The tiny house movement arose in the USA after many people lost their houses in the wake of the subprime mortgage scam. My motivation for designing an off-grid passive-solar tiny house on wheels arose from various frustrating delays and impediments experienced when trying to obtain council approval for a cottage, particularly with respect to the composting toilet system. Other  reasons people may choose a tiny house may be affordability, short build duration and transportability. Personal involvement with the build enables future ease of maintenance by the owner whether it be electrical (which anyone can perform with a low voltage DC system1), plumbing or structural repairs. Gas connections however must be done by certified gas fitters.
This particular design arose from my views regarding the drawbacks of living aboard a boat or a standard caravan, while also adopting some of the space saving innovations of such mobile dwellings. Internet research was also immensely valuable, especially viewing the numerous video clips of tiny houses on the web.
 Dimensional constraints of the road legal tiny house are outlined within the regulations of each country, in Australia the width being <2.5 metres and total height <4.3 metres. Allowable length of the trailer is apparently up to 12.5 metres, however that is far longer than is needed in practice, a trailer base length of less than 8 metres being sufficient for most folks2. Any longer may result in a heavy structure exceeding the towing capacity of the most powerful 4WD/SUV  ie. 8 metres (or even 7 metres, depending on materials used for construction) may be the longest practical trailer base, without having to resort to a Mack truck. Although personally opposed to the purchase of a 4WD for trivial commuting (eg one person driving10km to buy one litre of milk), I acknowledge the necessity for the one-off rental of a 4WD (or towing cab) for the single journey of the tiny house from the site of construction to the permanent destination.
Note: Australian regulations require at least one door be located on the left hand side or at the rear of the mobile home, presumably to allow safe ingress/egress when stopped by the side of the road. For countries with traffic on the right, presumably their regulation will require at least one door on the right hand side or at the rear of the structure.
This is not just an article about a type of house. It is an article about a change in lifestyle. It describes the special components which make up the house and the (trivial) lifestyle modifications required to drastically reduce one’s ecofootprint. For those who purchase the building materials (rather than salvage offcuts from building sites) the upfront cost may seem a little high, however never having to pay utility bills will result in huge lifetime savings3. More importantly, if and when the central utilities fail, you will be living comfortably while others are suffering.
Freedom from a mortgage. Freedom from utility bills. Freedom from the disruptions of grid failure. Freedom of movement. Ethical living without sacrificing comfort. This article promotes ongoing use of (low energy) electronic gadgets and electrical appliances for as long as we are able. It is not about reverting to the stone age and wearing sack cloth. It is not about deprivation.
Basic Principles
The key to minimising your ecofootprint is to reduce consumption by increasing efficiency and turning waste into a resource (granting that high safety and health standards must be maintained). If everyone in the rich world had vigorously pursued this principle twenty years ago (combined with reducing the rate of human reproduction) we would not be headed for global catastrophe now4. However voluntary mass reduction of consumption was never likely to happen, being in direct opposition to the "infinite growth on a finite planet" agenda of the psychopaths who control the establishment.
Nevertheless, the principle of making a little go a long way is also of prime importance when devising a lifestyle which will enable one to survive, even thrive, through the upcoming collapse of industrial civilisation and the die-off of the majority of humanity.
The major objection by the endless growth ideologues to the principle of reducing consumption, was their claim it would compromise the quality of one’s life, even lead to impoverishment (the same argument they used against reducing carbon emissions). Utter rubbish. It does involve some degree of lifestyle modification, however as will be shown, there need be no reduction in your quality of life, particularly as we are now able to access brilliant technology such as high output LED lights, photovoltaic panels (which have markedly fallen in price) and evacuated tube solar hot water heaters. Furthermore living in a small space is immensely liberating because it forces you to dispose of all non-essential crap in your life so you are no longer a slave to your possessions. Having said that, storage space in the tiny house is limited, hence it is expected you should also have a large external community lockup shed (at least the size of a triple garage) which may also serve as a workshop, a meeting place, a place out of the rain for your clotheslines and a storage place for boxed items (winter bedding, valued books, long term food stores, gardening tools etc). The large shed roof will be essential for additional rainwater collection. This shed, being a very basic structure, can be rapidly approved by council (building application submitted as a shed or a garage) and quickly and affordably built from a kit by a contractor to your specifications eg able to withstand 200km/h winds.
