Earthships and Ventilation in Cold Climates – Problem?

Ventilation and air quality is one of the last and most problematic issues I’m left with in regard to Earthships in cold climates. Cold climate is what I’ve experienced in a mild Romanian winter which includes snow cover, continuous (many weeks if not months) subzero temperatures and no sunshine (passive solar gain) for two week stretches.

To avoid confusion (as I have encountered it myself in trying to figure out this issue) let me re-iterate: the problem I am trying to outline here is not heat but ventilation – the removal of stale air and it’s replacement with fresh air. There is no question in my mind that no matter how efficient a properly insulated Earthship can be, in our Romanian climate, it will require additional heating. However heat and it’s origin does effect the flow of air throughout the house.

In this post I will try to outline what I’ve been able to figure out so far. The bottom line will be that in cold climates there is a ventilation problem. I hope this post provokes further input and conversation through comments. I would especially love to hear from people who have lived in Earthships in cold climates and their experience of ventilation and air-quality. Then, in a separate follow-up post I will try to present what seems to me like a potential passive, energy efficient ventilation solution.

Classic Earthship

The classic Earthship ventilation theory is simple and straightforward. Fresh cool air enters from the operable windows on the front face. This air is heated by solar gain, warm air rises and escapes from the skylight resulting in a continuous flow of fresh air through the living space.

The ventilation problem is already present in this simple model. What happens when it’s so cold that operables and skylights (both covered by snow) are kept close to keep heat in (and snow out). To my understanding there is no air flow.

 The only way to get fresh air in and stale air out is to let the cold in. Earthship theory would say that is not a problem because the thermal mass of the house contains enough warmth to compensate for coolth that comes in through the openings. In our climate I don’t think will hold true. I think we will have to heat the house in addition to water solar gain (hopefully much less then a house built above ground) and ventilating would entail precious heat loss.

Global Model Earthships

The Global Modal Earthships make two distinct changes to the elements of ventilation (actually there is a 3rd which I will address separately, see earth-tubes below). The first is the introduction of the corridor wall which separates the living spaces from the greenhouse. The second is the skylight over the greenhouse which comes INSTEAD of a skylight in each living space (I wasn’t sure about this until I encountered this video from Earthship Biotecture). In this configuration the greenhouse has been described as an air-lock that supposedly provides better climatic control by isolating and containing variations between it and the living space.

 There are now two ventilation circuits in the house. The first is between the outside and the greenhouse and the second between the greenhouse and the living spaces. The ventilation loop between the outside and the greenhouse is obvious and is similar to the classic Earthship approach.

I have some doubts how well the ventilation loop between the greenhouse and living space will work. As I understand it, if passive solar gain is the main source of heat then the greenhouse will always be warmer then the living space. This means that there may not be much flow from within the living space (cooler and heavier air) to the greenhouse (the already warmer and lighter air). It seems to me that the flow in the greenhouse may over-power the flow from within the room. This may be effected/controlled by alternating openings (eg: first ventilating the greenhouse, then closing it and ventilating the living spaces) and height positioning of the ventilation passages between the corridor and living spaces.

As with the classic greenhouse I do not see any potential for passive ventilation on cold cloudy winter days.

When a source of heat is added inside the living space and the hot inside it becomes warmer then the greenhouse – there can be a ventilating flow between the two spaces (and of course heat will be lost from the living space to the greenhouse).

If, in addition to the heat source, the front operables and skylight are opened then there may be some draw of fresh air from the greenhouse to the living space (and of course heat will be lost from the living space to the greenhouse and then quickly to the outside).

So, it seems that any ventilation will come at the expense of precious heat.

Earth-tubes

Global model Earthships introduce another element they call “Cooling Tubes”. These are tubes that are buried in the ground (~20 feet) behind the house and penetrate the rear wall.

They are intended to provide natural cooling. Warm air in the greenhouse is released through the skylight this creates a draw pulled in through the cooling-tubes. Warm air is drawn into the tubes from the outside, loses heat to the ground in which the tubes are buried and arrives cooler into the house.

This solution addresses ventilation in a hot climate, it does not address ventilation in a cold climate. However, I do believe it points in the right direction. More on that in an upcoming post.

14 Comments

  1. Posted January 21, 2012 at 12:39 pm | Permalink

    The problem with vents near the ceiling is that that is where some key solar gain is entering the living space. Maybe those vents are open windows. Why not just open the door and/or put the window vents above the door?

    For winter ventilation if it's serious, you can simply open the same vents for say 30 minutes and then close. I think a simple solution is just to open the window on the 2nd greenhouse glass and the room doors for a while, but not too long or you might freeze some plants.

    • iamronen
      Posted January 21, 2012 at 6:28 pm | Permalink

      I will address the issue of ventilation in a separate post … it is, I believe an important and neglected topic in Earthship design – especially for cold climates. To me, in the climate we live, releasing precious heat into the cold air is a very poor solution. I am happy to say that I already know of a better solution. I am now researching it and how it can apply to an Earthship. I promise to write about it extensively. It is a very important issue.

      • Kevin
        Posted January 24, 2012 at 7:01 pm | Permalink

        Are you willing to share the idea that you are researching so I can do the same?

        • iamronen
          Posted January 25, 2012 at 6:32 am | Permalink

          Already started doing that here: http://bhudeva.org/blog/2012/01/23/building-an-ea

          Now looking to integrate with existing Earthship design … stay tuned

          • KMac
            Posted April 23, 2012 at 8:51 pm | Permalink

            Built years ago; I'm in clay and a french drain was required 50' back to knock out horizontal lenses of silt.

          • iamronen
            Posted April 24, 2012 at 5:11 am | Permalink

            (a) what does your comment have to do with venttilation?
            (b) what are "horizontal lenses of silt"?

