This article first appeared in The Owner Builder 192 December 2015/ January 2016. www.theownerbuilder.com.au
By Maggi McKerron
Ten years ago I fell in love with a mountain. Mt Chiang Dao rises 2173 metres out of the forests of northern Thailand, its jungle covered peaks dressed in swirls of clouds. I leased a piece of land on a small hill facing the mountain. Under half a hectare, the land slopes down to a small rural Thai village under the mountain, clustered around the nationally famous Chiang Dao Cave.
Planning a B&B
I was approaching upper middle age and realised I needed to make some sort of plan for older age when my life might possibly slow down a little. This piece of land would be perfect for a B&B!
I did not have the money to develop the land, so I took off for the UK to make some. Although I am British, I was born in India and have always lived in Asia. Going to the UK to work was a challenging experience, as I had to learn to live in a western culture for the first time, at the age of 56.
While in the UK I took the opportunity to study natural building, beginning with an inspirational earthbag building workshop taught by Paulina Wojciechowska, author of the first book on earthbag building. Making a dome out of earthbags sold me on domes and round dwellings. I was determined to build round domes back in Thailand!
But using earth as the building material did not sit right with me. I am mildly asthmatic and need dry air and did not relish the thought of being enclosed in an earthen dome during six months of monsoon rains. I thought about rice husks. This is a product that no one wants. It takes ages to break down if added to compost, and is difficult to burn. It is also a desiccant, which means that it will draw moisture out of the atmosphere. Perfect!
After seven years in the UK I finally had enough money to return to Thailand. At least I hoped it was enough. There was no way I could calculate the costs of the buildings in any detail, as I did not really know how I was going to build my rice husk domes. I couldn’t find any information on the internet: no plans available, no books on building with rice husks. I worked out a financial guesstimate, which I finally reached in savings, and I bought a one way ticket back to Thailand.
My beautiful land was covered in towering brush and it was not until a team of machete wielding villagers cleared it that I discovered how steeply it sloped. What a challenge this was going to be!
I should mention here that where I was building, out in the scarcely populated countryside, planning permission, although preferred by the local council, was not an issue. In towns and cities I would have had to submit plans. My local council signed off the building after it was finished.
Beginning the build
Ready to begin my adventure, I posted on social media that I would welcome anyone who would like to help with the project, and people turned up. I hired some local day labourers from the village. We found the flattest area, at the top of the property, and one of the first steps was to prepare for a concrete base. I had been warned by locals that the termites were ferocious and there really was no alternative to concrete.
We marked out a circle 5.5 metres in diameter with some bamboo stakes. Then we got some tubing and filled it with water, and tried to find a level. No one believed what the water in the tubes was telling us, so I went and bought a spirit level. This confirmed the water’s message; there was still a big slope, even though compared with the rest of the land it looked practically flat. Leveling the area was our first task.
My very rough plan showed a concrete cap on the dome, as this was all I could think of to keep out the monsoon rain, so our next task was putting up six concrete posts to carry the weight of the concrete cap. Then the base of sub soil and stones went in, pounded flat
by enthusiastic volunteers, a trellis of bamboo for strengthening, a sheet of plastic as a damp proof membrane to stop moisture leaching upward, some sand and a final topping of concrete.
Now I needed to seriously consider the dome. I could not for the life of me work out how to construct it. Unlike earthbags, which are load bearing and could support a concrete cap, I was working with lightweight, not at all solid, bags of rice husks. I spent ages in hardware stores, second-hand wood shops and looking through books. I asked various local builders, but one after the other they shook their heads, mystified with the ideas of the crazy foreign lady.
At one point I decided to forget the dome and just build a hexagonal roof using the steel for conventional roof frames. One of the volunteers said: ‘But Maggi, your dream is a dome. You must follow your dream.’ So I thought again.
