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 Andrew Morrison of strawbale.com
There are many different approaches to framing a straw bale house; however, there is one in particular that I have used on the vast majority of my projects over the years. It is a post and beam frame system with roots in conventional framing techniques. Because I came to straw bale construction many years ago as a general contractor practicing conventional construction, I brought some of that detailing over. I should preface this article by saying that there are right ways of framing and wrong ways of framing. The system I describe in this article lands in the “right way” column, but so do many other styles. As long as you are working with a structurally sound and safe system that brings you the best results possible for your style of building, then go for it.
One of the first details that often surprises people is the spacing of the posts in the system I use. I hear people talk about wanting to reduce the amount of notching in the bales by spreading their posts out as far as possible. I disagree with this approach and instead keep my posts relatively close together: no more than 6’ apart. One reason for this is that when the bales are stacked in between posts that are set far apart, there is no point of attachment for the bales other than the top and bottom of the wall. As such, the wall becomes weak as it is stacked higher. When posts are set closer together, the notches at each location provide a point of connection to the frame and make the wall much stronger both during construction and for the life of the structure.
One way I keep the posts close together is by incorporating them into the window and door frames. By using 4×4 posts as the king studs I end up with wider nailing surfaces on either side of the opening. This allows me to attach the finish trim, plaster channel and/or plaster lath, and welded wire mesh around every opening with positive attachment to the frame. These king studs serve two purposes by providing the nailing surface and by acting as part of the overall structural frame. Because windows and doors are placed in many locations around the home, and because I otherwise limit my post spacing to no more than 6’, I can minimize the wall beam size as a result. This minimal wall beam is important because the bigger the beam, the more expensive it will be. Further, larger beams are made from larger trees (unless an engineered beam is used) and I want to reduce the size of the trees I am using in my projects for environmental reasons.
Okay, let’s take a look at how the system works and why it can save time and money in your building process. I’ll simply lay out the process so you can see, step-by-step, how it comes together.
By Huff ‘n’ Puff Constructions
Editors Note: We plan to have a comprehensive article covering as many of the tilt-up straw panel systems on the global market as we can in Issue #64 due out in July. Please also note that the images associated with the thumbnails on this page are of large size. We wanted to keep them original size to allow you to see details clearly.
Recent times have brought an increasing wave of environmental and energy efficiency awareness in the building industry throughout Australia. This increased awareness of the effect of logging on our forests, lakes, and streams, as well as heightened concern for the energy cost and efficiency of our buildings and ever-increasing costs of construction materials is bringing tremendous pressure for change to the Australian building industry.
A primary focus of this change is the development of alternative forms of construction for single and multi-family housing as well as commercial and industrial buildings. With a tradition that dates back almost 200 years, the Australian building industry has utilized timber extensively for use in wood frame construction, concentration on wood framing timber as the principal raw material for the structural shell of the majority of our housing and much of our light commercial structures has tremendously diminished our hard wood and softwood forest resources in Australia.
The cost of framing timber has more than doubled in the past five years. The price of timber is projected to continue to rise over the course of the next decade with additional concerns over the quality and availability of that timber. The price and in some areas the availability of energy has added a new and important factor in most building projects. With these facts in mind, the building industry, known for its rigidity and resistance to change, will have to look at replacement materials for framing timber in home and commercial construction.
We are in the process of developing and bringing to the market place a unique, and ecologically sound, structural insulated panel building system. These panels will be able to be put into place by two people. This structural panel system provides a cost-effective, building system that is based on an environmentally responsible manufacturing process.
Huff ‘n’ Puff Constructions are manufacturing a structural super insulated panel that uses as its core material waste agricultural cereal straw from wheat and other cereals commonly grown in Australia.
With the recent high rise in energy costs and energy availability this product’s value to the builder and his client is a product that is more important now than ever before. THE SITUPS* is highly competitive to conventional building methods. With the reduced construction time, energy savings, non-toxic nature of the product, and strength and durability of the product indicate we have a building system whose time has come.
It was on the banks of the Murrumbidgee River at Hay that we made our first SITUP. This event was first published in The Last Straw many moons ago now. It involved a BIG chain saw and a jumbo straw bale 2.4 m x 1.2 m x 1.2 m (8’x4’x4’). We made three panels out of the one bale and had a lot of waste with the “method” we used at that time. Back to the drawing board… [Huff ‘n’ Puff shared this technique in TLS #24, Winter of 1998]
In between building straw bale houses and wineries we kept on refining the process over the past 8 years. Eventually we got an order to make 60 x 2.4 x 1.2 x 150 mm panels for a straw bale house that we were building in Kangaroo Valley, near Sydney. These panels were to be used for the internal walls and are non-load bearing.
We had these internal panels tested at the University of Western Sydney. Our tests were to establish their load bearing and wind loading capacity. They did not pass muster for load bearing but showed us their potential. However the size of 150 mm wide proved to be very hard to manufacture and will need a lot of refining in the process to make them a worthwhile proposition.
FIRST LOAD BEARING PROTOYPES
After many experiments and research we have chosen a method that we feel has the potential to change the way we build with straw bales now and into the future. We also realise that several straw panel systems are now on the market in parts of Europe and Canada. Our opinion is that more is good and will only lead to the acceptance of building a house, flats and even high rise units and many other types of building by adopting straw as the medium in tilt-up wall technology.
We have now completed two SITUP buildings in New South Wales. One close to home in a suburb of Wagga Wagga, and the other on a farm near Yass, which is close to Canberra. We are now filling an order for a three-pavilion SITUPS home in the Hunter Valley of New South Wales.
