How to incorporate passive solar design in your building, using thermal mass and insulation.

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Passive solar design is the starting point of sustainable building. Once one understands the basic principles of using the abundant natural renewable resources at our disposal we become more creative in our approach to design, more in tune and observant, reconnecting us with the natural rhythms that surround and sustain us, if only we would pay attention. Sustainable buildings save money, reduce your carbon footprint and provide a healthy living environment, transforming buildings from consumers of energy to producers and forging buildings that meet our needs.

From a permaculture perspective, incorporating these aspects into the design of your home are excellent examples of several permaculture design principles. To mention the most obvious: Observing and interacting with your environment to make the most of the sun’s migration, catching and storing energy, using and valuing renewable resources and services, integrating functions and elements rather than segregating them and obtaining a yield from the planet’s most abundant energy source, the sun.

Passive Solar Design uses the energy provided by the sun and stored in the earth. First we need to look at how this energy is utilized by defining insulation and thermal mass and then look at the strategies of how to incorporate them into our designs.

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Lebone Village launch

Imagine being outside on a chilly Free State winter morning with the sun just coming out and starting to gently warm your body. Now imagine being told to take off your shoes in order to trudge in icy cold mud. I glanced at my fellow volunteers and I saw a collective dissent quietly dawn on our group – this is not what we signed up for!

Mandela day

It was the morning of 18 July, Mandela Day, and we were all gathered at Lebone Village on the outskirts of Bloemfontein to volunteer our 67 minutes for the orphans. We were standing in a circle around Peter McIntosh, who was valiantly demonstrating to us the endeavor of making adobe bricks.

Peter McIntosh demonstrating how to make cob

Peter McIntosh demonstrating how to make cob

The mix using ingredients easily available for the project was chosen after rigorous testing. According to Peter, the mix will differ in every situation, depending on the composition of the ingredients used. The chosen mix for the adobe bricks at Lebone Village was as follows: collect two parts red earth, 2 parts sand with rubble, one part fine sand and two parts water in the centre of large piece of 25” thick canvas material.

Now mix it all into clay with your feet by walking back and forth through the cold, wet mixture. When the cob mixture starts to flatten out, pull the canvas up-and-in towards you from the corners to bring the clay mixture back into the centre of the canvas and into a manageable heap. Now start stepping onto it again. The clay is the right consistency when you can make a ball with your hands and pull it apart into two separate pieces without it crumbling. Adding straw to the mud mixture assures bricks that are well insulated against cold and heat, the more straw you add, the better insulated your bricks.

Adding water

Adding water

Adding straw binds everything together and adds insulation value

Adding straw adds insulation value

Lots of people turned up

Lots of people turned up


While the majority of us were still apprehensively contemplating the prospect of braving the cold and mud with naked feet, one person rose to the occasion without hesitation. In the spirit of “first being a follower in order to be a leader”, Itumeleng Santo started pounding the mud into clay with some über cool dance moves. Itumeleng is an out-patient at the University of the Free State’s Dept of Occupational Therapy’s clinic at the MUCPP offices in Rocklands location. He is severely impaired due to a brain injury that he suffered during an assault. For Itumeling, taking part in the Mandela Day activities at Lebone Village was therefore also a day of getting therapy without being given therapy. The Dept of Occupational Therapy vision is to support and treat their disabled and impaired patients in such a way that they will be able to return to their families and communities and be able to fully participate in community activities again. The aim is for such patients to become fully functional individuals who can partake in economic activity and contribute towards their own livelihoods.

The MUCPP clinic of the Dept of Occupational Therapy is not only for patient care and therapy, but it also serves the wider community as a place where youth can hang around after school and in this way be kept off the streets. Heidi Morgan and Bronwyn Kemp, who run the clinic, aspire to teach these children skills that will help them to create their own employment upon completing their school careers. Learning how to make adobe bricks and tire pounding for alternative and natural building practices are two such skills.

This notion of self-empowerment of the impaired, disabled and destitute was the golden thread that ran through the activities at Lebone Village on the morning of Mandela Day. Stakeholders from support institutions to the disabled came from all over the Free State region to learn the new green building techniques of making adobe bricks and pounding tires. These are skills that they intend to take back to their home towns and villages, skills that they hope will enable them to become self-sufficient and self-employed, able to earn money and make a living for themselves, without being a burden to their families.

Getting our feet dirty

Getting our feet dirty

Peter McIntosh demonstrating putting cob into the brick mold

Peter McIntosh demonstrating putting cob into the brick mold

With the ice now literally and figuratively broken by Itumeleng, the rest of us started to get into the spirit of the day. The extra brave ones took of their shoes and started pounding cob with their bare feet. The more modest traded their shoes for gumboots to get the job done.

Some started working the cob with their hands. Anita put on some vibey music and soon the day was in full swing. Volunteers started forming little groups, each group working their cob on their own piece of canvas. Some people would collect the pounded cob and compact it into wooden molds set out by Peter for this purpose. These mudbricks would then be left to dry in the sun for several days, where after they will be ready to use for building.