I found reinforced steel rods, rebar, bendable and long. I could buy quite thick pieces and long enough to go from one side of a dome to the other. First a piece of rebar was bent into a circle to go around the building, sitting on the top of the concrete posts. Then up went the rebar making the dome shape and we wired it onto the posts and horizontal rebar. Using different thicknesses of rebar and adding bamboo we made a dome shaped trellis.
The bamboo for the trellis in the dome came from bamboo poles we harvested from the land. These we cut and prepared and wove as needed. We used the same trellis idea for the walls, and our bags of rice husks would be attached to this frame. The whole thing looked like a giant bird cage!
The windows and doors were added as we built the bamboo trellis. This was complicated as the walls were going to be quite thick, so windows and doors needed frames to sit in. We learned as we went along. At no point in the building did we use any electrical tools – there was no electricity!
Rice husk walls
Filling in the walls came next. I found a place that sold second-hand polypropylene bags and had bought several hundred. Then I found a rice mill that agreed to fill the bags for me with their waste husks, 200 a week. These we had been collecting in preparation.
The first layer of bags was filled with gravel to guard against water and moisture damaging the walls, with a layer of sand on top of that, then the bags filled with rice husks. We experimented with different types of string, and different knots and found the method that worked best. They went up quickly and easily in a couple of days, and soon we were at the level where the curve of the dome began.
The bags were too big. They would be too unwieldy and heavy to attach. We had to empty them, refill them with less rice husks, then tie them up in the shape of a sausage. Our sausages were quite complicated to put up as we were attaching them to the inside of the dome to continue the inside line of the walls.
The dome looked wonderful! The next step was to put on the concrete cap. We used plastic sheet covered with chicken wire and put the concrete on top. We made deep overhangs to protect the walls.
The last step was the mud on the walls. It took a while to perfect our recipe as putting plaster on bags of rice husks is not the same as putting it onto earthbags or straw bales. The bags were not solid, so plaster had to be built up slowly in several layers until it was firm and strong. Then a final layer of lime plaster, followed by some decorations, and our dome was finished!
The big lesson I learned was never to put a concrete cap on a dome in the kind of climate found in Thailand. It cracked, and cracked again! But because the rice husks dry out so easily it has not caused any lasting problems. The second lesson was to attach the bags to the outside of the dome trellis. Much easier!
Three years have gone by since the beginning of the adventure. I have three domes and five roundhouses with thatched roofs. All the buildings with their thick walls of rice husks covered with earthen plaster are cool in summer and warm in winter. I have a beautiful home, made from three of the five metre roundhouses, joined by thatched walkways. My B&B is up and running. And every day and all day I can see my mountain. My dream has come true.
Maggi will be running a roundhouse building workshop in November 2017. See website for details: www.chiangdao-roundhouses.com
Links & resources
Sharing her adventures of living – and building – in Chiang Dao, northern Thailand.
Chiang Dao Roundhouses
Set on the side of a hill overlooking the spectacular Mt Chiang Dao, offering rice husk workshops and B&B accommodation.
Carole Crews leads us on a journey through the parts of our home made with earth and water, but also tells an important story along the way.
We review the first comprehensive how-to guide covering the topic of earthen floors. Find out why you should have it in your natural building library.
by Tom Woolley
Ed Note: More in-depth information on hemp lime will be in Issue #64 due out in July.
