I believe and have passionately shared my belief that hemp-lime construction is one of the best methods of construction available today (at least in the Romanian climate in which we live). We were planning to build with hemp-lime and our architect designed a magnificent house for us – unfortunately we could not afford to build the house so the project stopped and we are living in the slightly renovated traditional Romanian house on our property.
Building with Hemp was going to be an uphill effort. It was difficult to source materials (we finally found some hemp in neighboring Hungary) and natural hydraulic lime (NHL) is also a rarity here (we found it imported from Italy and Germany). It also seems we would have had quite a challenge mixing the hemp-lime mortar since the best suited tool (pan mixers) are not to be found here. We also had a relatively short window-of-opportunity to build since hemp-lime needs to set (~8 weeks) before the first frost appears – and it arrives early here. So despite our passion and investment in hemp we can say in retrospect that there were many cues pointing us away from it.
When we realized that there wasn’t enough money to build the designed house we started looking at ways to scale down and simplify the house so that we could build it. One of the things we explored were the foundations. Though we had relatively cheap foundations they were still a major expense in the project.
Our house is to be built on a gentle south-facing slope and the plan was to excavate so that the back of the house the excavation was about 1 meter deep. Then we would fill the entire surface with rocks – starting with large rocks (~40cm) and then adding layers of smaller and smaller rocks until we arrive at gravel and sand. On top of that there would be a concrete slab which we preferred to avoid but was required due to the green-roof planned for the house.
With these foundations planned and in mind I first came (about a month or two ago) across two new (to me) themes: rammed-tire construction & underground houses.
Rammed tires is a method of construction where used car-tires (abundantly available is modern garbage) are packed full of dirt and stacked to create a thick monolithic wall that is its own foundations. These need to be built on undisturbed soil and no additional foundations are required. Inside they are finished with earth.
Underground houses (though they may conjure up uninviting images of war shelters) is an approach to building houses that are to some degree (many options here) surrounded by earth. Though there are numerous advantages to this the one that stands out in my mind (as we are living in a small and inefficient house that consumes loads of firewood and the work involved in it) is energy efficiency. Regardless of how you deal with the house fabric (insulation, thermal mass, etc.) when you build a house above ground and its freezing outside then you need to deal with subzero-temperatures surrounding the fabric of the house. When you build a house underground and its freezing outside then you are dealing with a relatively warmer (~10 degrees Celsius) and steady (a couple of days ago I witnessed an almost 20 degree Celsius shift in 4 or 5 hours!) surrounding. In the summer when its hot outside the earth is relatively cool so that works for you too.
So, with that in mind, I’d like to qualify my initial statement in that hemp-lime construction is one of the best methods of construction available today IF YOU ARE BUILDING ABOVE GROUND.
You can’t get far reading about rammed tires without coming across Eartships. An Earthship is a concept developed (if I am not mistaken – way back in the 70′s) by Michael Reynolds – an American architect. His vision is to create an autonomous house generating its own electricity (solar/wind) and water (rain run-off collected from the roof) all built with waste materials that mankind has generated in abundance (tires, beer-cans, wine bottles, etc.).
Ironically my first (and still leading) impression is that it is an impressive vision (amazingly elaborate and thorough) but also one that is anchored in the indulgent and abundant USA mentality (a recurring symptom in most of the “green” construction methods I have come across). Though Earthships are designed to be owner built they are still very expensive and a far cry from becoming something anyone on the planet can afford to live in.
We could not afford to build an Earthship based on the template described by Michal Reynolds and we are very well off compared to the general population of Romanian villages. So bringing Earthships into our context is quite a challenge.
Gradual Self Build
There are numerous benefits to Earthship construction compared to hemp-lime construction and though I will mention some of them there is one that outshines all of the others.
Earthships are designed to be owner built and indeed my searching and reading online seems to indicate that Earthship is one of the most popular self-build techniques for non-professional builders.
But in addition to being suitable for owner-built houses, Earthships can be built gradually. With relatively low costs we can start next year to pound tires that will make up the shell of our house. It may 2 or 3 years (unless we get help) but we can start and as we do that we can continue to develop our income stream and as funds become available invest more and more in the construction. Given that we have a temporary house to live in there is no need to wait, no rush and no pressure at all.
