Wouldn’t it be ideal if you could grown your own hemp and then use it to build your home? 1 or 2 hectares of hemp stalk is potentially all you need to harvest enough building materials to build a house. Imagine that – growing your own house! … but it isn’t a simple thing to do.
The hemp plant has four elements: seeds, leaves, fibers and a wooden core. The part you need for construction is the wooden core – also called the hurd or shiv. Separating it from the other elements of the plant requires effort. You need to grow the hemp, deffoliate it (remove the leaves) before harvesting, harvest or remove the seeds, harvest the stalk, let it ret (start decomposing so that the fibers can be separated from the hurd) and then decorticate it.
This finally step of decortication seems like the greatest obstacle – this is the process of separating the fiber and the wooden core. It can be done either through massive manual labor (of which I don’t yet have all the details – but it involves collecting the harvested stalks into small bales and then beating them to separate the fibers and wooden core) or in an industrial process. The indutrial process is usually designed to extract the fibers, the actual wooden shiv is simply a left over of that process.
It would be so much easier to grow your own construction hemp if decortication could be avoided – and this may be possible but my understanding is that it depends on the climate you live in. This research paper on Hemp-Concretes claims that it is possible to create hempcrete using both shives and fibers – BUT it is important to note that the research focuses on the structural aspects of the resulting hempcrete. It does not address the effect of fibers on insulation and breathability of the hempcrete.
Introduction of fiber to the hempcrete mix can cause humidity problems. When fibers are clumped together they tend to draw moisture and that is not something you want to happen in your wall. According to Steve Allin it is possible to add 5%-15% of fiber to the mix but not much more. This may be less of an issue in a hot and dry climate – but otherwise the risk seems unwarranted.
Maybe when the hemp industry matures it will be possible to cultivate stalks with very little fiber and a massive wooden core – which could then be used in whole? For now though it seems that self-grown hemp is not a feasibly reliable option for construction unless you have the means to decorticate it.
“… it’s not the materials but the builder that makes a building green”
Clark Snell,Building Green
I first saw a preview of Building Green (I think it was on Google Books) and wasn’t impressed by it. Then Ina & Sabin introduced us to it and loaned us their copy and I was really surprised by it. I have been immersed in the book and gained a lot from it. It doesn’t mention hemp-construction in any way. It does cover many other green building techniques and materials. But most importantly it is written with an appeal to common sense and with plenty of educational images which demonstrate that common sense really does work. Though I will probably not be using any of the building techniques mentioned in this book directly, I will be using a lot of my own judgement to make design & engineering choices and relate to solutions offered by professionals.
To me, the spirit of the book is best embodied in this quote which I have frequently brought up in conversations since it came to me:
“One the biggest sources of our environmental woes is the constant and polluting movement of humans about the planet. To create a sustainable lifestyle, we need to stay put more of the time and derive more of our social, physical and spiritual sustenance from our own backyards. For example, it takes a longtimeto build healthy soil to grow food; to build a network of friends and compatriots that will be the basis for community; to nurture the trees and other plants that will be part of a house’s cooling strategy. These things simply won’t happen if you aren’t sufficiently seduced by your home to stay there for the many years it will take to turn it into a real place that nurtures both its inhabitants and the environment. A “green” house, then, needs to be beautiful, a place that is as hard to leave as a lover and as unthinkable to neglect as your own child.”
As someone who has lived in rented apartments and houses all of my adult life and am now heading towards creating what may be our first and only house in this lifetime I can completely relate. I have been a tourist in most of the places I’ve lived – never quite made it to become a resident of the place.
I’ve been struggling to understand on if/why a concrete slab is necessary. I completely understand the need for footings and foundations – but slabs are not that clear. It’s somethinge eveyone seems to take for granted … but I am undecided on it.
Anyways … I did come across this excellent free eBook generously published by Cement Concrete & Aggregates Australia – which seem to have many more freely available resources on their website. IF we do end up building with concrete foundations (yep – that’s an if!) we will probably hire a contractor for it – it’s one of those jobs where DIY doesn’t seem to have much point/value. Even so – this eBook is a must read because at least I know what to expect, to relate to engineering/design choices and to make sure things are getting done right on site.
I will probably be spending some time with their resources – I’ll let you know if I find anything interesting 🙂
I found this inspiring post on do-it-yourself windows – I found it inspiring because it shows how far you can get on your own with only basic carpentry skills. The price from a professional craftsman was $5500 but in the end they were built in 4 days using $540 worth of materials!
Though I am wondering though if (1) this approach can be scaled up to a larger home and (2) if, with a reasonable investment in time and materials, it is possible to create longer-lasting and energy-efficient windows?