Before anyone gets their dander up, let me say I respect and appreciate
straw bale advocacy. It gets people to think about how they build, and the
idea of more environmentally responsible materials. And there is certainly
a lot of enthusiasm around building with straw,and having
house-raisings--all to the good.
However, I honestly don't understand what the advantages are, as far as a
building material, especially compared to well engineered systems with a
lot of field experience and manufacturing behind them. It's hard for me to
see how straw bale is ever going to fit into mainstream building.
First, it's only a wall system. People keep talking about how inexpensive
straw bale houses can be, but how is it that only replacing one component,
the wall, can lead to huge savings? What about lost floor area, compared to
conventional walls? How does that pencil out?
Second, can it really work in all climates? What about the moisture
transport characteristics of a straw bale wall in an air-conditioned house
located in a hot, humid climate like Washington, D.C? Is this a rot-proof
wall? Are the details worked out? For example, if the bales sit on a
concrete footing, what about capillary moisture getting into them?
Third, what are the structural characteristics? If straw bale is used as
infill in a post-and-beam wall, are the bales adding anything to the
load-bearing capability of the wood frame? To earthquake resistance? Where
bales form the structure, how would they respond to seismic loading? What
about shrinkage? How do you plaster a wall that's going to get shorter?
Fourth, how would this system be introduced into production home building,
with all that implies in the way of code approvals, materials testing,
manufacturing support, subcontracting businesses, or homeowner maintenance?
Fifth, does it have the flexibility to let the building be modified? How
does one remodel a straw bale wall?
Am I missing the point? Entirely possible. Maybe straw bale should not be
evaluated against standard practice; rather, its purpose IS consciousness
raising--and that's enough?
With respect, Mike
O'Brien & Associates
Environmental Building Consultants
Portland General Electric Earth Smart program
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