Earthship – Hemp Comparison
Beyond self build there are numerous points of comparison I’d like to make a note of in comparing hemp-lime build to an Earthship-like build. It should be said that what follows are things that matter to us including choices we may make that are not directly true to the core Earthship concept.
|Foundations||Like all natural fiber based walls hemp needs to be lifted above ground level so that it does not come in contact with water that may drain past the building. In our case the green roof required a foundation that could carry and distribute the load of a roof structure, earth, plants and snow.||No foundation is required. The walls themselves are a foundational structure. The tires, when rammed with earth way over 120kg each (they have to be packed in place because they cannot be moved). In addition the tire walls are either completely immersed or bermed with earth which adds additional support (and load on the walls!).|
|Floors||Both building systems can incorporate a variety of floor systems. In both cases, in our climate, there needs to be good thermal insulation (our floors can get to be very cold) and good vapor barriers|
|Walls||Hemp-lime is a non-structural material which means that it is not load bearing. Therefore hemp-lime walls are an infill for wood framing (usually either stick framing or post and beam). There is also need for shuttering (during construction) into which the hemp-lime mortar is cast.||Used tires pile up as garbage almost everywhere in the world – so besides the effort of finding it, sorting through it and transporting the tires to your build site there are no additional costs. It’s as simple as laying them on the ground and then the (very) laborious of pounding them with dirt. As we are not in a rush … we don’t mind taking the time to pound tires.|
|Finishing||Hemp-lime walls are porous and therefore breathable walls so they require a breathable finishing (usually lime-based). On the outside, regardless of finishing, the walls need to be protected with generous eaves.||On the inside tire walls are finished using natural earth finishes they I am assuming that lime can be used as well. This finishing is actually more critical in tire walls because the wall itself is not porous or breathable – so the finishing layer needs to be (for humidity responsiveness). The finishing is a pretty thick layers because first the gaps between the tires need to be filled to achieve a smooth surface – and only then can actual finishing layers be added. As for the outside there is no finishing issue since the walls are either buried or bermed (there is however an insulation issue – see below)|
|Doors||Our hemp house had quite a few doors designed into it. In that sense it was a typical house.||The original Earthships were, except of course for the entry to the house, without internal doors. They have evolved to the point where more elaborate internal design can lead to doors – so I’d say it’s pretty much the same as a regular house (although there is the option to build with much less doors.)|
|Windows||Windows in an above ground house are a pain. They are expensive (if you want good windows). They need to be installed with careful flashing to avoid leaks of water into the house. They need to be constructed and installed with precision so that they are also air-tight. In a do-it-yourself build they can be quite troublesome.||Earthships have no side windows – all the glass is in the front wall which is all glass – it is a relatively expensive element that requires basic wood framing, double-pane glass and very good flashing. The more modern Earthships actually have two glass walls – one is the outer wall which delineates the greenhouse and corridor to rooms; the other is the internal wall which encloses the rooms which is also mostly glass because we want as much sunlight to penetrate into the rooms. I have a feeling that the Earthship is somewhat simpler in this sense then a regular house – though I think the costs maybe similar if not higher.
Earthships also incorporate skylights primarily as a ventilation but also as a light source. This is something that can be self-built so the expense can potentially be somewhat reduced compared to ready made skylights.
|Insulation||Hemp walls need no insulation – they behave wonderfully both in terms of thermal mass and insulation. They do, as mentioned above, need to protected from moisture on the outside – wet walls are not good insulators.||Originally Earthships were built without insulation under the working assumption that they should interact with the earth itself. The modern evolution of Earthships in cold climates (where the earth, though warmer then the air, is still colder then a comfortable living temperature and could therefore suck heat out of the house) include insulation – usually rigid foam insulation (not very ecological) that is installed at a distance of about 1 meter from the wall itself (the space between the insulation is filled with earth).|
|Roof||Hemp homes can be built with almost any roof system. We were planning to build a green roof. Insulation is required and again can take on many forms.||Standard Earthship roofs are designed with a primary function (besides shelter of course) of rainwater harvesting. Here too insulation is a must and can take on numerous forms though standard Earthships use rigid foam insulation. We are currently leaning toward a green roof. This will deserve a dedicated post so stay tuned|
|Space Heating||Hemp homes can be very energy efficient if they are built properly which includes: airtightness, ventilation, passive solar, etc. But my intuition tells me that they still require heating which is can be a very challenging and complicated and expensive issue. Still they are above ground houses and need to cope with the dynamics outside environment (though the hemp walls, being constantly dry, tend to this very well compared to other wall systems).||Earthship heating requirements are probably much lower even then that of Hemp:
We are continuing to study and investigate Earthships and how they can apply to us. It feels promising.
We have been blessed with a temporary house in which we can live yet it is not a house which can become a house that supports and embraces us. This house is a wonderful shelter which can make building our new house a pleasant and healthy process.
The thought that we can begin a building process next year from mostly salvaged materials and then gradually move on with construction as work progresses and more money becomes available … and maybe move into a wonderful and pleasant house in 3 or 4 years is … joyful!