The tiny house diagrams are displayed just after this paragraph. You may wish to intermittently refer back to them as you continue reading, to better understand the ideas being described. The original scale was 1:50 which is not the case with these reduced pictures:
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Features of this Tiny House
Disclosures and disclaimers: I mention certain brands and models of items in this article because I have personal experience with them and know that they work, however I have no pecuniary interest in any of those companies. I have invented none of the items described here but have merely put things together in a package I deem most logical, efficient and suitable for my purposes. Readers are welcome to adopt any or all the ideas here for their personal use for free, but obviously need to conduct their own research and due diligence. Implementation will be at their own risk. They are not to use my design for commercial gain. This article can be freely copied and distributed ad infinitum for private use.
            The first and most important key component of the offgrid tiny house in my view is this one:
The urine separating composting toilet:
            There is a "yuck" factor among the uninitiated who imagine that a composting toilet located within a tiny house will result in terrible smells permeating the entire dwelling. This is completely untrue with regard to the modern well designed urine separating composting toilet. The "Nature’s Head" model designed for boats and caravans works very well. Other brands/models with similar features may work just as well. The "major" lifestyle modification required? Males must sit down when they pee. Get over it guys.
            Top priority is the sanitary processing of human waste. The standard centralised flush sewage system has been immensely successful in this regard and any transition to a different method must be at least as hygienic, to ensure health safety.
            Features of this composting toilet:
1.      Separation of liquid from solid waste is key. Old designs which mix urine and faeces in one chamber generate foul smelling pathogenic anaerobic bacteria, due to decomposition in an unaerated, liquid medium with a low carbon and high nitrogen mix (this can be useful if the intent is to harvest methane in a biodigester, but that is beyond the scope of this article). The simple act of diverting the urine away is revolutionary. Faeces and toilet paper are deposited in a "solids" bin, previously activated by peat moss or coconut coir. Immediately after deposition, the mixture is churned by a turning handle, then sawdust or wood shavings (preferably mixed with wood ash to reduce clumping and to aid smell neutralisation) are sprinkled on top, to seal off smells and increase the carbon content. A high carbon to nitrogen content promotes aerobic over anaerobic organisms. Continuous exhaust ventilation by an ultralow energy (computer type) fan promotes aeration and expulsion of odour to the exterior. A double lid system further ensures no smells escape into the toilet cubicle at all. If tiny fruit/vinegar flies inadvertently enter the system they can be controlled by adding diatomaceous earth.
2.      Urine may be collected in a bottle or drained away. On the rare occasion odour occurs,  this can be abolished by sprinkling sugar in the bottle. When the tiny house is permanently sited, the urine tube can be connected directly to the gray water piping for immediate drainage to the exterior, perhaps to a gravel bed. Ideally however gray water should be biologically processed in a reed bed then used to irrigate plants. Urine, being nitrogen and phosphate rich, is an immensely valuable fertiliser and should not be wasted.
3.      High volume use is not a problem. Even though the solids bin looks small it has ample capacity for continous use by a couple, especially because no liquid is stored within and the faeces compacts down as it decomposes. After 2-3 months as the "active" solids bin (bin 1) fills, it is replaced by an empty bin (bin 2). Bin 1 is covered by a lid with a vent and is put aside (outside the tiny house, say, in the shed) to quietly continue composting,. If bin 2 fills up after a couple of months but bin 1 has not completed its composting duration (at least a year) then waste from bin 1 (now quite innocous with an earthy consistency and odour), is tranfered to a heavy duty rip-proof waterproof bag and allowed to continue composting. Bin 1 and bin 2 are then swapped. Composted waste more than a year old can be used to fertilise plants eg fruit trees but never applied directly to edible crops eg the veggie patch. The only limitation to the volume of usage is the number of heavy duty bags available (high quality bags must be obtained which can be reused).
