Earthship Tire Off-gassing Research

Tire wall photo by Pratik Zaveri

We do not have a vested interest in saying that the off-gassing of the tires is a "non-issue." We do not believe that your health is a non-issue. Neither do the countries that have banned the use of tires in buildings. Because of laws prohibiting the use of tires, groups like Earthship Belgium are using earthbags instead of tires for their Earthships.

Just a few months ago, the tire off-gassing issue was raised again when The Washington Post did a story on a number of soccer goalies who have contracted cancer. Scientists and doctors began studying the unique subgroup, which led them to pose a link between the incidents of cancer and goalies who had played extensively on athletic fields paved with a form of AstroTurf that used crumb rubber from recycled tires in its makeup. While in its early stages now, this may ultimately prove to be fruitful research to the tire off-gassing issue. 

Here is what we DO know, from the scientific studies and best practices promoted by experts in the many fields which influence our assertion that the tires are dangerous, so you can decide what works for you!

The laundry list of volatile chemicals used in tires is alarming: 

·         Benzene inhalation causes cancer

·         Toluene inhalation causes cognitive disfunction

·         Arsenic inhalation causes organ failure

·         Acetone inhalation causes irritation of the throat and lung

plus heavy metals that include

·         Nickel inhalation causes sinusitis and cancer

·         Copper inhalation causes nausea and suppressed liver function

·         Cadmium  inhalation causes kidney disease and an increased frequency of kidney stone formation

Organic compounds in tires break down more quickly than the vulcanized rubber. Criteria which determine breakdown rate include: heating, friction (from movement), water trapping and freezing, and evaporation of plasticizers.

But here is where it gets REALLY interesting. Here are scientific studies done for several different materials, all of which are constructed of recycled tires.

According to the EPA report, “Scrap Tires: Handbook on Recycling Applications and Management for the U.S. and Mexico” from December 2010;

“These (tire) piles pose a public health concern. They are breeding grounds and havens for mosquitoes and other vectors, resulting in the spread of dengue fever, yellow fever, encephalitis, West Nile virus, and malaria. Improperly managed in stockpiles, in illegal dumps, and scattered along road sides, scrap tires are a significant border environmental problem as a result of the leaching process, fires hazards, and water contamination. Once ignited, tire fires are difficult to extinguish. When water is applied to fight the fire, serious air, ground water, and surface water contamination may result. Toxic emissions from tire fires, such as sulfuric acid and gaseous nitric acid, can irritate the skin, eyes, and mucus membranes, and can affect the central nervous system, cause depression, have negative respiratory effects and, in extreme cases, cause mutations and cancer.”

This 2008, but constantly updated ,report from Artificial Turf: Exposures to Ground Up Rubber Tires - Athletic Fields, Playgrounds, Garden Mulch by the firm Environment and Human Health, Inc. for the Canada version of the EPA

"The metals zinc, cadmium, and lead were also identified as contaminants from tire rubber released into ground water. With the exception of zinc, there are insufficient data to assess the health or environmental risks of any of these metals. It appears clear that the zinc levels are high enough to be phytotoxic if they enter the ground water or soil. It is doubtful that there is any human toxicity from zinc at the levels reported, but such a conclusion would have to be tested by more careful study."

"The particulate exposures due to tire dust and chemicals contained in the dust that can be released in the lungs are especially troublesome. Nearly every test adequate to assess the risk that was reported found one or two dozen compounds released from particulates. There are processes in the body that can release the chemicals contained in the rubber particles. Moreover, potent carcinogens are found in the tire dust. Only the assumption of limited exposure could support the conclusions of low cancer risk."

"In summary, the toxic actions of concern from the materials… include: Severe irritation of the respiratory system; Severe irritation of the eyes, skin and mucous membranes; Systemic effects on the liver and kidneys; Neurotoxic responses; Allergic reactions; Cancers; Developmental effects"

2012 Cal Recycles Report on Tire Breakdown, which states:

" Natural rubber alone poses a dangerous fire hazard and when heated to decomposition emits toxic fumes of SOx. Base materials used in polymer rubber production, such as butadiene and styrene, are suspected human carcinogens, and many of the polymer additives can cause systemic toxic effects."

