|
What
is "Sustainable Building"?
We're glad you asked! Buildings and the building process impacts
people and the environment in many ways -- from the materials that we
choose to the way in which we use them. Advocates of "sustainable building" or
"green building" consider the environmental impact and human
health implications of all building materials throughout their entire
"life cycle" -- during collection, manufacture, transportation,
use, and disposal -- and favour choices that use the least amount of
energy and resources, and offer the healthiest environment for building
occupants.
Can any
building be truly "sustainable"?
Although the ideal is to build a completely sustainable
building, this is not very realistic in today's world. Plumbing,
electricity and other modern conveniences and "necessities"
typically require the use of materials that have have been extracted, processed,
and shipped from far away. The tools and materials used in the
building process, even ones as simple as a hammer and nail, required
materials and energy to be produced. Sustainable builders strive
to be as conscious as possible about the materials and methods that they
use and work towards achieving the best version of sustainability within
the framework available.
Won't
the Big Bad Wolf be able to blow this building down?
Once
constructed, bale walls are very strong and stable. When tested,
bale walls have withstood the equivalent of a significant
wind of over 134 mph.
*ASTM E72 80 transverse load
testing of load-bearing straw bale walls, Building Research Centre of
the University of New South Wales, Australia, 1998
Won’t straw
bale walls be easy to burn?
No.
Loose straw would burn easily, but a tightly compacted straw bale has
too little oxygen to support combustion. Think of burning a piece
of crumpled paper versus a telephone book. When tested,
plastered bale walls have withstood temperatures of up to 1942˚F for two
hours; the temperature rise
on the unheated side averaged less than 10˚F.*
*ASTM E-119 Fire Test, SHB
Agra, New Mexico
, USA, 1993
Won’t a
bale home be likely to rot or mold?
“Straw bale walls do not exhibit any unique propensity for
moisture retention. It is clear that straw bale walls can function,
without incorporating an interior vapor barrier, in northern
climates.”*
*Strawbale Moisture
Monitoring Report, submitted to the Canada Mortgage and Housing
Corporation (CMHC) by Rob Jolly, 2000
What
about rodents and insects?
The
straw bale walls will be covered with about 1.5 inches of hard, earthen
plaster on both the inside and outside, creating a very strong deterrent
to critters. And unlike hay, the straw itself has no nutritional
value -- it is the stalk that remains after the seed heads, such as
wheat or hemp, are removed.
Are
straw bale buildings cheaper to build than conventional stick-frame
buildings?
The cost of straw bale buildings is comparable to conventional
construction, whether you build it yourself or hire a building
contractor. However, a well designed and built straw bale home offers costs savings in operating costs for things such as in heating and
cooling.
What
is the insulation value of a straw bale wall?
The
R-value of straw bale walls is an issue that has been debated in recent
years, with various testing facilities coming up with different
results. Early studies reported R-values in the R50 to R60
(RSI-8.8 to RSI-10.6) range. However, more recent tests
suggest an R-value of 28 (RSI-5) -- still a good return and
significantly better than that of a conventional 2x6 insulated wall of
R14 (RSI-2.5).
*"Energy Use in Straw
Bale Houses", Canada Mortgage and Housing, Research Highlights
Technical Series 02-115.
Is a bale home
less expensive to heat?
“Straw
bale construction, along with appropriate building conservation
technologies and simple passive solar design, could provide up to a 60%
reduction in building heating loads over current practice.”*
*US Department of Energy
(DOE) straw bale assessment program, 1995
Are
straw bale walls strong enough to hold up a roof? What about a second
story?
Yes,
you can build one or two storey load-bearing straw bale buildings. There
has been a lot of testing on the compressive, lateral and sheer strength
of bale walls. Recent compression testing of an earth plastered
straw bale wall at Queen's University in Kingston, Ontario, revealed
that the wall surpassed conventional
stick-frame walls in this regard.
Can
straw bale techniques really make a difference to the environment?
“The embodied energy for the conventional frame house was 509,000
KBtus. The embodied energy for the low impact straw bale house is 41,000
KBtus, or about one twelfth that of the frame house.”*
*Investigation of
Environmental Impacts, Straw Bale Construction, by Ann V. Edminster,
University
of
California
,
Berkeley
, 1995.
What
do you mean by "embodied energy"?
Embodied energy is the non-renewable
energy consumed in the acquisition of raw materials, their processing,
manufacture, transportation to site and the construction process.
It also includes the energy consumed to maintain, repair, restore,
refurbish or replace materials, components or systems during the
lifetime of a building.
Still
have more unanswered questions?? Check out this great FAQ page at
Camel's Back Construction's website at http://www.strawhomes.ca/faq.asp.
I'm sure they won't mind!
|
