Image Credit: Jonathan Query, IIIAD design/build
Image Credit: Jonathan Query, IIIAD design/build A STRAW BALE HOUSE IS A GIANT SCULPTURE. The deep, hand shaped walls helped influence the creation of this window seat and cabinet. The small opening in the plaster to the right is a ‘truth door’ where the straw can be seen.
Image Credit: Jonathan Query, IIIAD design/build WARMTH ALL AROUND. The Jotul wood stove is a major source of heat all winter long. Unfinished wood, slaked-lime plaster and rust colored polished concrete floors contribute to the cozy feel year round.
Image Credit: Jonathan Query, IIIAD design/build 准备粉刷. The crew covered all wood framing with building felt and put polyethelene over the bottom two courses of bales. Stucco sticks pretty well to straw, but wire mesh laced to the bales will give it a little more purchase. Among experienced straw builders, the consensus is that a continuous drainage plane is undesirable because it would prevent excess moisture from exiting the wall and wouldn't bond as well to the stucco.
Image Credit: Jonathan Query, IIIAD design/build THAT'S DETERMINATION. An early cold snap put a kink in the plan to wrap up before winter. The crew persevered and erected this heated tent to allow work to go on. It was November when this coat of stucco was applied.
Image Credit: Jonathan Query, IIIAD design/build THE FINAL COAT of stucco was applied when the weather got warmer. Venting at top of walls was added later to evacuate moisture, an unavoidable condition of bale houses built in climates with extreme weather variations.
Image Credit: Jonathan Query, IIIAD design/build AVERAGE NATIONALLY, BUT EFFICIENT FOR MINNESOTA: 92.5 MMBtu/year. The strawbale walls do a good job of keeping the 2560sq.ft. house warm. Most of the heat comes from locally harvested hardwood burned in a small woodstove. Propane is used for heating water, cooking and drying clothes.
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#Like an old fashioned barn-raising, this home was built with many hands
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Built before LEED and most green guideline programs existed, this largely straw-bale house in Minnesota established new building codes with its creation. Its biggest sustainable attribute may well be its collaborative approach.
Straw—a beautiful, hand-crafted material
In 1995, Ken and Laura had the idea of building a house on the north end of a meadow, on nine acres of forested land that descends at one end to the North Branch of the Sunrise River. With their long time friend, architect and builder Jonathan Query of the design/build company IIIAD, they determined it should minimize ecologic impact, be sourced locally, and cost little to heat and maintain. Having a limited budget, they also decided to use as much of their own and volunteer labor as possible.
This led them to straw bale and stucco, which they all knew little about. However, it held promise as a craft that they and others could learn quickly. Thus they, and the core construction team of friends and family, found themselves hosting workshops for an energetic group of volunteers over the 1996-97 building season. Together, they set courses of straw bale on vertical rebar pins and sewed chicken wire mesh to both sides of the wall with 3’ steel ‘bale needles’. With many friendly gloved hands, they slapped up three coats of fly-ash stucco on the exterior and slaked lime plaster on the interior.
Keeping it close to home
Using agrarian references, simple forms and a hybrid of materials, the house is centered on a three story stair tower which acts as a ventilation chimney. Constructed of 4” x 4” cedar, its columns are exposed on the inside and house deep drawers that nest with each tread and riser. Ken, who is also a cabinetmaker, made these in the straw bale, Quonset-roofed shop at the meadow entry, which was built first to accommodate indoor fabrication tasks. The rest of the house is post and beam, with a couple of small bump-outs in standard 2” x 6” wood studs.
The first floor would be concrete slab on rigid insulation if they were to do it again, but they went to great effort to make a sub-slab of straw bale and poured concrete (called a waffle slab). They now feel it represents too much labor and concrete to be worth the effort. The second floor is concrete poured on structural steel decking, for durability and ease of installation. Ken dyed all floors with iron sulfate and polished them to a rich sheen.
Some interior delights include columns sourced from a telephone pole fabricator, bought as rejects for the grand price of $1 per linear foot. All of the roofs and the elegant beams of what they call their ‘harvest room’ are resawn timbers from an 1890s creamery.
Energy usage
The home is so warm on account of the straw bale insulation that the sub-floor zoned hydronic heating system is used infrequently. Most of the heat needed comes from a Danish Jotul wood stove, which consumes two cords of wood (mostly oak) per frigid Minnesota winter. Walls with an R45 or R50 value, ranging in thickness from 18” to 22”, keep all 2560 square feet toasty. Additionally, about 400 gallons of propane per year are used for stove, clothes dryer, and domestic hot water.
Lessons Learned
Building your own house by hand is not for the faint of heart. The straw bale construction did not really result in cost reductions. But the volunteer work did, and they found it was joyous, arduous fun. An early and brutal winter blew away the hope of getting the house closed in before bad weather. They struggled to keep the straw bales dry and finish it under a heated tent that storms periodically ripped away. Come spring, they were forced to drill thousands of holes in the stucco to dry it out, and in places, remove decayed, rotten straw. Ken says the most important thing he wants to share about straw bale building is that in northern climates, the top of a wall has to be directly vented to the outside or an attic, even if moisture never touches the straw.
The inventive and artistic owners love the thick, shapeable walls, which they sculpted for playfulness and drama. They are pleased that many reclaimed elements in their house, like the magnificent creamery beams, may one day live in a third incarnation. They hope that the house itself will endure, like Nebraska’s 19th century straw bale homes—many with only a little flaking plaster, some 200 years on.
