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Construction Growing Food Hemp Hemp Research Resources

Self Grown Hemp for Construction

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.

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Books Construction Hemp Resources

Building with Hemp

There is only one book (worthy of being called a book) I know of (in English) – Building with Hemp by Steve Allin. It isn’t the one and only book you will need to actually build with hemp – but it provides the best overview, explanations and images I’ve encountered so far on doing so. It touches on many hemp-effected aspects of construction. You will still have to do a lot more inquiring and apply your own common-sense but this book will be an excellent road-map for you on your journey.

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International Hemp Building Association

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Construction

Learning from Passivhaus Building

The people of Green Building Store (UK) have generously produced and published a freely available online movie about some of the challenges they faced in a Passivhaus construction project in the UK. Though I am wary of taking on the Passivhaus standard as is (reservations I’ve written about in posts about Passivehaus and Rural Studio) I am also trying to be careful not to pour the baby out with the water. There is a lot of common sense in Passivhaus and much of it is excellently communicated in this movie. You can view all the parts here or possibly start with this embedded video and then continue to each consequent part:

So, with much curiosity and interest I watched the movie (reviewing some of the chapters numerous times) and made some notes of things that I hope to incorporate into our building process. This list does not include the core-issues of Passivhaus construction (insulation, minimal thermal bridging, air-tightness, ventilation and passive solar gain) which deserve careful context and consideration – especially when it comes to hemp-lime construction which introduces unique qualities to both the construction process and the resulting structure.

Design & Details

It is invaluable to spend time designing and paying attention to details before the actual construction process. Construction is an established process and skill which carries with it a taken-for-granted attitude. Professionals have a way of doing things and will prefer to do things the way they’re used to doing them – which may lead to cutting corners in design and to on-site improvisation.

This can be destructive in a project where new standards of building, new materials and new techniques are involved. Taking the time to plan things in advance, to drawing diagrams & making calculations creates a thoughtful path towards a desirable result. Of course it is inevitable that unforeseen challenges will arise during construction and that some changes and improvisation will be required – in which case a plan gives some indication of how far you’ve deviated and what you need to do to get back on track.

Special attention should be given to details. I’ve been working on a wall-to-floor detail for weeks – compiling all the information and knowledge I have come across, reconsidering it in the context of hemp-construction, our house design, minimizing costs, minimizing the use of concrete and relying on locally available materials. There is no ready-made template for what we are doing, there are many options to choose from, there are many considerationt to incorporate. We could take the easy path and hire foundation contractors and let them do their thing – but that would lead away from the kind of warm, pleasant, ecological and efficient house we hope to live in and bring us to the standard cold and humid house that contractors have been building in Romania for may years.

Team Work

A typical construction process tends isolate and compartmentalize knowledge and skills. We would consult with an architect to design our house. Then we would pass the plans to an structural engineer who would need to figure out how to support our house. Then we would pass the architectural and structural engineering plans to a heating engineer who will try to provide an adequate heating solution within the existing constraints.

This kind of approach can lead to an inefficient process and an inefficient house. A good engineer can provide a structural solution to meet almost any need – but at what price? How much extra work, materials, construction effort and waste may be required to implement the engineered solution? Similarly a heating engineer can theoretically heat any space – the question is how expensive and complicated will the system be and how much energy will it consume? This is a brute force approach.

We are trying to put together a team that will work together during all phases of the project. We’d like everyone to be there to provide input at every stage of the project. We’d like the architect to provide input on choosing good land and on siting of the house on it. We’d like the structural engineer to make suggestions on architectural decisions that may lead to simpler and more efficient construction using less materials. We’d like a heating-engineer to review the size of our spaces and to make suggestion that may improve the energy-efficiency of the house.

It takes integrated and out-of-the-box thinking to create the kind of integration that leads to a house that facilitates an “eco” existence.

Opening Details

I have been wondering about how to go about properly insulating openinsg like windows and doors. The movie offered some very useful tips about these issues and these are the ones I noted:

  • Windows should be placed at the center (depth) of the wall.
  • Windows should open inwards – placing the thicker part of the frame on the outside for better insulation.
  • Special sealing tape (such as Pro Clima Contega FC) should be applied between the rough structural opening and the internal wall and then covered by the the internal render.
  • Special sealing tape (such as Pro Clima Tescon) should be applied between the window frame and the rough structural openings.
  • A concrete slab should not extend to the door opening to prevent heat loss through it.
  • The door opening slab requires an insulated and weather resistant material (such as fiberglass).

A big thank you to the people at Green Building Company. This movie has been very educative and helpful.

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Construction Siting

Where to Place a House?

So you purchased some land and you are wondering where and in which direction to place your home?

We currently know of three considerations which pretty much answer this question:

  • We sleep with our heads in the east and our feet in the west.
  • We’d like to benefit from passive-solar heat – which means most of our windows (and thermal mass considerations) will be facing south
  • We’d like to have a great view

The order they are in is not random – it reflects our priorities. It’s hard to enjoy a nice view from a cold house. It’s also hard to enjoy a nice view in a warm house unless we sleep well. So sleep, warmth and view is how it goes.

Once that is set it can be useful to get more specific about the actual position of the sun over the months and seasons of a year. You can then place the sun relative to other natural elements in the landscape (hills, trees,etc.) and then decide where is best to place windows to make the best of what sunlight is available.

One way to do this is to actually be on-site for a year and make measurements. When this is not possible there are solar calculators to do the trick for you.

To do this you will need a solar map calculator – a few of which are available online:

  • I think the easiest and friendliest calculator is at PVEducation – where you can easily shift the time of year to see the solar path change.
  • A simple and useful charting tool I found (so far) is SunPosition Calculator which has basic free functionality and extended paid options.
  • A more complex and elaborate tools can be found at SunEarthTools.

To use these tools you will need to find the latitude and longitude of your site location. You can do that here or just search the Internet as there are many freely available online options.

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