Nestling "Walden-esque" next to its north woods pond, the Gundersen home takes its aesthetic cues and its structure from its natural surroundings.

Learning With The Land

Straw Bale and Agrarian Architecture
Roald Gundersen; La Crosse, Wisconsin

This article was first published in the Fall 1997 edition of The Last Straw, a resource journal for straw-bale construction. They can be contacted at PO Box 42000, Tucson, AZ 85733.

Straw-Bale Insulated A-Frame
Straw-Bale Insulated Greenhouse

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Working on Biosphere 2 gave me insight into what I really considered environmentally appropriate building. I came back to Wisconsin to explore a more accessible form of "ecologically active" or "living" architecture than was available in the Biosphere project.

Solar greenhouses and agrarian architecture are natural points of departure as buildings welcoming life other than human. By inviting life, particularly plants and soil bacteria, into our buildings, we can clean and recycle our air, water, and biological wastes onsite while producing food, solar heat and light. Extrapolate this integration of ecology with architecture from rural, to suburban, and even urban buildings, and - I believe - we could see the dominant predacious or parasitic forms of human ecology evolve into more photosynthetic and ecologically diverse cultures.

My point of departure is at America's grass roots: the family farm, a culture still alive and growing in Wisconsin. I see the solar greenhouse as the "new barn" at the heart of diverse organic farms growing crops year round. I see "sustainable" architecture in the old farm buildings throughout Wisconsin, built from locally-abundant materials. This is the work I'm building on. As with these buildings, my palette is locally-abundant rocks, dirt, sand, water and fast growing plants, primarily grasses and trees: hence poplar-pole frames and straw-bale construction...

Roald Gundersen pointing out details of interior construction.

Straw-Bale Insulated Roofs and Straw-Bale Solar Greenhouses

Like others, I thought it important to develop straw-insulated roofing systems because of the heat loss through roofs. A majority of a building's heating and cooling loads transmit through its roof. For single story homes, such as most straw-walled homes, the roof can account for 70% or more of the heating and cooling loads. So you want your roof to be well insulated. This is particularly true in Wisconsin where we can have more than a 150 F annual temperature variation. The following is an outline of some of the work I have done over the last four years in developing straw bale insulated roofs.

Gundersen home and solar greenhouse nestle in the snow alongside the pond, opening broadfaces to the warming winter sun.

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Straw-Bale Insulated A-Frame

Peeled pole frame erected, awaiting thin-shell structure and bales.

In 1993 my wife and I built a straw-bale insulated A-frame near La Crosse, Wisconsin. The 946 square foot home is built from site-harvested and peeled poplar and linden trees. We dried and bolted the poles together into equilateral triangle frames 24' on each side. We spaced the frames every two feet on center. Metal lathe and gypsum plaster span between the frames, creating a ferro-cement shell over a wood frame. We mined gold and orange-colored sands near the site to give the plaster finish a glowing integral color. Plasterers whom we spoke to said plaster over a ductile wood frame would crack like crazy. To date it has only hairline cracks at the eight-foot seams between lathe sheets.

Installation of the straw-bale insulation was the fastest and easiest phase of construction. First, before the bales were placed, we laid a 6-mil polyurethane vapor-barrier outside of the plaster and pole frame. We then stacked and packed the straw bales up the sides on exterior benches which are supported on the floor beams or straps attached to the shell. The benches were also very useful as scaffolding during plastering. The strap ends doubled as supports for the roof purlins and metal roofing. The bale stacking took six people about five hours to place over 300 bales up to a height of 30 feet. The bales reposed into the sixty degree angles of the A-frames. It was stable enough to climb, which we did during packing. The roof rides on the roof purlins, away from the straw by an inch or two, providing ventilation of the straw. In my annual inspection of the straw, it remains very dry and apparently unaffected by our humid upper Midwest summers. I plan to monitor the humidity in the straw more rigorously with meters.

Thin-shell structure being constructed.

Close-up of thin-shell structure underway.

Rising stately from the site, yet still in harmony with it, the Gundersen home seems the essence of "home" and "shelter" in its northern woods surroundings.

Dappled daylight streams through the south glazing of the A-frame structure, highlighting the peeled wood balcony and stair railing.

Sunlight fills the interior of the Gundersen home. It streams past natural branch supports that blend with peeled pole structure, antique stove and wood floors.

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Straw-Bale Insulated Solar Greenhouse

Growing wildly, even in the heart of winter the Gundersen organic garden bursts forth in the solar greenhouse sheltered from the elements by peeled pole structure supporting straw bale walls and roof.

