I'm not the Mike Reynolds who invented the Earthship, I'm the Mike Reynolds who thinks Earthships in Canada and other cold climates are a bad idea. A coincidence of names; just putting that out there so The Garbage Warrior doesn't get hate mail that belongs to me. 

Where did the Earthship come from?

It first showed up in New Mexico back in the early 70s as the brainchild of Architect Michael Reynolds. They called him the Garbage Warrior, and he was a pioneer of low-impact living in a time when few such visionaries existed. His work creating self-sustaining houses mostly out of garbage inspired countless others to build on his ideas. He continues to work tirelessly in drawing attention to the irresponsible waste of resources that plagues the globe.

What defines an Earthship?

It should be noted that "Earthship" is a registered trademark. You can build one and tell your friends it's an Earthship, but a home whose construction was not authorized by Earthship trademark-holder Michael Reynolds cannot officially bear that name. So don't mistake this for being a fluid and collective movement advancing the cause of eco-harmonious housing; this is a branded, for-profit enterprise led by a larger-than-life figurehead. 

The Earthship in a nutshell:

  • Tires filled with packed soil are used to build the main support walls; aluminum cans and mortar, along with glass bottles, are used to build interior walls.
  • Earthships (by their own definition, at least) are passively-heated from the sun and thermal mass; the north side is buried underground, though buildings in colder climates seem to  include wood stoves.
  • Power is generated onsite by photovoltaic solar panels and wind, propane is typically used for cooking, and in colder climates water heating. 
  •  Rainwater is collected, stored in large plastic cisterns and filtered for residential use; waste water is treated on site and used for growing food.
  • The south-facing wall is all windows and acts as a heat collector and greenhouse where food is produced all year.

That's all great stuff and it seems to work fine in New Mexico, but now they want to take the show on the road, and this is where it can get a little touchy. If it's as good as they say and suitable for all climates, then it should stand up to scrutiny one would think.  But, pointing out flaws in either the design tends to offend Earthship enthusiasts, or 'green disciples' as Reynolds calls them. 

Building a house is a huge investment and there are too many false assumptions and obvious contradictions to accept the Earthship at face value when all empirical evidence says that it can't possibly do what its designer says it does when exported from a desert to a cold climate. So at risk of ruffling some feathers, we think this needs a close look before it takes hold in Canada as Reynolds hopes. 

My background: I worked for Greenpeace, I had long hair, I drove a VW microbus and I loved everything about the Earthship in the late 80's. I did not dive into this looking to shred it just for kicks, but to look with fresh eyes beyond the image and holistic appeal that I remember from decades ago. 

Earthships in appropriate climates:

New Mexico has a mild, arid/semi-arid climate, which is characterized by light precipitation, low-relative humidity and an abundance of sunshine, so there is no better place to build an Earthship.

The website still claims they are 'comfortable in all climates' and there is endless talk about how they are built with natural and recycled materials, have no energy bills, use no fossil fuels, are passively heated and cooled and occupants live in harmony and balance with the earths natural cycles. This is nothing near to how they are actually being built anymore, but facts seldom interfere with the spreading of a familiar and comforting gospel.

Just so you know we are not putting words in his mouth, here is Mike Reynolds speaking a couple of years ago in a video titled 'New Solutions Guide'. The following quote starts, of all places, at about the 4:20 mark. 

''Each building is a living breathing cell that is getting everything that its inhabitants need from an encounter with the natural phenomenon of the planet, like the sun, like the rain, like the gravity, like the wind, the condensation, the convection, all of the natural phenomenon of the planet are studied and observed and built into these buildings so that they, through encounter with the natural phenomenon become a living breathing organism that takes care of people, and doesn't need fossil fuels.''

Variations of that are repeated anytime a microphone gets turned on at an Earthship site, even in buildings where none of that is even close to happening. Like an Alberta Earthship owner, whose intentions I have no doubt are the purest, echoes much of that sentiment while stoking a wood stove in a house insulated with foam panels that has a propane-powered clothes dryer, cook stove and water heater. 

