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Brighton Earthship

June ’16

Overview

Earthships go back to green building experiments in the US in the 1970s. There are four principles involved:

  • that they can be built with fairly unskilled labour
  • that they are low energy
  • they can utilise waste materials in their construction
  • they can be off-grid (or autonomous in Brit-speak)
Earthship Brighton

Brighton Earthship

The Brighton Earthship has not actually been used as a house; rather a community facility, but it has been quite well monitored for internal temperature and humidity.

Problems with the Earthship concept

The history of earthships is important to understand because it explains a lot about why they are less relevant in the UK than in areas like New Mexico where they originated.

Three factors differ very considerably

  • building land is much more expensive in the UK
  • the climate is very different
  • being off-grid is much less common here

Taking these in turn, they combine to make earthships almost an irrelevance in the UK

The price of land

Because we live in a fairly densely populated country along with the fact that we adhere to a (fairly) strict green belt and National Parks policy it means that building land usually constitutes a large part of the price of building a house. Along with this, council planning departments put strict limits on the dimensions of a house, how many stories there may be, how much land must be devoted to car parking etc.

Consequently every square metre of space that can be used for living in matters. The idea of having large areas of thermal mass or conservatories or restricting the hight to a single storey is often not feasible. Earthships are basically single storey, use up much space for thermal mass (in the north facing wall) and involve a lot of waste space in the form of poorly insulating tyre filled walls and often a conservatory with a trombe wall. This conservatory tends to become too hot to use in summer.

Earthship interior

interior view with the conservatory on the left

The UK climate

Earthships depend on thermal mass to save on (mostly solar) energy. The idea is that you have a huge bank of earth on the north side of the house. When sunlight enters from the south facing windows on the south side, the heat finds its way to this bank of earth, heats it up and is stored there until needed.

Now where this principle works best is in a desert climate where it is hot during the day and cold at night. The thermal mass stores all the excess heat during the day (keeping the space cooler) and then lets it out at night (warming the space up). It acts like a flywheel, levelling out the peaks and troughs. All well and good in a climate like New Mexico. But what happens if you have a six week cold spell? Or a long hot spell? In a cold spell the thermal mass gives up most of its heat in a few days and then you have to put the heating on. Conversely in a long hot period the thermal mass gets warmed up in a few days and cannot then absorb any more heat.

A long cold January, February and March is going to need a hell of a large thermal mass to get you through. That is not to say it can’t be done. see Inter seasonal heat storage.

Off-grid

Earthships tend to be off-grid in terms of water sewage and energy. This makes a lot of sense if you have bought some cheap land in the middle of New Mexico (or Australia etc.) but usually in the UK it makes more sense to connect to the grid, with one possible exception. (see sewage below)

Of course you might have a kind of libertarian anarchist take on life which involves a sort of “F**k the energy companies” approach to life (but then you pretty quickly fall prey to the large multinational battery companies to store your solar energy)

Off grid water is a bit of a problem simply because of the volume needed. If you do the calculations you find you need a large area of ground to catch enough rain water, even if you use very low flush or composting toilets (although drinking water itself need not be a problem). See Rainwater harvesting.

Solar energy storage, i.e. in the form of batteries, is a bit of an unknown at present. Up till now lead acid batteries have been the type mainly used. They are fairly nasty environmentally, are very expensive to purchase, need considerable maintenance and monitoring, take up a fair amount of space and only last about seven years. The emerging electric car market seems to be driving development of better batteries to the extent that battery backup might become a common feature in housing within the next decade. However it still makes sense to be connected to the grid so as to be able to sell surplus power into it and draw off it when needed.

The exception to being off-grid, mentioned above is with sewage. This is about the use of composting toilets and on-site grey water treatment which keep the nutrients and humus for the garden rather than letting it pollute local watercourses. This also results in a 30% reduction in use of water (for flushing toilets). Brighton Earthship has both low-flush toilets and composting although the flushing toilet has run into problems. Grey water recycling is handled through planted containers within the building. However there are now Building Regulations which govern how grey water can be used.

Do Earthships work in the UK?

Well probably not very well. The best source of reference at present is an excellent book called “Earthships in Europe” with a chapter called “Passive Solar Design and Monitored Thermal performance”. A series of graphs show that the couple of examples in the UK have not lived up to expectations in terms of thermal performance. The graphs indicate that indoor temperatures fluctuate in line with external ones. This is not what should happen because the thermal mass should, in principle, smooth out the variations in internal temperature. Earth rammed into tyres is not a particularly good insulation material and neither art bottle walls.

Possibly – burning timber

A better option is the Passivhaus concept, possibly combined with new developments of the Walter Segal method of self build (if you want to do most of the work your self) or combined with SIPS if you want a ready made system.

 

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