Lou Host-Jablonski is principal architect with Design Coalition, Inc., of Madison, Wisconsin. Since 1977, his projects have included multi-family housing & co-housing, childcare centers, new homes & additions, community-built projects, museum exhibits, and community centers. Lou's areas of professional focus are resource-efficient ('sustainable') design & planning, and environments for children. He speaks regularly to student and community groups and gives frequent media interviews. Lou lives in a straw-clay home, has been active in his progressive EastSide Madison neighborhood for going on 4 decades, served on Madison's influential Urban Design Commission for 12 years, and helped the city to write and implement its "GreenPrint" as chair of the Sustainable Madison Committee"
Hi Lou, Thank you so much for doing this interview with me. There are many different natural building technologies. Would you tell us why did you choose Light Straw Clay (LSC) in the first place?
When I came out of architecture school in the mid-1970s I closely examined every construction system I came across. Back then we didn't speak of "green" buildings nor have the concepts of "sustainability" that we talk about nowadays. But as a young designer I quickly learned how wasteful construction could be, especially in the U.S.A. I began studying advanced, alternative construction techniques.
I wanted everything in one package. My ideal system would be low-toxin, affordable, local, materials-efficient, building code-friendly, contractor-friendly, beautiful, long-lasting. It would be energy-conserving, especially in our challenging Upper Midwest USA climate extremes (Wisconsin for example is moist (± meter of annual precipitation, humidity 20 to 100%) with a broad temperature range, -40 to 38°C in a normal year). And it would be robust, resistant over time to molds, vermin and such, and forgiving to build with.
Impossible, I know; all construction systems have their limitations. But when I discovered light straw-clay in 1990, I realized that it had the potential, with some research work, to come the closest to my ideal system.
You have been researching and building with LSC for over 20 years. Your team has become one of the world leaders in this field. You are working on book of LSC, which we are looking forward to. Can you tell us what surprised you the most over these years while working with LSC?
'Surprised' is a strong word; as an LSC researcher, I work with our team to anticipate and eliminate surprises, at least the unpleasant kind! But if instead of 'surprise', you say rather 'insights', there have been plenty.
A big one is the direct relationship of density of LSC versus its insulating ability. Another is how important clay quality—and clay testing— is to the final LSC product. Another is developing an understanding of the physics of moisture movement in and through a wall due to the presence of clay. Another is how easy and seductive it is to 'build heavy' with LSC, and lose insulation value thereby. I'll say a little more on those topics below…
Other insights, of the delightful kind, came from our scientist Douglas Piltingsrud. He devised a way to make reliable measurements of decomposition inside a wall without disturbing it. He uses thermocouples and sensitive temperature probes, because microbial activity creates heat, as anyone who has managed a compost pile knows. Douglas also pointed out that no matter the various densities of LSC mixes, for a given volume the amount of straw is always the same. Only the amount of clay/earth varies. Which makes sense, since earthen materials are generally conductive of heat, not insulating. More earthen content = more heat conductivity.
But I would say that occasionally I do feel surprised at the angst, sometimes even anger, behind some responses we hear to LSC. Mostly of course these come from people who haven't explored very deeply into comparative construction methods. When some folks see the video of our on-site construction process https://www.youtube.com/watch?v=7J0862TFPwU for example, they might say, "It's ridiculously mechanical! All that equipment and energy use! Natural construction should be simple! All you need are hands, feet, a bucket and a shovel!"
What they are failing to observe of course is that all construction requires certain skills, tools and knowledge, no matter what systems you are using. Sorry, but building something well is actually a rather complicated activity, as people who do it for living know. And compared to conventional construction — where all of the factory processes to extract materials and make the insulation and the plasters, with the specialized machinery and all of its energy use, pollution and such is hidden many miles away — with LSC everything is right there on the site. No matter how simple or technical your chosen methods, with LSC what you see is what you get. And it's under your own control, to manage as ecologically as you wish.