          • KMac
            Posted May 27, 2012 at 12:01 pm | Permalink

            you mentioned that you were constructing in a clay setting, my experience has been that water travels along silt lenses (deposit) sandwiched between the clay, depending on your topography cartesian properties in clay regions can be present (as is the case in my area) this requires that you cut the silt lense (french drain) and drain it away from the building so it does not impact the earthed umbrella.

          • iamronen
            Posted May 27, 2012 at 12:46 pm | Permalink

            true 🙂 that is one of the elements of the Passive Annual Heat Storage solution: http://bhudeva.org/blog/2012/01/23/building-an-ea

            I was wondering if french drains around the periphery of the house were enough or would it better to create more dense drainage with additional branches beneath the floors.

          • KMac
            Posted June 2, 2012 at 11:16 am | Permalink

            To qualify my experience, I have a 4' earth cliff on the west, north and east walls. If you are not employing an earth cliff, pay particular attention when you remove your top soil to the clay and look for any evidence of silt lenses/deposits. If you see any evidence then employ additional drainage. Otherwise leave the clay intact and use stone or pit-run under your floor and slope the clay floor away from the structure. Further to your expertise, I am looking at removing the current roof and employing PAHS to alleviate the temperature/air movement conditions of the house. Although I am pleased with the thermal mass design and lowest winter temperatures in the house for the past 20 years not getting below 48'F with no heating, if the addition of PAHS could increase that temperature while providing adequate air movement I would consider the expenditure. Opening the skylights to achieve air movement is a problem when it is -10'F outside. Any further comments or correspondence would be greatly appreciated.

          • iamronen
            Posted June 2, 2012 at 1:42 pm | Permalink

            Thank you for sharing your experience.

            Given our clay-rich soild we do not view earth-cliffs as a feasible approach. We intend to build with tire-walls all the way down.

            From the excavations we've done so far there weren't signs of silt deposits however the ground is extremely saturated and the water table is fairly high (probably ~10+ meters where we intend to build). Are you suggesting that the to slope the clay away and then simply level it with stones or gravel? If so:
            1. Would you install drainage pipes in the stones?
            2. Would you at least install an east-west drainage pipe to drain water from beneath the stones?
            3. How much of a slope would you create?
            4. How would such a stone sub-floor meet the internal dividing wall?

            In what kind of climate is your house built? If you have earth-cliffs would I be correct in assuming that there is no insulation? Do you need a lot of energy to heat the house beyond its ambient temperature?

            Indeed opening skylights does not seem to me like a feasible or responsible solution in our climate. Also, skylights are an added complexity and point of weakness I would be happy not to have to deal with.

  2. Paulette Chretien
    Posted December 20, 2012 at 8:57 pm | Permalink

    Well, why not set up some type of heat reclaim surrounding pipes that pump the air through either the flooring or if you must vent to the outside, over copper pipes with water, oil or some type of heat absorbing salt water flowing through or in them. You could also force the air over conductive ceramic tile or plates that reabsorb the heat. Seems like there are enough clever people involved in this issue to be able to come up with a means of reclaiming heat in cold countries. That heat loss could also be a means of melting snow and thereby providing extra water during the winter months could it not?

    • iamronen
      Posted December 29, 2012 at 3:22 pm | Permalink

      Most heat reclamation systems are complicated, expensive (to purchase, install, use, maintain ..) and power consuming.

      Fortunately, there seems to be a much better solution … accumulating heat during the warm months in the earth immediately surround the (uninsulated from it) house … and then benefiting from that heat naturally radiating back into the house during the winter months. More on this here: http://bhudeva.org/blog/2012/01/23/building-an-earthship-in-a-cold-climate-stop/

  3. Posted April 2, 2013 at 11:24 pm | Permalink

    Hi, really interesting inquiry!
    Heat recovery ventilation, also known as HRV, does not need to be expensive or complicated.
    HRV design and implementation is actually understudied, but it is the only solution forward to airtight envelopes for energy reduction (and/or plants to consume CO2)
    Here you will find a neat diy example built with cardboard (cardboard HRV’s help humdidity control):
    http://cheap-easy-living.weebly.com/index.html

    We have further information at the Center for Applied Building Science:
    http://www.facebook.com/CenterforAppliedBuildingScience

  4. Posted July 17, 2014 at 1:15 pm | Permalink

    We are currently building an earthship in Teton Valley Idaho at 6500 feet and have long winters. It is very important to us to be breathing the wonderful clear air of this pristine environment and not stale air / polluted air that may build up inside a sealed house. The diy HRV systems look interesting, but at this point I believe we will choose to put a conventional HRV or ERV system in our house that adds fresh air to the house while capturing heat at an efficiency of over 90%, which is pretty good. In our climate, you would never want to just open a window in the winter time to get fresh air, as the temperatures can easily be well below zero degrees outside.

    We are looking at these two options:
    The Ultimate Air 200DX, which is an ERV system also helping to retain humidity
    http://www.ultimateair.com/

    and the much simpler and easy to install Lunos e2
    http://foursevenfive.com/product-category/ventilation/lunos-e2-2/

    These cost a bit of money, but the second one runs on 1.5W and is expected to run for 100,000 hours, providing our family with fresh air throughout the year. It basically is a small heat capturing ceramic unit with fan which is installed into the wall at each end of the earthship. then it blows air one direction (one end blow air out of the earthship, while capturing the heat that blows out into the ceramic core, while the other fan blows air into the earthship). Then after 70 seconds it switches directions and now such outside air through the heated ceramic core into the space, and the other end blow air out. this goes on and on.

    I hope this is helpful.
    Christian

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