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Better Quality, Ecological Correctness through Sustainable Design – TLS #59

By Bales, Community, Design, Fire, Uncategorized, Water No Comments

This article appeared in TLS #59.

by Ken Haggard and Polly Cooper – California, USA

Adopted from an article that appeared in Home Power Magazine.

Straw-bale cottage during construction.

Straw-bale cottage during construction.

Like many other architectural firms in California, San Luis Obispo Sustainability Group architects had been designing building that utilized passive solar for many years. Like many other architectural firms around the country, and around the world, in recent years we found ourselves shifting our design work to “sustainability,” an extension of passive solar design concepts.

The definition of sustainability we use in our work is to use resources that meet our needs but do not compromise the ability of future generations to meet their needs. As our firm and the work we do evolved, our practice has evolved to encompass broader issues including life cycle impacts of materials, miniaturization of infrastructure, health issues in buildings, permaculture and landscape regeneration.

By 1994, we had developed a comfortable working environment, consisting of a mix-used passive solar complex that included an office, shops and a residence on an old trout farm adjacent to the Los Padres National Forest, 12 minutes north of the city of San Luis Obispo. Little did we imagine that we would endure the trauma of losing nearly everything we owned or that this tragedy would afford an opportunity to redevelop our complex based on our new knowledge of sustainability. In August 1994, the 41 Wild Fire that burned 40,000 acres/16,200 hectares in our area destroyed our entire complex, and forced us into applying these broader principles of sustainable design for ourselves. Once we got over the initial shock of losing an extensive library, slide collection, office and home, it became more and more obvious what an opportunity our natural fire-oriented local ecology offered us – we could start from scratch and build sustainably, without the problem associated with retrofitting existing structures.

One of the first things we realized was that the fire had left us with a large inventory of building material. (We had several strawbale benches on the site before the fire. They turned out to be more fire resistant than most of the stucco-, tile- and metal-clad buildings in the canyon.) It had killed most of the mature trees (except for 2/4 of the fire-adapted oaks), and these trees were now available to use as lumber. We would never have dared touch them while they were alive. In addition, the massive opening-up of the landscape afforded by the fire allowed us to examine our aging infrastructure. We realized it could be redone in a much more sustainable way. Landscape regeneration became an everyday reality, not some theoretical subject. We suddenly could do things that we had only talked about, but never had the time to do – like getting off the electrical grid.

cottage2

Completed straw-bale cottage.

Right after the fire, it was necessary to develop a base of operations – a place to store tools, plan from and live in. We attempted to combine this need with several others, such as providing future retreat for guests and visitors, as well as a demonstration workshop for our senior sustainable design architecture class at Cal Poly State University. The result was a 500 sf/46m2 cottage that we built on a slab that was left from a shed we had removed long ago. his was one of the few slabs in the canyon not destroyed by the re, because it supported no flammable building at the time. For the structure of this building, we used fire-damaged telephone polls with a truss joist frame. We built the walls from rice straw bales laid on edge, which provide good insulation. In addition, the stucco finish provides interior distributed thermal mass. For the ceiling, we used wheat straw bales laid flat between TJI rafters, which also provide good insulation. The roof is corrugated steel sheet, and includes a 4-ft.x 8-ft/1.2mx3.4m skylight with skylid (movable insulation) unit. Our electrical power came from a Pelton wheel (a microhydro system) on the creek connected to storage batteries.

The construction of this building used healthier building materials that produced less waste. The unused straw was used for erosion control on the site. The building also gets much of its heat from the sun, and uses waste as a resource. In addition, the structure served as a prototype to test details that we planned to use in the larger buildings.

