An Interview with Sigi Koko interviewed Sigi Koko for a podcast that you can hear at that link. Below are some of her comments:

I have a graduate degree in architecture and I then had worked for a construction company doing just conventional housing construction to get some experience building so that I could talk to builders better and know what their job was like a little bit better. And then I worked for an architecture company and then soon as I was done with my apprenticeship, I was outta there.

To me natural building is using the materials that you have available locally, that you have in abundance, that you can harvest without harm, and using those materials to build the most energy efficient building that you can. It doesn’t mean everything is dug out of your yard to build your house, but the goal is to use as many natural materials, as many materials from nature in our surroundings as possible.

So generally that means a pallet of generally agricultural fibers. So we’re talking straw, right? We’re talking clay from the ground, stone. And if it can be respectfully harvested or locally harvested in a respectful non environmentally damaging manner.

There are examples of natural buildings everywhere in the world. 70% of the world  population lives in a home that has clay in it, for example. Some of that is necessity, some of that is tradition, and some of that, in the U.S., it’s getting back to something that was there for a really long time. I would say if you live anywhere in the U.S. you could certainly find someone who understands how to design and/or help you build a natural building.

I would rather have lots of different building designs, lots of different looks, lots of different aesthetics, lots of different functionality. And then have this material palette that can be used to make the building look however you want that’s also then healthy. That also has a low carbon footprint and that are just beautiful homes, right?

If I’m building something that I’m calling a natural building, I want it to be energy efficient. I want it to close my water loop. I want to clean the water that I use. But I sure as heck also want it to be really healthy, right? So buildings that are made with straw and clay… they actually clean the air, right? So like the clay has this ability to absorb toxins and encapsulate them. So you’re in this sort of breathing lung building. It’s like something that cleans your air.

I’m not a big proponent of taking one design and then putting it everywhere in the world. That’s not logical to me. You should be able to look at the building and tell what climate is it in, right? If it has a flat roof, could it be because you’re collecting water? You live in an arid climate and you’re using the roof to collect water. If you have a very steep roof, okay, maybe you get a lot of snow there and you don’t wanna have the snow pile up on your roof, right? You should be able to look at the building and say, oh, that’s a hot climate. Oh, that’s a cold climate. Oh, that’s a four season climate. She must get a lot of rain. If you can’t look at the building and tell where you are in the world I lose the point.

If you have a road noise in one direction, maybe you wanna build something so that you protect yourself from the noise of that road. If it’s really windy in one direction, maybe you wanna orient it so that you can plant a row of evergreen trees with low branches like junipers or something so that you block the wind. Definitely the angle of the sun, because that’s sort of your magic in terms of energy efficiency, because if you face the equator, the sun is high in the sky when it’s hot out, and it’s low in the sky when it’s cold out. And so you can capture the sun in that low angle when it’s cold, when you want the sun, and you can shade yourself from the high sun very easily with just a little bit of a rim on your roof. And so using that, that orientation to the sun is definitely a big one.

If there’s a dramatic slope, you might wanna step down the slope. There might be deer paths, there might be things you see, right? A view that is, oh my gosh, we have to look at that tree, or that stone, or that, whatever, right? So all of those variables get mapped out on the site, and then you start orienting the spaces with all of those things in mind. So it’s like this gigantic puzzle that you’re solving. To me the solution has everything to do with the aesthetic criteria of the client and the functional criteria of the site.

So I wouldn’t say on a flat piece of property let’s go underground, right? On a hill property, maybe part of it wants to be underground. So in, in Iceland, for example, they have a higher ground temperature than we do, where you have thermal activity in the ground, the ground temperature’s around 57 degrees, so the ground temperature doesn’t change and the outside temperature does this day and night. It’s going up and down, up and down. You can create a consistent temperature inside a building by using the thermal mass of the earth to create that constant.

But there’s moisture in the ground, so how do you keep that moisture out? And usually that’s not a natural solution. You can’t put windows if it’s underground. So it’s hard to balance your daylight. It’s hard to get good airflow if you can’t get a window on the other side. So there’s pros and cons for sure to building underground. But I wouldn’t say you should always do X. It’s certainly something you can have in your wheelhouse to connect to that mass of the earth.