Here is how Mike Reynolds described that very house in the Calgary Herald- Canada is tremendously interested in this kind of a building,” he said. “A building that does everything for itself, totally off of every grid and they’re warm. It gets very cold (in Alberta) and the building has no backup heating whatsoever, it doesn’t need it.”

How does a wood stove not qualify as backup heat? And when did propane stop being a fossil fuel? You don't have to dig very deep here to realize that what is being claimed is not what is actually happening. If you wake up in a house that is 14°C  (as these lovely people do) and you need to keep a fire going all day to warm it up, your house is not staying warm by itself. 

In reality, an Earthship in Canada is a predominantly passively-heated home that burns biomass and fossil fuels for supplimentary heat and power; it is insulated with foam panels on the walls (we found no mention of floors) and includes thermal mass inside of the building envelope.

I'm not here to criticize the fossil fuel use or foam insulation, but it's no more a 'natural phenomenon' or 'living breathing organism' than a normal basement with exterior foam insulation.

Unfortunately for many Earthship owners around the world, including insulation in the design was a revelation that only occurred to Reynolds after 30 years of telling people they didn't need it. 

Reynolds describes the addition of insulation as 'turbo-charging' the Earthship, and in a 2009 Youtube seminar he describes it. Even though it was in about 2005 when this design improvement happened (which was decades after basement insulation was already standard practice), he speaks as if insulating below grade thermal mass walls was his own idea, and gave home insulation a new name - Thermal Wrap

"If the Earthship were a gasoline engine, Thermal Wrap and double or triple greenhouses would be fuel injection. I am ready to race any conventional heating system." - Michael Reynolds, Earthship Biotect

Thermal mass does store and release heat, but the magic happens by separating the interior and exterior environmental temperatures, not by joining them. He seems to have realized that now, at least with walls, but being late to the game he is also a bit behind in knowing the amount of insulation that really should be installed as well as where to put it. Example:

The three images below are thermal models showing what you could expect from a concrete floor in a typical Canadian or cold-zone climate in northern USA; first un-insulated, the second insulated to meet Building Code (R10) and the third insulated to R20, the minimum we would recommend in Canada or colder States for comfort and a good return on investment.

Modelled using a 4-inch concrete floor, you can see that in the first image on the left (un-insulated as an Earthship is) the extended colour gradient from warm to cold shows that heat lost to the ground below is evident to a depth of many feet, while in the images with insulated floors you can see that much more heat is contained by the insulation. Also worth noting is the light red colour of the Earthship floor, indicating a cooler temperature that the white-coloured insulated floors, which is less comfortable for occupants. 

© Denis Boyer

As the ground in Canada is below 7°C in winter, if an Earthship in Canada truly did warm a house to a comfortable temperature, it would disprove the second law of thermodynamics which states that heat moves from warm bodies to cold. If heat were able to move from areas of cold to areas of warm – like from 7°C ground to any house kept at 8°C or higher - then one could also expect to see lakes freeze over in summer.

We all know that doesn’t happen, yet Michael Reynolds is still convincing Canadians that our frozen landscape will somehow heat their home. Believing that requires dismissing the basic laws of physics, and you would have just as much luck roasting marshmallows over a block of ice. Cold things won't make you warm, end of story. 

With mechanical assistance and an input of energy (like a heat pump), you can extract heat from the ground in a cold climate, but Earthships don't have heat pumps. 

If you still think the Earthship is the answer then please read on before you drop your life savings on one, even if you're already cheesed-off at me for having the audacity to pop the hood on this thing to see how it runs. If you find flaws in my analysis then please make mention in the comments below where you think I screwed up and I'll be more than happy to discuss. If you are here reading because you want to live in a home that harnesses heat from the sun and ground to keep you warm, we can help you with that in our passive solar home design pages.

1. Thermal mass:

The biggest flaw in the Earthship design can be traced to the misconception that the ground will keep you warm in all climates. Yes, the ground will add warmth to a cold house, but only up until the point that the temperature of your house and that of the ground reach thermal equilibrium, meaning they are equal. This is known as the Zeroth law of thermodynamics

According to Ecohome Engineer Denis Boyer, "The ground temperature in the Montreal-Ottawa corridor at a depth of about 10 feet would range from 6.3°C (43°F) in January to about 3.4°C (38°F) in April. At a lesser depth, the ground would be even colder during that same time frame."

