The following list of questions and answers is rather random and arbitrary. I am answering questions as I think of or receive them. Hopefully most of your basic questions will be answered here. I should have done this three years ago but for some reason I didn't...so give me some time to get it all up. Thanks, Robert.
- What about fire?
Answer...During construction, when loose straw is everywhere, straw bale buildings are subject to fire, and indeed, houses have burned at this stage. This is also the stage where occasional vandalism has occurred in the form of deliberate fire. It is important to keep a clean building site during construction to including bagging of all loose straw, and do not allow workers to smoke.
However, once the bales have been stuccoed outside and plastered inside, the bale walls are very fire resistant, with a considerably higher fire rating than stick construction. We have seen several examples where after a vicious fire, only the straw bale walls were left standing. Many controled fire tests have been conducted under "laboratory conditions". Check DECAT in my links for results. Below is an e-mail I recieved with a fire story.
125 REM John (firstname.lastname@example.org) - no homepage - 2000-12-27 07:04:05
Hi, I have been thinking of building a straw house for some time. I just need the land and I am working on that. A close friend of mine built a 5000 sq. ft. home in Arizona . He had a mishap, I thought I would share with you.
His tractor bent the water pipe going into the house. He got out the tourch and started the repair. After about 20 minutes, he got it changed out. Later that day his wife noticed the smell of smoke, and sure enough it was coming out of the roof.
They called the fire department who got lost on the way but finally showed up. They cut a hole in the side of the house and pulled out the bales which were smouldering. As soon as the bales were exposed to the air they caught on fire.
The fire chief was so impressed the house wasn't burnt to the the ground, he said he would recommend straw bale to anyone. A normal house would have been burned to the ground . The damage was contained to the small area where the tourch had set it off.
What about insects?
Answer...Insects can and do get inside the wall cavities of standard stick construction. Usually, except for termites, they do not cause serious problems. With straw bale construction, the bales are encased on all sides, usually with plaster and stucco an the flat walls, and are sealed top and bottom to greatly reduce access by various insects. Unlike stick construction their are few and small wall cavities for insects to hang out in. In areas where termites are a problem we use termite shields as in standard construction.
What about moisture?
Answer...As with wood, the straw bales should be kept as dry as possible throughout the building process. In an ideal world, they will be reasonably dry when you buy them, you will keep them dry while you store them, and dry during wall construction. In reality, bales sometimes get wet...but they usually dry out to below the accepted maximum of about 20% moisture content. When bales maintain a greater than about 20% moisture content, they can decay, and molds and fungus can develop.
In hot, dry, windy climates like say Arizona, no matter how wet bales get they usually dry out if the moisture is not encased and can escape. For this reason, vapor barriers are usually not recommended. In wet and humid climates, straw bale construction has been successful, but more effort must be exercised to keep the bales dry.
In any case, good building technique includes providing large roof overhangs, keeping the bales well above the ground level, not using vapor barriers, using porches to protect bale walls, and of course, keeping the bales dry...as you would most other building materials.
Why use straw bales for home construction?
Answer...A few of the more common answers are:
1. Straw bales are a renewable resource that is often wasted or burned. If we can use them for construction, we may reduce the amount of wood that goes into housing...and farmers will have another income source.
2. Thick (about 16 to 24 inches) firmly packed straw bales are highly resistant to the flow of heat and cold, thus there "R" values are very high compared to that of standard 2 x 4 construction. This can translate to greatly reduced energy bills for the life of the house. Combine this with a little passive solar heat and you may be able to beat the strangle hold of the energy companies.
3. With the thicker walls, the lack of a wall cavity (drum), and the slightly irregular walls after plaster, straw bale houses are much quieter inside with sophisticated acoustical properties. You won't know what I am talking about until you spend some time in one.
4. In the Southwest United States, for example, straw bales houses have taken on the prestige of high end adobe houses found in the Santa Fe, New Mexico area but at a greatly reduced cost in time, energy and money. And in the do-it-yourself/alternative community, straw bale, with cob, rammed earth, timber frame, among other techniques, has revitalized the interest in smaller, energy efficient, very personal and spiritually lifting alternatives to industrial housing.
How can I learn more about straw bale construction?
Answer...There are several good books available on straw bale construction in the larger book stores, such as The Straw Bale House, Build It With Bales, and Straw Bale Building, and others. Or get a subscription to The Last Straw (see links) and consider buying all the back issues. You will then know a lot about the subject, and you can always attend a weekend or full week workshop and learn all you need to build. Occasionally, I do a workshop when things fall together. Let me know if you would like to attend one in Colorado in the summer, or Arizona in the winter.
