- How do earthships perform in the NZ climate?
- Does the use of tyres pose health or environmental risks?
- How do earthships cope in earthquakes ?
- Can I get a permit to build an earthship in NZ?
- How much do earthships cost to build in NZ?
- Can you put me in touch with professionals who know about designing and building earthships?
- How do earthships perform in the NZ climate?
Earthships have been built in other countries with damp climates like ours, like Scotland, England, Holland and British Columbia (Canada), where there do not appear to have been any reported problems with Earthships built in more recent years. Mike Reynolds would be the first to admit that the evolution of earthships has been a trial and error learning process and some of the earlier European earthships did get a bit of a bad rap for mould and mildew. Refer to the Earthship Europe website for more info about the problems encountered there or read the Earthships in Europe book . In environments such as ours, a watertight vapour barrier, good ventilation and adequate sun penetration (by keeping the depth of the building to 7m or less) is critical. Also it is important to reduce the moisture content of the earth inside the tyres and inside the vapour barrier to begin with as if this gets wet with rain it can take a long time for the building to dry out. New Zealand is different from other damp climates in that we often have intense driving rain rather than the soft drizzly kind which requires particular attention to weather-tightness. Due to the leaky building fiasco, consenting authorities in NZ are likely to be quite strict about how earthships comply with the weather-tightness criteria of the building code.
Some of the concerns raised with regard to the European earthships are worthwhile being aware of and considering in the context of where in NZ you are building, as there are quite big differences in average temperatures, winter daylight hours, number of clear sky days, and rainfall between the south and north of the country and between the east and west coast of the South Island. It probably makes sense to insulate underneath the entire earthship (walls included) instead of just insulate the thermal wrap to avoid problems caused by thermal bridging – this is where a difference in temperature between the insulated and not insulated part causes moisture to gather at that point.
Data on earthship performance does not appear to be readily available other than for some of the earthships in New Mexico which has been written up in the Australasian magazine ‘Renew’. An independent study by Martin Freney from the University of South Australia shows in this chart that the thermal performance of an earthship is far greater than other earth building techniques such as mudbrick, rammed earth and strawbale which have been tried and tested in NZ. The lower the heating and cooling load of the building, the less heating or cooling is required to keep the inside air at a comfortable temperature (ie the lower the load, the better). For more of Martin’s research on earthships see: http://www.earthshipironbank.com.au/research.html.
2. Does the use of tyres pose health or environmental risks?
Tires are made of rubber, carbon black and other chemical compounds which raises questions about whether the chemicals in the tires of an Earthship building are able to off-gas into the air or leach into the soil. A studyby the University of Wisconsin-Madison reported on the Earthship Biotecture website investigated whether this is in fact an issue. The following is a summary of information on this page.
To assess the risks to human health and environment posed by the use of recycled tires in Earthships, one must look at the pathways of exposure, and the state in which this potential contaminant exists. The conditions for rubber to degrade would be high temperature, exposure to light, or the presence of strong oxidizing chemicals. None of these conditions exist when a tire is entombed in an Earthship wall surrounded by packed earth, vapor barrier, stucco, and paint. The argument has been made that tires must off-gas because “old tires smell.” The reason “old tires smell” is due to the photo degradation of rubber. Essentially what happens is that photons from light bombard the rubber and knock atoms from the long rubber polymer molecules. This causes the rubber to degrade, and smaller molecules to vaporize. In the absence of light, this does not happen.
Tires are not exposed to light when used in an Earthship. In order for the tires to affect the indoor air quality of an Earthship, the tires must off-gas vapors which must travel from the tires, through the walls, into the living space of the Earthship. The production of such vapors will be proportional to the vapor pressure of the compounds producing the vapors. The vapor pressure of carbon black is extremely low. In other words, this chemical produces almost no vapor. What this means is that the potential for tires to affect indoor air quality will be severely limited by the extremely low vapor pressure of the source chemical.
In order for a tire to affect water quality, it must come into contact with water, and release chemicals into the water. In a properly designed and constructed Earthship, there will be no flux of water through the wall. Therefore, no water will contact the tire. In the unlikely event that water should contact the tire, the water will not become contaminated because carbon black is insoluble in water .
3. How do earthships cope in earthquakes ?
This post provides some answers to this question.
4. Can I get a permit to build an earthship in NZ?
You can legally build a 10 square metre structure without a building permit, as long as it has no plumbing or cooking facilities.
And if it is to be a dwelling, there must be a primary dwelling already on the property. However here is the catch – even if under 10msqm a buiding still needs to comply with the building code and since there are no approved standards for tyre wall construction then an engineer is required to design and guarantee the strucure. A geotechnical engineer will need to confirm the bearing capacity of the ground below.
In order to get a permit to build and earthship in NZ the engineer then needs to provide a PS1 to Council with the completed building consent documents. This PS1 is a legal document. It means the engineer takes full liability for that structure to perform in all situations, including an earthquake. On completion of the build the engineer will provide a PS4. This states he or she has inspected all aspects of the build and confirms it is as per their documentation.
Brian Gubb obtained a building consent in 2004 from Waikato District Council to build a earthship inspired tyre building in Ngaruwahia. The information on the Councils property file is public information and can be accessed here. Since consent was granted for the Gubb earthship, the level of information required for building consent applications has increased tremendously and also the building code has changed with regard to owner building and got a lot stricter in terms of water tightness and other areas of building performance. Liability now for professionals in the building industry has also increased by a huge amount with changes introduced to the building act and the building code.
Councils that people have spoken to regarding building permits to build earthships in NZ are generally quite positive when you talk to them in concept terms, however what they actually require in terms of paperwork before they say yay or nay is another thing. One thing for sure is that the earthship plans that you can buy from Earthship Biotecture are nowhere near the level of detail that is needed for a building consent application in NZ. NZ licensed architects and engineers need to sign off on plans and involving these professionals is not a cheap process, however that’s not to say it can’t be done. Gus and Sarah Anning have proved that a consented Earthship building is completely possible in New Zealand today. Best to direct any further questions to them personally about how the building consent process for Earthship Te Timatanga went for them.
5. How much do earthships cost to build in NZ?
How long is a piece of string? The cost of building an earthship in NZ depends on how big it is, the design, whether you pay others to do it, or do the build yourself with volunteer labour. If you pay others then it’ll probably cost similiar to a conventional house if not more.
Mike Reynolds has often suggested that the cost per square foot for an Earthship is about the same as the local cost for a conventional home of similar size. While Earthships have reduced costs for most of the main building materials, by using waste products, they typically invest more upfront in the services for the home (Rainwater harvesting and PV solar generation capabilities etc) hence the costs balance out.
Brian Gubb managed to build his home very cheaply (< $50K) using almost 100% recycled materials and building it himself. However it doesn’t have all the full earthship systems in place and the single outer wall of recycled greenhouse glazing isn’t as effective as the two layers of double glazed glass (with airlock/greenhouse between) that Mike Reynolds has in his earthship designs.
Earthship Te Timatanga is a very classy building that was featured on Grand Designs NZ. Being such a novel building project they were fortunate to receive quite a lot of discounts and sponsorship from product suppliers. Best to direct any further questions about the costs of the Coromandel earthship project to Gus and Sarah personally.
6. Can you put me in touch with professionals in NZ who know about designing and building earthships?
The following professionals were involved in the Coromandel Earthship project:
Engineers Richardson Stevens