Do Earthships work in cold climates?

Despite the good intentions, Earthships in cold climates come with a much heavier environmental cost than they claim and contradict the laws of physics.

Earthship in Taos, New Mexico
Earthship in Taos, New Mexico via Creative commons

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. 

So where did the Earthship come from?

It first showed up in New Mexico back in the early 70s; it was 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.

Why do people love Earthships so much?

Because it's basically the coolest fort ever - an underground hideout made with dirt and stuff you find, no need for external power, it stays warm all winter and cool all summer, no trips to the grocery store, no parents to tell you what to do. It's you living in harmony with the universe and its natural systems - earth, wind and fire. But the real stuff; not the 70s funk band.

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.

  • 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 are passively-heated from the sun and thermal mass; the north side is buried underground.
  • Power is generated onsite by photovoltaic solar panels and wind, though buildings in cold climates at least seem to include propane generators and woodstoves.
  •  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. So, time to take the show on the road - right? This is where it can get a little touchy. If it's as good as they say then it should stand up to scrutiny, but pointing out flaws in either the design or the doctrine tends to offend devoted followers.

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 disclaimer: 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 see what true value and hard facts lay beyond the image and holistic appeal. This is a great message with the very best of intentions, just a poor understanding of how its own goals are best achieved. 

Earthships in appropriate climates:

New Mexico has a mild, arid/semiarid 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 it is 'comfortable in all climates' and there is endless talk about how it is built with natural and recycled materials, has no energy bills, uses no fossil fuels, is passively heated and cooled and occupants live in harmony with the earth. 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 their mouths, here is Mike Reynolds speaking in a video posted less than a year ago titled 'New Solutions Guide':

''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 nothing but 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 backup 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.”

Most people would probably say that a woodstove qualifies as backup heat; they are often a primary heat source in a house so I don't know how you could conclude otherwise. You don't have to dig very deep to find that what is being said does not always match what is actually being done.

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 any of that and it does work, but it's no more a 'natural phenomenon' or 'living breathing organism' than a normal basement with exterior foam insulation and a standard concrete foundation. Unfortunately for many Earthship owners around the world, including insulation in the design was a revelation that only occurred to him after about 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 long after it was already a common building 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 climate; first un-insulated, the second insulated to meet Building Code (R10) and the third insulated to R20, the minimum we would recommend in Canada for comfort and a good return on investment.

Modelled using a 4-inch concrete floor, you can see that in the first image (un-insulated as an Earthship is) the 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. 

Thermal image of how an Earthship works
Thermal image of how an Earthship would work in Canada © Denis Boyer for Ecohome


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 in winter 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 swimming pools and 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 homes. Believing that requires dismissing the basic laws of physics, and you would have just as much luck roasting marshmellows over a block of ice. Cold things don’t make you warm, end of story.  

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 heating pages. 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. 

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. The ground can add warmth to a cold house, but only up until the point that your house temperature is equal to that of the ground. 

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 much cooler than the 58° Fahrenheit listed on the Earthship website that claims this works anywhere in the world.

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 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". So really only the front third of the tire wall is acting as thermal mass in the way Reynolds claims it is. 

The only result of including extra dirt inside the insulation is increased greenhouse gas emissions and wasted money because you now have to buy more foam boards to insulate the top of that 5 foot strip the entire length of the building or the Thermal Wrap would do nothing at all. 

See the basement pages in our building guide for more on proper below-grade construction practices. 

2. Low-density living:

There are lots of us on the planet and there simply isn't enough room for all of us to have an Earthship. Go ahead and buy a chunk of land and shoot for autonomous living, we have no criticism of those who do not want to be dependent on conventional housing infrastructure, but do so for reasons of quality of life and self-preservation only. 

Earthships are not the silver bullet that will resolve global housing issues; if your mission is truly to lower your personal impact on the planet, then find a well-built condo near the shops and services you use with good public transportation close by. 

Low-density communities inevitably lead to significant carbon emissions through transportation needs, and most often with more than one family vehicle being required. If Earthship proponents are having a 'gotcha' moment thinking the electric car trumps that, then you better have really deep pockets to pay for a solar array capable of powering all your transportation needs.

3. Reducing pollution:

If your local grid is fed by renewable energy, then it can be more ecologically responsible to hook up to it for power than have a solar array that stores power in batteries filled with rare-earth metals, and far less harmful than burning fossil fuels the way cold climate Earthships seem to do. Being off-grid in no way equates to being 'green' if you are forgoing renewable energy to burn fossil fuels instead. 

