Getting Closer to smaller living: Stage 1 - Planning

I am planning on a mobile version of a micro home.  I want it to be 14 foot by 8 foot with a 13 foot height.  but I may do an initial test building smaller.  I can use a pair of harbor freight 4X8 trailers to make a light tandem that is 12 feet long.  This can hold a 6 foot wide micro home on it.    This would be more of a "camper" than anything, so  it will be easy to sell when I am ready to go full scale.

Planning out the design is a bit tough.  I want to be self sufficient in that I do not need to be hooked to any utilities if I do not need to.   That means solar for power, and propane tanks for gas.  Along with having to have water and sewer storage on board.  This means building like a RV is built.  I also need to think of weight of the whole thing. Typical micro homes like the tumbleweed homes are incredibly heavy.  5800-7500 pounds means you have to own a 5mpg gigantor truck to move it.  SO compromises can be made and changes in design to decrease weight are needed.    Interior walls can be 2X2 lumber to save 1/2 the weight, and instead of expensive hardwood, buy cabinet grade 1/4 inch thick plywood to sheath it.  you get a luxury wood wall at 1/2 the weight. You can go even lighter if you use composite paneling.  And save a ton of money.  Outer walls can be 2X2 walls just like how a RV or Camper is built, but you space the studs closer together.  again thinner plywood for sheathing and to add more insulation, you attach foam board on the OUTSIDE of the studs and then attach the sheathing.  this way you can have 3 inches of hard foam board insulation in the outer walls and cut a lot of weight.  Ceder shake siding is light, but pine is even lighter if you plan on staining and sealing it.  look at your siding choices and weigh them.

Wood windows are nice but vinyl is lighter.  steel roofing is also a lot lighter. and unless you plan on walking on the roof, you do not need 3/4" sheathing up there as well.  you can save 40 pounds per 4X8 sheet if you go with 1/4 inch thick everywhere.

Solar power.  If I figure that a mini fridge, a small microwave, a laptop, and other smaller electronic and electric items are used, I can get away with about 300 watts of solar,  that is 3 100 watt panels that can easily be packed up into the home when travelling and produce 1800 watt hours of electricity in a 6 hour day.  6 batteries will give me 3 days worth of power and a single 2500watt inverter/charge controller will give me AC power for the Microwave and other items when needed.  All lighting will be 12V low voltage LED as well as the wireless router with 4G for internet everywhere.  Typical power consumption at it's worst will be less than what I generate per day so the batteries will stay topped up unless I get a week of darkness.

I am trying to figure out if a 12,000btu RV furnace is enough for a micro home.   This would give me the ability to have "central heat" in case I want to spend a month in Minnesota during January.  I have also discovered that bathroom and kitchen  vent fans can be created by using Marine Bilge vent fans.  they are 12 volts and are standard 3" and 4" duct sizes.

One added idea I have is a ventilation fan.  adding in cold air intakes under the home that will be duct-ed inside.   IF I open the loft windows and the vents hot air will draw in cold air from near the ground and make the home cooler in hot weather without spending any money. I just have not figured out how to insulate them for colder weather.