Cob is the same material as adobe, which is a combination of clay, which is sticky, sand, which is like a tiny stone, right? So it’s very strong to push on, and then straw fiber or some kind of agricultural or natural fiber. And the fiber gives it tensile strength. So you have fiber that’s tensile that can pull, you have sand that can push, so it’s strong in pulling and pushing. And it has clay that sticks everything together like glue.

And the difference between cob and adobe is that adobe are formed into bricks and then dried in the sun, and cob is built monolithically in place. So that’s literally the only difference. Different parts of the world actually have different terms for cob. “Cob” is the British term.

Straw bale is basically you’re building a masonry house, but instead of bricks or concrete blocks, you’re using big fuzzy straw bales. But otherwise, same idea. You lay one row, you put the next one offset so that they interlock, you pin them together, you plaster both sides. When you’re stacking, there’s only straw. When you’re done stacking and you have a wall, then you put usually plaster on both sides. You can also put siding on the outside if you want siding.

And then hempcrete is a combination of, it sounds like it’s concrete, but it’s not. It’s hemp hurd fiber. So hemp hurd is the woody stock part of a hemp plant, and they chop it up so it looks like little twigs. And they’re hollowish, and you coat that with lime. So a particular type of lime called hydraulic lime. And all that means is it’s a lime that is calcium carbonate, which is what limestone is, what marble is, right? And it reacts in two ways to harden into like a mortar almost. It reacts with CO2, so it pulls CO2 out of the air into the lime. And it also, because it’s hydraulic, it reacts with water. So as soon as you start mixing it and you add water just like cement, when you add water, it starts to harden. So some of it hardens with the water, some of it hardens over time by pulling CO2 in. And basically you have this hemp, you coat it in the lime, so it looks almost like a really gross rice crispy treat.

Straw bale can be either structural or infill. Hempcrete has to be infill, so it needs some other structural system. You need a cavity to put the hempcrete in.

Straw bale and hempcrete are insulation materials. That means they slow the flow of heat through the wall, whether it’s you’re warming the inside space and it’s winter outside and you’re trying to keep the heat in instead of having it travel out; or where you are, it’s hot outside and you’re trying to stay cool inside. You keep that heat from coming in. So either way, an insulating material blocks that thermal flow. The more insulation you have, the more you block that flow from ever entering.

Cob is what’s called a mass material and a thermal mass. Instead of being a block to energy transfer, it has conductance. It can allow heat energy to flow through it, but it flows through and gets stored in the mass, like a battery.

So if you’ve ever had aluminum foil in the oven, right, and the oven could be 400 degrees, and you pull it out and you can touch the aluminum foil almost immediately, it’s because the aluminum foil conducts that heat energy so quickly that the heat leaves and you can touch it. If that were a mass, like a stone and you stick it in the oven, it would stay warm for a really long time when you pull it outta the oven. And that’s the property of thermal mass. It’s like this battery for heat energy. So it’s completely different kind of material than insulation. And when you use them in combination, so an insulating material outside, so create a bubble between you and outside, and then put lots of mass materials like cob, like thick plasters, like adobe, like rammed earth inside, then you create the most energy efficient building that you can.

So as an example, the very first straw bale buildings were built in the 1800s, 1880s. When the straw, the bailing machine was invented. They very quickly figured out that the barn where the animals were was warmer than the house and they started building. In Nebraska where there weren’t a lot of trees, they started building with straw bales. And some of those original buildings are still standing today. The oldest building in a humid climate is in Alabama. It was built in the 1930s, also still standing today. None of them have mold problems. So let me explain why.

Any biodegradable material like wood, which we build with all the time. So wood and straw are actually very, very similar materials. It’s just the shape . It’s literally if you took wood and you made straws out of it, you would have exactly the same thing as what’s in a straw bale. And any biodegradable material needs moisture in order to decompose, and mold also needs moisture in order to bloom. So there are mold spores everywhere, right? Everywhere. Right here in this room right now, there’s mold spores. In your room. I’m sorry to tell you, there’s mold spores. But they need both the microbes that cause decomposition and mold spores need 18%, consistently 18% moisture content in order to flourish.