4.      Being a non-flush toilet, fresh water savings are immense. Standard "water saving" flush toilets use up to 6 litres for a half flush and around 9 litres for a full flush, valuable high quality fresh water being discarded down the sewer. In the case of a urine separating composting toilet, if flecks of faeces fall on the rim of the solids aperture, they are easily dispatched by a spray of fresh water with a water pistol, no more than 100ml per use. Some amount of fresh water in the solids bin is helpful to enable a slightly moist environment for biodegradation.
5.      Warming the solids bin. This last point is one I am personally addressing by a method not mentioned by the toilet manufacturers nor councils as far as I am aware. Aerobic decomposition of faeces proceeeds much faster at higher temperatures. Some systems (eg certain SunMar models) use electrical heating elements which may consume 100 Watts, a huge drain on one’s precious electrical resource and completely unviable for the offgrid low energy system. Substantial heat is generated by the decomposition process itself and the slightly insulating sawdust/wood ash layer sprinkled on top helps retain some heat. Nevertheless the process may be impaired in a cold climate especially in winter. One way to overcome this is to configure your toilet cubicle such that the solids bin is directly heated by the sun’s rays through a large double glazed window. Configuring your toilet cubicle as a greenhouse, so to speak5. This mandates that the cubicle be sited on the North side of your tiny house in the Southern hemisphere (South side if you live in the Northern hemisphere). Obviously you will install a retractable opaque screen inside the window, deployed during toilet use.
Solar principles:
It is expected the house will be moved very rarely and will be stationary almost all the time. When parked long term, weight should be taken off the tyres by placing multiple jackstands under the chassis. If the wheels are removed, Council will regard it as a fixed dwelling, subject to all Council regulations and approvals, hence leave the wheels on. Footings can be concreted into the ground near the corners, with anchor points to chain the chassis down and render the structure cyclone resistant.
Sited on a fixed location, the design can and should incorporate solar principles. Orientation of the broadside of the house toward the sun is key, North facing if you live in the Southern hemisphere and South facing if you live in the Northern hemisphere. Hence my design will have to be laterally inverted for Northerners (unless you like the evening rather than morning sun in your lounge).
It is important to have a tree free margin around the home for many reasons. Shading will defeat the aims of passive solar heating6 and reduce insolation for your PV panels and evacuated tube array. Overhanging branches can pose a risk of deadfall damage. Birds perched on the branches may leave droppings which enter your rainwater system. Leaves falling on your roof and sliding into your gutter may clog your rainwater collection system and promote bacterial contamination. Perhaps most crucial of all in the Australian context, nearby trees may pose a high risk of bushfire damage in the summer.
The three main aspects of passive solar heating are high insulation, large double glazed windows and thermal mass within the house. Extreme passive solar house designs in Scandinavia and Canada demand near airtight sealing to prevent hot air escaping and cold air entering – which will result in suffocation unless there is also heat recovery ventilation (which requires energy). Annoying condensation also occurs without adequate ventilation. We will not delve into such an extreme design here.
Traditional passive solar houses have depended on concrete floor slabs for thermal mass,  which is obviously not feasible for a mobile house on a chassis with limited weight capacity. Furthermore, copious use of concrete, with its high embodied energy and carbon emissions during manufacture, may be anathema to the readers of this article. The thermal mass used in this design takes the form of water contained within the internal tanks of the house. Any of you who have a greenhouse with a huge tub of water sitting in the centre will appreciate this feature. Optimally the water tanks will be made of stainless steel (rather than, say, fibreglass) and painted matt black to facilitate rapid transfer of heat to and from the air of the cabin. The lounge seats will be located over the tanks but no weight will be borne on top of the tanks. The lounge base will consist of upright posts supporting the seats, but this base will have no side panelling, to allow direct contact between the walls of the steel tanks and the atmosphere of the house.
Obviously when the house is towed, the tanks should be empty.
