Straw and Solar: A Perfect Renewable Match Mark Hawes c. 1993 Mark Hawes Words: 1858 It is late October and an early winter storm is blowing through the Sangre De Cristo Mountains of Northern New Mexico. Outside wind gusts of 30 to 50 mph are blowing around any odd bit of construction material that is not covered or tied down. Trees are leaning with the wind. Inside, where I am working Ä running ceilings on top of my vigas (log joists) Ä I am unaware of the storm until my friend, Ralph Towl, comes in the front door. Only then do I come down off my ladder and stare outside at nature's bluster. I am surprised and happily amazed Ä because the inside of my straw bale house is so quiet and calm. I decided to build a straw bale house after reading about one built near me in Tesuque, New Mexico, last summer. I was going to build adobe, but this article made so much sense environmentally, I knew I had to try straw. Millions of tons of straw/crop refuse are burned yearly in the fields across America Ä 200 million tons nationwide! Since straw can be grown many places (one to two tons of straw grown per acre), and the existing supply is inexpensive, straw seems a natural alternative to milled lumber. I could see saving millions of trees annually and reducing the burning of crop refuse Ä cleaner air on both ends. And a new source is grown every year. Talk about renewable and earth friendly! I have just completed my straw house (except for interior finishing) and could not be more pleased. But that's only half the story... The same summer, I visited a friend's machine shop Ä complete with band saw, grinders, drills, and so on. All of this operates on solar power high atop a mesa overlooking the Rio Grande. Needless to say, I was impressed, and walked away with a subscription form to Home Power. Ah, what a gift! Like so many others, I too was suddenly obsessed with the idea of living off the grid. Starting with Solar The idea of independent power really captured me, and Home Power helped me see what others had already done. But, I took a leap of faith early on. I bought a used solar system out of the Santa Fe paper (before I really knew what an inverter did). For $1200, I bought a Trace 2012 inverter, a Heliotrope charge controller, eight Trojan T-105 batteries, an ARCO 100 Watt TriLam photovoltaic (PV) module, and fifteen 11 Watt amorphous PV panels. I bought an old travel trailer frame, chopped it down and welded a smaller frame together. Then, I built a housing box on top of this. I bought eight 51 Watt Kyocera panels Ä 408 Watts peak power from the sun Ä and 16 Trojan L-16 lead acid batteries to store the power (1050 Amp-hours). I used the Trace inverter and Heliotrope charge controller that I had bought second hand. The power trailer was installed with all breakers and fuses as per STI's diagram in issue #26. Brad Rose and Michael Maddex of !Solar Works! in Espanola, New Mexico, did all wiring/configuration on all solar systems. This power trailer solar system not only produced all power to build my house, but it also housed all my tools during building. This system will be installed in my house permanently next spring. POWER TRAILER DIAGRAM HERE In addition to the power trailer, we have a solar well system and another system powering the small travel trailer we lived in during building. For the well system, ten of the used amorphous PVs fill four Trojan T-105 batteries. We use a 1300 watt PowerStar inverter to convert the DC electricity from the batteries to ac electricity to power a Goulds ac pump. The 1/3 hp pump delivers 7-11 gallons per minute from a 60 foot depth. The small travel trailer is powered by the used ARCO trilam PV panel, two Trojan T-105 batteries, and a 200 watt PowerStar inverter. Both systems use Sun Amp charge controllers. SYSTEM COST After six months of working and living with solar energy, I cannot stress enough the great performance of today's solar technology. The power trailer ran everything we asked it to Ä power saws, table saws, drills, often multiple tools and the ever-present radio all at once. It even ran an airless paint sprayer! The other systems performed just as reliably. The well system functioned flawlessly and the travel trailed system ran lights, radio, and a TV/VCR combo without a hitch. And all throughout the summer, I couldn't begin to draw my batteries down. (By the way, the 200 watt PowerStar is amazing in its ability to supply your basic electric needs.) 'Nuff said. On to the Straw Bales The first straw bale homes were built before the turn of the century, and research is still conducted on straw bale construction. Matts Myhrman (Out on Bale, Unlimited) and Ralph Towl, independently went to the Nebraska Sandhills to view and study existing straw bale homes. Some houses were over 80 years old and many are still inhabited. Interior wall removal has revealed bales that look like they were installed yesterday instead of decades ago. All Nebraska houses have straw load bearing walls with usually a hipped roof attached to only stacked bales for support. This is called "Nebraska Style" in the vernacular. Most areas with building codes take a dim view of Nebraska Style despite standing evidence to its ability to withstand wind and weather. Storms across Nebraska can be as fierce as anywhere Ä but modern municipalities need stronger and more documented evidence to allow Nebraska Style building. Research is currently underway at the University of Arizona to substantiate code allowance of Nebraska Style. At the moment, building codes in New Mexico and most of Arizona require post and beam construction, with straw bales used only as "fill" for the walls. They also require an engineer to stamp structural details and plans. If you are lucky enough to live in an unincorporated/non coded area (like Cochise County, Arizona), "Nebraska Style" is the way to go. I was required (as one of the ten straw bale permits granted in New Mexico last year) to build post and beam and incorporate other structural safety measures. But my costs were in line if not below the industrial mean. My house also was built with resale in mind, so