That's a reasonable average to assume for Canada, and much cooler than the 58° Fahrenheit listed on the Earthship website that claims an Earthship works anywhere in the world.

Rather than the ground being a source of heat, in a minimally-insulated Canadian Earthship you will be dumping heat into the ground without insulation under floors anytime the indoor temperature rises to about 7° Celsius, which is pretty much every house in Canada one would hope. 

According to Reynolds, the key to the 'Thermal Wrap' design is putting the insulation several feet further back from the tire wall to increase the dirt mass of the wall (to about 7 feet he said in a video), which is said to improve performance, which it simply does not do.  

Denis Boyer goes on to explain - "Except for water and other materials with very high conductivity, due to the relatively subtle variations in temperature that any passively-heated house could expect to see over a 24 hour cycle, only the first 6 or 7 inches of the wall would show any noticeable temperature change through absorbing and releasing heat".

That means only the front third of the tire wall is acting as thermal mass in the way Reynolds claims it is, and none of the several feet of dirt behind it. Putting the insulation so far back means you now need to buy more eco-friendly styrofoam insulation boards to insulate the top of that 5 foot strip, for the entire length of the building, or the Thermal Wrap would do nothing at all. And more heat will also escape through the top insulation, so the only tangible result of that design modification is increased material costs and increased heat loss.  

2. Reducing pollution:

If your local grid is fed by renewable sources such as hydroelectric or wind power, then there is no need to install your own system to reduce your personal emissions. Again, go ahead and set up a solar array and battery backup for your own security of power, but if going 'off-grid' means you need to burn fossil fuels instead of tapping into clean energy from the grid, you are increasing your carbon footprint, not reducing it. 

All of Quebec is on renewable power, as is much of British Columbia and a growing percentage of many other provinces. Clean power currently provides a total of 18.9% of Canadian electrical needs

3. Material conservation and re-use:

It is obvious that the clean stacks of XPS foam boards I saw in several Earthship videos were not recycled, and they certainly didn't come naturally from the earth. That would then require the purchase and shipment of petroleum-based products that use blowing agents with very intensive greenhouse gas emissions (GHGs). This is obviously not a critique of home insulation, but I do question his choice of XPS foam over less environmentally harmful products.

Alex Wilson, founder of the Resilient Design Institute on XPS foam- Blowing agents create tiny bubbles of gas that are, in effect, the insulator in foam. They used to be chlorofluorocarbons (CFCs) that were banned for damaging the ozone layer, and were replaced by HFCs [that] don't cause ozone damage, but are more than a thousand times worse than CO2 as greenhouse gases.

The only way choosing XPS foam over other types of insulation will make the planet greener is by helping frozen tundra come back to life. For help choosing the most Eco-friendly rigid foam insulation panels, see here.

'We have been doing it now for so long that we really can't find better materials to build with" - Mike Reynolds, Earthship Biotect

It's not that he couldn't find better materials, he just walked right past them without knowing it. Right next to XPS foam in any building supply store would be a stack of EPS foam that uses different blowing agents that have much lower emissions, and they're much cheaper as well. Beside that would be a stack of rigid mineral wool, a board insulation made from stone dust that has no chemicals and contains a minimum of 75% recycled content. Or go with something completely natural like Hemp Insulation Panels. 

The interior walls are certainly beautiful, but sequestering thousands of aluminum cans in a wall is not necessarily a great use of metal in an age of resource depletion. In 1972 no one was using them, or old tires, so he was in fact doing the world a favour back then, but not anymore. Mineral extraction is quite harmful to the earth, and that metal would serve the planet better if it were recyled.

Recycled rubber roof shingles - Eco-friendly Green Building, or not?


4. Water conservation:

The Earth already has a natural system for treating and storing rainwater, though out of necessity Reynolds reinvented that system using plastic pipes, filters, plants and huge plastic cisterns. Kudos to him, that was a brilliant move to supply water to a home in a desert. But it is completely pointless in most remote areas of Canada and results in unnecessary costs, increased maintenance, and more embodied pollution due to the purchase of huge plastic tanks and equipment. 

