Thursday, October 29, 2009

SO...why BALES?

As people learn about our project, they invariably ask "why BALES?"  or say "I've never heard of a house built out of hay"...  These are almost always followed by concerns about fire, water, or mice.  These are perfectly reasonable things to ask, and since this method of house construction is pretty far from the mainstream, I've come to expect it.

Why we're building a super-insulated zero- or near-zero-energy home is a whole different discussion, and will be the subject of a future post.  For now, let's assume we want a super-efficient house we can heat with very little fuel or effort, and address the "why straw?" part. Since I like pictures, and this part is all text, I'll try to be brief.  Instead of long and tortuous text, I'll create a numbered list of the top 10 reasons, which will be easier on all involved.

1.  Straw is warm.  Straw bale walls are highly insulative -- they have a high R-value when built with care, so less energy is required for heating and cooling.  This is our most important design goal.  Air sealing is also important -- sealing all the leaks and drafts we can find.

2.  Straw is cool.  Highly insulated buildings are not only warm in winter, but cool in summer.  And, let's face it -- they are also pretty darned cool!  Keep in mind that insulation and air sealing prevent the movement of heat, so it doesn't matter if you are trying to keep the heat in during a cold winter, or keep the heat out during the searing heat of summer.  Insulation is good;  more insulation is better;  and much more insulation is "much more better!"

3.  Straw bales and Thermal Mass.  Straw bales are covered with plaster, and plaster is heavy stuff.  The plaster adds thermal mass to the walls, which absorb heat whenever its available, and can radiate that heat back out into the room when the temperature drops a bit.  In the summer, this helps keep the room from getting too hot, and overall helps to "keep an even keel" and moderate temperature swings in either direction.  The plaster here is thick, too.  We're not talking about a skim coat that 1/8" thick, or a 5/8" sheet of drywall, either.  The plasters on the interior walls will end up being between 1.25" and 1.5" thick, which will add a few tons of thermal mass in a highly usable form -- thick enough to hold a lot of heat, thin enough to be heated through, and diffuse enough to have a large area for heat absorption and radiation later.

4.  Straw is low-energy.  Low embodied energy means less energy goes into making it and getting it here.  No mining and refining and casting and curing and all that -- just baling and trucking -- roughly 80 - 90 miles.

5.  Straw is a waste product.  We're making use of something that is a by-product of the grain industry.  This straw comes from Wheat and Barley grown in Southern Quebec, about 80 miles north of here.  Other uses are for animal bedding, mulching gardens and paths, and for adding fiber to plasters and cements.  In some places like California, huge amounts of straw are burned just to get rid of it, which causes a LOT of air pollution.

6.  Straw is local.  Our bales come from less than 100 miles away.  That lowers the amount of fuel needed to get the raw materials here.  Most dimensional lumber from fir or spruce arrives here from far-away places like Idaho and British Columbia, so this demonstrates that a relatively local waste product can have new life as the walls of our house.

7.  Recycling.  In essence, using straw -- a by-product of growing Wheat and Barley (and in some areas Rice or other grains) -- is recycling something that might have otherwise gone to waste.  We're also re-using a 150-year-old timber frame that was about to be demolished and burned.  That frame already lived a life as living trees, another "life" holding up a home in Rumney, NH for150 years or so (and a barn in Peacham, VT for about 110 years), and now a new life holding up our house -- all within a radius of roughly 40 miles.  The wood in our frame grew just a few miles from where originally sawn and constructed, about 15 and 40 miles from here.

8.  Fire Safety:    Straw bale walls are FAR more fire-safe than conventionally framed, "stick-built" walls.  WHAT???  Yup.  Tightly packed straw bales structures smolder and char, but resist burning.  After the plasters are applied, there is very little oxygen available, so bale walls tend to smolder in place, buying precious time for firefighters to arrive and put the fire out.  During construction, with straw chaff lying everywhere, fire safety is pretty darn low, so we're anxious to rake up all the trimmins' and get them out of the house!

9.  Mice and Varmints:  If straw is a warm & cozy place for us to live, how about those cute fuzzy little woodland creatures?  "Won't animals eat your house?"  "Won't mice move into your walls?"  Well, reasonable questions.  First, we're using straw, not hay.  The seed heads have been removed, so there's no nutritional value to the straw, and no attraction to hungry critters.  Mice could burrow into the walls and nest there, and if not properly built and sealed, they probably would.  If the walls are raised up above the ground, and very tightly packed together, this threat is minimized.  Once the plaster is on, they will be sealed out.  Remember, the plasters are thick -- nearly 1.5" of pretty tough and hard stuff, so mice would have to really want to get in! Anywhere that cracks develop in the plaster, or cracks between the plaster and the wood frame, they will have to be sealed without delay to keep critters out.  We also have a cat, Buster, who's a great mouse-hunter.  If any little mousies do manage to get in, they had better not chew through the inner plaster, or they're toast!

10.  Straw helps spread the word.  Straw bale homes are still odd enough to draw attention to the project.  People I don't even know -- or don't know very well -- feel free to ask about our unusual home, and in small-town Vermont, word travels pretty fast.  That helps bring up all these questions, and provides an opportunity to raise awareness of energy issues, and how wasteful and un-sustainable conventional building practices are.  If someone has a 2500 sq. ft. home that requires 1000 gallons of oil to heat, they are paying about $2,500 on oil.  As oil prices rise, and its supply begins to tighten, and then dwindle, they will be paying $4,000, $6,000, $8,000 and so on...  Building a home that requires much less fuel (oil, gas, propane, electricity, pellets or cord-wood), means you can continue to live there without having to rely on unstable fuels that come to us at very high cost, and you won't have to go broke trying to stay warm.  We can also lessen the "need" to kill people in other countries to maintain our addiction to oil -- more about that later...

11.  Straw bales are more fun.  There -- that's 10.  Anyone who's read all 4 books in the Hitchhiker's Guide To The Galaxy trilogy will see what I mean.


Anonymous said...

MY grandson attended a private pre-school in Freeport, Maine last year, and the enntire building was of straw bale construction. For vertical posts in key locations, they used whole trees with some major branches left on (debarked, sanded and sealed) and with site made wood doors using branches for door handle - you had a sense you were in the woods in this building. Inside in the main hall that services the 4 classrooms and office, there was a "window" in the interior plaster, so you could see the straw bales inside the wall. Beautiful and functional building...Ken Slater

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