When Rachel Bevan and I did the research that led to the publication of Hemp Lime Construction in 2006-7 (IHS BRE Press ISBN 978-1-84806-033-3) we had a fairly good idea of the location of every building using hempcrete in the UK and Ireland. Seven years or so later it is impossible to keep track of the use of this remarkable composite building material as it has become commonplace in the UK. This is good news because it is evidence of the widespread acceptance of this excellent sustainable way of building. However once such an innovative form of construction becomes so widely used there is also a risk of careless and poorly supervised construction, detailing and specification if it is used by people who expect it to behave like ‘conventional’ materials. Fortunately a new book : The Hempcrete Book: Designing and building with hemp lime will soon be available . By Alex Sparrow and Will Stanwix it will be published by Green Books (ISBN: 978 0 85784 120 9 )*** and will set out guidance for best practice in building construction for hemp lime
Hemp Lime construction is a method for creating a natural “concrete” which provides a solid wall system either cast around or within a timber frame structure. The composite uses small pieces of hemp shiv or hurd, which is the chopped up woody core of the plant and then mixed with water and a special lime binder mix. It is incredibly strong almost as soon as it is cast into formwork or sprayed onto permanent shuttering. The formwork can be removed almost straight away or left on for 12 hours before casting the next lift. It then takes a couple of weeks to dry out and longer to gain its full strength. Sceptics often ask, “why use hemp, and why not use wood chips or straw?” people often say (there is an inbuilt prejudice because of its relationship to Marijuana). The best way to convince such people is for a practical demonstration and it is possible to see straight away the strength of the composite. Hemp is much tougher and can cope with moisture better than other cellulose materials.
The resulting composite provides a solid wall with superb air tightness capabilities and very good insulation. Its density of 300-400 kg/m3 is strong but light and contains air pockets in the tubular hemp plant structure giving a “u”value of about 0.2 for a 300mm thick wall. (Lambda 0.06/mK). In practice the thermal performance of hemp lime, or hempcrete as it is often called, is enhanced by its thermal mass and thus the actual performance of a building is often much better than predicted by the abstract thermal resistance figures. Hemp Lime also has the benefit of being full breathable and hygroscopic so that humidity is controlled. Because of this it has been adopted by major commercial food and wine storage companies* to insulate storage warehouses as the walls provide a stable temperature and indoor climate without the need for heating, cooling or air conditioning. Hemp lime insulating walls have also been used by the British Musuem for storing special artifacts.
Hundreds of social housing schemes and one-off private houses have been built using hemp lime and it has also been used in major public and educational buildings, 5 or 6 storeys high.
Hemp lime is versatile so it can be used as an infill in multi-storey construction, in floors and roofs, as a renovating or insulating plaster and as an external render for straw bale buildings and other eco forms of construction.
Supply of materials has not been fully sorted out yet. Hemp shiv or hurd is readily available but not always in the right place so it has to be transported from processing factories where the hemp fibre is stripped off the plant. The hemp fibre is a valuable crop with a thousand uses, so the shiv used for building is almost just a by-product. Making or sourcing the lime binder is also tricky. There are a range of proprietary products available such as Tradical, Batichanvre and recently Ciment Prompt [French]. These are not always available from local suppliers of building materials. It is possible to mix up your own binder but it is essential to use the right materials with careful quality control. The binder is largely lime based, mainly hydraulic lime but some hydrated lime and or cement is also added. There have been a few “cowboys” who have been supplying hemp and lime materials that are not fit for purpose and this has led to a few building failures. Their main mistake has been to use cheap hydrated lime, often too much water and hemp fibre as well as shiv. One company even says it is more ecological to use the whole of the hemp plant even though this invariably leads to a soggy mess. We are working hard to establish proper standards. Sadly the internet gives people partial information about how to build with hemp lime and makes them into overnight experts.
In some ways hempcrete is easy to use and is even tolerant of misuse, within limits, but this means that there are many dangers and possible pitfalls. On the other hand, once you become aware of its advantages it is hard to find another way of building walls, (and possibly floors and roofs), that can meet so many of today’s demands of sustainable, healthy and energy efficient construction so successfully. As pressure builds to meet ever more strenuous energy efficiency targets, many weird and wonderful building techniques and materials have appeared in the market. While some mainstream architects and clients have embraced hemp lime quite quickly the construction industry is still largely wedded to synthetic petrochemical based methods of construction that contain many risks both to the health of building occupants and the planet. Valuable and non-renewable fossil fuel resources produce significant CO2 emissions even though ironically they are being used to reduce such emissions! Recent research shows that many so-called low or zero energy buildings consume more energy in producing the materials and construction (embodied energy) than is saved in the lifetime of the building. These synthetic quick fix approaches to building also present serious fire hazards, emit toxic chemicals. Leading to poor indoor air quality and pollute the planet when disposed of in landfill. Despite this the devotees of “Passiv Hause” in the UK tend to use synthetic materials, though there are a handful of Passiv Haus projects in Ireland that have been built with hemp.
