June 9, 2015
Newcastle University’s engineering faculty recently did a study into the thermal properties of rammed earth. Earth Dwellings constructed a unstabilised rammed earth wall and Hillary Wong, under the guidance of Dr Michael Netherton, tested the wall in a hot box to determine the thermal properties of rammed earth. Rammed earth is often classified in terms of it’s R value, which is it’s steady state, or how it responds to a singular temperature change. In real life, the daily temperature changes dynamically, hot in the day, and cold at night. So test were conducted using a dynamic thermal analysis which gives a T value.
Hillary’s investigations showed that “Earthen materials are ideal substitutes for small to medium scale constructions, reducing carbon emissions and prolonging the use of non-renewable materials like steel and cement. Earth building materials require negligible embodied energy and also require low operational energy due to their superior thermal performance. Rammed earth possesses good thermal performance characteristics, however the steady state thermal resistance or R-values required by Australian energy efficiency schemes are not in accordance with the materials actual thermal superiority when tested dynamically. There is speculation about the inaccuracy of steady state analysis and the need for dynamic thermal analysis to determine the true thermal performances of materials. These current energy efficiency schemes (using only steady state parameters) are holding back earthen materials from being classified as a complete sustainable material.”
“A steady state and dynamic thermal analysis of a 300mm thick rammed earth wall was conducted to establish a full understanding on its thermal behaviour. As expected, the steady state and dynamic tests demonstrate contradictory results with steady state R-values showing poor thermal performance and dynamic T-values showing good thermal performance. A comparison between this rammed earth wall specimen and concrete panels proved that even though two materials can both be seen as poor thermal performers when steady state conditions are considered, the dynamic analysis can prove which material is truly a better thermal performer. This comparison proved that rammed earth is a good thermal performer, whilst the concrete panels were considered poor performers for both steady state and dynamic analysis. Rammed earth was also compared against an insulated cavity brick wall. Rammed earth’s thermal performance was found to surpass the performance of insulated cavity brick wall.”
“This proves that rammed earth has superior thermal performance. It clarifies that the dynamic thermal response of materials should be taken into account when analysing the thermal performance for energy efficiency schemes. Dynamic thermal analysis shows an accurate depiction of thermal behaviour and should be considered as a more appropriate test method as structures are exposed to dynamic diurnal conditions throughout their lifespan. The conclusion that rammed earth is a superior thermal performer proves that building with this earthen material can significantly reduce the operational energy of the structure. The near stable temperatures achieved inside the building decreases the need for additional heating and cooling, which is the main contributor to energy consumption in structures. This low operational energy combined with low embodied energy presents rammed earth as an ideal sustainable material for future construction.”
This shows the true value of rammed earth especially when used with good solar passive design !
April 29, 2015
This is a repost of an article published by theconversation.
It’s fair to say that rammed earth, as a construction technique, has stood the test of time. It has been used to create buildings around the world whose beauty and robustness are still visible today, like the Alhambra in Spain and the Great Wall of China, both built more than 1,000 years ago.
Traditional rammed earth is made of a mix of clay-rich soil, water and a natural stabiliser such as animal urine, animal blood, plant fibres or bitumen. It is then compacted inside temporary formworks that are removed after the mix has dried and hardened. The resulting structure can withstand compressive forces of up to 2.5 megapascals (around 10% of the average compressive strength of modern bricks).
The walls can be reinforced using embedded timber beams or bamboo grids, and of course they need some architectural features to protect them from the rain and wind. Historical examples of buildings made of traditional rammed earth can be found in South America, China, India, the Middle East and North Africa.
In Europe, especially in France, Britain and Germany, traditional rammed earth is enjoying a resurgence, and several modern buildings have been constructed using the technique, such as the three-storey rammed earth home shown below, built in 2008 in Austria.
Stephen Dobson, Ramtec
In the past 30 years a new version of rammed earth has appeared and gained popularity in certain parts of the world, such as Australia, California and Canada. Called cement-stabilised rammed earth (CSRE), it consists of a mix of low-clay soil, water and cement. Like traditional rammed earth, this mixture is compacted inside temporary formworks and left to dry.