Electrical system:
A 24V DC system is the most efficient for this size of dwelling and avoids excessive complexity. It is best to source as many appliances as possible which run directly off 24V DC, in particular the fridge/freezer which ideally should use an ultra efficient Danfoss type compressor. The market for such appliances is however much smaller than the mains voltage AC appliance market and you will still need a pure sine wave inverter (rated at, say, 3kW) to intermittently power certain other appliances eg washing machine, home theatre system etc. Use of portable electronic devices (smart phone, tablet and laptop computer – which, with a USB tuner can double as a TV) is encouraged as they consume little energy. Adapters to convert 24V DC to the charging voltages of these mobile devices are readily available.
These days, very few new home occupants bother with fixed telephone lines because mobile phones adequately meet their communication needs and the declining cost of mobile broadband internet access enables most web based needs to be met.
Some may advocate a 12V DC system because more 12V DC appliances are available on the market than those that run on 24V DC, however for a 12V DC system,  heat energy losses in wires longer than the length of a car will be excessive unless you resort to expensive and unwieldly thick cables.
Some may advocate a system where all appliances are run off mains voltage AC, fed from a central inverter which is in turn fed from the batteries, a DC source. Even though inverters these days are fairly reliable with good longevity, the central inverter powering everything does represent a single point of weakness in the system, failure of which will render the entire household paralysed. Furthermore there is continuous drain of power from the inverter in the form of heat loss, even when all other appliances are off. Additionally, AC appliances themselves tend to be ultimately DC powered (AC power goes into the device, eg an LED light, then is rectified to DC, which then powers the light). The rectifier is another source of energy loss (as heat) and another layer for potential failure (if it fails, the whole appliance fails, even if the LED is still perfectly functional).
Power sources and batteries:
By far the most important source of power will be photovoltaic panels which may be placed  on the roof or ground (higher risk of shading if located on the ground but easier to clean, adjust and if necessary fold and pack away should a storm threaten).
My preferred specifications are:
PV panels: 1kW in total (perhaps four 250W@24V panels)
Deep cycle7 lead acid batteries: 520Ah@24V in total (two separate sets of two 260Ah@12V batteries connected in series). AGM is preferable if you can afford it.8
The lead-acid capacities cited above are around 3 to 4 times that of most sailboat electrical systems. Standard caravans tend to have only one 100Ah@12V battery (less than one tenth of this system) as they are meant to be continuously recharged by the electrical system of the towing vehicle or a mains supply. The system specified here should suit the needs of any cautious users, apart from those enduring the prolonged darkness of winter at very high latitudes. The only devices with continuous drain are the fridge/freezer (however there will be minimal electrical drain in deep winter, especially if the fridge is relocated outdoors under cover) and the composting toilet fan (the latter consuming next to nothing). The washing machine will consume the greatest power intermittently. However if only used once or twice per week and only during sunny days, it should not significantly deplete the batteries. Obviously you should choose a front loading machine with the best energy and water savings ratings.
Rooftop PV panels can be angled during the Spring equinox to suit the summer sun and during the Autumn equinox to suit the winter sun. Angling them more frequently may not be worth the hassle unless they are ground based. MPPT voltage regulators/chargers are about 25% more efficient than PWM chargers but significantly costlier. I intend to use 40Amp smart MPPT chargers, one for each battery bank and have personally used the "Tracer" brand which has also been described in ReNew magazine. I used it for a 12V system although it can "autosense" if the system is 12V or 24V. Some chargers are falsely advertised as MPPT but are actually PWM. Try to find reviews on the web of the brand and model that you intend to purchase, buyer beware.
Ideally the negative terminals of each battery bank should be grounded.
Low voltage cutoff devices between the batteries and the central battery switchboard/bus will help prevent inadvertent overdischarge damage of the batteries.
Top-up charging after several overcast days may require use of a diesel or petrol generator (hopefully only on very rare occasions) however if a marine type 24V DC microwind turbine is  incorporated into the system9, it is very unlikely top-up charging using fossil fuels will ever be needed, unless your location is devoid of wind.
Shallow cyclic draining of your battery system should extend its life well beyond ten years. Abuse will kill it within two years.