The ground will automagically take your waste water and turn it into clean drinking water that you can access with a well, so let the earth do its thing. That is the entire premise of the Earthship, no? This is one of the more obvious head-on collisions between ideology and common sense, where homeowners are burdened with unnecessary complication and cost for no reason other than maintaining the image of the Earthship brand. 

You can still harvest rainwater that falls on your roof, all that takes is a rain barrel, and an outdoor garden to make great use of it. 

5. House Dimension:

The shape of an Earthship is typically very narrow and very long. This is by no means an optimal shape for material conservation or energy conservation. Example - a 25 foot deep house by 80 feet long would be 2,000 square feet and would have a total of 210 feet of exterior wall. Compare that to a 40x50 foot house, which is also 2,000 square feet, but has only 180 feet of wall exterior wall. That translates into - less building materials to purchase, less labour, less exterior wall for heat loss and the same amount of living space. Take a look at Passive solar home design page to learn how to passively heat a home.

6. Health risks:

The tires of an Earthship may release brominated flame retardants (PBDEs) into the air of an Earthship, which is a synthetic material derived from petrochemicals that is toxic to humans through long-term exposure. 

Mike Reynolds says it's safe, but he says a lot of stuff that doesn't add up so I personally would want to see some research on healthy indoor air quality before I spend the rest of my life living inside a stack of old tires. 

• Allergic rhinitis, asthma, respiratory infections, eczema and rheumatism are all diseases that are linked to mold exposure, which is a common problem with poorly-insulated homes, particularly poorly-insulated basements with high-humidity that have not been designed to manage moisture properly. This is pretty much the definition of an Earthship in the way it would perform in Canada.

Growing food in a cold-climate greenhouse creates a very humid environment, and a fundamental principle of the Earthship is food production on the south facade and transferring that heated air into the living space. So in order to take advantage of that passively heated air, you will greatly increase the interior relative humidity of your house.

Combine that with un-insulated exterior walls and you have the ideal environment for condensation to collect and mold to form. And as it requires more energy to heat humid air than dry air, higher relative humidity will also lead to increased heating demand or make your home feel even more cold and miserable.

We are strong proponents of greenhouses, even in cold climates and small scale food production, but they are not an environment that is sensible for human habitation as they won't heat in cold climates.

healthy levels of relative humidity in a home
According to health Canada, the optimum range of relative humidity for a healthy indoor environment would be between 30 and 55 RH, above or below those levels increases the risk of respiratory issues. © Health Canada


7. Ventilation:

Heat recovery ventilators (HRVs) are mandatory in performance rating systems like LEED, Novoclimat and Passivhaus. They are also mandatory in some regional building codes, but they are not found in Earthships. Instead, an Earthship gets ventilation through what they call earthtubes, and ventilation openings in the roof.

In the Earthship Seminar 2009 video, Reynolds speaks of 'ventilation without heat loss' in winter, right before describing how it works - you open the greenhouse skylight and the hot air rushes out, creating a vacuum and drawing in fresh air through the earth tubes.

If you intentionally release heat you worked hard to collect, to me that qualifies as heat loss, especially if you have to compensate by burning fossil fuels to warm your house again. A good quality HRV can extract up to 90% of the heat from exhaust air; the 'earth tubes' in an Earthship extracts none. Depending on the zone you live in, you should even check the difference between HRV & ERV systems to see which to choose.

8. Passive heat vs. growing food:

Earthships are equiped with a greenhouse for producing food throughout the year. A humid environment like that should be kept separate from living spaces for home durability and the health risks mentioned above, in which case you would be choosing food production over passive heat gain in living spaces.

To know if that's really a good idea for the planet, you would need to realistically calculate how much food you could produce in that space compared to how much heat could have been passively generated and decide which improves your carbon footprint. We would argue for the heat gain. 

To have any reasonable semblance of feeding yourself and your family you would need a garden somewhere in the area of 10,000 square feet. Growing a bit of food in your living room is wonderful, but it will not offset your carbon footprint anywhere near as much as a passively heated house would. Earthships don't produce anywhere near enough food to merit basing your entire home design around it. 