But it is an order of magnitude stronger, withstanding compression forces up to 40 megapascals, giving it similar strength and durability to concrete. This means that walls do not need special protection from rain and wind because they are strong and durable, especially if reinforced with steel.
Sustainable building blocks
Both traditional rammed earth and CSRE have several characteristics that make them an attractive choice of building material. The main ingredient is soil, which is cheap (if not free). In remote areas, building with local soil means significantly reducing the costs of transporting construction materials to the site.
The building technique is very straightforward. In general, only one experienced builder is required on site to instruct labour force about how to construct the formwork and mix the materials. The rest of the work can be done by untrained or unskilled people from the local community, creating jobs and reducing the costs of transporting and accommodating workers from elsewhere.
Although rammed earth does not have very good insulating properties, the walls are very thick (typically 250-800 mm), meaning that rammed earth buildings can easily produce comfortable indoor conditions in hot and arid places. Rammed earth walls breathe, hence they can regulate the indoor relative humidity, making it suitable for people with respiratory problems.
And finally, the final texture of rammed earth walls is unique and beautiful, so they typically do not need any plaster or render.
Ramming home the message
There are currently several projects around the world that aim to promote rammed earth as a sustainable and cost-effective construction technique.
My colleagues and I are working with the WA Department of Housing to investigate the use of CSRE in remote Indigenous communities. Gaining the trust of the Indigenous population has been so far the most difficult aspect of the project.
Meanwhile, in the United States, Colorado University is starting a similar project to look at the possibility of building rammed earth homes on Native American reserves.
Rongrong Hu, Xi’an University
Rongrong Hu, Xi’an University
Most impressively of all, China’s Xi’an University of Architecture and Technology has developed a project to help rural communities build new houses using both traditional and modern rammed earth. The scheme has successfully helped the local population to create entire new villages built with rammed earth.
But rammed earth is not only applied in affordable housing projects. Strangely enough, the other most common application is in expensive residential buildings designed by eccentric architects for wealthy and environmentally concerned clients. These houses usually end up in and and design magazines and are considered real pieces of art.
Stephen Dobson, Ramtec
So, why isn’t everyone using it?
Rammed earth has been used for centuries, but today its use is limited to specialised projects like the ones described above. Why is it not extensively used around the world, for ordinary buildings like offices and houses?
One of the major reasons is likely to be a lack of knowledge. Although rammed earth itself is old, our research is quite a new field compared with other more traditional construction materials like concrete, steel, masonry and timber. Unfortunately, a lack of research means a lack of understanding of the material and its structural properties.
Another obstacle is regulation, or a lack of it. In Australia, as in most countries, there is no building code for rammed earth buildings. The prospect of working with an unregulated construction technique would discourage many engineers and architects.
The good news is that the interest in environmentally friendly and affordable houses has never been bigger. Researchers from different backgrounds (engineering, materials science, architecture, chemistry, and more) are beginning to investigate the different properties of rammed earth with the aim of promoting this construction technique.
While it might not be as grand as the Alhambra, the chances of finding yourself inside a rammed earth building in the years to come are growing.
April 28, 2015
We are partnering with the University of Western Australia and the WA department of housing using a Research Council of Australia grant to investigate the appropriateness of rammed earth for indigenous housing. There are two complete houses that will be monitored for two years with sensors in each room and several walls. It was great to visit the site and see that houses being lived in and appreciated.
The two houses are identical except for one was constructed using insulated rammed earth and the other was uninsulated rammed earth. Hopefully we can compare the thermal performance difference and try to measure the effects of thermal bridges inherent in the insulated rammed earth.
These thermal mass walls are already working well in the Kalgoorlie climate with occupants expressing the excellent comfort levels. Nearly all houses in the area have evaporatuve air conditioning that uses huge amounts of energy and water. The occupants expressed their joy of being comfortable in a naturally conditioned house on a hot day.