If one has access to a a stream which never runs dry, then a microhydro system providing a continuous electrical supply will be more than sufficient to run your space heating, electric hot water heating, a microwave oven, electric toaster, electric kettle and induction cooktop10. In the absence of this rare luxury however, it seldom makes sense to convert precious electrical energy to heat. Becoming dependent on microhydropower can be a problem though. Such a mechanical system is less robust and less dependable than PV panels. Breakdown of the microhydrosystem will be much more disruptive to the lifestyle of the inhabitant who is used to a surfeit of continuous power.
Fresh water usage:
Only one raingutter at the low edge of the roof is needed as the longitudinal ridges and troughs of the corrugated roof will direct rainwater flow accordingly. The "first flush" system will eliminate gross contaminants. The area of the roof and the size of the internal watertanks may or may not provide sufficient fresh water for the inhabitants, depending on how the water is consumed and the amount of local rainfall. An additional 2000 litre external rainwater tank will be useful and any alternative backup sources of fresh water eg dam, streams, springs, bore water etc will always be welcome. Your external shed (which should have a much larger roof area, being a communal building) should also have the largest feasible rainwater tanks attached, perhaps 40,000 litres, which will be needed for permaculture purposes. Australian council regulations specify that for offgrid properties at least 10,000 litres must be preserved for firefighting in a separate tank. In some council areas the 10,000 litres can be preserved at the bottom of the drinking water tank by having the off take for drinking above the preservation level.
The first principle must be to reduce consumption. Huge water saving (compared with a standard dwelling) will already have been accrued by adoption of the non-flush composting toilet.
More water conservation can be achieved by one’s method of washing. Lazing for half an hour under the shower is obviously not an option. Ever since the severe drought affecting Brisbane some years ago, I have adopted a method which uses less than 3 litres for a complete, thorough hair and body wash. The key item is a wash cloth about a fifth the size of a bath towel. The hair is wet first, then thoroughly scrubbed with soap or shampoo, then rinsed, the soapy water from the hair now wetting the entire body. The wash cloth is now wet and impregnated with soap and the whole body is thoroughly scrubbed with this cloth. The cloth is wet with fresh water again and the body is scrubbed again. This can be done a third time with further dilution of the soap. Final rinse from the shower over the hair and whole body eliminates any soapy residue. Less than 3 litres in total easily!
What if the first flow of water from the shower is uncomfortably cold? Simply collect the first flow cold water in a bucket while the tap is in "full hot" position till the water becomes warm, then turn the tap to the warm setting for your body wash. Put the initial cold water in the bucket aside to use for washing dishes later. Due to the close proximity of the hot water cylinder to the shower compartment in this design, there will be very little time lag till you receive hot shower water anyway, so this may not actually be an issue.
Drinking water: generations of rural Australians have lived healthy lives drinking unfiltered water directly from their rainwater tanks, however I personally prefer to filter tank water before drinking. Some ceramic filter systems are designed to last many years, the filter being "recharged" by scraping material off the ceramic filter every so often. Some may wish to boil their drinking water if there is concern of contamination from the roof or tank. I have personally used diluted bleach to "disinfect" water tanks previously, which kills most but not all microorganisms.
Gray water: Effluent from the kitchen, bathroom (including urine) and washing machine cannot be stored in a tank without rapidly turning manky and should be immediately drained externally. During initial setup of your tiny house, the gray water can be drained into a gravel pit but ideally in the long term, the waste water "experts"11 recommend draining gray water to an open reed bed for bioprocessing, then sent onwards to irrigate plants in a permaculture enclosure or greenhouse. Gray water is a valuable resource which should not be wasted. Low phosphate detergents and soaps with no additional chemicals (eg perfumes) should be chosen.
Solar hot water (evacuated tube) system:
In high latitudes in winter, the evacuated tube system is more efficient than a flat panel system and can cope with frost levels down to minus 20 degrees C. This will obviously only be deployed after the house has been transported to its permanent destination as the tubes are fragile and easily broken during transportation. Rather than locate the heavy hot water cylinder atop the tube array, which may require rooftop reinforcement, it is best to keep all heavy items low in the house, to ensure a low centre of gravity and improve stablility, which is important when encountering strong winds.