RE builders without resale in mind can do it considerably cheaper. But, regardless, the bonus is you've got a tremendously efficient house. The Straw Bales The main concern with straw bales is keeping them dry. Hay and straw are both baled, but are entirely different animals. Hay will decompose and is an attractive meal to many creatures. Straw, on the other hand, is tough, fibrous grain stalk. Straw resists rotting and is no temptation as food. However, straw will rot with repeated or prolonged exposure to water. Micro fungi and mites can live in wet straw, so buying dry bales is important. Bales on the bottom of a field stack may have fungi, but most stacked straw weathers well and is resistant to moisture absorption. It rained hard several times on bales I used as weights to hold plastic down over the main stack and after one or two days of sunshine the moisture meter showed them almost identical to the covered bales. Straw can be stalks of wheat, barley, oats, rye, flax, or rice, (or even tumbleweed) and are baled at different times around the country. As a rule you can "reserve" a specific number of bales with a modest holding deposit. In fact, as straw's popularity grows, I would encourage people to network and reserve. Supplies in certain areas can be depleted, and from a cost viewpoint, the closer the supply, the better. Straw is baled with two-wire or three-wire balers. Two-wire bales generally measure around 18 inches wide, 14 inches tall, and 44 to 48 inches in length. Weight can range from 40 to 65 pounds depending upon the pressure setting on the baler. Three-wire bales are about 24 inches wide, 18 inches tall, and 44 to 50 inches in length. Weight can approach 100 pounds, but generally stays between 70 to 90 pounds. Straw baled with too much compression can lose its R value. Bales should be firm and stiff but not solid or rock-like. R values for straw bale walls range between 32 to 45 as a rule. I used two-wire barley bales at about 50-55 pounds weight each, firm but not too compressed Ä perfect for high R value walls. My Straw Home The foundation is a continuous concrete pour for the post and beam construction with an eight inch stem wall brought to grade. The pitch roof was built with recycled 2x10 inch lumber and insulated with fiberglass to R-30. Straw bale homes require slight changes for plumbing and wiring. All plumbing is buried below frost line Ä it can reach 35ø F below in New Mexico Ä and comes up through the floor. Electrical wiring runs below the floor and above the ceiling. The code for New Mexico allows wires 1 1/4 inches into walls without conduit. My exterior walls were "stacked" in about 1 1/2 weeks by basically two people, Ralph Towl and myself. But stacking can be done in as little as two days with several people (or perhaps a weekend workshop). The bales are "pinned" Ä the first layer is stuck in dowels coming from the floor joists and we used rebar to pin higher layers. My stack was not usual as I chose to custom fit and notch the final row of bales around the vigas and furred down ceilings. (Vigas are peeled tree trucks, about 8-12 inches round, that are commonly used as joists in adobe construction down here in Arizona and New Mexico.) The forgiving nature of this wonderful organic building resource is one of its greatest assets. Ralph and I used a hand hay saw and a sun powered Sawzall respectively, to modify and notch our bales as needed; other people like electric chain saws. Once stacked, bales can be kicked, shovel thumped, and trimmed up as needed. Windows are simple. Bales are modified and rewired to fit around a dimension lumber buck frame. Holes are drilled inside the frame and 3/4 inch dowel are driven into the stacked straw bales supporting the bucks. We mounted the windows 2-3 inches in from the outside and beveled the corners of the bales on the inside to let in more light. Once the bales of straw are stacked, the 18 inch walls are stucco meshed. Mesh is run on both sides of the straw wall and sewn/ wired together, then stuccoed exactly like adobe or stick/plywood walls. But unlike adobe walls, walls go up very rapidly. Unlike log or stick framing, very little lumber is required Ä and no insulation is needed. Other siding options are viable, but they require furring strips, etc. Finished plastered walls look almost exactly like the double adobe walls found in older New Mexico homes, or can be sheetrocked or paneled to look like any standard room. I started my house with efficiency and environmental concerns as well as aesthetics and wants. The graceful curves of my sculpted straw walls fit alongside any hand-built adobe of days past. Geographical distribution of straw bale houses is more widespread than one would think. Below is a map of straw bale structures throughout the United States (reprinted with permission from Matts Myhrman's newsletter, The Last Straw.) It seems that straw bale buildings manage quite well even in wet humid climates. There are reports of an eight year old hay bale building in Alabama with no problems. SCAN OF U.S. Straw has been widely used across the country and grows well in many places. The time-weathered examples of its durability still stand in Nebraska (and are lived in). I think that straw bale building could revolutionize the building status quo. With its wonderful insulation properties, straw gives people home that can be heated and cooled with very little use of resources. In fact, active heat is scarcely used in some solar-oriented dwellings. And it's quiet! The age of sun and straw has arrived. Photovoltaics and straw bales combined with passive solar orientation give one the perfect cost-effective, low-impact house for the future. Access Author: Mark Hawes, Sun Bale, 4122 E. Kilmer, Tucson, AZ 85711 ù 602-326-8430 Information and Networking: Matts Myhrman & Judy Knox, Out on Bale, Unlimited, 1037 E. Linden Street, Tucson, AZ 85719 ù 602-624-1673 Designer/Builders: Steve Kemble & Carol Escott, Sustainable Support Systems, P.O. Box 318, Bisbee, AZ 85703 ù 602-432- 4292. Jim Peterson, Resourceful Nest, P.O. Box 641, Livingston, MT 59047 ù 602-222-0557