Sustainable Materials

In sustainable design circles, there is a lot of talk about the advantages of using regional materials. As practitioners, we always had nagging doubts about how much of this is truth and how much is idealized theory. Once construction of the guest cottage was underway, we turned our attention to testing this theory. There were several stands of mature trees on the site, especially in the creek areas. The oaks, Sargent cypress and several pine species were native. The Douglas fir and redwoods were not, although their natural range on the coast extends to just 10 miles/48 km north of the site. They were planted 33 years ago when the trout pods were developed. After the fire, all the redwoods put our new growth immediately, and three-quarters of the oaks sprouted from at least part of the remaining trunks. The other trees were killed. We now had an opportunity to do what passive solar applications do – use resources directly on the site rather than importing them from far away and exporting the impact elsewhere.

We felt obligated to mill the dead trees into lumber for reconstruction. We hired sawyers to do this during the fall of 1994, suing a wood Miser portable mill. Both we and the sawyers were amazed at the quantity and quality of wood produced in this relatively small area. We harvested 22,000 board feet of lumber, enough for construction of the other buildings with enough left over to be a storage, rain and sun protection chore. The economics of this also created the unusual condition of using straw-bale construction in conjunction with heavy timber construction, as it was more economical to mill big pieces rather than small ones.

The result of this experience was very interesting. The wood we obtained cost about the same as it would have from a lumberyard, but the quality was much higher. In addition, all phases of the life cycle of this material – source, transport, processing, use and source regeneration – happened on the site. Waste could not be exported elsewhere. It became a resource used for erosion control and organic matter for the regenerative process.

It became obvious to us that although the first costs of both milling our own lumber and buying it from a lumber yard were about the same, the long-range environmental costs of milling our own was much less. These costs are not often accounted for in our present economic system.

The Studio/Office

interiorThe next step was construction of the studio and office, completed at the end of March 1995. Because of the function of this building, we placed great emphasis on natural lighting in addition to the passive solar design. The studio/office is also off-grid, powered by photovoltaic (PV) panels over the library/research area, with a Pelton wheel on the adjacent creek for use as backup in the winter when the water is high. (Two streams fed by the nearby mountain range flow through the property.) The studio/office is heavy timber-frame construction with straw-bale infill.

The south side of the office is configured to allow maximum sun penetration in the winter and begins to shade itself in early April. During the summer months, it is totally in shade, picking up sun again in late September. Parts of this facade are view windows, part unvented 12-in./30cm Trombe walls that also act as shear walls, and part 9-inch-thick/23cm water tanks below the south-facing window on each end that act as indirect gain passive heaters. The Trombe walls and water tanks are painted with a selective surface paint on the sun-facing side.

The wiggly light shelf on this south facade serves two purposes: providing summer shading of the windows and low water tanks and throwing light deeper into the building in winter. This office is also designed for maximum night ventilation. Summer breezes generally flow from southwest to northeast, so the air moves through the long dimension of the office. These breezes, coupled with the large amount of distributed thermal mass in the building, keeps the interior temperatures below 79oF/26oC, even when daytime summer temperatures are quite hot, occasionally reaching 110oF/43oC.

The Residence

The two-story residence of the complex was completed in October 1997. We used construction techniques similar to those in the office, except that the heavy timber structure is placed 6 in./15cm inside the straw-bale walls. This configuration allowed us to expose the beautiful timber frame and create a continuous two-story straw-bale wall without interruption of the north side. The curves of this wall were very easy to achieve with straw bales without any added expense. This is the best arrangement of the timber structure and bale walls we’ve found to date. There are remarkably few cracks in this wall. The contrast to the stuccoed wood shear walls on the east side is very telling.

The residence uses interior 8-in./20cm concrete block walls as shear walls, thermal mass and decorate “gates.” Besides south-facing glass, skylights provide direct gain, with skylids as thermal control. We’ve found that this system offers more flexibility in the fall and spring than fixed overhangs.  The El Nino weather pattern sometimes produces a very unusual cool late spring, which we cannot respond to in the studio with its fixed overhangs. The skylight/skylid arrangement in the residence did allow us to respond to these unusual climatic conditions. The residence is also off-grid, powered by the PV system and Pelton wheel backup that provides electricity to the rest of the complex.