The tubes are best permanently angled steeply to suit the winter sun to prevent them overheating in summer. In locations with excessive insolation eg the outback or desert, tubes can overheat and explode and a flat panel system may be more suited there. With exponential global warming, living in the outback or desert, even if you have a borehole with limitless water, is probablly inadvisable. Even if you can survive the heatwaves by retreating to a hole in the ground, those heatwaves will devastate your crops and livestock.
Circulation of the water may be best achieved by a pump system that I have personal experience with (albeit a flat panel system: the "Heliatos"): A small 10W photovoltaic panel is mounted adjacent to the evacuated tube array. This PV panel is dedicated to run a small electric pump which is active only when the sun shines sufficiently. Water is pumped from the cold water tanks to the evacuated tube array then to the hot water cylinder. When the latter is full, the water keeps circulating between tubes and cylinder. When the sun goes down the pump stops and hot water remains stored in the cylinder. I am unaware if a thermosiphon system which does not require an electric pump has been invented (and proven to be reliable). If so, that would be a great option.
I have no plans for a "boost" system with supplementary LPG, because evacuated tubes work well even on semi-overcast days and the idea is to reduce complexity and reduce use of fossil fuels. Furthermore extra hot water can always be prepared atop the wood stove if there have been extremely overcast days.
LPG stove and wood stove/heater:
Even if/when the global economy collapses down to a tenth of its present state, in between episodes of turmoil we should still be able to obtain LPG or CNG cylinders for the next 15 years or so. Conventional gas (not shale gas or coal seam gas) is the least CO2 emitting of the fossil fuels. An LPG cooking system is therefore included in this design. However there is an important space adjacent to the LPG stove dedicated to a mini wood stove, which will be used to keep the cabin warm on winter evenings if the "greenhouse" heat from the water tanks has depleted after an overcast day. Just as greenhouse solar heat can be transferred to the water tanks in the day, heat from the wood stove can also be transferred to the water tanks at night and enable residual cabin warmth after the fire is out.
Safety considerations are vital. Apart from designing the setup such that heat from the stove can never ignite anything indoors (eg heatproof tiles under and around the stove, safety sleeve around flue as it passes through the roof etc), it is essential to ensure there is never any risk of oxygen depletion or CO2 poisoning within the cabin. External intake of air into the combustion chamber will prevent the former and an airtight vertical flue will prevent the latter. If there is risk the flue may serve as a lightning conductor, it is simple to ground it externally by means of a broad copper strip. Alternatively you may wish to install a dedicated lightning rod, especially if you also have a TV aerial which may attract lightning as well.
Of particular interest is the "rocket" wood stove/heater. This was originally designed to benefit people in the third world by reducing harmful smoke emissions and increasing combustion efficiency (it uses less than a quarter the amount of wood of a conventional fire). This brilliant device can help save our lungs and our forests. Unfortunately at this time no rocket stove model is certified for indoor use by councils or the EPA and can only be adopted at individual risk.
The multipurpose lounge/dining/study/entertainment area:
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The plan views of the lounge shown above are self explanatory. The standard cushion sizes are based on a particular "Ikea" outdoor cushion type and extra cushion covers are therefore easily and affordably obtainable, however the reader will obviously have their own cushion preferences. The back cushions, being vertical, do not allow for lumbar curves, hence scatter cushions will be necessary which, with fresh covers, can double as pillows for the guest(s).
The table, with folding side flaps and detachable legs, has to be custom made and will have two heights:
–        long table legs for dining table height allowing ample clearance above knees, when used for dining or study purposes
–        short table legs, where the table surface is below that of the seats such that when cushions are placed on the table top, their surface is flush with the seat cushions and a double bed is created.
The lounge can be converted into a home theatre by appropriate placing of retractable projection screen, LED projector, bluray player (or laptop computer) and speaker system.