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

4. Material conservation and re-use:

I have a hard time believing the XPS foam panels I saw in a nice clean stack in a video were 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 materials, 

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.

To be accurate, they are 1430 times worse than CO2 as a greenhouse gas, so the only way choosing XPS over other types of insulation will make the planet greener is by helping frozen tundra come back to life.

'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 a bit cheaper. 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. 

Recycled rubber roof shingles
Recyled rubber roof shingles © TRACC

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 he isn't anymore. The metal would be better off recycled and there are many new uses for old tires now, including durable building products.  

Alternatively, why not build a straw-bale house instead? Straw is a natural material, it has a good R value, building with it sequesters carbon, and depending on whether or not you are comfortable living at 6° Celsius, it would be either way more comfortable or way more efficient than an Earthship. It's certainly more natural and ecologically responsible than insulating a house with a mix of XPS and spray foam the way Reynolds suggests.

Or how about a cellulose wall? Cellulose insulation comes from recycled newsprint, and like straw, building with it sequesters carbon and it insulates very well. So how about a slab-on-grade house with recycled concrete, FSC certified lumber and dense-packed cellulose? And why not use recycled synthetic gypsum board so those pop cans be recycled and turned into more sensible products?

5. Water conservation:

We are strong advocates of residential water conservation and rainwater harvesting, particularly in urban areas. Mike Reynolds is an excellent ambassador on this front and is drawing attention to a pressing global issue.

His technique for supplying water may be crucial to the success of an Earthship in arid climates, but in areas of low density and demand (the kind of areas you could expect to see an Earthship built in Canada) it is not such a great concern.

The Earth already has a natural system for treating and storing rainwater; the soil filters water and it is stored in natural underground cisterns called aquifers. Out of necessity he reinvented that system using plastic pipes, filters and huge plastic storage containers, which is brilliant in a desert but completely unnecessary in most remote areas of Canada.

Rainwater harvesting
© Ecohome

This is yet another case of a head on collision between Earthship ideology and common sense, one where homeowners are burdened with unnecessary complication and cost for no reason other than maintaining the image of the Earthship brand. 

The cheaper and 'greener' option in such locations would be letting the earth work its magic and accessing that water by digging a well and pumping water up with renewable power like solar panels, or even the grid if you're one of the millions of Canadians who are served by clean power.

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

6. House Dimension:

The shape of an Earthship is very narrow and very long. This is by no means an optimal shape for material conservation. Example - a 20 foot deep house by 100 feet long would be 2,000 square feet. Assuming it is half buried, that is 120 feet of exposed wall and an additional 120 of below-grade wall built with foam panels, for a total of 240 feet of wall. Compare that to a 40x50 foot house which is also 2,000 square feet and has only 180 feet of wall in total. Less material, less labour, same amount of living space. 


7. Health risks:

• 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 and without a building envelope that properly manages moisture. This is pretty much the definition of an Earthship.

• A greenhouse is 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. This of course increases the odds of having mold and mildew issues; and as it requires more energy to heat moist 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 and small scale food production, but they are not an environment that is sensible for human habitation.

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

• The tires that make up the walls of Earthships may adversely affect interior air quality; there is a shortage of reliable research on this front. When not properly sealed (which they aren't, as it is not seen as a concern by the brand), Earthship occupants may be exposed to brominated flame retardants (PBDEs), a synthetic material derived from petrochemicals which are 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 air quality before I spend the rest of my life living inside a stack of old tires. 


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; an Earthship extracts none.

9. 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 just don't produce enough food to merit basing your entire home design around it. 

The thing is, if you're thinking of an Earthship you'll need a sizeable piece of land, so why not go for the healthier and more efficient passive 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.

10. Cost:

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 do it 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 powering yourself harmoniously using the aforementioned 'earthly phenomena', don't forget the cost of a woodstove, a generator, propane tanks and tens of thousands for a solar array and battery backup system.

Rainwater collection and treating your own grey and black water will take many thousands as well. This is another noble undertaking in an urban center rather than hooking up to a sewer, it just doesn't come cheap is all and a septic bed does pretty much the same thing. 

Our conclusions on Earthships:

The Earthship 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 home building 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 really good HRV 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 tires and put it under the floor as well. If you have to, do it 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