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Choosing The Best Bales
for the Job
Now
that you have an understanding of your land and a home design
that fits that understanding, you need to know where your bales
will come from. In fact, it is best to secure your bale
source while you are designing so you know exactly what size
the bales will be. This is important during the engineering
and/or framing design. There are many farmers out there
with available bales; however, don’t buy from just anyone. Instead,
know what to look for and buy the best bales you can find in
your area. The price difference should not vary that
much, so a little extra effort is worth it.
VISUAL INSPECTION
 Pay
attention to the color of the bales. This simple detail
is a tell tale for the history of the bales. Have they
seen weather? Have they been stored properly with enough
ventilation? The appearance of surface mold is a good
indicator that the bales have been wet in the past or improperly
stored. If there is a lot of white dust released from
the bales when you hit them, they may have considerable interior
mold; in other words, mold you cannot see on the surface of
the bale. To be sure that the dust released from the
bales is mold and not dirt, use your nose. If it is mold,
the smell is unmistakably musty. If you discover upon visual
inspection that the bales are water damaged, moldy, or otherwise
not in good condition, don’t investigate any further
as using these bales in construction will jeopardize the integrity
of the house.
BALE DENSITY
The density of the bales is another important factor to be
aware of. In fact, most building codes that recognize
straw bale construction call out a specific density requirement. For
example, here in Oregon, the code says “Bales…shall
have a minimum calculated dry density of 7.0 pounds per cubic
foot (1.10 kN/m3).” If you do not know the density
of the bales, you will not be able to guarantee the building
inspector of the quality of the bales. A simple field test
of a bale’s density can take the stress off the inspector
and therefore off of you!
MOISTURE CONTENT
Perhaps the most important factor when choosing bales is their
moisture content. If a bale reaches a moisture content
of over 20%, it has reached the level in which mold growth
and decay can take place and can be sustained. Once that
level is reached, it is difficult to reverse as the decay process
produces the two things the bales need to rot: moisture and
warmth. When measuring the moisture content of the bales,
keep in mind that they will take on or lose moisture in response
to ambient moisture in the atmosphere. It is important
to get accurate readings of the bales, not the atmosphere. In
other words, do not measure the bales in the early morning
when dew may affect the reading. Check the bales during
the most neutral time of the day so that the reading is accurate
and truly representative of the condition of the bales.
 In
all, there is much you can do to identify quality bales. Use
your eyes, your nose, and your common sense along with whatever
science your local codes require to make your decision. Use
local bales if you can find them. The further away from
the building site they are, the more impact on the environment
they will have. They will also be more expensive if they
are transported a long distance. After all, transportation
is not as cheap and clean as it used to be! The bales should
be of the best quality you can find; however, you could search
for the perfect bale for the rest of your life. Therefore,
once you find bales that meet your criterion and are within
your price range, buy them and move on to the next step of
the design/construction process.
Tomorrow we'll take a look at Framing Considerations
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