"The tire filler, carbon black, is mildly toxic by ingestion, inhalation and skin contact."

"Isoprene is a mild toxic by the pathway of inhalation. It also reacts with air and ozone to form dangerous peroxides. Butadiene is a confirmed carcinogen and teratogen in animals and a suspected human carcinogen. Inhalation of high concentrations of butadiene can cause unconsciousness and death. Human systemic effects of butadiene by inhalation include coughing and hallucinations. Styrene is a suspected carcinogen. It has been found to be poisonous by ingestion, inhalation, and intravenous routes."

"Zinc oxide is added to tire rubber at relatively high concentrations. Zinc oxide is moderately toxic to humans by ingestion. Some human systemic effects associated with the inhalation of zinc oxide are chills, fever, tightness of the chest, and coughing."

The 2013 report: Draft Screening Assessment for Carbon Black produced by Environment Canada, which states:

"Increased incidences of lung tumors were observed in female rats exposed by inhalation to the only or lowest concentration (of carbon black) tested..."

This 2008 report from Liberty Tire, which states, specifically about off gassing:

"The 2007 EEDEMS report mentioned above raised concerns about health effects on the crews installing crumb rubber athletic fields in poorly ventilated indoor areas and recommends a minimum air renewal rate of 2 vol.h-1. A 2006 study conducted in Norway drew a similar conclusion... These recent findings are consistent with those of a 1999 Taiwanese study that identified temperature and age of the recycled rubber material as the primary factors in VOC emission rates."

And then you read statements from industry professionals dealing with tire decompositions in their everyday lives, who say things like...

"While the levels of chemicals off-gassing from indoor play spaces was considered below the threshold where the chemicals are harmful, it is worth noting that indoor spaces showed up to ten times as much volatile chemicals in the air. If you want to err on the side of caution, you may want to consider refraining from using recycled rubber mats indoors, where there is a minuscule but present danger that could deem recycled rubber unhealthy." in "Are Recycled Rubber Mats Unhealthy?" by Lara Stewart at BrightHub based on the research noted  in the first report we suggested reviewing.

"Minor off-gassing is an issue with rubber flooring. The gasses have an odor but will not release hazardous chemicals. In some cases, products with recycled content are included with caveats regarding where they should be used. Rubber flooring made from recycled automobile tires is a good example--the caveat is that these products should not be used in most fully enclosed indoor spaces due to offgassing concerns." from "Building Materials: What Makes a Product Environment Friendly?"at Earthwise.com

"Do not use rubber flooring, such as that made from recycled tires, in enclosed areas because off gassing can continue for years." "Healthy Indoor Environments"  at The Sustainability Project.

But then, to be fair, we cannot ignore this archived, undated, report from Humbolt State University, which addresses the risks in earthships directly.

“Reusing our worn out tires is of course better than throwing them into a landfill, but many of the current reuse applications found in our society come with significant environmental impacts.  

One appropriate use for old tires is in Earthship homes.  A question we frequently receive … is if the tires used in these projects pose health risks through offgassing or chemical leaching.  “it depends”. 

The specific constituents contained in a given tire (e.g. arsenic, aluminum, cadmium, chromium, manganese, mercury, lead, sulfur, and zinc) are dependent on the tire’s type, age, and manufacturer.  The location in which the used tires are placed is a critical factor that determines how much of each mineral constituent is leached.  Tires decompose when exposed to high temperatures, sunlight, or oxidizing agents.  None of these elements are present when a tire is packed with soil and surrounded by a stucco barrier inside an Earthship.  That being said, the tires used in Earthship walls are of minimal risk to inhabitants because they have little potential to decompose.

…used tires most likely do not pose a health risk if they are rammed with earth and sequestered in a location away from exposure to sun or moisture… EPA researchers have acknowledged that the current literature we have pertaining to the health risks that used tires pose is incomplete, and that further study should be conducted before used tires are used in applications where humans are exposed”

Once you have read some of these reports, or just the excerpts we have included here... ask yourself, is it worth the chance you take? If your answer to this is yes, Part 2 of the book has suggestions for making them work. If the answer is no, then Part 2 will also offer viable alternatives!

