Intangible Details

I've been wrestling intangible details in my head for what seems like forever.  Here's the jist of the structure and rough sequence of events for the building process:

Foundation:
I'll be building the 16' long trailer frame from scratch to take advantage of the maximum legal road width in my state that doesn't require any permitting.  After much searching, I found Benco Steel had astoundingly lower prices, about half, and free shipping semi-locally as long as I ordered 250 pounds of steel (easy).  It turned out much cheaper than buying new and probably similar to used, but I'm getting exactly what I want, though no paint.

Load Bearing Structure:
It's like a post and beam timber frame structure, just with steel.  3" x 1/8" HSS Square colums at the corners and 4" x 5.4# channel (C-shaped in cross section) for the perimeter of the roof (headers, end rafters, plus a steel rafter in the center).  Many 10" x 1/4" triangular gussets in the corners for diagonal bracing.

 All in all materials broke down like this:
Steel with some cutting - $1200
Axles and other trailer hardware - $1200
Wheels and tires - borrow from a friend (hopefully, otherwise $650)

Structural Engineering:
I used Web Structural(free, simple) to design the "girders" of the trailer and the headers using the best of my understanding of structural engineering, but also more or less mimicking designs for trailers of similar size and intent and seeing if they passed or failed in the design program.  Eventually I'd like to have this design verified by a structural engineer so others could feel comfortable copying it, but I feel plenty confident for my personal use.

Roof:
A thoughtful builder friend advised I use Georgia Pacific brand "Framing Series" Southern Yellow Pine 2 x 4's for the 3:12 pitch roof if I wanted to put my rafters at 24" o.c. instead of the home milled lumber.  The GP SYP has been selected/graded and is also harvested sustainably, milled, and distributed locally.  Rigid 3.5" poly-iso insulation will go between the rafters.  Another 1" layer of continuous insulation on top of the rafters followed by 1" x 4" poplar nailers or possibly ZIP t&g plywood.  Standing seem metal roofing will top it all off.

Subfloor:
2" thich home milled poplar, "biscuit" jointed at 1', spanning 4' from joist to joist.

Framing:
Between those corner columns on three sides will be home milled tulip poplar 2" x 3" framing, the fourth (16ft, south facing) wall will have a 6" poplar beam with live edge supported by two 6" square poplar beams.

Insulation:
I picked up some salvage 3"(actually 3.5") poly-isocyanurate foil-faced rigid foam insulation through Insulation Depot.  They work within the U.S. as a sister company to a roofing company and store the insulation in warehouses near the job site where you can pickup the insulation.  I had to drive a couple hours to Charlotte, but I think it was certainly worth it.  It was $600 for 30 panels (about half the price of new).

*Pros: pre-off gassed, no additional manufacturing, poly-iso has the highest r-value (resistance to heat transfer) per inch of all common insulating materials, about r-8 per inch

*Cons: only one side had decent foil coverage, the other was pretty much worthless for a vapor barrier, ask before you buy.  I had them send me pictures, but I guess I was only seeing the good sides.

Siding:
I was fortunate enough to get to fell 3 large and 3 small Tulip Poplars back in the spring on the property where the structure will soon{enough} reside.  When properly timed (mid/late May to late June) the bark of tulipifera Liriodendron can be peeled off in sheets.  Natural Plywood!!!  1" x 4" "nailers" will be screwed through the insulation to the studs with 6" screws every 2', then the poplar bark will be screwed to those nailers.  Tyvek housewrap or similar under it all.

Inner Walls/Ceiling:
1" x 12" grain matched home milled poplar will go between the wall framing (which will also serve as the trim) and cover the rafters on the ceiling.

Openings:
DIY fixed windows from double-gifted HURD triple pane low-e casement windows (a few fogged up within warranty so they replaced them all) with a gifted sliding glass door on the south wall.