And so if you keep your wall dry, which kind of a goal in a building, generally. If you keep the walls dry, it will last forever. Just like wood, right? If you can build with wood, you can build with straw, it’s literally the same material. It’s just shaped differently. There are examples of moldy wood buildings, but it’s not because of the wood, it’s because of how the wall was constructed. And there’s a leak somewhere and there’s condensation inside and it’s not breathable.

There’s two ways that moisture can get inside of a building. There’s literally liquid water. And then there’s humidity. So liquid water, rain, and a burst pipe. That’s the two ways liquid water’s getting in there.

So rain is easy. Get the bales up off the ground so that where the rain splashes on the ground can’t wet the bales the same place every single time. And give yourself a nice hat on your building. Nice deep roof overhang so that you’re taking the water off the roof and taking it away from your wall. And then I like to create redundancy at the top of the wall so that there’s two ways for water to go to the side of the bale instead of inside the bale. So just in case there’s a roof leak someday, which happens, it can’t drip inside the wall and you don’t know it’s there until it’s too late.

And then the second would be pipes. And the simple rule there is don’t put pipes in outside walls, period. No matter what you’re building with, don’t put pipes in outside walls. It’s the dumbest place to put a pipe. It’s just how you design where the plumbing goes. So that’s liquid water.

And then humidity. It’s only a problem if it can hit something cold and condense. Now it’s a liquid. Now it can build up over time and cause that wall to get wetter and wetter.

So the way that you keep humidity from condensing inside is also two strategies. One, put vapor permeable. It’s also called breathable, but it’s a terrible term. Vapor permeable materials on all sides of the wall. And all that means is that humidity can go through and exit in either direction freely. So you’re not blocking that humidity from transferring through the wall. And now it can’t build up because it can always have an exit.

And the second is eliminate cold surfaces inside your wall. So no metal. When you have a glass of ice water, ice tea, in the summertime when it’s really, really humid and you put it down and water forms on the outside, you don’t want that happening in your wall. And so that’s it. It’s that simple. And, and really those principles should hold for every single wall system, even conventional construction. They should be breathable finishes and no plumbing and get the bottom up off the ground and put a good roof overhang and eliminate condensation points. And all buildings would be built better if we did that.

The roof system is often conventional.  The difference there would be if you have a living roof and those have very low maintenance, basically weeding it until the plants can take off, and then they’re usually self-sufficient after that.

Maybe you replace a stud and drywall wall with cob or adobe or rammed earth so that you get that mass inside. It’s a clay wall and nothing’s gonna happen to it. And same with straw bale or hempcrete. They’re just inside your wall. They’re insulation materials. You don’t have to maintain your insulation materials. It’s really about the finishes then. Your finishes that might be different are on the exterior commonly. I would say you can put siding on any of those. Often it’s a lime plaster, which is limestone. I’ve been doing this for 25 years and I’ve had one client ever do anything to the exterior ever. That’s probably close to 50 projects. There’s less maintenance with the natural building generally, because it’s a higher quality construction.

Clay plasters are essentially made from clay soils or pottery clay. They can be pigmented, and they’re also extremely durable.

My first project was a two year project where I co-designed it and then helped construct it. So one project, two years. The second project, one project one year. And then from there forward it was between two and three, maybe up to five projects a year, and right now I have 11 projects that I’m working on.

It went from three to 11 since COVID. And I think it was just people sitting in their space for that long and looking around going, oh, maybe this could be different. Or, oh, it would be really nice to have a bigger office, you know, whatever.

My favorite foundation is called a rubble trench foundation. It was Frank Lloyd Wright’s favorite foundation. You dig a trench under the structural perimeter of your building. You line it with something called a filter fabric, which just prevents small particles from coming into the trench from the soil. You fill it with gravel, like the same gravel you would put in your driveway. So fairly large gravel. You tamp it so that the gravel just locks, and then you put a very small amount of concrete on the top.

So I would say there’s three paradigms that I usually have in terms of how it gets built. I would say this is the most challenging piece. The way that I work is I will teach whoever’s going to be in charge of the natural building pieces, I will come and teach that. But most architects don’t teach how to build the building, right? They do drawings and then it says stud wall. And every builder knows what that means.