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Earthship Research: Kruis and Heun

Nathanael J. Kruis and Matthew K. Heun 
Analysis of the Performance of Earthship Housing in Various Global Climates. Proceedings of ES200; Energy Sustainability 2007; June 27-30, 2007, Long Beach, California. Link to Complete Report pdf Here

This 2007 study was conducted from two engineering PhDs at Calvin College in Michigan.

Their report was formulated to determine whether the 3 bedroom Global Model earthship design meets the comfort, electrical, and water demand for several North American locations. The research team studied both actual and theoretical values from simulations on industry-standard software, and determined the financial implications of earthship construction compared to the same floorplan expressed as a standard wood-framed house with batt insulation in each of the areas studied, including Alaska, Hawaii, New Mexico, and Michigan.

In this study, the team stated that for the environment inside an earthship to be considered comfortable, it must be between 21°C (70°F) and 28°C (82°F). They then studied the temperatures inside simulated and actual earthships over time. What they discovered was that the energy simulation programs were more forgiving than the actual earthship, and temps were routinely 3 degrees more comfortable in the simulations than in actuality during noon heat peaks and rainy periods.

What these graphs above, which we marked up from the study, illustrate is that the earthship does not perform up to expectations, except in summer, which leads credibility to the assertion that many have made that the pitched windowwall is actually a detriment. The reason the summer works is because it is when the greenhouse is shaded from the sun, which is too far north at this time to overheat it. Once the sun starts moving south again, those spaces will overheat in latitudes below Anchorage, for at least 1 month in Grand Rapids, and for as many as 8 months in Albuquerque. One can say that opening the windows can fix that, but those months INCLUDE winter, and when you have3 got below freezing temps and blowing snow to contend with, that is not always a viable solution. Especially for your greenhouse plants which LOVE the tropical air but not so much bouts of tropic temperatures sandwiched between freezing periods that happens when the space is opened and closed up. The earthship design promise fails to perform in winter in high latitude areas, requiring backup heat and additional insulation at the perimeter of the building, on the greenhouse, and under the foundations and floors.

The staggering cost of installing adequate PV as delineated in the report further illustrates the negative economic impact of the build-out. The PV required to power an earthship in Anchorage is nearly $105k, for the very large array and batteries required to support the very cold and dark winter, as compared to the $29,700, required in Albuquerque, in 2006 dollars. Note: this is for equipment only and does not include installation, labor, or maintenance.

According to the research, a family of four living in an earthship would require 98 gallons (370L) of water per day, or 37,500 gallons (135,000L) of water per year. This suggests that the earthship is only really saving water insofar as it is able to use greywater for toilets. The use of water for faucets, washing machines, and showers… are all equal to that of regularly “efficient designed” buildings. The study confirms that rainwater collection is achievable in a wet place like Michigan, but not in Hawaii, New Mexico, or Alaska. This makes a backup water supply essential.

One of the most shocking revelations for us from this research was the realization that the most financially responsible earthship to build is a grid-tied one. In all the locations they studied, grid tied earthships performed overall very similarly, or even better, than a stick-built house. The only slightly higher additional cost at build-out of the grid-tied earthship over a stick system was fundamentally attributable to the additional catchment and greywater systems. Off-grid earthships tended to be between 30% more in cost over the lifetime in Albuquerque and Hawaii, 50% more in Michigan, and as much as 200% more expensive over the lifetime of the home in Anchorage.

Study Conclusions:

“The study has shown that the current earthship concept cannot provide: (a) a consistently comfortable environment solely through passive solar, (b) a consistent supply of water solely through catch water and graywater systems, or (c) an adequate supply of electricity through a PV power generator at a reasonable price.”
 
“In a tropical wet dry climate has to not need such intensive design of the thermal envelope… An equally sustainable and comfortable environment can be achieved with less material and a lower cost than the earthship design.”
 
Notes from the Hacking team:

Some of the assumptions they made in the research are actually TOO favorable towards viable performance evaluations, in our opinion.