Landscape Regeneration

exteriorOne of the unexpected joys of this whole ordeal has been to experience the rapid regeneration of the landscape following the fire. Fire is such an integral part of the native California landscape that everything is set up for it. The first spring was dominated by delicate fire poppies, which only appear in newly burned areas.   In this case the seeds had been waiting 60 years for their chance – it had been that long since this area last burned. The next year was dominated by morning glories, which spread all over the armature of the burned branches of earlier plants. The third year was the year of low herbal plants – sages, bush poppies, soap roots and others.  In the fourth year, we found the Ceonothus (wild lilac) dominating. The regeneration of oak and cypress trees then began to be much more noticeable.

The best wood for reconstruction turned out to be the Sargent cypress, used for the structure and trim. Alder was the best for cabinets. The cypress trees regenerated naturally because they were a fire species whose seeds are stimulated when they are burned. When the office was done, to commemorate the wonderful alder cabinet it contains, we planted several times the number of alders in the creek than were there before the fire.

Better Quality, Ecological Correctness

We’ve found that the application of our design theories to our own situation has helped convince clients and others that sustainability is more than just another theory. It is a way of achieving better value while simultaneously having far less impact on our planet. In fact, once we get beyond the fears of scarcity that haunt our industrial culture, we will see that these two values – better quality and ecological correctness – are interrelated.

Ken Haggard and Polly Cooper are principals with the San Luis Obispo Sustainability Group, 16550 Oracle Oak, Santa Margarita, California 93453; 805.438.4452, fax 805.428.4680 <[email protected]> www.slosustainability.com

Ed.Note – An article about the curved wall straw-bale workshop building (not pictured in this issue) at Ken and Polly’s complex will be included in TLS#60/Details, Details, Details. It’s amazing in its design and structure.

Fire in a House With Straw Bale Walls

By Fire, Straw Bale Construction, Walls One Comment

This article is original content and has not yet appeared in the printed version of The Last Straw.

No, this is not the house.  We dont have a picture of a bale house on fire!

No, this is not the house. We don’t have a picture of a bale house on fire!

This story is a reluctant one about a house comprised of both wood-framed and straw bale walls lost to a fire in 2009. The structure was built over a longer period of time than most main-stream homes.  The different phases incorporated the most appropriate materials at the time for the owners. We are excluding specific reference to the owners and the location of the building due to privacy concerns. For this article we will say that the building is in the central U.S. at approximately 8,000 ft elevation and the Owner’s name is Bob. In the end, it really does not matter who owns the home or exactly where it is. What we will focus on is the performance of the bale walls in the fire, the aftermath, and how the owners and insurance company feels about the whole incident.

The building was an un-permitted residence in a rural mountainous area. As mentioned above, some of the walls were wood-framed, others were built with bales. The bale portion of the structure was round, approximately 26′ in diameter, on a foundation that was an 8″x18″ concrete grade-beam supported by concrete pillars, with a yurt-style roof which included a “tension-ring” cable. The bale walls were Nebraska-Style (no posts) and had a 2×6 box-beam for the top plate with plywood on the bottom but not the top. The box-beam was filled with rigid foam insulation. Both the interior and exterior surfaces of the bale walls were covered with cement-based plaster. Two coats were present on the exterior and one coat was completed on the interior. There were relatively small areas not plastered on the interior, but the location of these un-plastered areas were not specified in my conversation with Bob.

The fire was started in the crawl-space of the framed portion of the structure by accident. It quickly spread throughout the framed structure and overtook the occupants who had to flee for their safety.  Bob is a local volunteer firefighter who was overcome with smoke inhalation and had to be taken away for medical care. He was present for a majority of the fire and taken away before it was extinguished. However, he has some interesting comments regarding the bale walls, how they performed and how they were affected by the fire. The family lost everything to the fire and is now picking through the remains.