Hempcrete is not only a low embodied energy material, it locks up CO2 in the building fabric. While land is required to grow it, hemp is also a valuable food crop and is used as an intercrop between wheat and other cereals. Those who are fixated on the ‘techy’ quick fix synthetic solutions, disparage hempcrete as being too slow to construct and dry out and not giving good enough thermal performance. However even the most deeply prejudiced, once they actually experience hempcrete, are soon won over. Despite the obstacles to using hempcrete, its rise has been rapid as it almost sells itself as a solution to producing environmentally friendly buildings. Hemp lime is widely used in France and recent workshops in Holland, Denmark, Sweden, Poland etc. have led to projects in many of these countries.
In many ways hempcrete is a touchstone to the adoption of a sustainable and environmentally responsible approach to building and renovation because it provides a key to solving so many problems that other materials and buildings systems cannot cope with. As hemp can be grown in so many parts of the world, providing it is not too arid, it can be a solution to insulating buildings in poorer developing regions as well as the gas guzzling western countries. Hemp provides food, oil, clothing, paper and many other products as well as building insulation and weather protection. Hempcrete in conjunction with timber, as long as it is used carefully, should last much longer than many of the petrochemical based greenwash materials being used today.
Designing and building with hempcrete is a real demonstration of a total commitment to ‘saving the planet” and protecting the health and wellbeing of building occupants. It’s an easy commitment to make because hempcrete is affordable, great fun to build with and ticks all the boxes that envirocrats can come up with.
*Companies like The Wine Warehouse, Marks and Spencers etc.
Tom Woolley was Professor of Architecture at Queens University Belfast from 1991 to 2007 and now works for Rachel Bevan Architects. He created the first strawbale building, in Crossgar County Down 1997, to receive full planning and building regulations approval in the UK and has gone on to be one of the pioneers of hemp lime construction. He has written a chapter about hemp construction of the new edition of The Art of Natural Building (Chelsea Green) to be published later this year. He will be running a workshop on hemp lime construction at the Endeavour Centre** in Ontario November 1 and 2, 2014 and lecturing at Ryerson University in Toronto on October 30th 2014.
Tom is part of a group of architects and builders that are establishing a hemp lime association in the UK. He is also on the European board of Natureplus, a certification system for ecological materials. www.natureplus.org
An example of a hemp lime building that can be rented as a holiday cottage can be found at http://www.irishcottagesdown.com/cottages/downpatrick/hempcottage.htm. There are links to some technical details and a video showing the construction process.
** Contact Chris Magwood for details
***The Hempcrete Book: Designing and building with hemp lime
by William Stanwix and Alex Sparrow
ISBN: 9780857842244 Full colour Hardback 272 Pages Publication October 2014
Pre-order The Hempcrete Book through www.greenbooks.co.uk and all good high-street and online retailers
To qualify for 20% off the cover price, join the pre-publication mailing list at http://eepurl.com/OMZoT
By Elaine Brett
Twelve years ago I had never even heard of building with straw. I lived in a four-bedroom colonial house in a subdivision in Maryland. The conventional American Dream – good job, big house, nice cars, the monthly lawn service, the health club membership, 24/7 access to shopping …
Then on my 49th birthday came the American nightmare. A wake up call from Mother Nature. Sometimes she needs to smack you hard to get her attention. My wake up was a cancer diagnosis that sent me spinning into a quest of asking questions and trying to understand “how could this happen to me?”
