For too long the insurance industry has held the owners of straw bale buildings captive while they sway back and forth with the prevailing winds when it comes to insuring our buildings. We begin to address this issue in the first of a series of articles on this topic.
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.
Alex Sparrow begins a two-part series on hemp lime, or hempcrete. Hemp lime is relatively new but is fast becoming part of the natural building lexicon.
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 Stuart Jeffrey Hart
Community Rebuilds is a nonprofit organization that builds straw bale homes for low-income families in Moab, Utah. The homes are built by volunteers who exchange their time for an education in natural building and sustainability. Our student intern volunteers commit to the entire 4 month build, participating in the foundation pour all the way to ‘key in the door.’ Our program is committed to replacing dilapidated, energy wasteful trailers, for highly efficient homes that use a fraction of the energy to heat and cool.
Community Rebuilds was been awarded this year’s “Innovative Path to Zero Waste Award” by the Utah Recycling Alliance. Here is how we achieved it.
To reduce the waste we produce on the build site, we follow the ‘Reduce, Re-use, Recycle’ principle.
Reduce – Our design choices help us reduce the amount of building materials that we use. When ordering roofing metal for example, we use Google Sketch-up, a computer-modeling program, to lay out the exact cuts needed. It shows us where the off-cut from one piece can be used elsewhere. This allows us to order the precise lengths of metal needed, meaning less materials are ordered and we produce the minimum waste possible. All lumber is ordered at lengths specific to the building needs. We order lumber lengths as close to the actual length needed to reduce the amount of material left. The conventional approach is to order only 16 ft lengths, then cut everything from those. The remaining pieces are often too short to be used and are discarded as waste.
A major design choice is for our houses to incorporate natural materials that are compostable. We choose to build the walls of our homes with straw bales, an agricultural industry waste product that would otherwise be burned. Extra bales and waste straw are composted. The homes we build have earthen floors and the walls and ceilings are plastered with earthen plaster. We use a combination of locally sourced sand, clay and straw for all of these applications. Plaster mix that is dropped during plastering or left over at the end is either re-hydrated and used again, or simply spread in the garden to become the soil.
Reuse – We incorporate used and repurposed building materials into our homes to reduce the cost of the homes and to reduce the amount of new building materials required. We construct non-load bearing interior walls with pallet wood salvaged from the local waste stream and earthen plasters. In addition, we reuse functional lumber, tiles, doors, windows, interior lighting and plumbing fixtures, sinks and toilets.
During construction we reuse our waste as much as possible and we try to incorporate other people’s waste material when possible. When sheeting the internal walls of our homes, we use drywall off-cuts from other build sites. Conventional construction crews will not use drywall scraps. Scraps will usually be the end of a 12′ x 4′ drywall sheet. We flip all the 4′ pieces horizontally and use them to span our 2′ on-centre framing. In our homes we piece together a total of 960 sq ft of ‘waste’ drywall. We mesh tape the extra seams and clay slip the gaps, and then our earthen plaster hides all. By collecting the salvageable scraps and using them in our homes we reduce the amount of waste destined for the landfill and save purchasing new materials.
When we are building with other conventional materials excess material and remnants are incorporated in the home as much possible. We use rigid foam insulation sheets to insulate our foundation and underneath the floor. Scrap from this process is saved and inserted into the roof cavity before we blow in cellulose. Some burnable wood scraps are collected together and used by the volunteers in their wood burning cob oven and communal fire pit. The rest is donated to a local family who use it to heat their house throughout the winter. We donated four cubic yards of burnable wood scraps from our most recent build.
We choose to use as little wood that contains glues as possible. This means that more of the wood scraps are burnable. It also reduces the amount of potentially harmful chemicals in our homes. To replace OSB sheeting on the roof, we use rough sawn 1×10 wood for the same price. We have replaced LVL beams with rough sawn 4×12’s. Both of these come from the Colorado Rockies where pine beetles have devastated huge areas of pine trees leaving them standing dead.
Recycle- We challenge ourselves to limiting our waste production to one domestic garbage bin (0.5 cubic yards) weekly. Our waste consists mainly of non-recyclable packaging and cumulates to an average of 8 cubic yards per build. By comparison, we estimate that local private contractors will dump approximately 30 cubic yards of waste during a similar sized build. To accomplish our low waste goals, we begin each new home build by creating pallet-recycling bins on our construction sites. Metal, plastic, cardboard and wood scraps are stored in them. When we need a small piece of lathe to patch a crack, some wood for blocking or cardboard to protect our floor a quick check of the recycling bins can save cutting a new piece. Once the build is over anything that hasn’t been used is recycled. At the end of our previous build we recycled one cubic yard of scrap metal and one cubic yard of cardboard.
Our goal is to create a quality affordable product with minimal waste and environmental impact. In doing so, we educate the next generation of builders how to move towards zero waste. Our students learn how the current building methods are wasteful and inefficient and how, using just a small amount of planning, we can change the home construction paradigm for the better. We are building homes in a smarter, more sustainable way. Our homes’ energy performance, thoughtful construction methods and quality stand as an example for our volunteers, the community and the construction industry as a whole.
Jeffrey was an apprentice and natural building instructor with Community Rebuilds from 2012 – 2013. He is now heading home to his native England to build small, affordable, straw bale homes using the Community Rebuilds volunteer/educate model. He can be found at www.jeffreythenaturalbuilder.com.
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).