>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.
Hey Mike,
No dandruff here! These are all very valid questions. I'll try a stab at
answering them, but more extensive answers can be found on the Strawbale list
- search the archives at CREST, or ask the question of the participants there
directly.
>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?
This is very true. A lot of people get all excited about how much money
they're going to save by having a workshop or two and getting their friends to
build their house for them. Of course, they're not taking into account the
fact that the wall system is somewhere in the range of 10-15% of the total
cost of any house, and that the finish-out counts for a large share. Sure,
there are storys about people who have built themselves a strawbale house for
$30/sf and less, but what kind of finish are we talking about here? And does
that count the sweat equity? (often not). If anything is going to kill off
the strawbale wave that's sweeping through right now, overselling the
short-term economics might be it.
>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?
To be determined. Expect to start hearing some horror stories in 5-10 years,
from people who took the chance and made some mistakes. The details are being
worked on, and fortunately we do have a lot of experienced builders involved
who can recognize potential problems and adjust the building method to fit.
For example, laying the first course of bales on sleepers or other moisture
barrier to protect against capillary action.
>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?
Some testing has been done, more is in the planning stages - specifically,
there was talk recently on the SB list about using a particular university's
new "shake" table to test the seismic characteristics. Most of it at this
point has been anecdotal evidence - the unplastered SB under construction that
withstood 2 hurricanes, somebody's experimental plastered strawbale benches
that survived the wildfires in California, etc.
Shrinkage appears to be minimal, and the bales, like most materials, stabilize
over time. It is suggested that bales be "tight" to begin with, and often
there is additional compression of the completed wall by allthread/wire/roof
weight/other. Plastering is typically not performed until the building has
settled for at least a month, and often the final coat is not attempted until
a year later. Visit a few that have been around for a while, and see for
yourself. Any structure will move some - I've seen a number of non-SB
buildings that have cracked stucco too.
>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?
Codes are now in place in many areas, and are being introduced in many others.
It's gotten so commonplace that the folks on the SB list have actually been
known to announce: "Pop The Cork! (Yawn...) XXX County just approved..."
The rest - well, we'll see. Most of the processes are not that different from
conventional building - there are masons for the stucco, electricians still
tie their wires the same (though they may run them a little differently),
plumbers still follow the same rules ($*it flows downhill/payday's
friday/don't chew your fingernails), etc.
>Fifth, does it have the flexibility to let the building be modified? How
>does one remodel a straw bale wall?
"Watch out with that axe, Eugene". The usual destructive tools - sledge
hammers, wire snips, etc will work for the demo part. Or are you asking how
does one account for removal of a significant portion of load bearing wall?
In a similar way to any other load bearing wall you remove - you have to find
new ways of bearing that load. Take out the old, put in the new - whether it
be new loadbearing straw and plaster, or some other materials. Some
modifications may be impossible with this method, others may be much easier.
Many are planning ahead by framing windows such that they could be easily
converted into doors later, including frames in the wall to later knock a hole
through to an added room, etc.
>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?
I don't think you're missing the point. I think you answered your own
question there. Much of what we're seeing with the SB movement is a reaction
to standard practice and the problems that have evolved from it. The present
wave are the do it yourselfers, the dreamers, the independents. Will
mainstream America buy in? Maybe. Eventually. But I don't expect the
average career oriented yuppie type to jump for a SB. Will the popularity of
SB affect standard practice? Quite possibly, especially in some areas. It
may primarily serve to pave the way for acceptance of things like the
manufactured straw panels, straw and soymeal "plywood", and other innovative
uses of non-wood materials that can help reduce our wood consumption. It may
also point out to a lot of people who wouldn't have figured it out on their
own that you Don't have to settle on buying a crummy tract home in a crummy
suburban Planned Community. You can make other choices, you can be involved
in creating your own housing. And, let's hope in creating real, living
communities.
BC
--Bill Christensen billc@greenbuilder.com Sustainable Building Calendar at http://www.greenbuilder.com -------------------------------------------------------------------------- Sustainable Sources - Internet Solutions with an Environmental Perspective info@greenbuilder.com BBS 512.462.0633 Telnet://fc.greenbuilder.com:3000 WWW http://www.greenbuilder.com/ __________________________________________________________________ This greenbuilding dialogue is sponsored by Oikos (www.oikos.com) and Environmental Building News (www.ebuild.com). For instructions send e-mail to greenbuilding-request@crest.org. __________________________________________________________________