Other design comments
Windows and doors:
The reader may have noted my obsession for numerous windows and transparent doors. Effective ways to prevent claustraphobia in a tiny dwelling are:
–        to ensure that you can enjoy external panoramic views through many large windows
–        to ensure that plenty of light streams in during the day and
–        to use light coloured walls
Excessive direct sunlight through the North facing windows can be controlled by external awnings and/or by internal pulldown blockout screens (the former being much more effective). Abundant opening windows allow for cross ventilation on hot days.
Full-width staircase along end wall (rather than ladder) to access loft:
This is a unique configuration as far as I am aware (although I have seen designs with staircases along the long wall of the tiny house, or transversely half-width across the mid section). To me, the novelty of a ladder wears thin after a couple of uses and I much prefer the convenience of simply walking up broad steps. The substantial area under the steps must not be wasted and is used to house the washing machine, hot water cylinder and shelving for pantry items. To maximise under-stair space, some of the steps are supported by vertical posts suspended from a horizontal structural beam (the vertical posts double as safety rails).
Slots for kitchen waste (for composting) and other waste (for recycling or burning):
Here is a simple system adapted from a boat:
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Al fresco enjoyment:
A timber deck can be built on the sun facing side, under a retractable awning.
Construction materials:
Construction materials used must be the choice of the owner (who may leave it up to the builder, if they are not the same person). Needless to say, quality components must be chosen for longevity, durability, strength and the structural flexibility to cope with road journeys. Optimal strength to weight ratio must be considered, both for the sake of towing the tiny house, as well as avoiding excessive long term load on the chassis, even when stationary. Caravan windows tend to be double layered acrylic rather than double glazed glass, for good reasons. It may be advisable to build the house to basic lockup stage only, then transport it to the final destination as an empty shell, where it will be properly fitted out (heavy batteries, washing machine, fridge etc only installed at final location).
Those of you who may know house builders may have access to the excess offcuts from their building sites. Such high quality, brand new but "surplus" offcuts may be sufficient to construct even two or three tiny houses, material which would otherwise be discarded.
The tiny house community:
Below is one possible layout for a tiny house community:
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Residents will come together frequently for many reasons: to grow crops and care for livestock in the common permaculture enclosure, to provide mutual help for maintenance and repairs, to meet and decide on community matters, for entertainment, companionship and for celebratory meals. It is helpful however for participants to have their own private dwellings that they can retreat to in the evenings, rather than be in everyone’s "hair" 24/7 if they all lived in a single large communal dwelling. Furthermore separate dwellings ensure that residents take responsibility for their own resource consumption and will face the consequences of their own profligacy and carelessness. For example if one irresponsible individual in a large communal household depletes the cooking gas, depletes the batteries by leaving appliances on, or depletes the water supply, this affects everyone and could lead to disaster and major conflict. Separate tiny houses enable resilience and if one household inadvertently faces a problem such as water depletion from a ruptured pipe, the other households will remain completely unaffected and can help with repairs and support the household facing difficulty.
Potential criticisms:
I am not a technocornucopian. I view centrally controlled utilities (particularly "big" electricity eg nuclear fission or coal) as doomed in the long term (possibly even short term). On the other hand I can imagine some criticisms from "hard core hairshirt collapsitarians" who may object to my advocacy of low energy, distributed technologies. Whereas I do view the eventual collapse of industrial society as inevitable, the process is likely to be stuttering (short of global nuclear war). As long as we are able to utilise LED lights, fridges and washing machines etc with minimal carbon emissions, it will be foolish not to do so. Going cold turkey is always more painful and may be potentially fatal, compared with gently weaning ourselves off our industrial/fossil fuel addiction and I advocate the latter. Survival is certainly more likely with a soft landing than a hard one.
Geoffrey Chia, February 2015
Many thanks to the Architects: Will Gray for drafting the beautiful architectural diagrams (I made some crude alterations, also the ugly cartoonish diagrams are mine), Lara Nobel who has patiently and generously offered immense help over the past couple of years with regard to passive-solar off-grid cottage and tiny house concepts and designs (as well as physical help carrying materials and installing composting toilet and solar battery systems) and Andrew Carter for thoughtful ideas and practical help.
Also thanks to Dr Doone Wyborn, Geologist, Engineer and energy expert and Dr Jane O’Sullivan, Agricultural Scientist, for their helpful critiques and corrections regarding this article.