I'm also surprised when occasionally some strawbale proponents may feel attacked, somehow, when I explain the advantages of adding clay to a wall, or point to LSC's centuries of successful history in Europe. I understand the feeling — it takes years and a real investment of study and passion to gain expertise with anything, and one may become quite attached to one's methods as the best and only. But this attachment can sometimes veer into what I might call 'construction zealotry', and perhaps obscure good ideas from elsewhere.
I love what you said regarding straw-clay versus strawbale: "I have become convinced from my investigations over the last 20+ years that straw-clay is a construction method that is more durable and more tolerant of all of the environmental conditions and human errors that a wall system must endure". Can you tell us a little more about LSC and the human errors here. What are most common and less common ones? Any examples?
What I meant is that LSC is somewhat forgiving of on-site weather conditions and construction blunders, in general and in this case compared to simple untreated bale construction. This is a practical buildability concern.
A story to illustrate: some years ago we were helping to build a LSC house with a First Nation tribe in the forests of northern Wisconsin. Construction was running late into the year, and the roofing shingle delivery was delayed. So before the snows descended and halted construction, asphalt paper was stapled down to temporarily protect the roof over the winter. Before the shingles could be installed however, an early Spring brought high winds that blew off some of the asphalt paper. Heavy rains followed, cascading down the roof sheathing and draining surely hundreds of gallons of water directly into the top of one of the LSC walls. Disaster.
We traveled to the site to evaluate. Any other wall system would be trashed under these circumstances, and we expected exactly that. But when we took many core-samples and measured internal wall temperatures to check for decomposition, we discovered none. The low winter temperatures had prevented microbe growth, even as soaked as the wall obviously was. We had dodged a bullet. We shingled the roof immediately and allowed the wall to dry out. We watched the wall carefully as it dried over the subsequent months and we decided it was serviceable.
Obviously this is not ideal, certainly not recommended construction practice. But it does serve to illustrate the robust and forgiving nature of LSC.
Buildings have many enemies and we cannot eliminate the really big ones: gravity, UV sunlight, earthquakes, people. Moisture, on the other hand, is one big foe that we can control. That is, moisture in all of its forms, threaten a building both during construction and during the long years of the building's service life. We design with good foundations and sizable roof overhangs, but we always assume that moisture will find a way to enter the parts of a building anyway, someday, somehow. So we also provide moisture with exit routes.
With a straw bale unprotected during construction, one soaking rain and it's game-over for the bale. Especially in our moist climate, an untreated bale has no way to dry from deep inside, so it must be removed or else it will stay damp inside and rot. In contrast, the hydrophilic nature of clay is actually a mechanism which actively draws moisture from the interior of the wall to the surface. The clay in LSC provides a means, integrated throughout the wall, for it to dry itself from the inside out, forever.
For our house myself and my fiance Arek have chosen a very low density LSC 350kg/m3. What is your opinion about very low densities LSC 300kg/m3 and less? What are your experiences? Have you encountered any particular issues with low densities?
The walls of my house are about 235 kg/m3 in density. After 15 years so far, they're just fine. The key to successfully making low-density LSC walls that are cohesive is well-dispersed, high quality clay slip (we call "slip" the mixture of water and clay/earth). By high quality, I mean slip made with an inorganic earthen material (loam) that contains a high percentage of clay, which is as low in silt as possible and hopefully with no sand. We are fortunate that in our area we can usually source high-clay content loams.
To achieve walls of ±210 kg/m3 and lighter, we use only loam with a clay content of 40% or better. The tables at our website [www.StrawClay.org] shows the mixes needed and various properties for a range of densities of LSC. I must not fail to mention here that a laboratory test is crucial of any loam you intend to use for LSC construction. If you care about creating a well-insulating wall that is also strong and cohesive, you must know accurately what your loam contains — the percentages of clay, silt and sand. Ribbon- or jar-tests are of no help here; they're too inaccurate.
