… and read the book Passive Annual Heat Storage – Improving the Design of Earth Shelters by John Hait.
- Should Earthships be insulated? Yes (but not in the obvious way it’s being done today).
- Should Earthship floors be insulated? No.
- Can an Earthship provide a comfortable (21c) climate using passive means during the winter season in a cold climate? Yes.
- Can heat be collected and stored during the summer for a winter with very little (mostly cloudy) passive solar gain? Yes.
- Can an Earthship be properly ventilated without having to sacrifice precious heat? Yes.
- Are skylights a must? No.
- Is the corridor wall (introduced systemically in Global Model) Earthships required in cold climate? Not necessarily.
- Can an Earthsip be built in clay-rich expansive soil? Yes, if the soil kept dry.
When it comes to cold (moist and frozen) climates like ours here in Romania, there are quite a few things that felt, to me, incomplete, missing or even wrong in Earthship design (including the latest and greatest Global Model). To me what was missing most is the lack of explanations of how things work and why they are designed the way they are. I could not find satisfying answers in any of Michael Reynolds’ Earthship books (Earthships have evolved way beyond their description in the original Earthship books) nor online in many of the documented builds and open discussions about Earthships.
Then a few days ago I published this post about ventilation problems in an Earthship and began to compose my thoughts for a follow-up post. The solution seemed to come in the form of earth-tubes. The first resources I came across (pretty much as they were presented in the search results) were:
- Wikipedia – which provided basic technical information.
- The Natural Home – which provided a convincing argument for earth tubes.
- BuildItSolar – which raised some questions and left me with some doubts.
Luckily I stubbornly pressed through a few more pages of superficial search results and on the 3rd or 4th page found an article by John Hait inaptly titled Umbrella Home. The article blew me away. I ordered the book and couldn’t put it down – I read it word for word in just over a day and will be re-reading many parts of it again.
The book truly lives up to its subtitle “improving the design of earth shelters”. Not only does it open a door to a much deeper understanding of earth-tubes but to do so it introduces a fantastic concept of a large insulating/blanket which surrounds an earth-sheltered house in which earth-tubes can really come to life.
The core idea (backed up by accessible explanations and practical research) is to create an insulated and water-proof blanket that encompasses the house and a large area (~6 meters) around it (which can be achieved with more or less the same amount of insulation materials used for standard wall insulation).
This insulated umbrella creates a large body of earth which is dry and functions as a huge thermal battery attached to the house. The house itself acts as a solar collector to slowly charge the immense thermal battery during summer. Then, during winter that battery slowly discharges heat back into the house.
Earth tubes are used with this umbrella (in a way that could not achieved without the umbrella) to passively generate both ventilation and temperature regulation (cooling & warming) of the house. Because the earth-tubes run through the thermal battery surrounding the house they work as a super-efficient heat exchange system. A passive air-conditioning AND heat-exchange system that is simple and affordable.
As a cherry on top - imagine running an uninsulated water supply pipe under the umbrella and having water preheated to 21 degress (celsius) during winter (cold water supply has to be insulated under the umbrella). As someone who washes dishes with freezing-cold water (unless I fire up the wood boiler) I am watering at the mouth at the thought of washing dishes with passively heated (no additional energy expense or effort) warm water. Not to mention energy savings in heating bathing water.
This may cause a problem with Earthships that include rain-water harvesting stored in buried cisterns. The cisterns, if buried close to the house, under the umbrella will become a source of warm water. Cold water would have to be cooled somehow and I don’t know what effects this may have on the stored water. Since we’ve decided to forgo rainwater harvesting and put in a green-roof this is not a problem for us.
If you’ve already built an Earthship in a cold climate and it isn’t functioning as well as you thought it would I believe that at least some of the measures described in the book can be added to your Earthship to make it a much better home.
I don’t recommend trying to implement this from the basic information in the article. I STRONGLY recommend reading the book word for word. It is educating and empowering and fun to read.
I am now (again) heading back to the drawing board to revisit and rethink our house design. I feel I know better now and I am grateful to John Hait for his work and for making it available to others.