
houses is in the long-term fuel reductions
owing to the high level of insulation. Heating
costs can be reduced by up to 75 per cent
annually compared with conventional-style
housing, and the savings therefore continue
to accrue throughout the life of the building.
Acoustically insulating
Strawbale walls are also super-insulative
acoustically. There are two recording studios
in the USA built of straw bales for their
soundproofing quality and insulation, as
well as one in Wales, the Strawdio. Strawbale
wall systems are increasingly being used
near airport runways and motorways as
sound barriers in the USA and Europe.
Amazonails is pioneering the use of load-
bearing strawbale party walls as thermal
and acoustic barriers for semi-detached
houses.
If the surplus straw in the UK was baled
and used for local building, at least 430,000
houses could be built per year. That's almost
half a million super-insulated homes with a
negative carbon footprint.
Low fire risk
Structurally sound
Plastered strawbale walls are less of a fire
risk than traditional timber-framed walls.
(See Appendix 2, Frequently asked ques-
tions.) Research in the USA and Mexico has
shown that “a straw bale infill wall assembly
is a far greater fire resistive assembly than
a wood frame wall assembly using the
same finishes.”*
Bales of straw are more than adequate to
carry typical loadings of floors, roofs and
winter snow. They have passed loadbearing
tests both in the laboratory and in practice,
and are used to build houses of at least
two storeys. Imagine placing a new sheaf
of photocopy paper on the floor and then
standing on it. It squashes down with your
weight. Now ask two or three friends to
stand on it with you - it doesn't squash down
any more than it already has done. This is
what straw does. We know how much a
densely packed construction-grade bale will
compress under load, and once we've made
Affordable
Straw is currently produced surplus to
requirements and a construction-grade bale
costs about £2.50 delivered or 80p from
* 1996 Report to the Construction Industries Division by Manuel A. Fernandez, State Architect and head of Permitting and Plan
Approval, CID, State of New Mexico, USA
.