It seems logical that these people who are ‘of the earth’ would be suited to well designed earth houses.
April 26, 2015
Architizer is the largest platform for architecture and design online. They recently celebrated earth day with some great examples of an eco friendly construction method, rammed earth.
“As an eco-friendly alternative to concrete, rammed earth has been trending for a minute; suffice it to say that the sustainable and cost-effective building solution has come a long way from ancient times. By using natural and usually local materials like sand, soil, clay, chalk, lime, or gravel, compressed into blocks, rammed earth buildings have low embodied energy and produce little waste. Moreover, the composite material is attractive as a means of passive climate control — and, if these projects are any indication, aesthetically, as well.”
More info at Get Down to Earth: 6 Examples of an Eco-Friendly Construction Method. Whilst there you can find more information and great images on rammed earth at this link – Rammed Earth: Sustainable Design’s Eco-Chic Flower Child.
March 18, 2015
March 8, 2015
Fastcompany.com recently published an article on the 5 Trends Shaping the future of Architecture. They asked 2015’s most innovative companies to predict how the industry may evolve.
One of their predictions was for the re-use of ancient materials like timber and rammed earth.
“The newfound availability of cross-laminated timber panels, engineered to be stronger and more fire-resistant than traditional wood, has allowed architects to build taller and taller with timber. But wood probably isn’t the only ancient building material we will rethink in the next few years, Weyer predicts.”
“There are new methods constantly being tested,” he says, like rammed earth, an ancient technique (using a dirt mixture) that is still used to build houses in places like Australia, South Africa, and the southwest United States. “Technological advances in wood/timber construction have made it possible for us to re-image some well-known building types,” he explains. “I would expect that other technologies will have a similar impact in the near future.”
January 27, 2015
The use of insulation is required in cold climates for external walls. I have had a problem with them in that the life cycle analysis doesn’t look so good. Buildings all have a lifespan, which appears to be decreasing, and the styrofoam insulated rammed earth walls are not able to be put straight back into the earth like traditional rammed earth walls.
In the plastic age we live in, styrofoam is the worst offender of a legacy we are leaving in our environment. Our seas are increasingly being loaded up with microscopic broken pieces of plastic that will never disappear. This is killing wildlife and entering our food chain!
The book “Plastic Ocean” is an excellent book on the subject and does offer realistic solutions to this massive problem.
I recently found a great alternative to using styrofoam in insulated rammed earth, Mushroom Insulation. It will ‘soon’ be available commercially from ecovative, as insulation with a comparable R and cost to styrofoam. Made from agricultural crop wastes, it is ultra rapidly renewable, low embodied energy, Class A fire rating (ASTM E84), Ultra low VOCs (ASTM E1333) and is safe and easy to install.
January 9, 2015
A recent article in London’s Evening Standard newspaper reports on the growing uptake of earth as a great interior product. It is all well and good that it looks beautiful, but this trend also gets me excited as internal earth and its thermal mass features have the best thermal performance attributes.
Having the thermal mass internally, means it is isolated from the outside and makes it easier to store the coolth or warmth in the thermal mass. It operates like a thermos stores warm (or cold) water. if it is keep sealed the water will stay warm (or cold) for quite a long time. If you take the lid off the water will cool very quickly. If we use good cross ventilation on these walls in summer and good solar passive design to allow for heat gain in winter, the building envelope will perform exceptionally well!
November 6, 2014
A recent entry in the Mud House Competition was from Marta Glowacka and Riccardo Mariano from Berlin. Other than visually amazing, it was quite an interesting concept. The traditional fired clay pots are filled with sand soil and saw dust combinations. Even though this entry wasn’t a winner in the NKA foundation Mud hut competition, I do hope it does inspire others!
I could see variations having small gaps between the pots to allow great cross ventilation. Alternatively in temperate climates, pots could be filled with water (the highest rated thermal mass) on the equator /sun side and an insulative material like rice husks on the other side. Obviously there would be many technical issues to be solved, but is a creative form of earth building using local materials and trades.
November 5, 2014