September 15, 2020

Building a Climate Cabin | Part II | Laying a Foundation

Join Mikael as she makes her way through the earliest challenges of constructing an eco-conscious small home.

Mikael Maynard
September 15, 2020

The foundation for the climate cabin has been poured and is setting as I write this! It has been a few days since the pour and every time I walk past the gray slab glistening in the steamy Georgia heat, I see a beacon of inspiration for the process to come. I am also starting to gain a deeper understanding of what it feels like to be in a 600 square foot space as the slab so graciously outlines it for me. 

Some days it feels so small and others so big — but, regardless, the blank canvas and its inherent destiny to transform and grow as it is built really excites me. 

Can you tell this process has really got me daydreaming? The dreamy ideal of building a house surrounded by nature on a beautifully productive farm was the backdrop to many of the stories I read growing up! 

Well, the real-life story of the climate cabin starts with laying a foundation, and that’s what I want to talk about today.

First, some background for those of you who, like me, aren’t expert carpenters: Foundations are the crucial first step to a durable structure. Done properly, a foundation supports the weight of your walls and roof while keeping the earth’s moisture from seeping into your home. It should also be able to handle the weather, temperatures and soil conditions of the environment it is placed in. 

In the case of the climate cabin, the order of materials used is earth, rebar, visqueen, then concrete.  I really thought there would be more to it — and don’t get me wrong, there is A LOT of precision, skill, talent and hard work that goes into laying a sturdy foundation — but I guess I never realized that bare earth is just inches below the concrete slabs on which many of us live so much of our lives. 

That realization inspired a great sense of awe and appreciation for the skilled crafters, tradesmen, and carpenters (in our case, Michael Shellman) who create this cohesive bond between rigid foundations and one of earth's most complex ecosystems — soil! 

Now that you know why I have such an appreciation for structural foundations, let’s dive a little deeper into the details of the climate cabin’s foundation. To start, let me tell you why we chose concrete, since many of you are probably thinking it doesn’t seem like the most sustainable option. 

There was a time when to me a sustainable home was one made directly out of the earth surrounding the house. I imagined the picturesque cob or strawbale homes that are very popular in the northwest United States. As much as I love the idealistic vision of a home sculpted right out of the earth beneath me, I have to remember — the climate cabin is being built in a swamp! It is hot and, oh my goodness, is it humid. The rains can be torrential and unforgiving, and the land on which the Johnny Appleseed Organic Village sits is already known to hold water.

Believe me, we looked into a few different foundation options before we chose concrete. The primary alternatives we considered were hempcrete and reclaimed brick pavers.  

Through our research, we came to discover that hempcrete would be a poor choice for a place that stays humid and wet for a large portion of the year.  To use reclaimed brick pavers, we would have had to pour a typical concrete foundation anyway, since the pavers themselves wouldn’t be strong enough to hold up the walls and the roof! Therefore, we decided to go with only concrete because It was readily available and we knew that it would be up to code — an important factor because we want the plans for this cabin to be accessible to everyone. 

From a sustainability perspective, it will be durable and long lasting, and its close connection to the earth will actually help to incorporate passive cooling in the summer and heating in the winter.

With that being said, the creation of concrete has a significant environmental impact. According to the Portland Cement Association, concrete is made up of 8% air, 7-15% cement, 14-21% water, and 90-75% aggregate (course and fine). Some mixes also include ingredients like fly ash that is a biproduct of coal combustion – not something I want to be in the concrete that I am going to be walking and living around. 

Other than the fly ash it seems relatively harmless right? Air? Water? Rocks? Those are all natural substances. But what is cement, and where does this aggregate come from?

The majority of commercially-available cement is composed mostly of calcium carbonate in the form of limestone — but in OUR case, it is also composed of a specific form of calcium carbonate called aragonite. I called the owners of the concrete company we used, to ask where they sourced all of their ingredients, and they informed me that the aragonite gets shipped into Jacksonville, FL, from the Bahamas. 

I looked into the quality of environmental care that goes into that process and unfortunately, I did not find any good news. There are whole islands in the Bahamas that are being dredged from the seabed up for their sand!

Beachrock in aragonite sand beach (San Salvador Island, Bahamas) (15807387450).jpg

To top it all off, according to Chelsea Harvey at Scientific American, “It single-handedly accounts for about 7 percent of all global carbon emissions, according to estimates from the International Energy Agency. That makes it the second-largest single industrial emitter in the world, second only to the iron and steel industry.”

The owner of the company then explained that the aggregate comes from a quarry in the middle of the state of Georgia. If you search image results for “aggregate quarry,” the pictures you see obviously show a slew of environmental health concerns, and reporting on this topic bears out what your intuition is probably already telling you.

One thing you should know about me is that I have a slight tendency to get into an “all-or-nothing” mindset. With that in mind, you can imagine that learning all of this made me feel like I “failed,” but I quickly realized that, in the grand scheme of things, pouring 1,080 square feet of concrete isn’t the end of the world. We even did the math to figure out the carbon footprint of our concrete foundation thus far — roughly 38 metric tons. According to The Carbon Farming Solution by Toenesmier and Chelsea Green, some multi-strata agroforestry systems are able to sequester 4.1 tons per hectare per year of carbon. [Brakas and Aune, “Biomass and Carbon Accumulation in Land Use Systems of Claveria,“ 170.] Since the Climate Farming methodology we’re implementing is designed to be at least as environmentally beneficial as the one used in the study, we have the capability of sequestering 33.21 metric tons of C02 within one year!

Clark Snell and Tim Callahan touched on this topic beautifully in their book, Building Green – A Complete Guide to Alternative Building Methods. They said:

“Foundations often set us dreamy idealists squarely in the modern world, whether we like it or not, the fact is that your hip eco-natural building might be best served with a foundation made using heavy machinery and some amount of poured concrete…Concrete is a versatile material that’s been used for thousands of years by humans in different parts of the world. There are several good reasons why its used for foundations: (1) it can be made to order, creating a variety of structural strengths; (2) it can be formed to almost any size and shape, acting almost like a poured-in-place rock; (3) it employs widely available, naturally occurring materials; (4) it’s relatively easy to learn how to use; and (5) it can be incredibly strong and durable. The downside is that it has a high embodied energy (the amount of energy required for its production, transport, and use) and causes pollution… The main problem with concrete is simply the obscene amount that’s produced worldwide each year…  It’s a wonderful, versatile material that should be respected and used carefully. For builders, that means two things: (1) design intelligently and (2) build smaller… (Callahan, Snell 140)”

Clark and Tim really hit the nail on the head when it comes to this topic, I could not have put it into better words. 

I can confidently say that designing intelligently and building small are two things that we are definitely doing to lower our impact, decrease carbon emissions and make this climate cabin a true testimony to its name.

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Mikael Maynard

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