Finish Floor:
Grooves routed parallel with the subfloor to accept pex and aluminum heat transfer plates for radiant floor heat.  1/4" Hardi-backer to aid in helping the floor feel warm.  An undecided selection of tile and/or marmoleum and/or cork.

Greenhouse/Bathhouse:
Once the structure is moved to the site (likely via u-haul) a structure will be bolted together and to the main structure composed of DIY SIP panels.  This will be a place where almost all the "moist" activities will occur:  Shower, Wood Fired Hot Tub/ Water Tank, Seedling Growing, Composting Toilet, Cooking.  The central 8' of this roof will be transparent/translucent dual panel material as well as more triple pane HURD windows all along the south/front side.

Rooftop Deck:
I haven't fully figured out how this will be attached, but it will also be in 4' x 8' DIY modules probably covering the full 8' x 16' rooftop.  Hopefully it will serve as a shady, breezy summer hangout area with the simple addition of a canvas awning.  It could be disassembled in the winter or the snow could easily be shoveled off when necessary.

Utility Shed:
The last additional building comes again in 4' x 8' DIY SIP panels to make an 8' x 8' shed connected to the main structure which will house the deep fridge,freezer, battery bank and serve for additional storage space.  It can be accessed through the back/north wall of the main structure or through it's own outside door.

Systems:

Electricity:
I'm currently intending to setup a micro hydro system in the nearby creek.  My calculations show that I'll need around 3kW(kilowatts) per day or about 125 watts of  continuous power to keep things going in the peak heat of summer.

Air Conditioning:
While the summer temperatures in Western North Carolina rarely cause this Georgia boy to break a sweat, the humidity and resulting mold has brought many-a-sneeze.  Fortunately mini-split air conditioners are being made to run off DC, it's actually more efficient because their motors are DC anyways, so now power inversion necessary, plus the motors and fans can operate at many speeds to avoid unnecessary power cycling of the unit.  Some simple BTU(british thermal unit) calculations showed that I'd consume very little power to keep this running in the summer to keep humidity at a non-favorable level for mold growth.

Potable Water
Fortunately there is already a gravity fed spring system setup on the property that historically overflows year-round (fingers crossed) which I'll setup to get overflow from the tank so as not to inconvenience the landowners' water needs.

Hot Water:
In the summer, a simple "black pipe" solar hot water heater should keep me satisfied for washing dishes and the occasional hot shower (I generally prefer to get in the creek in the late afternoon).  More ideas at Build it Solar.

In the winter, a wood fired hot tub heater will heat water in a 250-300 gallon livestock water tank housed in an insulated wooden box with a removable lid for the occasional therapeutic soaking.  Generally this water will be slowly circulated under the floor of the main structure to provide slow even heating, hopefully firing of the stove twice a day will not make the greenhouse excessively hot.

Food Storage:
A Sundanzer deep fridge and deep freezer should keep things cool and well stocked with food for the winter.  I also plan to bury a few barrels as micro root cellars.  The loft space in the main structure will be good for Sweet Potatoes and Butternut Squash which like it "high and dry".  And of course the garden will be right outside hopefully allowing me to bear witness to many more bountiful growing seasons.

Humanure:
A simple composting toilet, similar to those I have seen in odorless action.  I've got PLENTY of sawdust after milling all the lumber.  Though I also intend to experiment with producing biogas to cook with.  Urine, conveniently sterile unlike its counterpart, mixed with water(50:1) and applied to nitrogen hungry crops like corn and sqaush makes for some great fertilizer.

Cooking:
I plan to start off with an apartment size range in the greenhouse, but changing over to wood burning apparatuses like a cook stove, cob oven (probably outside, on it's own mini-trailer), rocket stove.  Or possibly running the propane range off of biogas.

General Storage:
The loft space will be made up of 2 4' x 8' platforms at either end of the main structure, probably with a translucent rice paper door.

CHOP WOOD, CARRY WATER, BEFRIEND GRAVITY. MORE LATER....