The thing is, if you're thinking of building an Earthship you'll need a fairly large piece of land, so why not go for the healthier and more efficient passive heating option and build a greenhouse somewhere else on your property? The reason you can't is because it doesn't fit with official ideology and image.

9. The cost of building an Earthship:

This is not a cheap or easy way to build, period. Along with significant material costs, the labour required is nothing short of biblical in proportion as you will need to ram dirt into some 800+ tires with a sledge hammer.

Unless you have a year to kill and plan to fill those tires yourself, you will either need to pay someone to do it or have a small army of volunteers, which is how most Earthships seem to be built. This is a very powerful brand and there are no shortage of people willing to do hard labour just to be a part of it. Regardless of whether you pay them or not, this is an incredibly labour intensive way to build. 

As for operating your home harmoniously using the aforementioned 'earthly phenomena', don't forget the cost of a woodstove, a generator, propane tanks, foam panels and tens of thousands for a solar array and battery backup system. You'll need a lot more than tires, dirt and pop cans. For an example of a Green Build that costs the same as a regular home build, see the EcoHome Edelweiss House.

Our conclusions on Earthships:

This is a concept born of wanting to tread lightly on the earth; we have nothing but great words to say about the motivation and ingenuity shown by Michael Reynolds in developing this building system some 40 odd years ago in a desert.

But it's hard not to conclude that he is now more focused on promoting his brand than the true cause of low-impact living. Otherwise the design would be adapted to specific environments and unnecessary elements would be omitted. Instead, he uses a loose interpretation of the laws of physics to create a very believable but inaccurate narrative to sell the Earthship brand and image in climates far beyond their functional range.

The leading edge of high-end Green home building design has advanced so far beyond the Earthship that it is simply irrelevant at this point. The same could be said of countless other brilliant inventions 40 years after their inception; pioneers in any field should feel proud when that happens. The Earthship deserves a place in the history books but it should also stay there, or at least stay far away from Canada.

For any design to really compete in Canada as a low-carbon footprint and high-performance building, it would need to include a significant amount of insulation, an airtight building envelope, triple-pane windows and a heat recovery ventilation system to name but a few features. 

If you've read this far and are still hell-bent on building an Earthship, we would recommend installing at least twice as much insulation as he says, put it right against the back of the tires and put it under the floor as well (6 to 8 inches would be wise). Use EPS foam instead of XPS, it's much cheaper and will result in about 200 times less greenhouse gas emissions. And what is most desperately needed is an HRV or ERV for energy efficiency, durability and occupant health. If you have to, do all this stuff at night when he's not looking. 

Some other reflections on Earthships around the globe:

''Most intelligent readers have an E.A.S. — that is, an exaggeration alert system (also known as a bullsh*t alarm). Unfortunately, Reynolds’ statements frequently set off my E.A.S. ''

- Martin Holladay Green Building Advisor

''The facts of habitation and performance in Mr. Reynolds’ presentation were very thin, all glossed over quickly as though they were undisputed truths ''

- Voussoirs Blogs on architecture

"The failure to insulate under the floor (on Reynolds insistence that is was unnecessary) was the result of the success of this strategy in New Mexico. Unfortunately temperature analysis of the Brighton Earthship has demonstrated that the lower ground temperatures in England cause an un-insulated floor to act like a bottomless drain on the internal heat rather than a store for it. The team have learned from this, but it is a mistake that could have been avoided had other advice been heeded."

- Things that wind me up Blog

"Because Earthships are not designed for their specific climate, they tend to have hot and cold spots. The Earthship literature tells us that “the average temperature in an Earthship is 70 degrees.” That sounds really comfortable, right? Except that temperature is based on an average of 365 days. The research and experience of many owners tells us that up to 70% of those days will include extended periods of over and under-heating - an Earthship is often hotter than comfortable between 10am and 7pm in summer and colder than comfortable between 7pm and 9am in winter."

-The myth of thermal comfort, from Hacking The Earthship Blog

To find inspiration on how to build true Eco-Friendly Green homes in a cold climate see here, or for a finely engineered solution to high performance check out Passive House certification here from North America's favorite no-nonsense Green Building Website, EcoHome