Building an eco-house

Get It Lowveld
Igniting Change: Spark Festival in Get It Lowveld
January 30, 2018
Putting the “O” back in optimal growth
February 11, 2018

As I drive down the dusty path of The Oaks road, just outside White River, a collection of smallholdings and plots appear all around me. I enter a gate, park my car under a tree and stroll down towards one specific house. A stylish rectangular earth home with a grass roof appears in front of me.

Michael Matthews, creator and owner of the house,greets me at the start of his walkway, which slopes down gently through his garden. Michael is the Program Director for the Casterbridge Music Development Academy (CMDA) in White River. He also has a background in broadcast journalism and engineering.

Michael designed and built this unique home eight years ago, winning an AfriSam innovation award for sustainable construction. The eco-house features rammed earth walls, geothermal cooling, grey water recycling, solar water heating, it has the potential to be completely off-grid and is passive by design.

“I went through a very passionate enviros phase, so I built something which was low in energy,” Michael explains. His focus was on this, because he believes everything is about the use of energy. “Modern houses use vast amounts of energy, whether it is electricity or something else. You are using energy to heat it and to cool it”. Michael learnt very soon that his house works extremely well when the sun shines.


The shape

“The biggest thing about it is the shape, it is basically a straight rectangle”. While pointing to the front north facing side of the house, Michael explains how the sun heats up the wall in the winter, but never touches the wall in the summer. “I get free heating in the winter and I get no heating in the summer,” he explains, seeming chuffed with his creation.

There is also a downside to a design with a long thin shape like this. “You tend to have a dark side and you tend to have a light side in the house,” Michael adds, as he shows me the “darkest room”in their modern home. It isn’t even that dark.

Rammed earth and thermal mass


“The walls are 450mm thick; this is rammed earth. There are bricks there in the foundation, because we didn’t want damp to come into it, but this is soil,” Michael explains while touching the textured surface, with layers of brown, beige and a splash of earthy red peeking through.

“The one issue with a rammed earth construction, which is an alternative construction like straw bale houses, is that it is not a recognised building standard,” Michael adds intently. “If you build a house out of this, you cannot get a bank loan.”

They built the concrete columns first, but the soil (which is mixed with lime) was hand compacted. The thickness of the walls means it holds a huge amount of energy; that is what we refer to as thermal mass. The outside of the house can be hot, but the inside can stay cool. “That is without a doubt the most important thing about this house.”

Besides the thick walls, there is also 200mm of soil and grass on top of the concrete roof, which means the house is completely insulated from above.




Michael and his family uses very little water in their home. They don’t have any bathtubs, as they require vast amounts of water to fill up; they have low pressure and low flow showers.

They started with rain water harvesting off their soil and grass roof, but it doesn’t work that well yet. “The idea was that the soil will filter the water. But it takes a long time for the soil to stabilize to the point where when the water runs through, it clears. It is only starting to run clear now”. Instead, they have started harvesting rain water off their shed; when the water runs off a tin roof, it tends to be a lot cleaner.

Michael isn’t too stressed about his roof, because they have a borehole and they also recycle their water. All their grey water flows through a reed bed filtration system:“We have a reed bed down there,” he says, while pointing to the bottom left corner of the property. “All the shower water, basin water, washing machine water; all the water comes straight in here,” he explains as we inspect the reed bed.

“It flows through here once and it ends up like this,” he scoops up the fairly clear and odourless water in his hands. “Then this goes into another tank, which fills up the toilets.”


Three solar panels are used to heat the water for the house. They also have a fire boiler which can be used to supplement the warm water andit can be pumped through the floor for extra heating.

“The solar reduces its production when it is overcast; you have a lower output and a higher demand,” Michael explains while showing me the solar room. They have decided to switch over to gas as well; since then they have never had to move back to electricity at all.“If we had a two week period of overcast weather, we might have to switch over to Eskom.”

Composting, worm farm and worm tea

We take a stroll back to the house to inspect Michael’s worm farm. “This is the easiest and most successful thing we have,” he states enthusiastically. “Anything organic, we just throw on here,” he adds while showing off his worms in the compost, collected in a concrete type basin. “When it rains, the water runs through and collects in a tank underneath here. I can then pump out the worm tea.”

“People talk about worm tea as being this magic thing you pour onto your plants. It is all the nutrients and minerals which have leeched out in liquid form,” he explains as he points to the compost. “It is supposed to be very fertile. You can go down to the gardening shop and buy worm tea, which is outrageously expensive.”


Included in all of Michael’s efforts to create an eco-house with a low impact, is a biodigester. A biodigester is a device or structure in which the digestion of organic waste matter (by bacteria) takes place, producing a burnable biogas.

“The idea was that you could get off the grid gas with it,” Michael says while looking for a lighter. “The toilet runs into the biodigester and you could add more organic matter. As it breaks down, one of the by-products is methane.”

Unfortunately Michael’s biodigester has a crack in it at the moment, which is causing a leek. “It isn’t working as it should, but you can get it working to the point where you could be independent of gas, water and electricity.”

Is it worth all the effort?

“A lot of stuff we have designed have become a bit irrelevant,” Michael admits. “The most important aspect is the shape of the house. If every house was built like this, it would make a huge difference.”

Besides going through all of these environmentally friendly efforts, Michael has become a bit of a cynic towards this style of building. “I now think that this is a massive waste of time,” he states. “There is only a handful of people who build like this, because they understand the consequences of what we are doing.”

He has changed his attitude and wants to tell people to burn as much fossil fuels as they can and to cause as much global warming as possible, because then we will finally hit a boundary. “Everybody is suddenly going to have to respond like Cape Town: Oh my gosh, we have to do something!’’ he exclaims.

He feels that there is no point to being an island in a space where everybody else is not properly prepared. “You sit there and you start saying to people, ‘you need to change, you need to change’, when actually nobody changes unless they really have to.”

If you want to hear more about Michael Matthews’ thoughts on building passive eco-houses, be sure to catch his talk at Spark Festival 2018, from 2 – 4 March.



Pin It on Pinterest

Share This
%d bloggers like this: