The majority of conventional Oxford Brookes-educated architects and home designers will consider me being barking mad to try to unearth the uneasy topic of earthbag buildings, but here we are. Sandbag buildings we’re all familiar with – sandbag walls are great as flood barriers or temporary military buildings. Bullets don’t go through earthbags, don’t ricochet and don’t create shrapnel.Earthbag buildings, due to their unconventional status, are largely underestimated these days. They are probably the most affordable substantial buildings available to DIY builders. If you have a site, you’ll only need to spend money on sacks, dome frame and some fixtures/fittings. The main material is all around you (underneath your feet, to be precise) and it is free – sand, soil, fine gravel – anything can go in your earthbags.
By the way, a single-storey sandbag house can withstand the fiercest earthquake and it is fireproof.
Are Earth Sheltered Buildings Green?Compared to earthbag buildings, earth sheltered homes are not 100 per cent green. The majority of eco-friendliness associated with earth sheltered homes comes from passive solar energy and insulation features. If the house is properly solar-oriented and packed with earth where necessary, you will save great deal of money off your heating and cooling bills. However, with earth sheltered homes there come several issues.
In order to build one properly, you’ll need much more concrete than during a conventional build because it is essential to get the house watertight and make sure the back wall can bear the weight of the Earth. Thus, it might take up to 20 years for your eco-friendly earth sheltered home to become carbon neutral.
Remember that when it comes to embodied energy (grey energy) necessary to produce cement and the total CO2 balance of laying the concrete, for every pound of concrete you use there comes almost a full pound of CO2. That’s the main reason I am convinced that screwpile foundations are the right way forward!
Then there are lighting issues with earth sheltered homes. If we stay true to the very idea of earth sheltered homes, the back of your dwelling will be rather darkish.
But having said that, there are issues with earthbag buildings too. For example, you’re always limited by the size. Although there are some in existence, generally speaking, it is a silly idea to build a multi-storey earthbag house.
Sandbag houses are not entirely green too. You’ll be using lots of sacks. And although the purists preach burlap bags, it makes more sense using the white sugar bags made of polyethylene strips. Rats and bugs are not too keen on eating polyethylene and it is less prone to rotting.
Still, earthbags enable you to build a permanent green house without ever visiting a build store.
So How are Earthbag Buildings Made?
It all starts by digging trenches for foundation. When it comes to foundations of an earthbag building, there are a few ways to approach it. You can pour concrete in the trench, instantly rendering the house non-green; you can use old tyres, fill the gaps with stones or you can use rock-bags for the foundation (bags filled with heavy soil and stones).
You want your earthbag building to be roundish; dome shaped ideally. Although some people treat sandbags like any other conventional building material, there will be folk reminding you that corners and sandbags don’t get well together. I’m inclined to agree with them. Veeery fiddly; you’ll find it hard to get the corners right. Sandbags seem ideal for making dome homes. To get any decent living space within your home you’ll probably want to link/intersect several domes. Building large dome homes from sandbags can be too dangerous.
The finishing of the dome top needs proper planning. Although it is possible to stack the sacks in a pyramidal way so that each sack stops the bottom one from moving by applying its own weight on its neighbour, building safety regulations (and common sense, really) will ask for a sub-structure to support the dome building roof. It can be a frame made of wood, rusty pipes or any other material that is capable of bearing the weight.
Although walls of a finished dome can be left as is, it is highly recommended to apply lime plaster. The roof can be clad with reclaimed slates.
Soil provides an amazing thermal mass so both earthbag and earth sheltered homes will remain cool in summer and keep heat in the winter. It can be a challenge to get a planning permission mainly because of the unconventional look of green buildings. It is very unlikely that they will allow you to build a weird eco-house amidst a neat English terrace, however, the further out of town we go, the easier it is to get a planning permission.
Pics by: http://www.flickr.com/photos/organicarts and Malcolm Wells.