I'm chattering here about insulating value and not enough about wall integrity/stability. Clearly, it's possible to mix LSC with poor clay, or so little clay, or install it poorly, such that it would lack cohesion and fall apart. That would be bad! An exploration of the buildability limits and mix options is a longer discussion, perhaps for another time. But I do note that your home's construction method using horizontal wooden shutters (in the U.S. we would term it "skip sheathing"), while it may consume more lumber overall, does have the advantage of being able to provide good long-term wall stability, no matter how light you mix the LSC.
In terms of research finding, would you please share with us the results of very low densities LSC? Lots of people in Poland are worried that LSC take long to dry and can go wrong all the way because of the moist and only a bit of clay in the mixture. This make people go with strawbale instead.
In Poland, do you use cellulose insulation? It is common in the U.S.; it is made from ground-up newspapers, with a little boric acid added for fire resistance. Contractors install it by blowing with a machine, either dry, or damp to make it a bit adhesive. If you are familiar with this type of moist-blown cellulose insulation, you will understand the parallel to LSC: both are damp installations that dry out over some weeks/months, depending on ambient conditions. In a proper LSC installation the mix should be only slightly damp, not wet.
Good clay and proper dispersing of the clay allows you to use the minimum amount of water in the LSC mix, which translates into faster drying times. In working with high-clay loam, the challenge comes in dispersing it effectively and thoroughly in water. It's possible to achieve full dispersion in low-tech ways, although it is time consuming and labor intensive. We're developing medium-tech equipment to efficiently disperse clay and quickly mix slip with straw, and are working on ways to make the process more understandable, accessible and affordable.
For us these issues are very important because our winters are long and cold. We're trying to improve LSC because we are unwilling to cede energy performance just because we prefer to build with natural, local materials. We now commonly build LSC walls of 38cm (15") thickness and achieve densities in the range of 210 kg/m3 (13-14 lb/ft3 — in fact density comparable to that of a common straw bale). Conductivity is 0.087 W/m°K (R±1.7 per inch). We couple this with a "blind stud" wall framing system that minimizes lumber with very little thermal bridging, for quite good structural and thermal performance overall.
We've been developing techniques to make very light straw-clay, reliably and in real-time on a construction site, because the insulating value of LSC varies directly with density. Lighter LSC walls insulate better, along a predictable curve. Franz Volhard of Germany demonstrated this in the mid-1980s [his new book: www.degruyter.com/view/product/457066], and our Forest Products Laboratory in Madison, Wisconsin confirmed it in 2004 [PDF report available at:http://www.designcoalition.org/StrawClay/research/rvalue.htm]. Our plan for the upcoming LSC book is to provide more complete information and practical, hands-on advice. A Polish translation would be fantastic, if that is in the stars.
Would you like to tell us a little bit about your Polish roots Lou?
My grandfather and grandmother were young Polish immigrants to the U.S. around 1900, he as a laborer from Chodybki and a large nearby farm with a Russian landlord and she as a small child from Poznań. Years later they met and married in Milwaukee, Wisconsin and had 4 children. My father spoke only Polish until starting primary school; then his parents required all their children to learn and speak only English. Milwaukee at that time had many diverse immigrant communities, so it was important that they would blend in. I remember my father telling us that there were likely more Jablonskis in Milwaukee than in Warsaw.
I speak no Polish, but I've always wanted to find a way to visit Poland. Our family has heard rumors of a small place where live many tall Jablonskis. Of our 10 siblings no one is shorter than 183cm, including the sisters, and two brothers are 2.06m and 2.08m. Someday I'd like to find that place.
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| Lou guides the students of Spring Harbor Middle School in building a LSC teaching greenhouse, Madison, Wisconsin, USA |
Thank you again Lou. It was a pleasure to talk to you.
To find out more about our favorite natural building technology Light Straw Clay please go to:
https://www.youtube.com/watch?v=7J0862TFPwU
http://www.designcoalition.org/articles/Natural_LHJ/liteclay.htm
http://www.designcoalition.org/articles/Lansing-LHJ/research/Ktesting.htm
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