This project had closely followed my return to Wisconsin after the success of my first solar greenhouse - an 1800 s.f. building in Minnesota which has operated since 1992 without a furnace. The owners grew a nice crop of tomatoes in the winter of 1996 while temperatures outside plummeted to record lows of 50 degrees below zero. Since moving back I've been developing cold-climate greenhouses and more broadly "living" architecture, looking for an opportunity to test some of these ideas further.

In 1996, I received a Wisconsin Department of Agriculture grant to build a 2800 s.f. straw-bale insulated solar greenhouse. The resulting building is roughly 140 feet long by 20' wide. Its structure is made of site-harvested black locust which is a fast growing and extremely strong and rot-resistant legume abundant throughout this area. It is also considered a waste wood, and is used mostly for fence posts and firewood.

This time I thought, "why not peel the trees standing," using a ladder and climbing equipment. Surprisingly, this was four times faster than ground peeling! I peeled 23 trees, 30 feet high, in nine hours, or the equivalent of over $600 of dimensional lumber (the most I've ever made in a day). Peeling while standing also allows the trees to stand dry, check evenly and it reduces handling weight by as much as 50%. Other advantages of this technique are that I can harvest the standing, peeled trees when needed. The majority of branches and bark are left to decompose on the forest floor - not in a lumber mill. Afterwards the forest stand is thinned and improved.

Pole-frame of greenhouse, showing lithe structure awaiting bale-infill insulation.

After dragging the trees to the site, I notched, bolted, erected and laterally-braced the pole frames. We pneumatically stapled wound wire fencing over the north part of the shed roof frame. We had a baling party with high school students. Bales were stacked in straight columns in wire valleys between the poles. The wound wire held the bales in place well, but we also had a sill plate which we packed the bales against. The seams between bales were stuffed with straw flakes requiring most of the roof baling effort. We then laid 2x4 roof purlins across the bales, roughly leveling them with more straw flakes.

Next we began sewing the purlins through and around the wound wire fencing and back around the purlins. Corrugated metal roofing was then secured to the purlins. I had planned additional cross bracing but omitted it when the structure stiffened greatly from baling. Apparently the bales were resisting inward movement in compression and the wound wire was resisting outward movement in tension. This created a remarkably strong roof diaphragm. The previously bouncy roof had also gained 12,000 pounds. With annual high winds of up to 80 miles per hour in the Midwest, straw roofs have the added advantage of being heavy (Farmers will often leave bales in their barns to help prevent them from blowing over).

Building with Raw Wood In the Midwest, the issue of using wood in construction seems moot - it is all around us falling down and rotting. Efforts to eliminate wood from construction may be misguided if they result in the use of less renewable and more energy-intensive and polluting materials like steel and concrete. Instead we may need to rethink the use of wood in construction. On our 140 acres of land, 95% is forest, much of which is too thick for any tree's benefit. The harvest of wood for our house improved the variety and health of the remaining forest by removing some of the pervasive poplar trees. I selected poplar because of its abundance and image as a waste wood. It grows fast, nails and bolts well, and it has one of the best strength-to-weight ratios of any wood species (or of any material).

A major revelation I had in working with poles was how much stronger natural wood was than dimension wood. Wood in its natural state has its concentric fibers intact throughout its length. In milling, lumber loses its concentric and continuous fiber structure and is much more subject to breakage. Also, milling a 2 x 4 creates 80-90% waste, requiring a tree of sufficient girth and age, usually no less than 40-60 years old, before lumber can be milled. Almost all the trees we used were less than 20 years old and two to three times as renewable. Foresters usually waste these trees in thinning a forest. We could use this waste stream for pole-frame structures while we improve the forest stand for mill timbers. The huge waste stream from the milling of dimension lumber has led, in part, to the creation of glued particle- and chip-board products that deteriorate rapidly with humidity and often release toxic formaldehyde compounds.

"Agrarian architecture" finds its expression in the sweep of the solar greenhouse, rising in harmony with the forms of the site's natural vegetation.

The challenge with using pole framing is how to build "inaccurately," or with a low construction tolerance. Dimensional lumber homes usually are built to better than 98% accuracy (1/16" in a foot). Our A-frames walls/ceilings may be off by more than 1/2" in a foot, a similar tolerance to straw bales. This has resulted in a wonderful sculpted organic interior; more like the roundness of our bodies than the boxes most of us live in. If we don't have to refine materials to such a precise degree, we won't have to pay for the time energy and waste it requires to do this.

Approach to the site emphasizes the importance of the agrarian to the project, as the solar greenhouse opens up to the south sun.

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Roald Gundersen is an architect specializing in the design of low-cost solar cold-climate greenhouses. He was inspired to his current work by his brief introduction to straw-bale construction from work shops held by David and Matts Myhrman in 1992. He can be contacted at Gundersen Design, 507 Main Street, La Crosse, WI 54601; (608) 452-3894; <roald>.