• The team assumed that the earthen walls perform the same as concrete, and they did not take into account the “voids” where the walls use applied earth stucco, in lieu of rammed (most often between the tires), which have different thermal behaviors. They even mention that they do not count the seasonal moisture content of the soil, which makes earth highly conductive when wet. This also negatively affects thermal behavior so this could be a real issue.
• They assumed that the earthships they studied had double-pane windows. We have not seen that many earthships with double-pane windows installed on the window wall.
• They did not address the issues of air leakage and infiltration, which are common in these builds, and have major implications on actual heating and cooling loads.
• They assumed that the building used energy star appliances, which happens only in the high-end earthships, from our experience.

This research points to several resolutions we must find if the earthship ideals are to be realized. The chapter that addresses the issue in Part 2 of this book is listed after the issue if we address it:

OVERHEATING

Ventilation – Natural Ventilation Strategies and Indoor Air Quality

Dehumidification – The Reality: Humidification Matters

Shading – Passive Solar Design: Overhangs

Losing the pitched (angled) window wall – Enclosure: Walls: Earthship Sloped Window Greenhouse

UNDERHEATING

Installation of backup heating

Use of slab and foundation insulation

COST OF PV

Will come down with time

Used a grid-tied system to use the grid as a battery

Size  – Create an Efficient Floorplan

Smarter electrical loading  – Mechanical Systems: Electrical: Power

RAINWATER CATCHMENT DOES NOT PRODUCE ENOUGH WATER

Use best practices in water management - Rainwater Harvesting and Collection

Have backup water source

AFFORDABILITY

Size  – Create an Efficient Floorplan

Financial Planning - Where is the Money? How to ACTUALLY afford to pay cash for your home

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Earthship Research: Freney, Soebarto, and Williamson 2013

Martin Freney, Veronica Soebarto, and Terry Williamson
 Thermal Comfort of Global Model Earthship in Various European Climates. Proceedings of BS2013: 13th Conference of International Building Performance Simulation Association, Chambéry, France, August 26-28, 2013. Link to Complete Report pdf Here

This study from 2013 was completed by three academic researchers from the University of Adelaide in Australia. Their efforts were an expansion of previous studies cited herein, and evaluated the Global Model Earthship in both actual and simulated thermal performance scenarios in Taos, New Mexico; London, England; Paris, France; as well as Albacete, Seville, and Valladolid in Spain.

One of the main impacts of this study was to identify that the inner earth temperature, which MR assumed was 58 degrees everywhere, actually varies dramatically by region, based on factors including local temperatures, water table, soil type, wind, humidity, and rainfall. And that this temperature difference requires a build-out utilizing extensive insulation under the slab and around the foundations and exterior walls in places where the inner earth temperature is lower.

This earthship study was based on a 2 bedroom Global Model earthship oriented at 10 degrees east of south. The area of the building is 1,720 Square Feet (SF), or 160 Square Meters (SM). Of that, 60 SM, or 645 SF, (38% of the floor area) is greenhouse. This earthship has “upgrades” including a west entry vestibule and east double-door garden entrance, and uses rigid insulation vertically in the berm approximately four feet, or 1200mm, from the tires.

As these researchers noted, “schedules for opening and closing of vents in the greenhouse roof were informed by occupant surveys and on the advice given by the architect”, which points to one of the lingering performance and maintenance issues of the earthship’s natural ventilation systems.

Of particular note in this study was the use of an accepted international standard for thermal comfort (ASHRAE 55-2010) which is more stringent than those used in previous studies.

Additional notes included within the report which may be relevant: 

“The extreme outlying temperatures that were measured (in the on-site testing) are not predicted by the simulation.” 
 
“… the coldest temperatures were… in the morning (6-8am) followed by a steady rise in temperature until a comfort level was obtained.”

Thermal Performance graphs from the report, with notations of what the charts mean added:

Figure 8 - London: Additional heating is required 8 months a year. The greenhouse is too cold to grow plants and cannot be amended with additional heat without addressing humidity control as well.

Figure 9 – Paris: Additional heating is required 8 months a year. The greenhouse is too cold to grow plants 8 months a year and cannot be amended with additional heat without addressing humidity control as well. AND the greenhouse requires additional cooling 3 months a year.

Note: Both Paris and London performed under the higher comfort levels of previous studies (were much too cold, comparatively) for more than 40% of the year.

Figure 10 – Valladolid: The greenhouse is too hot 9 months a year and additional cooling and/or ventilation is required. Additional cooling is required in the main body of the house September through November.

