frequently asked questions (FAQ)
How is construction with rammed earth more sustainable?
Is a rammed earth house energy efficient?
What’s wrong with traditional building methods?
Are the labour costs too high?
What is it like to live in a rammed earth home?
What’s in the walls?
The inside and outside portion (or wythe) of each wall is made from local soils. Selection of appropriate earths is assisted by a computer study of grain sizes and textures. Soil mix design is crucial to the success of rammed earth. Our soil mix surpasses the specified engineering standard by more than 50% as determined by cylinder crush tests. The addition of a small amount of cement ensures that we can meet these standards with any local soil. We also use special additives that ensure the walls are waterproof. In the middle of the wall is 6” of polyisocyurnate insulation. This allows the wall to retain the solar energy stored in the inner wythe. The entire wall assembly is reinforced with rebar for additional structural support and to tie together the inner and outer wythes.
How is construction with rammed earth more sustainable?
Much of the interest in rammed earth comes from its potential to lower our carbon footprint. Standard stick frame buildings require millions of acres of forest, transported over large distances, processed by milling and treated with toxic chemicals to prevent rot, mould and insect damage. Rammed earth uses local unprocessed subsoil with only a small percentage of processed cement. Stick frame housing has an expected lifespan of less than five decades, with most of the materials ending up in a landfill site. A stabilized rammed earth house will last for centuries, at which time the materials could be reused for more rammed earth.
Is a rammed earth house energy efficient?
Rammed earth is excellent for passive solar heating (see Thermal Mass below.) Our house has no furnace and is comfortably warm. Only a small amount of additional heat will be needed for cold cloudy weather. The need for cooling energy is also eliminated when building with rammed earth. While building the house during the intense heat waves of the 2010 summer we were able to retreat to the cool dryness of our garage despite the fact that this unfinished rammed earth structure lacked doors, windows or insulation in the roof. A future small solar electric array will allow the house to be zero energy.
Why does thermal mass matter?
When designing a passive solar house (which is a house heated by the sun shining through the windows) the challenge is always to store the energy. Any house will warm up when it’s sunny, usually too much, but it will also cool down quickly when the sun is gone. Older heat storage solutions have included concrete floors, Trombe walls (a thick wall just inside the south windows, blocking the view), rocks, water (in pools or bottles in various locations), underground tunnels, etc. Rammed earth walls give ample thermal mass, acting as a huge heat sink. A typical stick frame house has one or two tonnes of mass; 50 – 100 tonnes is considered the minimum necessary for heat storage. In the construction of our house, the 6” of insulation in the middle of the wall leaves 6” of rammed earth in the interior of the house, plus the two 18-inch uninsulated interior walls, yielding 530 tonnes of thermal mass.
What’s wrong with traditional building methods?
Ultimately the issue is sustainability. Can the planet and the people on it survive if we continue to build as we’re doing currently? Obviously, the answer with stick-frame building is a resounding NO. Merely the loss of a carbon sink due to clear cutting has a profound effect on the most pressing issue of our time – global warming. Add to that the enormous carbon footprint of the embodied energy of processing the wood, transportation and building technique. Then consider the energy cost of heating and cooling the buildings and the prodigious waste of energy and resources associated with construction, maintenance and disposal of what are essentially temporary structures. All of which doesn’t even begin to consider the health costs of toxic materials, moulds, combustion, etc.
Are the labour costs too high?
It is certainly more labour intensive to build rammed earth than standard building methods. The majority of the cost of building rammed earth is labour; the material is “dirt” cheap. Why is this a bad thing? Is it preferable to spend money on toxic, energy intensive, highly processed materials or to provide a living to a group of generally young people interested in making a difference in the world?
What is it like to live in a rammed earth home?
The rammed earth environment is like no other. To live in a rammed earth house is to live in natural comfort, to enjoy the quiet beauty of rammed earth walls during the day and at night to breathe easily and sleep soundly in an environment where the walls contain no toxic materials and the temperature remains constant throughout the day and night no matter what changes occur outside.