General Specs and Team
| Location: | North Branch, MN |
|---|---|
| Bedrooms: | 3 |
| Bathrooms: | 2 |
| Additional Notes: | House:2560 sq.ft. Cabinetry shop:1,900 sq. ft. Total cost:$150,000 (mostly volunteer labor) |
Architect/designer:Jonathan Query, III ADBuilder:III AD, Ken the Rickettes Builders, plus lots of lively volunteers
Engineer:David Morris
Construction
Foundation:perimeter grade beam (shallow frost-protected foundation with 2-in. XPS rigid foam apron; slab on grade for both structures (R-10); straw bale cast in slab for house (R-45)
Walls:Straw bale (nonload-bearing, with modified box columns of 2x4s sheathed on all sides with 1/2-in. plywood); some 2x6 framing; timber frame interior columns, 4x4 cedar columns in stair tower; bale walls, R-45; 2x6 with fiberglass batts and 1-n. XPS foam on exterior (R-45); timber frame infilled with 4-in. polyisocyanurate rigid foam (R-21)
Windows:argon-filled, low-e (Marvin Integrity)
Roof:timber frame with structural steel decking covered in 5-1/2-in. polyisocyanurate rigid foam and standing seam metal roofing (R-45)
Garage:detached carport
Energy
- Long east/west axis optimizes solar gain
- Daylighting
- Generous eaves (3 ft. to 4 ft.) to augment thermal mass gradient
- Energy star appliances
- Some CFLs
Energy Specs
Heating/cooling/water:radiant floor heat, zoned; Combi-core hydrojet propane water heater (46-gal.) for radiant heat and domestic hot water (Bradford White); wood stove (Jotul); passive ventilation; back-up split-system air-conditioning unit with dehumidifier (Goodman);
Annual energy use:92.5 MMBtu; approx. 2 cords of mostly red oak; 400 gallons propane and 2500-kWh electricity
Water Efficiency
- Low-flow showerheads
Indoor Air Quality
- Low-VOC finishes
- Whole-house passive ventilation
- Heat-recovery ventilator (Broan)
Green Materials and Resource Efficiency
- Straw-bale construction
- Reclaimed timber framing
- Job-site recycling close to 100%
- Advanced hybrid framing
- 30% fly-ash stucco
- Minimal site disturbance
- Natural materials used wherever possible
- No MDF or particleboard
Certification
First code-approved straw bale residence in Minnesota
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Building Code Approvals
Although not thoroughly explained, Ken and Laura probably had a hurdle to pass with plan review, permits and inspections. Although not specifically within the prescriptive provisions of any traditional building code, a straw bale house can be accepted through use of the International Residential Code that is adopted by most jurisdictions. Section 104.11 of that code states in part:
R104.11 Alternative materials, design and methods of construction and equipment. The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code. Compliance with the specific performance-based provisions of the International Codes in lieu of specific requirements of this code shall also be permitted as an alternate.
该语言允许许可证申请人比率nalize the safety of any material as long as it meets the intent of the Code; that of safety. Interest in straw bale is gaining in popularity and is an excellent choise for a green home. It is built with a sustainable material. It is very energy efficient and cost effective. It is a great choice for an owner-builder. If you have an interest in this type of home, start discussing the proposal with your local Building Official for a path toward compliance with the building code. It may require a Registered Engineer to perform a structural analysis. In any case, there are several designs available that will help you with your project.
Re: Building Code Approvals
Back when I lived in Minnesota, I was one of the many hands that hoisted some bales at and smeared some plaster on this place. They did have hurdles getting it through the approval process, and in the end the local jurisdiction basically told them to follow the Tucson/Pima strawbale code (a bit about that code and others below), which, written for a desert climate, wasn't always a very good match for Minnesota conditions. But the house is apparently doing well despite some setbacks. It's a gorgeous place.
I wrote a little history of and roundup about strawbale codes in Environmental Building News in Feb '06 -
http://www.buildinggreen.com/auth/article.cfm/2006/2/1/Ten-Years-Later-Strawbale-in-the-Building-Codes/
Here's the first paragraph:
"Ten years ago, Environmental Building News (EBN) reported on the first building codes for strawbale construction (see EBN Vol. 5, No. 1). The State of Nevada had recently passed a mandate requiring local jurisdictions to permit strawbale buildings, and California had approved voluntary guidelines that could be adopted at the local level. On January 1, 1996, the County of Napa, California, adopted that state’s strawbale building guidelines, becoming the first government body to officially adopt a strawbale building code. The next day, the City of Tucson and County of Pima, Arizona, adopted one that had been in development there for more than two years (and upon which the California guidelines, along with most subsequent strawbale codes, were based). Later that month the State of New Mexico approved a draft of Standards for Non-Loadbearing Baled Straw Construction, which was adopted into its state building code in 1997. Over the next half-dozen years, strawbale codes were adopted in many California jurisdictions, as well as in parts of Texas, Colorado, Arizona, and Nebraska, and the entire state of Oregon."
An early proponent of strawbale construction, David Eisenberg (director of the Development Center for Appropriate Technology
http://www.dcat.net
which was honored with a USGBC Leadership Award in 2007, and given the Affiliate Of The Year award from the ICC that same year), developed guidelines for successful working relationships with local officials when making unusual proposals several years ago. I can't seem to Google up a copy; chances are they're available in a back-issue of The Last Straw.
http://www.thelaststraw.org/
R-value Myths
稻草是一个美妙的建筑材料,but there's no need to exaggerate its insulating qualities. The numbers that have been demonstrated in reputable labs and that are now being included in the International Green Construction Code are R-1.3/inch for flat bales and R-2/inch for on-edge bales, with whole walls at R-30 in either orientation. That's still 50% better than current energy code wall standards for cold climates but it doesn't meet super-insulation standards of R-40.
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