Facts About Rammed Earth

Stabilised rammed earth is one of the most environmentally-friendly and energy-efficient construction materials in the world.  Why?  Rammed earth is environmentally-friendly because it has low embodied energy.  This means it has very little impact on the environment both in its production for use as a building material, and its lifetime as part of the building.  Rammed earth is energy efficient because unlike most other building materials because if the climate is right (cool night air for passive cooling) it is possible (with correct design) to build a true solar-passive rammed earth home which requires no air-conditioners or space heaters at all.  That's a big difference to both the environment and your pocket!  How does rammed earth do this?  The answer is in utilising correct solar passive design, and use of the high thermal mass.

In climates where there is a distinct variation in day and night time temperatures, rammed earth is the ideal choice for a true solar passive and environmentally-friendly home.  In such climates it is possible to design and create a home which does not require artificial heating or cooling.  However in tropical climates where there is very little difference between day and night time temperatures, rammed earth or high thermal mass does not work so well.  In extreme cold such as alpine areas insulated rammed earth is the best solution as the requirement for internal space heating cannot be avoided in such sub-zero temperatures.

There is no doubt that rammed earth is one of the most environmentally-friendly building materials in the world.  However, rammed earth does have a low R-Value.  The key to the superior energy efficiency of rammed earth is its high thermal mass. Because heat and cold takes so long to transfer through the thick rammed earth walls, high thermal mass can actually keep your house cool in summer without any air-conditioning, and warm in winter without any heating!  (When true solar passive design is incorporated)  In some climates, winter space heating may be required.  In winter, when the house is warm inside the thermal mass will hold the heat and act as a passive heat bank.  In summer, the high thermal mass will keep the internal room temperature many degrees less than the outside temperature, removing the need for air-conditioning.

Myth #1 - Energy efficiency

The marketing strategies of various companies and the media have confused the public by claiming that energy-effiicient homes are the best for the environment.  The truth is that only correctly designed solar passive homes are best for the environment.

Don't confuse energy efficient home design with solar-passive design - they are not the same!  True solar-passive design means designing for climate.  A solar passive house will by its very nature be energy efficient, however a house which is claimed to be energy efficient is not necessarily a solar passive house and therefore is not the best choice for the environment.  The reason is simple - the wide-spread misunderstanding of R-Value.

Myth #2 - R-Value

Don't be fooled into thinking that building with a construction material which has a high R-Value and a high star-rating is the most energy efficient home you can build.  If a house claims to be energy-efficient because it has a high star-rating it simply means the house uses less energy.  Less energy than what?  Less energy than the same house without insulation?  Having a high R-Value it will certainly give you a high star-rating in your energy efficiency assessment, and a house with high R-Value will certainly help your air-conditioners and heaters to run more efficiently there is no doubt about that.

Without all those air conditioners and/or heaters running all day and all night to keep your high R-value and high star-rating home a constant temperature inside, that 7-star house built with high R-value alone (no thermal mass) will very quickly become a hot-box or sauna in summer and a freezing cold coolroom in winter!  With a rammed earth home that just wouldn't happen!!   A rammed earth house correctly designed for climate using true solar passive principles you won't' need air-conditioning anyway!  Sometimes you don't even need heating either!  (in colder climates where there is not sufficient daytime sun you will need a heat source in winter)

Don't be fooled into believing that a house with a high star-rating and high R-value is the most energy efficient house you can build.  If there is no significant proportion of thermal mass then the occupants of the house will not survive without air-conditioning in warmer climates.  All those air-conditioners just can't be good for the environment.

Don't be fooled into believing you are going to reap the solar passive benefits of rammed earth in multi-story construction either, unless you have correctly shaded the sun-facing walls from the hot summer sun!

Fact #1 - Thermal Mass

Thermal mass keeps the internal room temperature stable due to the length of time required for heat to transfer through the walls.  For example a 300mm thick rammed earth wall will take 8-9 hours for heat to transfer through the wall to the other side.   The solar passive building designer must ensure that summer sun does not shine directly on any sun-facing walls but at the same time allow the direct sun on the walls in winter for as long as possible.

This will allow the warmth from the sun to be absorbed by the walls in winter when it is needed the most.  Insulated rammed earth contains insulation which is placed in such a way to slow the heat transfer even further.  This is great in sub-zero temperatures however in warmer temperatures the insulation will have a detrimental effect as it will prevent the warmth of the sun from being stored in the wall.

Conclusion

In current times the search for sustainable building methods has resulted in rammed earth gaining immense poplularity among those who wish to build with environmentally-friendly and natural building materials.  Rammed earth is now highly sought after as one of the most environmentally-friendly construction methods in the world and its popularity is rapidly increasing.

Since the inception of our weekend training workshops in October 2010 we have trained many people in the art of stabilised rammed earth construction.  What prompted us to begin teaching was our desire to educate as many people as possible in the virtues of stabilised rammed earth and its use as one of the most environmentally-friendly construction materials in the world and dispel the myth about assessing energy efficiency on high R-Value alone.

Our rammed earth courses are suitable for people of all ages and all levels of construction knowledge.  Our course participants are both male and female, and range from the complete novice with no previous construction experience right through to a variety of home handyman, construction tradesmen and even registered builders.  Everyone receives the level of tuition they require.

 

I hope you enjoy the new website, please feel free to let us know if you have any suggestions.  This website has been created for you - the rammed earth enthusiast and builder.

 

Sharon Ponsford
Environmental Designer
Rammed Earth Living
& Studio West Design

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