EARTHSHIP HOME FOR WAI­HEKE

A prop­erly de­signed earthship re­quires no heat­ing or cool­ing, pro­vides its own power and wa­ter sup­ply and treats its own sewage.

Element - - Business - By Liz Ross

The early ex­am­ples of the “earthship” build­ings looked like they were per­fect for hob­bits, but times have cer­tainly changed. Made pre­dom­i­nantly of earth-filled tyres and other re­cy­cled ma­te­ri­als, an earthship uses en­ergy from the sun and ther­mal mass con­struc­tion to nat­u­rally reg­u­late in­door tem­per­a­ture. Ori­en­tated to max­imise so­lar gain, the north side of an earthship has a glass green­house “air­lock” that helps with tem­per­a­ture con­trol, and the home treats waste­water by pass­ing it through botan­i­cal cells, pro­vides for food pro­duc­tion and supports a row of pho­to­voltaic pan­els.

An earthship is more than an eco-build­ing style, it is an in­te­grated, sys­tems-think­ing ap­proach based on physics and biology in­side a phi­los­o­phy of work­ing in har­mony with nat­u­ral phe­nom­ena to cre­ate a home that takes care of you. They are the brain­child of US ‘bio­tect’ Michael Reynolds, who has been re­fin­ing earthship build­ing tech­nolo­gies over 40 years. He has vis­ited New Zealand twice in the past year and is cur­rently de­sign­ing his first New Zealand Earthship house for own­ers Dana Dar­win and Liz Ross on Wai­heke Is­land.

“Sus­tain­able Au­ton­omy for Ev­ery­one” sum­marises Mike Reynolds’ phi­los­o­phy , as earthships sup­port a move away from cen­tralised in­fra­struc­ture and to­wards in­de­pen­dence and re­silience.

Part of the earthship de­sign phi­los­o­phy is us­ing re­cy­cled re­sources that are abun­dant ev­ery­where on the planet. All over the world used car tyres tend to be a mas­sive waste prob­lem. Th­ese are the core struc­tural el­e­ment of an earthship with around 1000 needed for a three bed­room house along with other re­cy­cled ma­te­ri­als such as glass bot­tles, alu­minium cans, and card­board. Earth, as well as more con­ven­tional build­ing ma­te­ri­als such as con­crete and steel rebar are also used. Card­board is used to line the bot­tom of tyres be­fore they are packed firm with earth. “Bot­tle bricks” are cre­ated by cut­ting of the ends of glass bot­tles and join­ing them to­gether. Th­ese are placed in within in­te­rior and ex­te­rior walls to al­low por­tals of coloured light to shine through which makes earthships not only func­tional but also beau­ti­ful. Alu­minium cans are used as bricks and space-fillers to re­duce the amount of con­crete needed.

The large ther­mal mass of the earth-filled tyres com­bined with more earth sur­round­ing the tyre walls on three sides, cre­ates a large ther­mal ca­pac­ity for stor­ing heat. Through­out the day when the air is warmer than the mass, ther­mal en­ergy is ab­sorbed into the tyre walls, when the air cools, the ther­mal en­ergy is re­leased by the tyre walls thereby pro­vid­ing a con­sis­tent am­bi­ent tem­per­a­ture through­out the year with­out ad­di­tional heat­ing or cool­ing.

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.

Earthships have been built in a wide va­ri­ety of cli­matic con­di­tions in­clud­ing damp cli­mates like Canada’s west coast, Hol­land, Eng­land and Scot­land. In th­ese en­vi­ron­ments the wa­ter­tight vapour bar­rier, good ven­ti­la­tion and ad­e­quate sun pen­e­tra­tion are crit­i­cal. Be­hind the tyre walls, an earthship is wrapped with a layer of high den­sity rigid in­su­la­tion sur­rounded by a plas­tic or rub­ber (EPDM) mois­ture bar­rier. Ven­ti­la­tion is achieved by work­ing with nat­u­ral con­vec­tion flows to bring air into the back of the earthship via un­der­ground metal tubes where the cool tem­per­a­ture of the earth cools it, and by ex­pelling hot air via vents in the ceil­ing of the green­house.

Pound­ing earth into tyres is labour in­ten­sive. How­ever on the pos­i­tive side, the earthship con­struc­tion process can be largely un­der­taken by peo­ple who are not trained builders. Fully func­tional earthships are es­ti­mated by Earthship Bio­tec­ture to cost the same to build (in­clud­ing labour) as an av­er­age con­ven­tional house, how­ever there are no on­go­ing wa­ter or elec­tric­ity bills to pay.

Grant­ing a build­ing con­sent for an earthship is not some­thing that most lo­cal author­ites in NZ have any ex­pe­ri­ence of and hence are cau­tious about. Af­ter meet­ing with Michael Reynolds in July Auck­land Coun­cil are pos­i­tive about ap­prov­ing the pend­ing Wai­heke Earthship build­ing con­sent ap­pli­ca­tion. With the project’s aim to be the first 10 Homes­tar rated res­i­den­tial build­ing in New Zealand, they would be crazy not to.

For more in­for­ma­tion on Earthships in the NZ con­text and the Wai­heke earthship project see earthship.co.nz

Liz Ross is build­ing New Zealand’s first cer­ti­fied earthship home on Wai­heke Is­land.

Four mil­lion tyres are land­filled each year in New Zealand, so re­cy­cling them for use in an earthship build­ing gives them another lease of life. Be­cause the tyres are com­pletely en­cased in earth they are not ex­posed to high tem­per­a­tures, sun­light or ox­i­dis­ing agents which could cause them to de­com­pose and leach or off gas. The Earthship sewage sys­tem dif­fers from the wet­lands ap­proach in that it pri­mar­ily treats the gray wa­ter in­side the build­ing and the sewage from the toi­let out­side of the build­ing, both in smaller ar­eas. Grey­wa­ter is the used wa­ter af­ter all re­cep­ta­cles ex­cept the toi­let.All house­hold sewage is used and reused in the in­te­rior and ex­te­rior planters, called botan­i­cal cells.

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