The SITUPS are currently 2.450 to 3.000 metres high and come in various widths from 600 mm to 1.2 metres. We can also make them between 350 mm and 450 mm wide. The cladding can be a variety of material from renders to weatherboard, corrugated iron and many other forms of external sheeting. Internally they can also be clad in render or Gyprock and various types of lining boards.
We are also developing a portable SITUPS factory to make these on a building site.
The SITUPS will greatly reduce carbon emissions from new buildings through savings during manufacture and the operation of the building. We already know this, having built many straw bale buildings since 1998 and together with 145 straw bale building workshops now completed.
Our goal is twofold; first, to reduce the carbon impact of modern buildings with the SITUPS and; second, to be able to utilize a waste product of our wheat and rice cereal growing in Australia where rice straw alone is burnt at an alarming rate. Some one million tonnes goes up in smoke (particulates and carbon) every year. Enough straw to build, say, 44,000 three-bedroom SITUPS homes on an annual basis and that is only from the rice grown in one area of Australia.
All the other benefits that come with straw bale homes that we have know of and practiced over the past 17 years apply equally to the SITUPS. The main difference to conventional building with straw bales is that the SITUPS are uniform pre-compressed at time of manufacture and hence are very fast to build with, saving time and money.
* The SITUPS is a registered trademark of Huff ‘n’ Puff Constructions
John Glassford and Susan Wingate-Pearse, The Straw Wolf and My Little Wolverine
Huff ‘n’ Puff Constructions
22-24 Moore Street
GANMAIN N.S.W. 2702.
61 2 6927 6027 Work
0412 11 61 57 Mobile
By Frank Tettemer, ONBC Director
This definitely was the most fun to be had all winter.
Timing is everything, and this year’s gathering of the clan at Camp Kawartha, near Lakefield Ontario, warmed my heart during one of the coldest of Canadian winters. With temperatures outside the straw bale conference room dipping to -24C (-11F) at night, the crackling fire in the wood stove provided a popular place to gather around over the weekend.
Tina Therrien’s welcome and opening remarks on Saturday morning lit the flame of curiosity and instilled the warm comradeship that nicely permeated the weekend conference. Her dedication to forming the Ontario Straw Bale Building Coalition 15 years ago, and her continuance as Chairperson has been instrumental in supporting this organization’s transformation into what it is today; the Ontario Natural Building Coalition. www.naturalbuildingcoalition.ca
Jacob Deva Racusin spoke of many things around building impact, social justice, and creativity. Lessons learned were all about making straw bale walls using additional layers and materials. The synergy of plaster, straw, cellulose, rain screens, and cladding can easily place natural materials into the Passivehaus world of warmth.
Chris Magwood’s presentation reached out to owner-builders, professionals, and designers, about the importance of setting goals and priorities, well before the excavator arrives on site. Emphasizing that everyone’s needs are different, and establishing priorities for each individual is the first step in good design. And when it’s time to compare different materials and building components, his new book, “Making Better Buildings”, covers everything vital and appropriate.
David Eisenberg’s warm voice and brilliant experiences always open my heart. While transplanting Kathleen O’Brien’s Emerge Leadership project to the forests and lakes of Ontario, he found fertile soil, within this group of 80 aware and alert natural builders. Though it must have been a challenge for him, to travel the distance with a temperature difference of +80F to -11F, ‘Desert Dave’ seemed undaunted, as he patiently germinated the seeds for emerging leaders, to carry on the work of building not just net-zero housing, but to develop ways in which every new building is restorative and adds benefits to the natural environment.
Dawn Marie Smith traveled from Victoria, BC to show us how to use alternative methods to achieve code acceptance and obtain that elusive building permit. Reaching for the carrot of sustainable building is not always easy, and the ASRi and their publication, the Alternative Solutions Resource Initiatives’ Straw Bale Alternative Solutions Resource (ASR) manual, has made the work of digging these carrots much more straight forward. I loved how her experiences with Emerge Leadership helped to add sprinkles of additional insights during David Eisenbergs’ presentation.
Relaxing after dinner on Saturday, we were treated to our own 5×5 slideshow – five photos from a couple dozen contributors – who each had five minutes to talk about their photos. Hilarious and inspiring, the show was a fun warm-up to the evening, that included libations from a selection of organic wines and craft brewed beers from the Bale Heart Bar, that livened up our senses for socializing, while singer-songwriter Rick Fines strummed and sang, caressing the spirit of inspiration in us all.
Did I mention how well we were treated and fed by the Camp Kawartha cooks? They really knew how to accommodate the evolved diets of our participants, with delicious meals and healthy snacks.
Thanks to all, for your spirited participation, in making this year one of the finest conferences ever.
Dawn Marie Smith – http://www.asri.ca/
Rick Fines – http://rickfines.ca/
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.
By Ryan Chivers
With the modern development of natural building technologies, there has been a resurgence and rediscovery of ancient and traditional methods of plasterwork. For over 10,000 years, in nearly every culture, humans have used lime as an applied material that serves as both function and decoration. From the frescoes of the Italian Renaissance to the sculpted bas relief masks of the ancient Mayans, the chemistry, durability and elegant beauty of lime has, until modern times, been a staple of art and architecture the world over. In the twentieth century, builders have all but forgotten how to work with earth and lime based mortars, and plasters. Thanks to the efforts of passionate builders, craftspeople, architects and designers, and many within the natural building community, these old ways are being revived and put into practice once again. Collectively we are relearning how to successfully formulate and apply traditional plasters, using locally sourced materials and modern tools.
The rich and mysterious culture of Morocco offers one example of an ancient lime plaster art, nearly lost, which is now enjoying a rebirth – Tedelakt