The fire quickly engulfed all of the wood-framed structure and spread to the floor and then the roof of the round bale structure. The roof of the round structure collapsed inside the bale walls but the bale walls themselves were still standing when the fire department , hampered by by the long driveway and 18″ of fresh snow, arrived on the scene 50 minutes after the fire started.   Due to smoldering straw the fire department felt compelled to knock the bale walls down to access smoldering area within the walls.  Eventually all the bale walls were knocked down and all of the smoldering extinguished. This process took five days after the initial incident.

Bob commented about how fast the areas with no plaster ignited compared to the bale walls covered with plaster. The windows and doors had been framed using standard wood bucks. These, in addition to the wood box-beam, became the main avenues for the fire to spread into the bale walls. It appeared that the fire moved down from the top and in from the window and door bucks. Had these areas been plastered, or concrete bucks used, Bob feels the bale walls may have been spared.

Due to the generally impenetrable nature of the walls they seemed to act as barriers to heat-flow in both beneficial and detrimental ways.  Bob had installed his solar PV array 10 feet from the bale structure. The PV panels were virtually unharmed due to the shielding nature of the bale walls. His wood-framed shop, situated approximately 30 feet from the framed portion of the residence, ended up burning to the ground from direct exposure to the heat of the fire. The drawback was that Bob felt the bale walls created an oven-like effect within the building, holding heat inside, keeping the temperature very high.  As a result, one of the losses was the family safe which was supposedly fire-proof.  It was unable to withstand the “heat-trap” surrounded and created by the bale walls.  From these accounts, It is clear that the bale walls have a very significant heat-shielding effect during a major fire event.

The entire structure was insured by Allstate Insurance.  Bob was honest with them at the time of insuring the building and did not hide the fact that part of the building incorporated bale walls.  Allstate did not seem to make a big deal of the fact either then or now.  It appears they are making a pay-out on the insurance policy.  This is good news to bale building owners everywhere.  An insurance company had the capacity to not focus on the fact that some of the exterior walls were made of straw and plaster.  It is not clear if they understood how stable the walls were during the fire since they did not collapse, like the rest of the structure.  The fact that the bale walls did not contribute to serious problems was probably one reason for the lack of focus.

Being a volunteer firefighter Bob was frustrated he could not help fight the fire that destroyed his own home.  He understood that following orders from his fellow firefighters to seek help for his smoke inhalation was the right thing to do.  When asked about how the fire was suppressed in the bale walls and why it took so long, it became clear that the ongoing smoldering was not going to stop on it’s own.  The walls needed to be broken up in order to access all of the smoldering spots.

It seems that there is a pattern among bale buildings that are engulfed by flames.  The walls remain standing as long as anyone is willing to let them stand.  The main reason they are taken down is to gain access to smoldering areas within the walls so as to eliminate any risk of spread and the accidental ignition of other fires elsewhere.  The fact that bale walls are very effective heat shields makes them good fire-separation wall candidates between living units, or uses, within a structure.  They remain stable throughout the fire event, which cannot be said of steel or wood-framed walls in low-rise residential or commercial construction.  The fact that they tend to smolder and require maintenance for days after the initial fire event costs money and resources, but weighed against the fact that they do not fail catastrophically means that they may be considered as life-safety elements in buildings with many uses and occupancies.

The lessons learned in this building are that bale walls are incredibly stable during a fire event, offer a thick shield to retard flame-spread, and are tough to dismantle, requiring many days and resources by the local fire department.  When put together it seems that the bale walls themselves had a much better track record than any other part of the structure.  Feel free to comment or add to the discussion by logging in and submitting your thoughts.

Bob says he will not rebuild with bales mainly due to the huge amount of labor involved.  He will probably choose to build with some form of ICF (insulated concrete form) and steel.  He and his family enjoyed their bale home, but the time and labor necessary do not seem as realistic the second time around.

All fires in bale buildings are felt throughout the community as a serious and deep loss.  Even though we do not wish for them there is a great deal to learn from each and every one.  We hope this account will help firefighters, insurers, designers and homeowners make the best decisions possible.  Please comment below and participate in the conversation.  We are interested in your thoughts.  Email the author with any specific question for the owner offline.