Peter McIntosh demonstrating putting cob into the brick mold

Peter McIntosh demonstrating putting cob into the brick mold

The teaching of green building techniques to the greater Mangaung community also served as the launch of the Lebone Village Climate Resilient Arts, Crafts and Cultural Hub and was initiated by Qala Phelang Tala, a non-profit organization based in Bloemfontein and associated with the Centre for Development Support at the University of the Free State. Qala Phelang Tala is Sesotho for “Start Living Green” and is the brain child of Anita Venter, a researcher at the Centre for Development Support. QPT strives to empower “change agents” through social entrepreneurship in order to create systems addressing housing, food security, water efficiency and energy independence that are resilient to climate change. Their slogan is “Learn by doing!” This means that they not only preach green building and sustainable, environmental friendly living, but they also practice, implement and teach these techniques. QPT head hunted and hosted Peter McIntosh from Natural Building Collective, who is one of only a handful of natural building experts in South Africa. His experience in sustainable living practices includes sustainable agriculture, off-grid energy systems and an array of natural building techniques, all of which is in fruition on Berg-en-Dal outside Ladismith in the Klein Karoo, a farm owned and managed by the community and educational non-profit the Klein Karoo Sustainable Drylands Permaculture Project, where he is a resident and member.

Some of the mudbricks that were made on the day drying in the sun

Some of the mudbricks that were made on the day drying in the sun

Contributed by Amanda de Gouveia on behalf of QPT. Photos courtesy of QPT. Please visit their Facebook page for more photos of the day.

Amanda de Gouveia

Amanda de Gouveia has been a research assistant at the Centre for Development Support at the University of the Free State since 2010, where she has mostly been involved in research projects on social development and local economic development. This has refined a unique repertoire of research skills, both qualitative and quantitative. She has also Masters degree in Research Psychology.



Getting a feel for Light Earth

by Peter McIntosh

What I find exciting about natural building is that there are as many ways of using available resources as there are cultures around the world. No absolutes in terms of technique, consistency, design and use of materials exist. People approach similar decisions based on their physicality, life experience and imagination. It is always interesting to me to observe how people I teach and work with approach the material and I try not to prescribe my methods of doing things on people before giving them a chance to display their natural ability or cultural diversity. The world will be a poorer place if natural building became as regimented as the conventional building industry can be. Natural building is not a one size fits all scenario. It can’t be as the materials always vary depending on what is at hand, from rock to wood or a multitude of earths. What works here may not work there because the earth changes or the type of timber in your area is different and has different uses. What this affords us, is to become more engaged with the material and not reliant on books and building codes. There is what works and what does not, and a world in-between.

I have discovered for myself a range of techniques that work and have come to understand that technique is as important as knowledge. Little things become as important as the big things. Just how you apply a plaster coat is as important as the recipe for the mix. A material may not work in a particular way, but if you change the technique, add more or less water, put the material under pressure or just simply allow it to breathe you may have success. When I feel ready to abandon an idea that I thought might work, I find myself wondering what I am missing, because you can be sure that others with the same materials have found a way.

Combining the same materials in different ways has different outcomes in terms of structural ability and how they perform thermally. Adding just a little straw to a mud-brick will double its insulating ability and increase its tensile strength. That is not to say you want the material to become more insulating; you may want it to be a heat-sink, to radiate energy or simply just lighten the material up.

A good example of a material that offers both good insulation and a solid feel, while not being so heavy, is a mixture of straw and clay. Or, what I call Light Earth. This technique uses a common practice of placing the material in a simple brick mould and has many other uses too, from insulation in roofs to the walls themselves. It can be shuttered in situ or simply stuffed into spaces, made into boards for the ceiling or bricks.

One method of making Light Earth that I have found particularly easy is to do is to make a circle out of straw bales and lining it with plastic to form a dam.

1_Building a dam

The dam is filled with water about a quarter of the way, after which you can begin adding clay.

There is no exact recipe and a little experimentation is required. The more clay you add the thicker the ‘soup’ will become and the denser the resulting bricks. The dryer the clay is when you add it the better because it then dissolves quicker when added to water. Powering the mixer with loads of feet works best and I have a hard time stopping folks from having a clay bath during courses. Once all the clay has dissolved it’s time to add the straw. A whole straw bale is mixed in using the same method, although this stage of the recipe requires a little more effort.

2_Mixing the clay soup

Once all the straw is thoroughly coated with clay it is removed in heaps and placed on the side of the dam to drain back in any excess liquid. The mixture looks like a bunch of wet straw and not a heap of mud.

3_Extracting the material

This wet straw is then pushed into a mould with care taken to avoid layering. If the block is to be used as a structural element, for example a wall, the soup needs to be more dense so that all the gaps between the straw are filled with clay, otherwise its fine to have some gaps. Scoop any excess clay off of the top and return it to the dam.

The block moulds may be any size and can be as thin as 50 mm and one meter square if they are to be used for making a ceiling, just as you would use with conventional materials. The blocks below are 300 mm by 300 mm and 170 mm deep. A huge advantage is that Light Earth blocks are less than half the weight of a traditional mud brick and with the added advantage of all that insulation. Of course, the weight and thermal conductivity will depend on the amount of clay you added in the first place. As a rule of thumb the material approaches the insulating ability of a straw bale wall when it is 200mm thick.

4_Material in brick mould

Keep adding straw till the clay soup is used up.

These blocks are practically indestructible and survive repeated dropping with no effect. They do however take longer to dry in the sun than a mud brick and a good run of clear sky is essential. They take around 3 days to dry sufficiently before they can be turned on their side to speed up drying, depending on the weather. After about a week they can be stacked with gaps in-between the bricks to finish the process off and covered while stored to protect against the rain.

To conclude, Light Earth is a very versatile material with so many applications just dying to be tried and it’s a load of fun to make. I wonder what would happen if you threw a few kids into the mix as well?

Photos 1, 2 and 4 were taken during a Natural Building Course at Berg-en-dal, which Peter McIntosh co-facilitated with Neil Smith.

Photo 3 was taken at the Tara Rokpa Centre in Groot Marico, a Buddhist retreat where Peter was involved in the building along with architect Paul Marais.

For more information on the courses that Peter McIntosh is involved with please visit our Events page.