Figure 11 – Albacete: The greenhouse is too hot throughout the year and additional cooling and/or ventilation is required. Additional cooling is required in the main body of the house October through December.

Figure 12 - Seville: The greenhouse is too hot throughout the year and additional cooling and/or ventilation is required. Additional cooling is required in the main body of the house October through December.

Conclusions: 

“The greenhouse... had average maximums and minimums either side of the acceptability limits indicating that it is generally not suitable for habitation.”

“This study indicates that backup systems are necessary and cold and cloudy climates; however the energy use is likely to be (roughly 15kWh/m2.yr), on par with PassivHaus heating energy requirements, due to the earthships ability to store and release heat.”

Notes from the Hacking team:

• The earthship studied in Taos was not occupied during winter of the onsite case study in which actual temperatures were recorded in the space. This could be a fundamental flaw, as it does not accurately document functional use patterns which in previous studies have indicated additional, large, spikes of cold and heat due to occupant use. However, the study aspects of other areas and locations should be accurate. 
• The research team tightened the requirements for comfort over most studies (using a CV(RMSE) of 10-20% in lieu of the ASHRAE standard of 30%.)
• Ideally, the next step in the research will address thermal bridging effects common to these systems.
• The impact of the earth tubes in the north wall of the greenhouse was not modeled.
• The research team determined their comfort assessments based on DAILY AVERAGE temperatures rather than addressing the range of daily temperatures their own data modeled, thus skewing perceptions of actual comfort. For up to half of each day, thermal comfort was NOT achieved.
• Ideally, the next step in the research will factor in inner-earth temperatures in  the areas tested.

This research points to several resolutions we must find if the earthship ideals are to be realized. The chapter that addresses the issue in Part 2 of this book is listed after the issue if we address it:

OVERHEATING

Ventilation – Natural Ventilation Strategies and Indoor Air Quality

Shading – Passive Solar Design: Overhangs

Losing the pitched (angled) window wall – Enclosure: Walls: Earthship Sloped Window Greenhouse

UNDERHEATING

Installation of backup heating

 Use of slab and foundation insulation

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Earthship Research: Earthship Europe

Earthship Europe
Earthship Performance. 2012. Digitally available at: http://earthshipeurope.org/index.php/earthships/performance 

Conclusions: 

"Reynolds explains… in 'Comfort in any climate' is that the temperature of the outer few feet of earth heat up and cool down in response to surface weather. However at about 4 feet (1.2 m) the temperature is more constant, around 58oF (14,4oC)… it sure is not the case in most European situations… you can take the years average temperature of your location and that is about the temperature of the earth at 1,5 m deep. The average temperature in Belgium is 9,8oC (49.6oF). So tapping into the earth will give you the uncomfortable feeling of 9,8oC, when you probably want at least 19,8oC… I expect this tapping into the earth has a negative effect on performance in many European countries. To me it made more sense to insulate underneath the entire earthship (walls included) instead of just insulate the thermal wrap.” 

"…huge thermal bridges. To most construction engineers in Western Europe it is well known that thermal bridges can cause moist and mold problems. The difference in temperature between the insulated and not insulated part causes moist to gather at that point. This is not prevented by completely sealing of water from the outside since the (moisture) comes from the inside. In time, when not properly handled, it will turn into mold."  

"Ventilating in summer when it is warm will not give a great deal of problems the Reynolds way. But winter time in cold and moist climates do need another way of ventilating." 

“…thermal mass. It is clearly made for a New Mexico situation. Longer days in winter, probably more clear sky days and less days with a grey sky no sun coming through… the few ours of sunlight on a very short winter day in Sweden (cannot) make the thermal mass work, provided the sky is clear blue and without any clouds. The amount of heat lost through the windows should be investigated, as should the amount of heat gained though them and those should be compared…”


This research points to several resolutions we must find if the earthship ideals are to be realized. The chapter that addresses the issue in Part 2 of this book is listed after the issue:

RECYLING

Understanding recycling  – Part 1: The Myth of Earthships and Recycling

and Part 1: The Myth of “A Radically Sustainable Home Made of Recycled and Natural Materials…”

UNDERHEATING

Installation of backup heating

Use of slab and foundation insulation

 

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