Where can I get bales and how much do they cost?
Answer...Straw is a by-product of grain production. When the wheat or barley or rice (for example) is removed from the stalk, the stalk (straw) is left in the field and must be dealt with. Sometimes it is burned, sometimes left in the fields, sometimes baled with a baling machine into typical bales tied with cord or wire and stacked in the fields. The grower may use some of it to bed animals and maybe sell some to feed stores who in turn sell it to gardeners and animal owners. Now some states require its use to stabilize and control erosion around construction projects.
You can buy it directly from the farmer or from a feed store. The cost of transportation accounts for at least 1/2 the cost per bale so you save if you can haul it yourself...few people have the equipment for that. Expect to pay somewhere between $1.00 per bale (directly out of the field), to a high of about $3.50 a bale delivered. A small house of about 30 feet by 40 feet (for example) would require about 250 bales for the walls at a cost of around $700. This will account for a small percentage of the total cost of the house.
How can you build a house from straw?
Answer...Think of the bales as huge bricks that are stacked up into a wall just like earthen bricks but because they are so much bigger, you need far fewer and the walls go up really fast...without the high level of skill required for regular bricks. Originally the (usually six courses of bales) were stabilized with rebar driven through the bales to pin them to each other and prevent shifting. Sometimes now the bales are stabilized with rebar or bamboo on the outside of the bale wall with ties through. And sometimes no stabilizers are used, the plaster added to the inside and outside adequate for the job.
The bales can sit on relatively conventional foundations such as a poured concrete slab or a wood floor over crawl space or conventional basement. The alternative builders may use a rubble trench or earth bags or laid rock or railroad ties for example.
The roof can be supported directly on the straw bales with an adequate top plate/beam to spread the load or the roof load can be carried on a relatively conventional "post and beam" system. Some people even set the bales inside a conventional 2x4 framed wall for added insulation. There are many possibilities...the system works. Usually the walls are then plastered both sides.
Where can I see straw bale houses?
Answer... Most of the straw bale houses build to date are in Arizona, New Mexico, Colorado, and California. Also parts of Canada, Australia and New Zealand. There may be straw bale houses in every state of the union and in every country of the world, no one knows how many and for sure, but their numbers will be relatively smaller than in the Southwest United States. You can call around to your local building departments and ask if any building permits have been issued for straw bale construction. It should be public information.
I know from hits to my web site, that there is a steady growth of interest and construction and suspect it can only continue given our current world wide energy situation.
What about building permits and insurance and bank loans.?
Answer...In some places in the Southwest US, it is not much harder to get financing, insurance and a building permit than for a convectional house because it has become commonplace. But in most states and counties in the USA you will have to accept the roll of pioneer, do a lot of hard work, planning and persuasion to get the house built. Generally the first SB in your area will usually be the hardest to get accomplished. If the first house is considered a success, the next one may be much easier. If the first is problematic and feathers are ruffled, it may become harder or impossible for the next person.
What's it gonna cost to build my straw bale house.?
Answer...I have been irresponsible and put out some pretty unrealistic cost per square foot figures as low as 15 or 20 dollars per square foot. At these figures, a 1000 sq. ft. place would only cost 15 to 20 thousand dollars. But these figures are for materials only, and do not include cost of land, paid labor, fees, utility connections, etc., etc. Do-it-your-selfers, off the grid, with no building permit required. have build for this and less.
But for most of us, the cost will be about what you would pay for a comparable conventional home in your area, with about the same design and size. With all else equal, your straw bale house will cost about the same as your neighbors similar stick house. Cost will go down in either case if you act as your own contractor, do much of your own labor and reduce the size and complexity of the plan.
In the long run the real savings come from lower energy bills for the life of the house. In todays energy environment, this can really add up.
Do mice and rats attack straw homes? I am thinking of building one in Australia.
Answer...Our family has a stick built cabin in the Colorado mountains that is regularly infested with squirels and "pack rats" because they naw through the siding and live in the wall and roof cavities...and nest in the insulation. With proper straw bale construction, the bales are well stuccoed and plastered (rendered) on both sides, the top and bottom of the walls sealed, thus there is no place for the critters to get into the walls...and there are no cavities to live in.
To date, I have not heard of a specific problem from mice and rats in a specific straw bale structure, but I know from personal experience, that they can be a major problem in "conventional" structures if you don't stay on top of the problem. If you know of any specific problems, please let me know and I will pass it on. Robert.
Check back for more questions answered. Robert.