One path of my quest (probably driven by my background as a chemist) sent me questioning the chemicals in my environment: the food I was eating, the air I was breathing, the water I was drinking, the lifestyle I was living, the buildings in which I was residing and working. The answers took me beyond the overt pollution of urban air and water to the hidden nooks of micro pollutants in synthetic materials, chemical food processes and endocrine disrupters in simple everyday products.
The quest also took me on another path. I began looking for a place to live clean and chemical free, or at least as clean as is possible. And that’s how I came to a small town in the North Fork Valley (www.northforkvalley.net) in Western Colorado.
This article appeared in TLS #59
by Tim Beatley – Virginia, USA
Reprinted with permission from Residential Architect magazine, November 2005.
We live in disconnected times. We occupy space but know little about it. Instead of joining communities or neighborhoods, we buy houses and make real estate investments.
Sustainable design offers us the chance to rekindle these lost connections, to rebuild knowledge of place. New residential development is commonly thought to bring more cars and traffic, higher taxes, overcrowded schools, diminished views, and open spaces. But there is a way to turn this around – if we can imagine new growth connecting with and strengthening our sense of place. This kind of green design might take many forms, but just a few possibilities are mentioned here.
One idea is to locally source building materials. In our globalized economy, such materials can originate hundreds or thousands of miles away from where they are eventually installed or assembled. They contain a high embodied energy, and their extraction often entails substantial ecological impact. Paradoxically, much of the practice of green building has emphasized materials, such as bamboo flooring, that are transported great distances.
We need to look much closer to home, to materials that nurture local livelihoods and reconnect us to place and land. An innovative sustainable wood initiative here in Virginia holds some clues and offers some inspiration. Operated by Appalachian Sustainable Development (ASD), it supports the local economy by working with small wood-lot owners who are willing to manage and harvest sustainably. The wood produced is beautiful, durable, and distinctive (more of the tree is used, with knotty “character” wood a key result), and it is certified under ASD’s Sustainable Wood label. It is then dried in a solar- and wood-waste-powered kiln and cut into flooring at ASD’s mill.
My family and I recently installed ASDcertified white-ash flooring in our home. As a result, I know where the wood was grown, and I have some assurance that the result for the landscape is not destructive but rather restorative. In this case, a sustainable material close to home was actually less expensive than its standard commercial alternative. It is a small expression of commitment to
sustainability but an important step on the way to a deeper connection and duty to place.
Using local materials is a growing practice in sustainable design communities. Innovative green projects like BedZED, the Beddington Zero Energy Development in the London borough of Sutton, have explicit targets for local materials. At BedZED, more than half of the building materials arrive from sources within a 35-mile radius of the site. Wood siding comes from local municipal forests, bricks from a local brick company.
In Western Australia, there has been a creative effort to nurture furniture building and wood artistry. Rather than exporting logs (or allowing them to be converted to low-value wood chips and then exported), there is a growing sentiment that these resources can be the foundation of a highvalue-added, labor-intensive economy, of which sustainably managed forests can serve as a linchpin. Among other steps, a forest heritage center and school of fine furniture making has been established there, and the number of outlets for locally made wood products and crafts is growing.
Much of our food comes from very far away. It typically travels some 1,500 miles from where it is grown to where it is eaten, according to the 2001 report “Food, Fuel, and Freeways,” and we are usually oblivious to these origins. New developments could begin to think more carefully about the food needs of their future residents, perhaps developing long-term relationships with local growers. This is essentially the concept of Community Supported Agriculture (CSA) residents buy a share in a local farm that provides (often delivered) a basket or box full of produce each week during the growing season. CSA farms are growing in popularity – there are now more than 1,500 of them nationally – and they could be offered as part of the package that goes along with a new home (or at least as an option).
Designing in opportunities to grow food directly is another way of promoting sustainability (and healthier living), strengthening place, and re-earthing us. This is a trend in Europe, where ecological, mixed-use projects such as Viikki in Helsinki, Finland, have left green fingers between major buildings for garden plots. Single-family homes might be designed to facilitate this as well. A model sustainable home in the Perth, Australia, suburb of Subiaco, for instance, includes extensive edible landscaping and a built-in raised-bed vegetable garden in its backyard. The garden is large enough to produce all the vegetables a typical family needs.