All remaining errors in this article are the sole responsibility of the author.
1.      No risk of electrocution with low voltage DC, however there is always a risk of short circuits and fires, hence robust connections and abundant safety fuses are always required.
2.      An 8.0m long and 4.3m high (throughout the entire length) tiny house with double loft design can comfortably accommodate a couple with two children (or two couples). Access to the second loft will have to be by ladder rather than a second set of space consuming stairs. A larger family (a couple with up to six children) can build two tiny houses which will still cost far less then half of a standard small house, even using the best quality materials.
3.      Mass adoption of tiny houses will result in the councils and local utilities going bankrupt from lack of revenue, which is why in the near future governments may outlaw or over-regulate them. Hence it is best to get in now under the radar.
4.      Some may cite Jevon’s paradox as an argument, to which I reply: Jevon’s paradox is not applicable to those of us determined to reduce consumption. It is not some inviolable natural law but a historical observation about the behaviour of certain people, behaviour which can and will inevitably change. Jevon himself was obsessed with the idea that economic cycles coincided with sunspot cycles and when this was disproved, he insisted that the astronomers had got their data wrong. If reality did not conform to his view then he insisted that reality must be wrong. He was a pioneer of trying to quantify economics mathematically, assuming perfectly free markets, perfectly free information and rational participants. History has proven such assumptions to be complete bunkum. Nevertheless many neoclassical economists still try to promote their field as a science, which it most certainly is not and continue to teach such rubbish in universities.
5.      Paraphrased question from Dr Jane O’Sullivan: Why turn the entire toilet cubicle, rather than the solids bin itself, into a "greenhouse"? Wouldn’t it be better just to have black coloured thermal mass on the outside of the bin? Or just insulate the bin, to preserve the heat it generates itself? My answer: On another project where the solids bin is located in a separate chamber under the toilet cubicle, I am indeed turning that chamber alone (which has thermal mass within the black coloured chamber walls) into a minigreenhouse. Due to the design of the caravan model of the Nature’s Head toilet, this is not possible for the tiny house project. Insulating the bin won’t work because the ventilating fan ensures that air in the bin is constantly changed, which will rapidly dissipate any heat buildup in the bin. However, if the air of the toilet cubicle is heated up and that is drawn into the bin for ventilation (then expelled to the exterior), that should keep the composting temperature several degrees higher than it would otherwise be (compared with if external cold air is drawn in the bin then expelled).
6.      The exception being if you live in a high latitude and have a deciduous trees in front of your sun-facing windows, hence providing shade in summer. These trees will shed their leaves in autumn and allow the winter sunlight in, enabling passive solar heating.
7.      Ordinary car/truck engine starting lead-acid batteries are not suitable, make sure they are deep cycle batteries.
8.      Lithium iron phosphate batteries are continuing to reduce in price and may be the best option soon. It is important to only shallowly discharge lead-acid batteries for the sake of longevity (discharge by not more than 30% on most days, occasionally discharge by 50%,  where the 24 volt system will show 24 volts at rest). Lithium iron phosphate batteries can cope with 90% discharge every day. Thus smaller amp hour storage is required. “LiFe” batteries are much lighter and great for mobile dwellings where weight may be an issue eg catamarans. However they require an electronic battery management system to ensure proper voltage balance between batteries, which is an additional layer of complexity.
9.      Even if the wind turbine produces high voltage alternating current at source, which is then rectified to DC after the dump load resistor, I have been advised that these AC turbines are specifically designed to ultimately feed either only 24V or 12V DC systems and the two types of turbine are mutually exclusive and not interchangeable. The advantage of high voltage AC being produced at the turbine means that thin cables can be led long distances from the wind tower to the point of use without significant energy loss before being rectified to low voltage DC.
10. My tiny house kitchen will not include any of these heat producing electrical appliances as I have no access to microhydro.
11. At any rate, the "experts" approved by the Council I have been dealing with. On the other hand I have been informed that nitrates denature quickly and rapid application to crops is preferable.