I try to include at least one thermal mass wall. Usually that’s clay. So it could be rammed earth, which is just clay and sand tamped until you physically turn it into stone. It could be cob again, which is the sculpted adobe. It could be adobe. It could be stone. So some kind of mass wall inside. And what that does is it helps regulate the temperature so that you don’t get big temperature swings inside. Cuz it’s that big battery. So that’s number one.

Number two is you could have all of the interior walls could be completely conventional. They could be studs and drywall. That’s fair.

And three would be some hybrid.  For example, the wall is a stud wall but it has lath on it. So like old lath and plaster homes. And then it has clay plaster on the lath. And so you’re building the wall conventionally, but you’re finishing it in a way that actually we used to do, but we don’t do anymore.

And then for sculpted bits, that is wattle and daub, which is the original lath and plaster, which is just woven. It’s like there’s vertical pieces and then you weave through it. In this case, we took invasive vines out of our forest and wove them through the verticals, and then again, just smear clay on it and then plaster it.

If you’re collecting water, I like to use metal for its durability. Or in Pennsylvania we have a lot of slate and we have a lot of barns that are falling down that have slate roofs. So you can get basically salvage slate from something that came down. So that’s one of my absolute favorites is to use slate. You have to make sure that the load of the building can handle the heaviness of the stone.

I would say there’s a couple different components that feed into health. The one we think about the most is the material toxicity. When you’re using materials from nature in general, you’re using materials that don’t off gas nastiness into your space cuz no one’s sprayed it with chemicals, no one’s dumped it in chemicals to keep bugs out, right? It’s just from nature in your house. So we’re talking clay, we’re talking natural wood, we’re talking natural sealers that are all durable and beautiful and can be really, really tactile.

So part of it then is also looking at the other materials besides what goes into the walls. So specifying cabinets that are low or zero formaldehyde. Eliminating particle board completely because it has a lot of formaldehyde. Formaldehyde is a carcinogen. Minimizing the use of plywood. So you can use solid wood there. We used to build long before we knew how to make plywood. So that means there’s a way to do it, and it doesn’t always mean more cost.

And then the last piece of toxicity in terms of what’s in your air that you breathe has to do with cleaning materials, which a lot of people don’t think about. So I educate my clients on how to clean. You can clean your whole house with vinegar, baking soda, lemon peel, like things that are not toxic. Murphy’s oil soap, I love. You don’t need to use bleach, you don’t need to use nasty nasties. And cleaning products are not regulated in terms of what they have. So people think, oh, if I can buy it, it must be safe. Nope, not at all.

The other piece in terms of health in a space is natural daylighting and what your heating system is and what your cooling system is. For example, natural daylighting means if you put windows on two sides then you get balanced light. You get light coming from one direction, you get light coming from the other, and you don’t get these harsh lines between light and shadow. That’s called glare. So your space is brighter and less glare. And it means you don’t have to turn an electrical light on, which means you also saved energy.

The other piece of having windows on two sides of a space is that if you open them, you will automatically create a pressure change in your space that will cause airflow. If you only have one window, you can’t naturally create airflow. If you have two windows, you can create airflow.

When I take people who have never been inside a natural home and I give them a tour, they step inside the space and you can audibly hear people take a deep breath.

We have in this country a disconnect between, for most housing stock, between the person who’s gonna live there and the person who makes decisions about design and construction. They’re not usually the same person. I work only with clients who make all the decisions about their space. That is not most people. And if we had real say we would prioritize energy efficiency, health, quality of the space. Most people, that’s what they want.

I mean, in short, it’s building the smallest space that accomplishes whatever the goals are. Each family might have different goals, right? So a couple with no kids has a different size goal than a couple with six kids. If you work at home, you have different size requirements. And if you don’t work at home, you know, what size is appropriate for any given family is gonna depend on that family. But then build the smallest thing, like don’t build big just cuz you can. Build the smallest thing that accomplishes what the goals were.

1 thought on “An Interview with Sigi Koko”

  1. Great interview!
    So informative and inspiring, not to mention chocked full of common sense practices, that help restore the health of our sick and dying natural environments. Thank you, Sigi, for all that you do, and thank you Mother Earth News, and Natural Building Blog for sharing.


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