Energy use is another way to reconnect with local places. Every place has opportunities to generate its own power, whether through wind, sunlight, or biomass. Strong European examples exist of communities that have been able to redirect community resources to local energy production. In Aeroe Island, Denmark, which aspires to be 100 percent energy independent, small power plants generate energy from the sun and from locally grown straw and hay. Expenditures for energy stay local and help to strengthen, not diminish, the region’s economy.
A more urban example is the redeveloped district of Vastra Hamnen in Malmo, Sweden, where a variety of renewable energy technologies and design ideas have been incorporated into dense housing and the ambitious goal of 100 percent renewable energy from local sources has been met. Energy production is a visible element of the community, with vertical solar hot-water-heating panels feeding into a district heating grid.
BedZED again offers inspiration with an on-site combined-heat-and power plant fueled by wood waste from tree trimmings. In Freiburg, Germany, the Solar-Fabrik solar-technology factory burns oil from locally grown rapeseed in a carbon-neutral cycle, further demonstrating the power of combining green and local.
The energy consumed by residents and the embodied energy associated with new building materials might also be compensated for in ways that creatively restore and renew bioregions. In the U.K., the Carbon Neutral Company works with banks and building societies to offer a carbon neutral mortgage, which provides for the planting of enough trees to cover the carbon footprint of the home and lifestyle of its occupants. In Australia, similarly, several banks are now offering carbon-neutral car loans. Habitat and place restoration can happen in many ways, of course, but local tree planting holds potential for productively harnessing the green sensibilities of people on behalf of place.
In an increasingly turbulent and globalized world, rebuilding lost place and human connections in a host of creative ways provides solace, strength, and reassurance. Sustainable design must strive not only to reduce its overall ecological impact, but to do so in ways that enable us to be truly native to place.
Residential Architect magazine www.residentialarchitect.com
Appalachian Sustainable Development
Beddington Zero Energy Development, an environmentallyfriendly,
energy-efficient mix of housing and work space in
Beddington, Sutton, United Kingdom.
Viikki Eco Neighbourhood Blocks – Finland
The CarbonNeutral Company, United Kingdom
Toward Sustainable Communities: Resources for Citizens and
Their Governments by Mark Roseland, Sean Connelly, David Hendrickson and Chris Lindberg.
Developing Sustainable Planned Communities by Richard
Franko, Jo Allen Gause, Jim Heid, and Steven Kellenberg.
Sustainable Communities: The Potential for Eco-neighbourhoods
by Hugh Barton.
Designing Sustainable Communities: Learning from Village
Homes by Michael Corbett, Judy Corbett, and Robert L. Thayer.
Fostering Sustainable Behavior: An Introduction to Communitybased
Social Marketing by Doug McKenzie-Mohr and William Smith.
Ecovillages: A Practical Guide to Sustainable Communities
by Jan Martin Bang.
Sustainable Communities: Learning from the Cohousing
Model by Grahm Meltzer.
Green Cities: A Guide for Sustainable Community Development
by Michael Bloomfield and Michael Lithgow.
Sustainable Communities Network www.sustainable.org
Links citizens to the resources they need to implement innovative processes/programs.
Intentional Communities www.ic.org
Information on ecovillages, cohousing, intentional communities, urban housing cooperatives and other related projects.
School of Living www.schoolofliving.org
Nurturing healthy, Community Land Trust Communities.
New Urbanism www.newurbanism.org
Many choices for living in more sustainable, convenient and comfortable places.
Tim Beatley is the Teresa Heinz Professor of Sustainable Communities at the University of Virginia. This article is based, in part, on ideas discussed in his book Native to Nowhere: Sustaining Home and Community in a Global Age (Island Press, 2004).